CA^ < a A MANUAL OP HYGIENE AND SANITATION BY SENECA EGBERT, A.M., M.D. PHOFESSOR OF HYGIENE, UNIVERSITY OF PENNSYLVANIA, FORMERLY PROFEHHOR OF HYGIENE, AND DEAN OF THE MEDICO-CHIRURGICAL COLLEGE; SOMETIMK MAJOR, MEDICAL CORPS, U. 8. ARMY; MEMBER OF THE AMERICAN MEDICAL ASSOCIATION, AMERICAN PUBLIC HEALTH ASSOCIATION, ETC. SEVENTH EDITION, ENLARGED AND THOROUGHLY REVISED ILLUSTRATED WITH 160 ENGRAVINGS AND 5 PLATES LEA & FEBIGEK PHILADELPHIA AND NEW YORK 1919 Copyright LEA & FEBIGER 1919 TO THE MEMORY OF MY FATHER, TO WHOM I OWE SO MUCH) TO WHOM I COULD REPAY SO LITTLE. THIS VOLUME IS MOST AFFECTIONATELY DEDICATED. 42453G PREFACE TO SEVENTH EDITION, Recent years have far eclipsed any equivalent periofl in the history of Hygiene and Sanitation, both in the practical application and in new developments of the principles. This advance is not only because of the intensive and universal use of the science by the armies in the great war, but also because, as was presaged in the two preceding editions, public health measures as factors in the common welfare and betterment of the people are being more widely apprehended and appreciated every- ^ where and measures insuring the improvement of the health of many are already completed or are in prospect of early achievement. Hence the revision for the present edition has been thorough and every chapter has been carefully gone over in order that its contents might be fairly abreast of the times. Perhaps it may seem to some that the author has been too conservative in retaining much of the old and in omitting some of the newer matters that have claimed attention of late, but it should be remembered that this is primarily a manual of fundamental principles ami that mere novelty is not a sufficient warrant for giving space to what is not as yet well established by thorough trial and test. Nevertheless all advisable pruning has lx»en done and considerable new matter has been added in the VI PREFACE endeavor to bring the book up-to-date and worthy of a continuance of the kindly reception it has had in the past. Especial attention has been given to the chapters on Sewage Disposal, Industrial Hygiene and Military Hygiene, because each of these subjects is now one of increased importance and in an era of marked advance. The first of them is developing rapidly on account of the growing realization of its influence upon the health and comfort of communities, both large and small. Moreover, the newer developments in the biologic treatment of sew- age promise much and are leading to a more practical solution of the general problem. The hygiene of industry and the occupations is con- stantly enlarging in scope and growing in interest and the inevitable and extensive expansion of industrial enterprises subsequent to the war compels attention to it as one of the most important branches of the science of public health. Likewise the part that Military Hygiene has played throughout the recent great conflict and the benefits that it has given to all the nations con- cerned, make its principles and its new development still of lively interest to every student of the same science. Hence the author has in his revision given special consider- ation to the chapters on these subjects without neglecting the others wherein the points treated are, perhaps, more stabilized. Knowing how fair and generous its former readers and critics have been, the author is once more emboldened to send out the volume in its new dress, trusting that it may still be of value in meeting the needs for which it was planned. S. E. Philadelphia, 1919. CONTENTS, CHAPTER I. Introduction 17 CHAPTER II. Bacteriology and Parasitology 36 CHAPTER III. The Atmosphere — Air 69 CHAPTER IV. Ventilation and Heating 101 CHAPTER V. Water 146 CHAPTER VI. Food 229 CHAPTER VII. Stimulants and Beverages 277 CHAPTER VIII. Personal Hygiene 285 CHAPTER IX. School Hygiene 314 viii CONTENTS CHAPTP]R X. Disinfection 338 CHAPTER XI. Quarantine 370 CHAPTER XII. The Removal and Disposal of Sewage . . . . . 389 CHAPTER XIII. Industrial Hygiene and Occupational Diseases . . . 439 CHAPTER XIV. ^ Military Hygiene 455 CHAPTER XV. Vital Statistics 494 CHAPTER XVI. The Examination of Air, Water, and Food .... 509 HYGIENE AND SANITATION. CHAPTER I. INTRODUCTION. Hygiene may be defined as the art and science that considers the preservation, promotion, and improvement of health and the prevention of disease. It treats of the laws of health in the broadest sense, and under the general term may be included a number of subdivisions. Thus, while Personal and Domestic Hygiene are resp)ec- tively more closely related to the affairs of the individual and the household. Sanitary Science also finds larger fields and broader application in the domain of Public Health and State Medicine, in the Hygiene of ]\Iunicipalities and of Occupations, and in that which especially relates to the physical welfare of armies, navies and other large and particular groups of men. A little thought will show that under the general head we may consider the preservation and promotion of health; practical disinfection and the means of avoiding preventable diseases; adaptation of diet and other factors to the prevention and cure of perversions of nutrition; improvement of environment; advances in sanitation and industrial hygiene, etc. Under one or another of these themes will fall the discussion of the air we breathe, the water we drink, the food we eat, the soils and sur- roundings of our dwellings and communities; and at the same time the study of the means of recognizing, avoiding, correcting, or removing all detrimental factors affecting any of these. In addition, there must be the . 2 (17) 18 INTRODUCTION study of climate and meteorology; of clothing and shelter; of the care of the sick, not only for their own sake, but that they may not endanger the well; the dangers of the abuse of stimulants, narcotics, etc.; the factors initiating and governing epidemics, and the desirability of chaste _ and temperate living, exercise, rest, etc. Parkes says that, "taking the word 'hygiene' in its largest sense, it signifies rules for the perfect culture of mind and body. It is impossible to dissociate the two. The body is affected by every mental or moral action; the mind is profoundly influenced by bodily conditions. (So is the moral conduct of individuals or communities.) For a perfect system of hygiene we must train the body, the intellect, and the moral faculties in a perfect and bal- anced order." Again, he says; "Looking only to the part of hygiene which concerns the physician, a perfect system of rules of health would be best arranged in an orderly series of this kind. The rules would commence with the regulation of the mother's health while bearing her child, so that the growth of the new being would be as perfect as possible. Then, after birth, the rules (dif- ferent for each sex at certain times) would embrace three epochs: of growth (including infancy and youth); of maturity, when for many years the body remains appar- ently stationary; of decay, when, without actual disease, though doubtless in consequence of some chemical changes, molecular feebleness commences in some part or other, forerunning general decay and death. In these several epochs of his life the human being would have to be con- sidered: First, in relation to the natural conditions which surround him, and which are essential for life, such as the air he breathes, the water he drinks, etc. ; in fact, in rela- tion to nature at large. Second, in his social and corporate relations, as a member of a community with certain cus- toms, trades, etc.; subjected to social and political influ- ences, sexual relations, etc. Third, in his capacity as an independent being, having within himself sources of action in thoughts, feelings, desires, personal habits, all SCOPE OF THE SCIENCE 19 of which affect health and which require self-regulation and control. Even now, incomplete as hygiene is, such a work would, if followed, almost change the face of the world .' * The preceding paragraph indicates the individual or personal aspect that marked the common concept of the subject until a comparatively short time ago. More recently the tendency is also to view its func- tions, opportunities and problems from a social and altruistic stand-point, and the field has so enlarged in this direction that it is questionable whether it may not be better to supplant the older word — Hygiene — when used to refer to the general science, with the newer term — Public Health and Preventive Medicine. But, after all, he who works to improve the sanitary condition of his neighbors and his neighborhood, no matter how extensive these may be in numbers and area, at the same time well serves his own interests, for not only is disease no respecter of persons, but its transmission and dis- semination depend very much upon one's relationships with others. The student will readily see that the scope of the science is so vast that in a limited work like the present one it would be impossible to go over the entire ground completely and thoroughly. The most that may be attempted will be to discuss its fundamental laws as we now understand them, especially those that are most closely connected with the conscientious physician's duties and practice, and to show the reasons for, and the advan- tages resulting from, the pursuit of hygienic measures and sanitary methods based on those laws and our experi- ence. Hygiene is, however, a science in the study of which common-sense must be freely used; and if the student will only bring this to his aid and add to it sincere consideration, he will speedily find that there is little that is difficult, beyond his grasp, or less than really fascinating. It has always been, as it always will be, an art to pre- serve health and to ward off disease. Hippocrates (400 B.C.) 20 INTRODUCTION was among the first to define principles of public health or sanitation. He summed up the knowledge of his day concerning hygiene under six headings, viz.: Air, Ali- ment, Exercise and Rest, Sleep and Wakefulness, Reple- tion and Evacuation, and the Passions and Affections of the Mind; and he even pointed out that there must be an exact balance between food and exercise, and that "disease would result from excess in either direction."^ The excellence of the Mosaic code is acknowledged by all sanitary authorities, and the effects of its observance are seen to this day in the comparative longevity of the Hebrew race. The Greeks cultivated to the extreme both the physical and mental faculties and had for their motto, A sane mind in a sound body. Recognizing the triune nature of humanity, we shall do well if we include with these the cultivation also of a spiritual health. The Romans, in their aqueducts for conveying water to the city and in the cloaca maxima, have left examples of sanitary engineering which are, in certain respects, not yet sur- passed. All of which serves to show that the ancients appreciated the importance of maintaining and improving health, and the influence of material conditions and environment upon sanitation. The development of hygiene as a science, however, has been within comparatively recent years. Perhaps the first great impulse among English-speaking peoples, espe- cially in matters pertaining to sanitation or "State Medi- cine," can be traced to the labors of Dr. William Farr, and to the establishment, through his efforts, of the British Registrar-General's Office in 1838.^ Since then 1 Treatise on Airs, Waters, and Places. (About 400 b.c.) 2 Note should be made, however, of the writings of Johannes Petrus Frank, in the first quarter of the nineteenth century and even earlier, and of Parent DuChatelet, between 1820 and 1836. Of the work of the former, it has been said that "It was the first orderly presentation of that which had hitherto been known upon these subjects, and was the first systematic effort to rescue from chaos such useful information as might be of service in the organization of a department of sanitary supervisors, or, as the author preferred to call them, medical police." A. C. Abbott, University Medical Magazine, July, 1900. VALUE OF SANITATION 21 the task of determining the principles and laws of health has been carried on with unflagging zeal by workers both here and abroad, and within the last forty years the knowledge gained in the new study of the bacteria and other microorganisms and their hosts, especially that regarding the causation and nature of infectious diseases, has furnished us with a wealth of iacts with and by which we may make the foundations of our science more lasting and secure. It would be wrong, nevertheless, to give the impression that hygiene is as yet an exact science. While it is rapidly attracting popular notice and attention, and has under the broader and more altruistic development already referred to, attained within comparatively recent years a dignity that it did not hitherto have in this new world, it is on a somewhat firmer basis abroad. Some of the best minds of the time are busy with many of its problems, and facts and laws are being made clear that more firmly fix or may altogether change some of our beliefs and our practise. Especially is such new knowl- edge to be sought for in the study of the prevention of disease, the domain of bacteriology and the parasitic diseases, and physiologic and biologic chemistry. Perhaps a few statistics will help one to realize that the study is not in vain, and that the promise of the future is even more brilliant than the results and achievements of the past. Three centuries ago the death-rate of London was more than 80 per 1000; now it is about 15 per 1000. It is computed that in the eighteenth century — the one preceding the introduction of vaccination — fifty millions of people died in Europe of smallpox alone; now it is almost an extinct disease where vaccination is compulsory, as in Germany. In 1872 Sir John Simon estimated "that the deaths which occur in England are fully a third more numerous than they would be if our existing knowledge of the chief causes of disease were reasonably well applied throughout the country, and that of deaths which in this sense may be 22 INTRODUCTION called preventable, the average yearly number in Eng- land and Wales is about 120,000." This result was actually more than achieved by 1889, and in 1912 the mortality-rate for these countries had fallen to 13.3 per 1000 of population as compared with an average of 22.6 for the decade 1862-71, this representing a saving of over 300,000 lives in the later year. In this country a like improvement is to be noted, though it is only within the last few decades that much attention has been given to sanitary affairs. The death- rate of most of our cities is being progressively lowered, though the populations are constantly increased by large numbers of ignorant and uncleanly immigrants. Im- proved sanitary laws are being enacted and enforced, streets better paved and cared for, houses more wisely constructed and ventilated, more attention given to iso- lating the sick and protecting the well, and the people in general are awakening to the importance of improving as well as maintaining the public health. New York City has reduced her death-rate per thousand within twenty-five years (1890 to 1915) from 25.4 to 13.9; Chicago, from 19.1 to 14.3; Philadelphia, from 20.76 to 15.6; Boston, from 23.4 to 16.1, etc.^ Notwithstanding the increase in population, there were actually 7780 fewer deaths in New York City (Manhat- tan Borough) in 1916 than in 1891, although the increase in population during this period was over 50 per cent., or almost one million of additional citizens. Similar encouraging, if not so striking, reports from many other cities enable their authorities to attribute the good results to advance in medical and surgical knowledge along the lines of preventive medicine, improved sani- tary surroundings, better water-supplies, cleaner streets, in- ^ The importance of such statistics is not fully appreciated Unless the reader remembers that in a city of, say, a million inhabitants a reduc- tion of the death-rate bj' one point means the saving of one thousand lives annually. RECENT VITAL STATISTICS 23 inspection of milk- and food-supplies, isolation and modem treatment of infectious diseases, additional public parks, etc.* Death Rates per Thousamd of Population 13 K t s in ion £ \ Rur OP St 17 » \ ITO,^^ / ^17 O lii— • 172 17 3 Vl-j \ > C ,53 X^ / \ ^r ^ IS« \ 15 4 \ / ^^^.. 1+4 14+ rto i t * i "N rt3 % % 1 13 + 9 f»7 *-— . 139 03 1900 1901 I90Z 1903 1904. 190S 1906 1907 1908 1909 1910 1911 t9lt Fig. 1. — A comparison of urban and rural mortality (in registration states as constituted in 1900) from all causes. COMPARATIVE DECLINE IN URBAN AND RURAL MORTALITY (IN REGISTRATION STATES AS CONSTITUTED IN 1900) FROM ALL CAUSES. Decline in '—Death-rates per 1000 of population.-^ doath-rate Av'ge Av'Ke •12fronj'00. 1900. 1905. 1910. 1912. 'Ol-'OS. 'OS-'Og. Actual. Pet. Registration states 17.2 15.9 15.6 14.6 15.9 15.5 Rural part of registra- tion states . 15.2 14.4 14.7 13.9 14. Cities in registration states .... 18.9 17.1 16.2 14.9 17.4 14.2 16.4 2.6 15.1 1.3 8.5 4.0 21.2 1 Twelfth Census of the United States, 1900, vol. iii; Vital Stotistics. Part I; and The Census Bulletin (104) on Mortality Statistics for 1908. 24 INTRODUCTION Other evidences of the benefits resulting from the appK- cation of the principles of modern hygiene are the marked reduction in the sick- and death-rates due to infectious diseases, and the gradual increase in the average expecta- tion of life in those countries or places where systematic prophylactic and sanitary work is being done. Thus, in the so-called "registration-area" of the United States the death-rate for diphtheria has dropped from 70.1 per 100,000 of population in 1890 to 14.5 in 1916; that of malarial fever, from 22.1 to 3; of typhoid fever, from 46.3 to 13.3; and of tuberculosis, from 245.4 to 141.6; while the general death-rate of the same 'area" has fallen in the same period of time from 19.6 to 14 per 1000 of population.^ Likewise, the average duration of life, according to high authority, is rapidly increasing — e. g., the rate of increase in Europe "during the latter half of the nine- teenth century was about seventeen years per century, and in Germany, where medical and sanitary science has reached the highest development, about twenty-seven years per century." The only comparative statistics available in this country are for Massachusetts, where life is lengthening at the rate of about fourteen years per century .2 Who then shall say that the study and practice of hygiene and sanitation — of preventive medi- cine — is of no practical value ? It will be well to note at this point the marked reflex influence that the adoption of an accurate or improved method for the registration of vital statistics has upon the sanitary status of any part of the population. Wher- ever a city or a State has adopted such a method there 1 It should be noted that the above rates are not strictly comparable, as the "registration area" has been materially changed and increased during the period in question. Thus, it represented 40.5 per cent, of the population and but 7.1 per cent, of the land area of the country in 1890, as against 70.2 per cent, of the population and 44 per cent, of the land area in 1916. 2 Report on National Vitality, Its Waste and Conservation: Irving Fisher, 1909. CONTINUOUS PROPHYLAXIS NECESSARY 25 has almost immediately followed an improvement in its morbidity- and mortality-rates, for which reason the conditions obtaining in the component parts of the total ''registration-area" of the United States are undoubtedly better than in similar or comparable portions of the remainder of the country. The registration-area is con- sidered to be the combined areas or localities where, in census years, "the deaths obtained from registration sources constituted 90 or more per cent, of the total (registration plus additions from enumerators), and the additions from the census enumerators' returns did not exceed 20 per cent, of the number reported by them"; and, in other than census years, where a similar accuracy of official registration of vital statistics obtains. Nevertheless, there is still much to be done. Tuber- culosis, which is said to cause from one-seventh to one- fourth of all the deaths in the civilized world, is a pre- ventable disease, and we now not only know its cause, but also have efficient means for cure in a large proportion of cases, as well as for its general prevention. So with a number of the other infectious diseases. Almost every day marks an increase in our knowledge of their etiology and the securing of immunity from them; and not only must physicians make use of this knowledge as they acquire it, and employ their utmost endeavors to secure the enactment and enforcement of sanitary laws and regulations, but they must also realize that a large part of their work lies in the enlightenment and education of the people in all matters pertaining to the public health.^ The plague that was the bane of Europe centuries ago ^ It is encouraging to find that, although over 10.5 per cent, of the whole number of deaths recorded in Philadelphia in 1916 were caused by con- sumption, a progressive and marked lowering of the death-rate from this disease in that city is taking place, and that, notwithstanding an increase in population of 76 per cent., the fatalities from this disease are but few more in number than they were over thirty years earlier. For example, the deaths from pulmonary tuberculosis in 1885 numbered 2821, and in 1886 were 2834, rates respectively of 297 and 292 per 100,000; while in 19 16 there were only 2916 deaths, or a rate of 170.6 per 100,000 living. 26 INTRODUCTION and that has been a scourge to Asia since, occasionally threatens us at our western gates and is rife in some of our newly acquired colonial possessions. The infectivity of pneumonia is not appreciated by the laity nor by many physicians. The death-rate (137.3) in the Registration area in 1916 due to all forms of this disease was almost as high as that for tuberculosis of the lungs (141.6) and was only exceeded by the latter and by that for acute endocarditis and other organic diseases of the heart (150.1). We must not forget that pneumonia, which can be so pestilent, is "more or less limited to centers, corresponding in the main to the most densely popu- lated area, with their allied conditions of squalor and poverty,"^ and that it is our duty and for our own safety to improve the sanitary conditions and environments of such areas and centers. With our present knowledge of the value of vaccination, there have been far too many epidemics of smallpox within comparatively recent years ? Carelessness in the application of protective measures has cost many lives and much money. There can be no safe cessation in prophylactic efforts. So, also, each and every one of the communicable maladies must be continually investigated and studied, and all positive information gained concerning them must in turn be imparted to the people who need protection against them. On the other hand, it is becoming more and more evident that any community may have good health, that is willing to pay for it, and that low sick- and death-rates largely depend upon an efficient administration of the functions of public health service. Order of Study. — In the preparation for a study like the one on which we are about to enter there is some ques- tion as to just what may be the most advantageous order and arrangement of the subjects to be treated. For in- 1 J. M. Anders, Journal of American Medical Association, May 9, 1903. 2 The deaths from smallpox in the registration-area of the United States for the years 1900 to 1904, inclusive, numbered 5898, this repre- senting an average annual death-rate of 3.7 per 100,000 of population. DUTY OF PHYSICIANS 27 stance, it would be interesting to discuss our science in its relation, in turn, to the individual, the household, and the people in general — that is, personal, domestic, and public hygiene; and to show wherein the treatment of these sub- divisions is similar and wherein they differ. Such a three- fold consideration would be not only logical, but extremely instructive as w^ell. However, since the bacteria and other microorganisms have been shown to have so important a part in many of the processes intimately connected with health and disease, it will doubtless be advisable to devote the next chapter to a brief review of the science of parasitology. This done, it seems to the writer that we shall, as beginners obtain a more comprehensive and thorough view of our subject if we pursue a method somewhat as follows: First, to discuss air, water, and food — three things essen- tial to life — in the varying conditions and circumstances under which they may affect the physical welfare, either for good or bad, of the individual or of the community. Then to take up, in such order as may seem best, the other themes, such as climatology, habitations, disinfec- tion and quarantine, disposal of sewage, clothing, exercise, school hygiene, etc., whose consideration, on account of their influence in the preservation of health and prevention of disease, is only a degree less important than those already mentioned. In this way, while the whole ground may not be covered, the importance of the various subdivisions may be estimated in their relationship to one another, and we shall be the better prepared to pursue the study as later opportunity may offer. It is doubtless in place just here to review briefly the reasons why it is the special duty of the physician to be able to recognize and correct insanitary conditions where- ever they may be found, and why he should make par- ticular and constant study of the science in all its branches and developments. Every true physician soon finds that the respect and affection of his patients and associates are worth far more 28 INTRODUCTION than mere mercenary gain, and that his highest aim should be to prevent disease rather than simply to cure it; and, though this may seem to militate against his personal in- terests, he is unworthy the name of physician if his object and purpose be solely or primarily to make money. How- ever, the observer quickly learns that in a community kept in good health and sanitary condition there will always be more or less need of a doctor's services in spite of every effort to prevent sickness, and that such a community will pay more promptly and more liberally for such services than one in which sanitary precau- tions are neglected. Health means ability to work and to earn good wages; and a healthy community means more business, more money, and more comforts. More- over, as a rule, good wages insure prompt and willing payment of the doctor's bills as well as of others. We may note here the close relations existing between sanitary science and social and political economy — a relationship which is very intimate, as we shall see from time to time in our work, for as. the physical condition of a people is bettered, it becomes more possible and more certain that they will likewise improve both mentally and morally. Again, though the science of hygiene and sanitation is comparatively a new one, public attention is being strongly directed toward it, not only because it vitally interests every one, but because new discoveries and new appli- cations of the laws pertaining to it are being constantly made, which are, in turn, swiftly given to the world by both the scientific and the popular press. This creates a demand for first-class investigators, teachers and workers, which demand is bound to increase in the near future and promises materially to exceed the supply. In fact, within a very few years not only the medical but also the academic and scientific schools of the country will doubtless be compelled by public opinion to establish in their faculties well-equipped and liberally endowed chairs of hygiene and sanitary science, and it will be from the ranks of the educated physicians of the country that these teachers NEED FOR TEACHERS AND SANITARIANS 29 and scientists must naturally come. It will not be long before the people in general realize that it is fully as important that the college student or graduate be instructed how to do his part in taking care of the health of himself, his future family and the community in which he is to reside, as that he shall be well taught in the abstract principles of theology or the classics of dead languages. So, also, considerably more time and attention than are now accorded to it should be given to hygiene in the work of the various normal schools for teachers. The graduates of these schools will have much of the physical as well as the mental welfare of thousands of young and growing children in their keeping, and it is unquestionably their duty to prevent or obviate the ills of school-life as far as lies in their power, and to inculcate and give instruc- tion in habits of living which will continually tend to preserve and improve the physical health of those under their care. The large proportion of young men in this country recently rejected as being unfit for military service because of physical deficiencies has awakened public interest to the importance of this subject as never before and methods and means are being sought whereby the tremendous loss in economic efficiency due to this cause may be prevented. There is also need for trained sanitarians in the service of the various states and the large municipalities, and there is now an actual demand for such men and women with no corresponding supply in view. Lastly, the time has come when a physician must neces- sarily have a knowledge of hygiene, preventive medicine, and sanitary science. Many states require as thorough examinations in this as in any other branch of medicine before granting the right to practise within their boun- daries. Even more so do the Army Medical, the Navy Medical and the Public Health Services of the Government, lay stress on this branch and the constant demand for an increased personnel in each of these as well as the experi- 30 INTRODUCTION ence gained by all three during the late world war, must emphasize the value and necessity of a thorough knowledge of hygiene, sanitation and preventive medicine on the part of those who may anticipate enrollment in any one of these branches of the public service. Moreover, the people generally, as has been intimated, are awakening to an interest in sanitary matters and the prevention of disease, and expect their physicians to be well versed on all pertaining subjects; if they find one lacking in knowledge or interest in this respect, they are apt to think, rightly or wrongly, that he will also be deficient in the other branches of medicine. Happily these causes all combine to place preventive on the same high plane with curative medicine, and the time has passed in which the chair of hygiene and pre- ventive medicine did not have a primary place in any thorough medical school. May the day soon come when it shall have at least equal importance in the curricula of all academic and normal colleges and schools! It is evident that the successful physician and practical student of hygiene must have a thorough knowledge of three things: (1) Health and its laws; how to obtain and preserve it. This of course, implies a knowledge of the human body and its functions, viz., of anatomy, physi- ology, and physiologic chemistry. 2. Disease and its causes and nature. He must also understand the dis- tinction between diseases due to causes external and those due to causes internal to the body; and that while some of these causes may be prevented or modified, others, with our present knowledge, may not be so readily overcome. 3. Therapeutic agents, both preventive and curative. He must be conversant with and know how to use those which he has at his disposal, including not only drugs, but also all substances and forces that he can make efficacious to his purpose. The workman must know his tools to be able to use them intelligently. Health is "that condition of the body and its organs necessary to the proper performance of their normal DEFINITION OF HEALTH AND DISEASE 31 functions"; and disease may be defined as "a condition of the body marked by inharmonious action of one or more of the various tissues or organs, owing to abnormal condition or structural change." It is, accordingly, well to consider briefly the nature and causes of disease, that we may the better understand the influence upon its pre- vention or production of all those varying factors, phases, and conditions of our environment which we hope to study in our work. Disease is a pathological or abnormal physiological state, not a spiritual thing; a condition, not a theory. Conse- quently it is to be fought and, if possible, conquered with matter, natural forces, and physical means, though not necessarily with violence. In fact, when once we under-/ stand the minuteness and delicate structure of the ulti- mate cells and tissues affected, we realize that oftentimes the gentlest application of the forces and means employed may be the most helpful and efficient. But when one has seen the ravages caused by disease, as revealed in the pathological laboratory and at autopsies, not to speak of its manifestations in the living as seen in the sick- room and in hospitals, I am sure that he cannot logically, even for a moment, give credence to those who proclaim that it can be dissipated by the mere action of mind or of faith or by any other than rational and scientific meas- ures. Virchow gave a priceless boon to modern medicine in his theory of cellular pathology and in showing its superiority to the old humoral theories and a priori rea- soning. He wrote " whatever outside of a cell acts upon it (abnormally), works a mechanical or chemical change within it, which change is disorder or disease." The sooner we realize that the laws of physics and chemistry govern cell life and action and, consequently, the func- tions and organs of the body, the more accurate will be the treatment and the more certain the prevention of disease. For convenience sake, diseases may be divided into two main classes, somewhat different in their origin, nature, 32 INTRODUCTION and character, although the line between the two is not always clearly marked. Diseases of the first class arise within the body, and may be called autogenetic. They are usually due to some alteration or disturbance of nu- trition and assimilation, such as irregular absorption of products of digestion; or of function, such as that of elimi- nation, to either of which, as well as to other similar causes, various auto-intoxications may be due. The sec- ond class comprises those which are due to causes from without, favored, it may be, by either internal or external predisposing conditions, but each malady of necessity depending upon the reception or inoculation of the spe- cial cause, which cause has the power of reproduction and development, of vitality and virulence. Such diseases are called contagious, infectious, specific, inoculable, or zymotic.^ In the first class, with our present knowledge, we may place such maladies as gout, diabetes, neurasthenia, etc.; while into the second will obviously fall all that are now known to be due to living "germs" or organisms, such as cholera, typhoid fever, malaria, etc. However, we must not overlook the impulses often given to the causation of certain members of the second class by faulty conditions of nutrition or assimilation, as is especially exemplified in many cases of tuberculosis. The char- acter of the soil may influence the growth and product of a plant almost as much as the species itself, and so the difference in constitution and tissue of individuals may 1 In this connection the following quotation from Sedgwick is inter- esting: "Diseases may be regarded as due either to defects in the con- stitution or construction of the vital mechanism, or else to external unfavorable influences acting upon it. From the point of view of origin or causation, all diseases may be divided into two classes, viz.: (I) Consti- tutional, or (II) Environmental. This classification, while open to many objections, is of the highest value to the physiologist and the sanitarian, for it brings the former lace to face with intrinsic, structural, or organic defects in the mechanism, while the attention of the latter is concen- trated upon those abnormal external influences which act unfavorably upon the organism, and which he must seek, and may be able to re- move." Principles of Sanitary Science and Public Health, 1902, p. 10. PROPHYLAXIS 33 materially determine the variations in symptoms and viru- lence so often manifested by an infectious malady. A third class or a subdivision of diseases might also be indicated, which would include those disturbances which are almost purely psychical and whose symptoms are largely notional and the result of perverted imagination or coordination. But it is a question whether the primary cause of almost all such disorders is not an altered and abnormal nutrition or functioning of the general nervous economy of the body or the symptoms simply reflex manifestations of irritative disturbances of distant organs. Prophylaxis is "the use of hygienic or other precau- tions conducive to the prevention of disease"; or it may be defined as " a series of methods or procedures whereby disease is restricted and prevented by suppressing or re- moving its predisposing conditions, and destroying or modifying the exciting causes." Its first function of sup- pressing or removing predisposing conditions is accom- plished by sanitation; the second, that of destroying or modifying exciting causes, is carried out by disinfection. The term "predisposing conditions" should be used in- stead of "predisposing causes," because these conditions,, cannot in themselves originate a disease, though they may make the system more susceptible to the exciting causes of a disease. For example, the predisposing factors of tuberculosis — "privation, depression, and excess" — are conditions, and though they often prepare the tissues for the development of the malady, it can only occur after infection by the exciting cause, viz., the specific tubercle bacillus. As we have, as yet, little definite knowledge of the exact nature of the exciting causes of autogenetic diseases, they being developed and elaborated within the body, and as disinfection, or the destruction and modification of exciting causes, is an important feature of prophylaxis, we at present naturally look for more immediate and satisfactory results in the application of prophylaxis to the second class of diseases; but this does not prevent or 3 34 INTRODUCTION restrict the employment of certain prophylactic measures in regard to the first class, such as the selection of proper diet, clothing, climate, etc., and the removal or counter- acting of all influences favoring malnutrition or imperfect and improper functional activity. We may therefore say that sanitation is the defensive, disinfection the ag- gressive part of prophylaxis. To suppress and remove predisposing conditions and to prepare the body to resist and repel the action of exciting causes, we must not only strengthen its powers of resist- , ance, but also make all external media as favorable to health and as hostile to the exciting causes as possible. The defensive powers of the body must lie in the indi- vidual cells and tissues of the body, including the vital fluids, and it is but reasonable to suppose that this repellent action to noxious substances is best performed when the cells and tissues are in most perfect health and most vigorous condition. This is not only good logic, but all experience and scientific research go to show that it has a firm foundation in fact. '''' We shall soon learn that purity of the external media and environment of the body is essential to its welfare and that of its component tissues, and that conditions of impurity in these media predispose to disease. We shall also learn that a proper and sufficient supply of whole- some food is essential to health, and that certain other factors, as sex, age, clothing, climate, etc., may act for ffood or ill in the determination of the balance between {health and disease. In other words, if we strengthen the ( resistant powers of the system to the fullest extent and re- move all predisposing conditions, in all probability the exciting causes will be inoperative in most cases, and there will be no incurrence of disease. This is the essence of sanitation : to secure perfect health, to increase the inher- ent power to resist noxious and harmful influences, and I to make all the surroundings and environments of the ^body safe and free from depressant factors. This applies equally to both classes of disease; for with healthy cells PROPHYLAXIS 35 and proper food there will not be faulty nutrition and assimilation or improper functioning and the consequent production of the exciting causes of autogenetic disease; and with a vigorous resistance and wholesome environment there is little opportunity for the germs of infectious mala- dies to obtain a foothold within the system long enough to reproduce themselves and cause their characteristic dis- orders. The best means, therefore, of preventing disease is to learn and apply the best methods of attaining and retaining a healthy and vigorous state of the system, viz., to determine and observe the laws of hygiene. CHi -lER II. BACTERIOLOGY AND PARASITOLOGY. The increase in the knowledge concerning the lowest forms of life, and the discovery that these often have a causative action in the excitation of many maladies, have greatly facilitated the study of the prevention of disease. In fact, it is largely to this advance in knowledge and to the confirmation of the germ theory that much of the success of modern hygiene and sani- tation is due. In addition many species of bacteria and other microorganisms are of extreme importance be- cause their function is that of scavengers, continually working to remove and convert the useless and harmful wastes of the world into material of high value as food for organic life; while still other kinds are being found to have great value in many strictly commercial processes. A review of the chief facts concerning them will therefore be in place at this time. The unicellular vegetal* microorganisms divide them- selves into two general classes with respect to their man- ner of reproduction, viz., those that multiply by budding — the hlastomycetes — and those that increase by simple division or fission — the schizomycetes. In the first class we have the hyphomycetes or mould-fungi, and the sac- charomycetes or yeasts, examples of these being familiar to everyone. However, it is with the fission-fungi, or bacteria as they are now more generally known, that we are most concerned as sanitarians, since they practically include almost all those vegetal microorganisms that are more or less closely connected with the production of disease as well as with the removal of offensive matter. Comparatively few of the yeasts and moulds are patho- genic, and then only indirectly or in a minor degree. (36) CHARACTERISTICS OF BACTERIA 37 Bacteriology, then, is the science of those unicellular vegetal microorganisms that multiply by direct transverse division (fission), or, as occasionally happens, by the development of spores. Its study consists in the examination by means of the microscope of the form and method of growth of these minute plants, in their artificial cultivation on or in suitable media, and in the determination of the effects of the inoculation of pure cultures upon animals. To these may be added another field of research that gives promisQ^ of much development in the near future, viz., the study of the chemistry of the bacterial products and of the reac- tions produced by their presence in culture-media and in living tissues. Although more than two centuries have elapsed since the discovery of the bacteria by Leeuwenhoek (about 1680), and though Plenciz advanced as early as 1762 what is practically the germ theory of today, most of our knowledge concerning the physiology, methods of cultiva- tion, and differentiation of the bacteria has been acquired within less than a third of a century. It is true that some earlier advance had been made in sterilization, and that Cohn, by establishing the fact of spore-formation, demolished the last arguments in favor of spontaneous generation and confirmed the science of bacteriology; but until the last three decades we had but little knowl- edge as to the means of separating and isolating the differ- ent species and making pure cultures, or of preparing culture-media, staining, etc. As has been intimated, the bacteria are unicellular organisms, usually multiplying by a process of cell-elonga- tion and fission. Being without chlorophyll, they cannot absorb and decompose carbon dioxide and ammonia, as do the higher plants; but require for their growth and nutri- tion organic matter — usually soluble albumin — in the pres- ence of moisture.^ Hence, they must be either saprophytes 1 It will be understood that these statements and many of those to follow are more or less general, and that certain species of the bacteria may present notable exceptions. 38 BACTERIOLOGY AND PARASITOLOGY or parasites. As the combination of albuminous organic matter and water is extremely common, so the distribu- tion of the bacteria over the earth is wide-spread and prac- tically universal. Some of the bacteria may, under adverse conditions, such as lack of nutriment or of moisture, too alkaline or too acid a medium, extremes of temperature, etc., or on the other hand, as a result of the attainment of a stage of maximum development, produce spores which are much more strongly resistant to deleterious influences than the Fig. 2. — Micrococci (gonococci) in pus-cells. X 1000. bacteria themselves. In this way the spore-forming species may often survive the action of disinfectants or other agencies that are sufficient to destroy other bacteria. Upon the resumption or recurrence of favorable conditions the spores develop into cells similar in form and nature to their parent cells. It is to be remembered that spores do not reproduce spores, and that "a single cell produces but one spore. "^ Abbott, Principles of Bacteriology, 1st ed., p. 31. CLASSIFICATION OF BACTERIA 39 Under the microscope the spores are seen as highly refractive, spherical bodies that stain with difficulty, and evidently have a very resistant envelope, probably of cellu- lose. The interior of bacteria and spores is protoplasm. So far as is positively known at this time, only certain of the bacilli form spores, while a few of the spirilla and one or two species of micrococci probably have the same faculty. Again, under certain peculiar conditions some organisms may develop another morphological change, the so-called Fig. 3. — Tubercle bacilli in sputum. X 1000. involution-forms. These are doubtless pathologically distorted cells, with probably diminished resisting powers, but which will revert to the normal type under favorable conditions, providing the unfavorable environment does not kill them. Lastly, at times certain individuals of a species seem to have departed from the typical form, but these departures are only different phases in the normal development. Thus a young bacillus may be shorter than the adult and look much like a coccus, or a coccus about to undergo division 40 BACTERIOLOGY AND PARASITOLOGY may be oval in shape and considerably larger than the quiescent members of its species. But one form of bacteria never permanently takes that of another — micro- cocci are always micrococci, bacilli always bacilli, etc. A thoroughly scientific classification of the bacteria is scarcely possible as yet, owing to our incomplete knowl- edge of their character, method of growth, physiology, etc. However, there are a number of ways in which we may subdivide them, none of them exactly scientific, per- haps, but still sufficiently accurate and convenient for our purpose. If we consider the bacteria as to form, we have: (a) micrococci, spherical in shape; (b) bacilli, which have one diameter longer than another; and (c) spirilla, spirals or segment of spirals.^ We shall have more to say hereafter of the characteristics of each of these subdivi- sions. Accordingly as they live best with or without air or oxygen they are aerobic or anaerobic. Again, they may be named according to their product — e. g., some produce colors, chromogenic; others pus, pyogenic, etc. Lastly, they exist and grow either as saprophytes upon dead, or as parasites upon living organic matter. We also say that an organism is optional or facultative when it is at one time a saprophyte and at another a parasite, or at one time aerobic and again anaerobic; and that it is obligate when it has not this property of changing its nature according to surrounding conditions. Some of the micrococci are named according to the manner in which they grow. If in pairs, they are called diplococci; in fours, tetracocci; in threads, streptococci, etc. Groups or masses of micrococci or bacilli held to- gether by a gelatinous substance are called zooglea. As compared with other bacteria, with one or two exceptions, we know but little about the spirilla. The germ of ^ Accurately speaking, some of the so-called higher bacteria have more elaborate development and distinction as to form, but as our pres- ent discussion has almost entirely to do with the phenomena of the lower and simpler bacteria, the former may henceforth be omitted from the discussion. SEPARATION OF SPECIES 41 cholera— the comma bacillus (?)— belongs to this class, and the cause of relapsing fever is also probably a spirillum. Most of the bacteria thrive best in culture-media that are neutral or only slightly alkaline, though a few species seem to do better in sHghtly acid surroundings. So, also, they do best at temperatures ranging between 20° and 40° C. (68° and 104° F.), though they may grow at any temperature between 5° and 43° C. (41° and 109.4° F.). Any marked deviation in the culture-media from the neutral point or continued exposure to extremes of tem- perature may either check the growth of the organisms altogether, and eventually destroy them, or may cause spore-formation, or the production of involution-forms, or a change in the composition and the character of the chemical products which the bacteria normally produce. This also holds good with respect to any other condition or substance that may be deleterious to the bacteria in their normal state; wherefore we shall see that such factors are important as having a decided influence in altering the virulence of pathogenic bacteria and in suggesting methods for bringing about a condition of immunity to their attacks. As it is rare to find isolated individual species anywhere except in pure cultures artificially prepared, it is evident that we must devise some way of separating the different kinds of organisms one from another. This is best accom- plished by the method suggested by Koch, viz., to intro- duce the mixed kinds into some melted culture-medium, like nutrient gelatin, which solidifies on cooling, but whose melting-point is not sufficiently high to destroy the vitality of the germs. If the fluid be well shaken, the various species will be distributed through it, and, upon cooling, each individual or group (zooglea) of individuals of the same kind will be fixed in its place and become the starting-point of a colony of that special kind. Moreover, if the gelatin before cooling be poured upon sterilized glass plates or into flat (Petri) dishes (Fig. 6), the subse- quent work of counting, examining, and making cultures 42 BACTERIOLOGY AND PARASITOLOGY from the colonies thus secured will be greatly facilitated, while by transplanting and repeating the process one or Fig. 4. — Spirillum of Asiatic cholera. X 1000. Fig. 5. — Bacilli of hog cholera, showing fiagella. X 1000. more times, absolutely pure cultures of each species in the original mixture may be obtained. STERILIZATION 43 Special care must be taken in this, as in all other bacte- riological methods or operations, to prevent contamination of cultures, media, or apparatus by other organisms which are almost omnipresent, and which would prevent accurate results or deductions were they not rigidly excluded or destroyed. Obviously, we may not use chemical disinfect- ants or antiseptics as a means of destroying the interfering microbes, for such procedure would kill or inhibit the growth of the bacteria we desire to cultivate; but we must sterilize by heat all the articles used, together with their contents. This, if properly done, does not affect the nutrient properties of the culture-media, while it does remove the danger of contamination already present. In sterilizing we may use either dry or moist heat, the latter being far more preferable in most cases, since to Fig. 6. — Petri double dish (now generally used instead of plates). be effectual it does not require so high a temperature nor so long a time as does the former. Moist heat, especially in the form of steam, is more penetrating than dry heat; beside, dry heat must be of so high a temperature that it may render useless for culture purposes such substances as nutrient gelatin. Glassware and the like, however, may be quickly and advantageously sterilized by dry heat. On the other hand, certain substances, like blood-serum, are spoiled for culture purposes even by moist heat con- tinued sufficiently long to kill the spores possibly present, as the latter require a higher temperature or more pro- longed heating to sterilize them than the bacteria without spores. Resort is therefore had to fractional sterilization in such cases, exposing the materials for only a short time to a temperature just sufficient to destroy the 44 BACTERIOLOGY AND PARASITOLOGY bacteria, repeating the process after an interval, say twenty-four hours, which is presumably sufficient to allow the spores to develop into bacteria; and again a third time, after a like interval, to insure absolute sterili- zation. Previous to sterilizing the culture-media and apparatus the test-tubes, flasks and similar vessels are stoppered with plugs of cotton-wool in order to prevent the subsequent access of contaminating organisms, and Fig. 7. — Steam sterilizer, pattern of Koch. these are afterward covered, when necessary, with rubber caps or paraffin wax to prevent the evaporation of the culture-fluids, or of moisture from the gelatin, etc. As a basis for a number of culture-media we may use beef-broth or bouillon, which is a fluid especially favor- able to bacterial growth in that it contains an abundance of albumin in solution. When a solid medium is desired, either gelatin or agar-agar (a gelatin-like substance obtained from Japan) may be added to bouillon, giving DIFFERENTIATION OF SPECIES 45 nutrient gelatin and nutrient agar-agar. Of these, the gelatin has a melting-point below the temperature of the human body, while that of agar is above; consequently we employ the latter when it is desired to cultivate germs that grow best at the body temperature, although the development of most bacteria is usually more rapid and characteristic upon gelatin. Blood-serum, sterilized and solidified, is also used for the cultivation of certain organ- isms, such as the diphtheria bacillus; and there are certain Fig. 8. — Arnold steam sterilizer. others which can best be identified by their difference in growth upon boiled potato, milk, etc. The differentiation of the various species of bacteria is to be made by noting their appearance and form under the microscope, whether they are motile or not, how they take different stains, etc. ; by observing their methods of growth in or upon different culture-media, and the color and appearance of the colonies, as well as variations in color, reaction, etc., in the culture-media; by notmg whether they are aerobic or anaerobic, or facultative, and 46 BACTERIOLOGY AND PARASITOLOGY at what temperatures they thrive best, etc. ; and finally by studying their action and the effect of their products upon living animals. In this way we may determine the char- acteristics of each individual or species, and will eventually have the data for a strictly scientific classification of the bacteria in general. For example, the organisms causing suppuration are usually micrococci, occurring in clusters (staphylococci) or in chains (streptococci); the cause of typhoid fever is a bacillus, and the cholera germ belongs to the spirilla. The tubercle bacillus stains with marked difficulty, but w^hen stained is not readily decolorized by a weak solution of nitric acid, as are almost all other bacilli. Some bacteria liquefy nutrient gelatin, others do not, and almost none liquefy agar-agar. This liquefaction is not a Fig. 9. — Ruled square for counting colonies. melting, but rather a kind of peptonization, since the gelatin will not solidify after this occurs, as it does after being subjected to moderate warming. Again, some bac- teria produce one particular color or chemical substance in the presence of oxygen, and another in its absence; some produce color only in the light, others only in the dark, etc. Finally, different pathogenic microbes cause differ- ent maladies when inoculated in animals or human beings, and the same germ may produce different results in animals of different species or families.^ The subdivision of the bacteria into saprophytes and parasites has already been noted. Therefore it must be 1 See Kenwood's Hygienic Laboratory, pp. 466-470; also McFarland's Pathogenic Bacteria, pp. 46-57. FUNCTIONS OF SAPROPHYTES 47 remembered that not all of these microscopic plants are disease-producers; much the larger proportion, in fact, being benefactors rather than otherwise to the human rac^. The function of many of the saprophytic organisms is to change dead organic matter into simpler chemical compounds and ultimately into end-products such as Fig. 10. — Pocket-case containing sterilized culture-tubes, platinum needle, and alcohol lamp, used for obtaining cultures for diagnosis, etc. carbon dioxide, ammonia, and water, these latter sub- stances being once more utilized in the nutrition of the higher forms of vegetable life, which are in turn necessary to the existence of the animal life upon the globe. One should also understand that some of the saprophytes in the soil seem to possess a constructive or synthetic p)ower, elaborating more complex plant-foods from the simple 48 BACTERIOLOGY AND PARASITOLOGY compounds mentioned. Indeed, it is only when the student of hygiene fairly realizes the wide scope of the functions of these minute but almost omnipresent scav- engers that he will comprehend the important part they play in the purification of our environment. In the air they possibly help the oxygen to destroy the harmful effluvia and exhalations of men and animals and the floating debris of organic substances; in the soil, the common receptacle of the wastes and refuse of vital activity, they quickly and continually convert these noxious additions into foods of the highest value to growing plants; in running streams and quiet pools they are of the greatest importance in the removal of the dangerous impurities washed from the surface of the land or recklessly discharged from human habitations, factories, and the like. And not only do the saprophytes help mankind in this way, but members of the class are beneficent in many others. For example, they enable those plants, the leguminosse, which yield us the largest supply of vegetable proteids, to derive much of their nitrogen almost directly from the atmosphere; they have much to do with the flavor and value of dairy products, and uses in which they may be employed in the domestic and commercial affairs of life are being newly announced from day to day. Thus we find the bacteria of this class, which comprises by far the greater number of known species, to be our benefactors and indispensable servants both in preventing the accumulation of noxious and harm- ful substances upon the earth, and in helping to produce the food which we eat and many other things that we need and use in our daily life. The parasitic bacteria, on the other hand, have their habitat in or upon highly organized living matter, and exist at its expense. They may also produce in their growth poisonous substances, called toxins and toxalbumins, that are either locally or generally harmful to the organism that is their host. It is needless to say that it is in this class that we find the disease germs, or pathogens as some THE GERM THEORY 49 would call them. It should not be forgotten, however, that the saprophytes, in bringing about the decomposition of complex organic bodies, may also produce ptomatns, which may or may not be toxic to animal life. Of these latter, we may instance as good examples the cadaveric poison of the dissecting-room or the dangerous tyrotoxicon, a by no means uncommon product in the decomposition of milk or ice-cream. But though ptomains may be more or less characteristic of the respective bacteria that produce them, each varies in its composition and properties accord- ing to the substance upon or in which it is produced, while the toxins are specific derivatives or "active prin- ciples" of their respective micro-organisms. In other words, different kinds of saprophytes may produce the same ptomain from a given organic substance, but each toxin is the product of its own particular species of bacteria and is independent of the latter's place of growth or environment. Considering for the present the pathogenic bacteria alone, we are naturally brought to the discussion of the gervi theory, which is, that the exciting cause of each contagious or infectious disease is some specific parasitic organism, and that each of these diseases is only communi- cated by the transference and development of its par- ticular parasite or germ within or upon the tissues of the infected individual. Consequently such diseases are trans- mitted from one person to another, or in some cases from animals to men or vice versa, by means of these micro- organisms, and the transference is by air, water, food or other fomites, or by direct contact. It is evident that if acquired knowledge establishes the truth of this theory, the prevention of infectious diseases is greatly simpli- fied and becomes merely a matter of combining effective sanitation, of which we have spoken, with the destruction of the specific exciting causes — i. e., disinfection. Nor is it essential that we any longer make the distinction between the terms contagious, infectious, zymotic, and specific, that formerly obtained, since they may practically be used 4 50 BACTERIOLOGY AND PARASITOLOGY synonymously. The first of these terms used to be apphed to those diseases which were beheved to be trans- mitted most frequently by direct contact, and infectious to those of which the transmission is usually by fomites. But we know that germs of the former class may be trans- mitted by air, water, food, etc., and those of the latter by personal contact, though the reverse is what usually happens in the respective cases. Occasionally disease occurs also by inoculation, the exciting organisms being introduced into the body either accidentally or intention- ally through some wound in the protecting skin or mucous membrane. The term zymotic was formerly applied to those diseases occurring in epidemics, and which were supposed to be due to fermentative processes: if used at all, it should be given to any disease due to a living germ. The term specific should only be given to those maladies which have a specific origin — i. e., which have been proved to be due to a single and particular organism. In this connection we may define an epidemic as "an outbreak of a communicable or infectious disease affecting a dozen or more individuals in quick succession before the recovery of the first case, whether arising from a single focus or several foci in a neighborhood."^ An endemic disease is one occurring more or less constantly in a cer- tain locality. When an epidemic extends over a very large territory, it is said to be pandemic. That all communicable diseases are due to vegetal germs or kindred animal organisms is more than probable, and while there are some for which this has not been fully proved, it is scarcely possible that any of these may arise from insanitary conditions alone without the presence of a living causative organism. The reasons for believing in the germ theory are based on empirical and logical facts as well as theoretical hy- potheses. Even if we ignore the scientific research work already done, it is evident that that which causes a disease ^ Committee of American Public Health Association, 1898. KOCH'S POSTULATES 51 — the contagium — must, when introduced into a susceptible person or animal, increase in quantity to an enormous extent. Note, for instance, the large quantity of actively virulent matter thrown off from a case of smallpox or scarlet fever, and yet how very little is required to initiate an attack of the disease. No lifeless chemical substance has the power of being increased to such an extent by simply finding lodgement in a suitable medium. The causative factor or contagium, whatever it may be, evi- dently must have life and the power of reproduction. Moreover, these causes of disease, when freed from the body, may be carried long distances, and may still retain for months or years their power for harm, only waiting a suitable field in which to multiply and cause the same malady as before. Such causes must therefore be capable of entering a state in which vitality is latent, and in which the reproductive functions are for a time inactive. But it is known that the spores of many bacteria, and some- times the bacteria themselves, may be carried afar, kept for long periods of time, and even exposed to wide extremes of temperature, without being killed or losing their power of reproduction and rapid multiplication. Again, we know that substances that are poisonous to, or that pre- vent the development of, these bacteria and kindred low forms of life, do, when properly used, prevent or remove the danger of contagion and infection. There is also in the development and progress of infectious disease a direct analogy to the phenomena of fermentation, whose causative organisms are of the same order as these which we are considering; the same rapid multiplication of cells in suitable media at proper tem- peratures — a period of incubation — and then changes in the infected body or host, which, after going on to a certain extent, check the further development and multiplication of the organism. What it is in the containing medium that checks the growth of the germ we may not be able to determine a priori^ but we may assume it to be something hostile to the contagium, as 52 BACTERIOLOGY AND PARASITOLOGY alcohol above a certain percentage in the fermenting medium is deterrent to the further growth of the yeast- cell. Lastly, if the proof of Koch's postulates is essential to the acceptance of a given microorganism as the cause of a given disease, we must believe, on the other hand, that a certain germ is a cause, if not the only one, of a certain malady if these postulates be proven with respect to the germ and malady. To determine whether an organism is or is not patho- genic it is necessary to experiment on living animals. To do this we must use pure cultures of the organism and carry out all our processes, including inoculations and autopsies, under strictly antiseptic precautions. For example, we may examine microscopically the blood and various tissues of a diseased animal; if bacteria be present in any of these, we make cultures from them, and if more than one kind of bacteria be present, the various kinds must be isolated and pure cultures made from each kind. When a pure culture is at last obtained, it may be studied both microscopically and as to its characteristics in various media and at different temperatures. Finally, healthy animals known to be susceptible to the disease in question are inoculated from the pure culture and, after the period of incubation, carefully watched for symptoms of the dis- ease.' Should these manifest themselves, the animal is killed and its blood and tissues carefully examined for the inoculated organisms. A similar study is to be made of each species isolated from the first animal. The postulates of Koch, which are necessary to prove that a germ is the cause of a given disease, are: (1) The microorganism must be found in the blood, lymph, or tissues of a person or animal sick or dead of the disease. (2) The microorganism must be isolated from the blood, lymph, or tissues, and cultivated in suitable media out- side of the animal body. These cultivations must be carried on through several generations until a pure cult- ure of the germ is obtained. (3) A pure culture thus SEPTICEMIA— TOXEMIA 63 obtained must, when introduced into a healthy and sus- ceptible animal, produce the disease in question. (4) In the inoculated animal the same organism must again be found. In the case of many diseases peculiar to human beings alone the third condition must remain undetermined and our chain of proof be broken, because we should not endanger human health or life by experimental inoculations. But in diseases common to man and animals the experi- ments necessary can be completely carried out, and where a germ can be proved to be the cause, according to these postulates, of the malady in animals, we can also fairly conclude that it is the cause of the same disease in human beings. The specific germs of a number of maladies com- mon to man and beast have thus been determined, together with those of a large number of affections peculiar to animals alone. Granting that a certain organism be pathogenic, infec- tion by it will depend not only upon the susceptibility of the animal or person concerned, but also upon the method of entrance into the body, the number of microbes intro- duced and present, and especially upon their degree of virulence. Thus, the tubercle bacilli produce effects of different character and gravity in different tissues, and it needs no argument to show that while the normal resist- ance of the body may be all-sufficient to overcome a few vicious germs taken in with the air, food, or drink, it may be entirely inadequate to resist and may quickly succumb to large numbers of the same enemy, especially if the virulence of the latter be enhanced, as we now know it may be, by various factors that thus assume great sanitary importance. Not the least of these are temperature and nutrient conditions, and change in potency due to growth and development in certain animal or human bodies. After infection or the reception of the contagium by a susceptible animal or person there is a period of incuba- tion before the manifestation of the characteristic sympH toms of the disease. This period is variable according 54 BACTERIOLOGY AND PARASITOLOGY to the disease or kind of germ, and during it the micro- organisms rapidly increase in numbers and in their conse- quent power for evil. After the pathological process is well under way we shall probably find one of two conditions existing, viz., that "in which the blood is the chief field of activity of the organisms,"^ and the vessels of the victim are swarm- ing with the • microbes — in other words, a true septicemia; or else one in which "the poisonous results are not neces- sarily accompanied by the growth of organisms in the tissues," these latter, in all likelihood, not extending beyond the lymphatic glands nearest to the point of inocu- lation — i. e., a toxemia. A good example of the former condition is furnished by a case of anthrax or of pyemia, and of the latter by diphtheria. However, we shall find in either condition that if we isolate the peculiar product or toxin of the specific germ, either from artificial growths upon or in culture-media, or from the blood or tissues of an animal sick or dead of the disease, and inoculate this into a susceptible animal, the general symptoms and results produced are practically the same as in an ordinary case of the disease. This goes to prove that the products of pathogenic organisms are toxic in character and harm- ful to the tissues, either locally or generally; that each of these toxic products gives rise in susceptible animals to characteristic symptoms which, taken together, constitute a specific disease, and that infection must be accordingly a biochemical and toxicological process. Another point to note just here is that these toxins are apparently harmful to the microbes themselves whenever they exceed a cer- tain amount, as is shown by the fact that most of the infectious diseases are self-limiting, and by the cessation of growth and even the death of the germs in the various culture-media aftier a certain length of time. It is but fair to state, however, that there are other possible expla- nations of this latter phenomenon, viz., an increase in the 1 Abbott, loc. cit. IMMUNITY 65 resistance of the infected body to the action of the germs and toxins, or, as in the case of culture-media, the marked change in reaction caused by the microbial products. Nothing that has been said in the foregoing pages should cause the reader to infer that all infectious diseases are caused solely by bacteria. Although the maladies due to the latter have thus far attracted the earlier and greater attention and study, a number of transmissible affections are now known to be due to animal organisms, and it is probable that still others will be added to the list. But whether a disease be due to bacteria, protozoa, or microbes of a higher classification, the general principles stated above will serve to give an understanding of their nature and mode of causation. Immunity. — Having thus obtained some knowledge of the exciting causes of infectious diseases and of how they act, one of the most important considerations is in relation to the prevention of the incurrence of these diseases by the well, and to the antagonizing or checking of the further action of the cause in those already infected. It is well to disinfect and to destroy disease germs whenever and wher- ever it is possible to do so, and at the same time to prevent in any manner their transference from unknown or inac- cessible sources to susceptible persons, but it is still better so to strengthen and fortify the human body that the microbes, even though received into it, will be unable to do it harm. Naturally our first desire would be to secure a permanent insusceptibility, if this might be had without too great risk or discomfort; but since this is rarely possible with our present knowledge, we must endeavor, especially when the danger of infection is imminent, to secure the greatest possible immunity even though that may be only temporary or incomplete. Occasionally we find individuals that possess extreme natural im- munity to certain maladies; observation shows that most well persons have fair protection in the case of ordinary exposure to infectious matter; and further investigation 56 BACTERIOLOGY AND PARASITOLOGY teaches that this protection is materially affected by such factors as one's state of health, occupation, age, or diet, or by injuries, drugs, fatigue, exposure to heat or cold, etc. But our desire is to know how to provide a positive immunity against each infection and for all persons. That we have the means of producing such protection with respect to one disease is well shown by the history of vaccination, and to another by the results obtained in our army and others in the recent world war from the general inoculation of soldiers against typhoid fever; and the work of many investigators in recent years indicates that the promise of similar results in regard to many other maladies is by no means vain. Certain it is that many human beings and animals have been rendered apparently immune to other fatal diseases, and the indications point to the probability that the human race will shortly have the same protection against most of the transmissible maladies that it now has against smallpox. "At present the chief successes of immunotherapy have to do with the bacterial diseases, but experiments show that the same principles prevail among the proto- zoan infections, and there is little doubt that as our knowledge of these maladies becomes amplified the benefits of immunological research will be found to be available in them. It is now universally admitted that microbes are pathogenic or disease-producing by virtue of certain poisonous metabolic products. ''These toxic products, embracing what have been vari- ously described by different authors as toxins, toxalbumins, and bacterioproteins, are all of proteid nature. Their physiological effects vary greatly among themselves, but they all have in common, and together with practically all heterologous proteid substances, the property of stimulating certain antagonistic physiologico-chemical reactions on the part of higher organisms, and hence are included in a group of miscellaneous character, to which the name antigen has in recent years been applied. By ANTITOXIN THEORY 57 antigen, therefore, is meant any substance capable of stimulating an antagonistic reaction when introduced into the body of one of the higher organisms. The nature of the reaction is, in itself, unimportant, so long as its tendency is antagonistic to the antigen."* Just here it may be well to consider several theories that have been advanced in the attempt to explain the phenom- ena of immunity. Of these, two have been practically disproved, viz., the exhaustion theory of Pasteur, which was that the pathogenic germs in their process of growth in the body removed some material from the latter neces- sary to their existence; and the diametrically opposite retention theory of Chauveau, which was that the germs produced some substance which gave immunity as long as it was retained in the tissues. On the other hand the phagocytosis theory of Metchnikoff and the humoral theory of Biichner have been practically established if considered as being duly qualified by the results of the research of later years. The phagocytosis theory is, that "immunity against infection is essentially a matter between the invading bacteria on the one hand and the leucocytes of the tissues on the other; that during the first attack of the disease the white blood-corpuscles gain a tolerance to the poisons of the bacteria, and so are able to resist the next incursions of the enemy and to attack and destroy the latter," the fact that they really ingest and digest the latter being readily demonstrable by the microscope. Biichner has apparently shown that the blood-plasma, especially that of immune animals, is bactericidal to many virulent germs, and he attributed this effect to the pres- ence in the fluid of certain proteid substances akin to globulin. These he termed alexins^ from a Greek word meaning to protect. Further, he believed that they act chemically in causing death of the disease germs, and that the increased amount of alexins in the blood of those » McFarland in Modern Clinical Medicine, Wilson and Salinger, 1910, pp. 909 and 910. 58 BACTERIOLOGY AND PARASITOLOGY who have acquired immunity is brought about by a stimu- lation or "reactive change" in certain cells due to the presence of the bacteria or their products. Moreover, this humoral theory serves to account for the natural immu- nity possessed by some individuals and animals, their body-juices presumably containing, through some cause or other, an extra quantity of the protective pro- teids. But an essential factor in securing immunity is the power of the body to resist or endure the poisons produced by the disease germs, something fully as important as its ability to destroy the infecting organisms. Consequently there is another theory — that of the antitoxins — which, in view of recent developments and the fact that it is capable of immediate practical application, is one of the most important thus far proposed. It is well known that the human system has the power of tolerating or accommodating itself to the action of almost any toxic substance — provided the latter be administered at first in sufficiently minute doses and then gradually increased — until it can in time withstand quantities that would quickly prove fatal to one unaccustomed to the poison. Ehrlich has further shown that with the toxic alkaloids of certain higher plants, after a certain degree of tolerance is attained the administration of the drug may be much more rapidly increased, and that while up to this point no apparent change occurs in the body-fluids, now, when the tolerance becomes so much increased, a new substance is produced in the blood which is capable of neutralizing the poison in not only the person or animal under experimentation, but also in others into whom it may be introduced. Further investigations have shown that this same production of antidotal or antagonizing substances may be brought about by the slow adminis- tration of the toxins of pathogenic bacteria — something not hard to understand when we remember that the bacterial toxins are just as much the products of plant-life as are the alkaloids that Ehrlich used, and very much EHRLICWS LATERAL CHAIN THEORY 59 like the latter in composition. On the other hand, the antitoxins, as the substances antidotal to the toxins are called, have been found to be albuminoid in character and similar in composition to the nucleins. In fact, attempts have been made to employ the latter in place of or in conjunction with the antitoxins, with results that have not been altogether without success. Much credit must be given to the labors of Behring, Roux, Kitasato, Haffkine, and others for the development of practical methods of using the antitoxins, methods which are now recognized as eminently proper and even superior to any others in the treatment of some of the most virulent diseases. The great reduction in the mor- tality from one disease alone — diphtheria — already at- tained through the application of this treatment almost exceeds expectation and belief, and the results with respect to tetanus, cholera and other deadly maladies have been likewise brilliant and add further glory to this new science of bacteriology. More recently Wright has shown that the blood contains certain substances which can so affect disease-producing bacteria that the leucocytes will more readily destroy them by phagocytosis. These substances, which he calls opsonins, vary not only in quantity in different persons, but apparently also in quality, there being probably a specific opsonin for each kind of pathogenic organism. Moreover, it has been found that in many cases the amount of influence of a given opsonin can be increased in the blood by appropriate inoculation of sterilized bac- teria of its particular kind; and, secondly, that by deter- mining a patient's opsonic index for a particular disease we can approximately estimate his power of resistance or degree of immunity to that disease. The opsonic index of an individual is the ratio between the phagocytic power of a certain number of leucocytes — as indicated by the number of bacteria taken up in a given time when acted upon by a unit of his serum — and the power of the same number of the same kind of leucocytes when the bacteria 60 BACTERIOLOGY AND PARASITOLOGY are acted upon by a unit of serum from a normal and healthy person. To some it may seem that either the humoral or the antitoxin theory is identical with the discarded retention theory of Chauveau; but it should be noted that accord- ing to the latter the invading microbes themselves produce the antidote or antagonizing substance, while Biichner's theory attributes this production to the integral cells of the body, which furnish the alexins normally in minute quan- tities to the blood, and asserts that the latter are germicidal to the bacteria themselves; and, on the other hand, the antitoxins, though produced like the alexins by body-cells, probably act chemically in neutralizing the bacterial poisons, and are dependent upon the prior presence in the body of the toxins, being a result of its acquired tolerance to the latter. With alexins or antitoxins it is evident that the immunity will last only so long as these sub- stances remain unchanged in the blood. However, there is no reason why the phagocytosis, humoral, antitoxin, and opsonin theories should not mu- tually support rather than tend to discredit one another. There seems to be good evidence of the phenomena upon which each of them is based, and even with our present incomplete knowledge of the blood and its component parts, it is not difficult to conceive that while the alexins, and later the antitoxins and opsonins protect the leuco- cytes by weakening the vitality of the microbes and neutralizing their products, the leucocytes thus guarded and in full vigor attack and make way with the bacteria, which have lost their power for evil. In other words, if the production of the toxins of an infectious malady is not too rapid, all four of these agents may combine to overcome the enemy, and not only to limit the disease, but also to give subsequent immunity for a more or less prolonged period. Much consideration has been given to the so-called lateral chain theory of immunity suggested by Ehrlich in 1897, since it serves better than anything else to aid EHRLICH'S LATERAL CHAIN THEORY 61 in the solution of many of the problems of this abstruse subject. It is primarily dependent upon the well-known fact that many poisons, including the bacterial and similar toxins, have a specific attraction toward and action upon certain cells of the body. Ehrlich assumes an extremely complicated cell protoplasm with many affinities for combination with external substances. These affinities may be hypothetically and graphically represented as slight protoplasmic protrusions on the contour of the cell-wall, and these affinities thus materialized he terms "lateral chains" or receptors. Now according to their particular and respective affinities the receptors attract to themselves the various molecular food particles that the cell needs, it being possible, however, for one receptor to have an affinity for several kinds of molecules. Such molecules capable of attraction and combination with the receptors are termed " haptophores." Accordingly, hapto- phores of a poisonous nature that have either entered or been created in the body may combine with certain receptors of a given cell, and if of sufficient number and virulence may altogether check the nutrition of and destroy the cell; but if not sufficient in number and toxicity, the irritation caused by the harmful haptophores only stimu- lates the cell protoplasm to the formation of new receptors of that particular kind in order that its nutrition and function may be maintained; and it is conceivable that through continued or repeated irritation the cell may create many more receptors than it needs, which may subsequently be separated from it and thrown off mto the surrounding fluids and spaces of the body as par- ticulate bits of a definite chemical substance with its own specific affinities and properties. Eventually, then, there may be prepared enough specific and extra recep- tors, either attached to or dissociated from the cells, to attract and unite with all the toxic haptophores likely to be present in the body fluids, now or later, so that the cells are no longer unduly irritated, but perform their functions in a normal manner. So, also, cells primarily 62 BACTERIOLOGY AND PARASITOLOGY lacking the appropriate receptors are immune against the molecules of a given poison. EhrHch's theory goes further, and, taking into consider- ation the known production in the animal body under stimulation by particular foreign and harmful cells, such as bacteria, of specific substances capable of dissolving and destroying the invading cells, assumes the production of linking molecules or amboceptors that will bring into contact and union the solvent or lysin and the particular cells which it is to destroy. Thus we can appreciate the identity of the receptors and antitoxins, and that the lysins just mentioned corre- spond to the alexins of Biichner. '* Acquired immunity depends upon the regeneration of receptors to compensate for those thrown out of service by union with useless haptophores. The increasing immunity characterizing immunization depends upon the regenera- tion of an unlimited number of receptors, so that the cell can provide for the ever-increasing number of haptophores brought to it and still have enough receptors remaining to carry on its own nutrition."^ MacFarland has prepared the following scheme to show the present state of knowledge regarding immunotherapy, its purposes and possibilities.^ IMMUNOTHERAPY. I. Prophylaxis. 1. Immunity Induced Before Exposure to Infection. A. Active Immunity. a. By inducing a mild attack 1 y r Tr • i n r xi, J- u ^i, r Inocula- f Variola, yellow of the disease by the use of ^^^^ i ^^^^^ a carefully selected virus. I • >. • By the employment of a J much-modified virus. Variola. Chicken cholera, anthrax, quar- ter evil, cholera, plague, typhoid. ( Jenner) . Vaccination ( Micro bination) (Pasteur). B. Passive Immunity. 1. By injection of antitoxic 1 Antitox- ( Diphtheria, teta serum. / ination. \ nus. 1 Medicine, June, 1903, p. 450. * Modern Clinical Medicine, Wilson and Salinger, 1910, p. 918. IMMUNOTHERAPY 63 2. Immunity Induced After Exposure to Infection and During THE Incubation Period of the Disease. 1. By the employment of comminuted tissue containing the essen- tial cause of the dis- ease in an attenuated form. Microbina- TION -} Rabies. II. Treatment. 1. By Producing Active Immunity. A. By Aiding the Bacteria-destroying Mechanism. a. By employing killed or modified cultures to excite phagocytosis through in- crease of opsonins, etc. Microbina- TION. B. By Aiding the Toxin-enduring Powers, b. By stimulating antibody ] formation during the I Toxina- course of a prolonged in- f tion. fection. I Acne, furuncle, carbuncle, chro- nic suppuration, chronic gonor- rhea, typhoid, Malta fever, tu- berculosis. Tuberculosis, lepra. 2. By Producing Passive Immunity. A. By injecting antitoxic serum to neutralize toxins produced in the course of the infections. B. By injecting antimicrobic serum to aid in the destruc- tion of the microbes through the action of the specific amboceptors. Antitoxi - NATION. Antimicro- bination. Diphtheria, teta- nus, snake-bite, hay-fever, plague tuberculosis, lepra. Cerebrospinal fe~ ver, gonorrhcea* plague, dysen- tery, pneumo- nia, erysipelas, scarlet fever, puerperal fever, typhoid, anthrax tuberculosis. Method of Preparing Diphtheria Antitoxin. — Within a comparatively short space of time the antitoxins have been discovered, tried, and practically adopted by the medical profession of the civilized world as a safe and efficient means for the prevention or the alleviation and 64 BACTERIOLOGY AND PARASITOLOGY cure of several of our most dreaded diseases. A short account of the usual method of preparing the antitoxin of diphtheria will therefore probably not be uninteresting. In the first place, it is necessary that the toxin of the disease should be produced, which is commonly done Fig. 11. — Filter for removing bacteria from fluid culture-media. by growing the specific organism in peptone-bouillon. When this has attained a powerful and definite virulence, as determined by its effect on small animals of known weight, the organisms are destroyed by some germicide, such as trikresol, or more commonly are removed by careful filtration from the bouillon which holds the Fig. 12. — Roux aseptic hypodermic syringe for administering antitoxin. toxin in solution. A sniall quantity, say 0.1 c.c. of the filtered bouillon is then injected into a large animal, such as the horse, which should be in good health, and which preferably should have been tested previously by inocula- tions of tuberculin and mallein to eliminate the possibility PREPARATION OF ANTITOXIN 65 of the presence of tuberculosis or glanders. After the injection of the toxin, the animal manifests for a few days the disturbances peculiar to the disease in question but usually in a minor degree, since the dose was pur- posely quite small in proportion to its weight. As soon as recovery is evident another inoculation of an increased dose is made, and so on until experiment shows that the animal can withstand practically an unlimited quantity of the toxic bouillon, and certainly an amount which w^ould have been quickly fatal before the first inoculation. This is evidence that the antitoxin has been produced and that it exists in approximately sufficient degree in the blood-serum, but positive con- firmation is secured by introducing a little of the horse's blood into a guinea-pig or other small animal that has received a surely fatal dose of the toxin bouillon. If it sur- vives, a quantity of blood is then drawn with the strictest antiseptic precautions into sterile flasks from the jugular or other large vein of the horse, the latter returned to its quarters, and the blood set aside in a cool place to coagulate. This done, the clear serum containing the anti- toxin is drawn off and to it is added a sfhall quantity of trikresol or other harmless preservative. It is now necessary to determine the strength of the serum. The fatal dose of toxin for guinea-pigs is readily found by experiment. Behring therefore suggested in the case of diphtheria antitoxin that the immunizing unit be taken to be 1 c.c. of a serum of which 0.1 c.c. would prevent edema and death in guinea-pigs when injected simultaneously with 10 times the fatal dose of the toxin. In other words, the immunizing unit was to be sufficient to overcome 100 times the amount of the toxin required to kill a guinea-pig. The antitoxin serums now adminis- tered are, however, much stronger than this normal serum of Behring's, the amount usually injected being equivalent to from 500 to 5000 or even more immunizing units, the weaker strength being used for immunizing those who have not as yet incurred the disease. 5 66 BACTERIOLOGY AND PARASITOLOGY Much depends upon the early use of the specific antitoxin in cases of diphtheria, and probably also in the other dis- eases for which this method of treatment is found valu- able, for it is not to be supposed that the remedy has any power to repair the organic lesions which have been caused by the action of the powerful toxins, and if the latter are permitted to act for a considerable time before being neutralized by the respective antitoxins, fatal or incurable damage may be done. That the antitoxin treatment is invaluable cannot be doubted. The statistics of Prof. Welch, of Johns Hopkins Hospital, founded on a very large number of diphtheria cases, "show an apparent reduction of case-mortality of 55.8 per cent.,'' and where the application was made in the first three days of the disease the mortality was only 8.5 per cent, in over 1100 cases as against a mortality of 30 per cent, or higher under former methods of treatment. Another interesting report is that of the Chicago Department of Health for 1896. In that city in that year there were 2436 cases of true diphtheria verified bacteriologically. The anti- toxin was administered to 2302 of these, with a resultant mortality of only 6.56 per cent., or 151 deaths. More- over, 2016 other persons exposed to the disease were inoculated with the antitoxin in order to immunize them, and of these, only 14 subsequently contracted the malady, and none died. Moreover, the average yearly death-rate from diphtheria and croup in Chicago for the pre-anti- toxin decade (1886-1895) was 140.2 per 100,000 of popu- lation, as against 41.8 in the antitoxin decade (1896-1905) and 21.7 for 1905. In other words, notwithstanding a great increase in population, the average yearly deaths from these diseases dropped from 1423 for the first decade to 693 for the second, and to 433 for 1905. Further comment seems unnecessary, but the statistics of the United States Census already quoted, showing a reduction in the death-rate from this disease from 1890 to 1916 from 70.1 to 14.5 per 100,000 in what now comprises VALUE OF ANTITOXIN TREATMENT 67 70 per cent, of the population of the whole country, is even more striking, especially as the gain must be attrib- uted almost entirely to the adoption and use of the anti- toxin. The results have been so positive, the advance so progressive, and any changes in the previous methods of treatment of the disease so slight as to preclude the possi- bility of doubt as to the wisdom of employing it both as a remedy and as a prophylactic. The immunity secured by the use of an antitoxin is almost immediate, an advantage often of the greatest importance; but since it is passive, the antitoxin having been developed outside of the person protected, it is more or less transient, and the inoculation must be repeated at intervals, or when danger of new infection is imminent. The same remarks apply to the use of antimicrobin, the product resulting from the gradual introduction of the bodies of killed bacteria rather than their toxins into susceptible and suitable animals. This latter gives rather a bacteriolytic form of immunity, and thus far is not so satisfactory as that due to antitoxin. On the other hand, immunity that is acquired actively, either by accident or by deliberate experiment, is slower in developing, but much more likely to be permanent. It is a result, as we know, of most of the spontaneous infec- tious diseases, though its duration in some cases is briefer than we desire. It may also be secured by prophylactic infection or by prophylactic intoxication. In the former we may use virulent infective matter in much reduced doses or quantities, or better and more safely as far as man is concerned, some form of attenuated virus may be employed, the infecting matter having been modified by development in animals of another species, or by heat, light, drying, electricity, growth in unfavorable media, etc. As an illustration, we have the modern vaccine virus derived from the cow which has entirely supplanted the former direct inoculation of matter from the human small- pox patient. As for prophylactic intoxication, we may use either the dead bodies of the infectious bacteria, as 68 BACTERIOLOGY AND PARASITOLOGY has been done by Haffkine in his work against plague and cholera, and more recently in antityphoid inocula- tion, or the products of the organisms derived from artificial cultures, as indicated in describing the produc- tion of antitoxin. Various factors, some still unsettled, must determine the advisability of the use in a given case of one or another of the above methods; but it must be remembered in regard to actively acquired immunity, that not only is it at times too slow in development to be of value after infection has occurred, but also that "the in- troduction of toxins or bacterial proteids after the onset of the disease may be not merely useless, but actually harmful by adding to the sum total of toxic material against which the tissues struggle." Nevertheless, experience will continue to show that whether one or all of these methods of securing immunity may be employed or whether others by which the body can protect itself may be discovered, sanitation and a con- dition of perfect health throughout the system are of the utmost importance in warding off attacks of or in securing immunity from any of the pathogenic organisms, and in withstanding their ravages should disease be incurred. A sound body therefore is a most vitally active and not simply a passive agent for the prevention of such diseases. CHAPTER IIJ. THE ATMOSPHERE— AHl. The composition of the atmosphere surrounding the earth is remarkably uniform. It is practically always the same everywhere, provided no obstacle be interposed to the action of those natural forces by which this uni- formity is maintained. This atmosphere is estimated to be about forty miles in depth, and its weight-pressure, of which we have a visible manifestation in the action of the barometer, upon the total surface of the adult human body is equivalent to that of about fourteen tons. Any considerable variation in this pressure may give rise to disturbances of health more or less serious, such as the cardiac derangements and "mountain sickness" experi- enced by strangers visiting high altitudes and by avia- tors, or the "caisson disease" of those who work in a compressed atmosphere. In fact, it is not improbable that some of the vague disturbances of comfort to which a large class of persons are subject during changes of the weather will hereafter be found to be due to the marked variations in this pressure at such times. The average composition of the air in its normal state is about as follows: oxygen, 20.96 per cent, by volume; nitrogen and argon, 79 per cent.; carbon dioxide, 0.04 per cent.; aqueous vapor, varying in amount with the temperature and other conditions; a trace of ammonia, and a variable amount of ozone, organic matter, sodium salts, etc. The variation in the percentage of oxygen may be from 20.87 in towns to 20.98 in pure mountain air or far out at sea; in the percentage of carbon dioxide, from 0.02 to 0.05. So far as we know at present, the nitrogen (69) 70 THE ATMOSPHERE— AIR variation is almost infinitesimal. The air is a mechanical, not a chemical mixture, and there is always some change taking place in the proportions of the various constituents. However, the mixture is maintained in its wonderful uniformity by the interdependent action of plants and ani- M.M.Hg. ALTITUDE 6000 FT. 14130 FT. ui30 ft. (sh'h^s.) PULSE RATE 100 135 , ■ / ■ 95 / / 90 130 .y 85 o^"' ..'' 80 125 V 75 \ 120 N^^^ ^ ^ 115 ■ PULSE RATE- BLOOD PRESSURE- Fig. 13. — Physiological changes due to rapid change in altitude. Average blood-pressure and pulse-rate of 22 young men. Adapted from papers of Drs. Gardner and Hoagland in the Transactions of the Ameri- can Climatological Association, 1905, xxi, 85. mals, and by the diffusion of gases, the law of which is that " a gas expands into a space in which there is another gas as freely and as rapidly as if there were a vacuum." Though this agency, like the other, is continually operat- ing, its results are greatly facilitated by adventitious air- COMPOSITION OF AIR 71 currents and by the application of heat. When a gas is thus diffused, it will not separate again from the others under ordinary circumstances. Oxygen is the most important of the above constituents. It supports all animal life; oxidizes, destroys, and renders harmless organic impurities, and by oxygenating the blood and oxidizing the food for our tissues gives heat and energy, the vital source of all our thoughts and actions. The supply to the atmosphere is constantly maintained by the higher plant-life, which decomposes carbon dioxide and gives off oxygen to the air. In man the greatest limit of life without oxygen or air is about four minutes. A decrease in the proportion of oxygen in the air does not manifest itself by untoward symptoms in the human body until there is less than 13 per cent, by volume; then as it falls lower and lower the respirations become slower, deeper, and more difficult, less oxygen is absorbed by the blood, and there follow dyspnea, asphyxia, and death. This may occur within a short time when the percentage goes below 8 per cent., and fatal asphyxia supervenes very rapidly when there is as little as 3 per cent, of oxygen. Some very interesting investigations made by the Medical Research Board of the Air Service of the U. S. Army in 1918 show that "in normal men characteristic alterations of function begin even with a slight lower- ing of the oxygen tension," and that "for all persons there are limits beyond which the body cannot com- pensate. In this respect there are the widest individual variations, forming a scale from the man with a weak heart, who can withstand scarcely any reduction of oxygen, up to the man whose respiration and circulation are of such adaptability and power that he can go to 25,000 feet and yet for a time be virtually normal. The strain imposed by altitude is closely similar to that induced by extreme physical exertion. In botli condi- tions oxygen deficiency occurs, but at altitudes and in an aeroplane the effects are the more subtle and dangerous because of the lack of stimulation to breathing and other 72 THE ATMOSPHERE— AIR functions that the increased carbon dioxide production affords during muscular exertion."^ The same inves- tigations show that while the rate of heart-beat has been found to accelerate in a few men at 17.5 per cent, of oxygen, corresponding to an altitude of 5000 feet, only 13 per cent, of those examined reacted in this way until the oxygen was reduced to less than 15 per cent., and that " the pulse-pressure remains fairly constant in most men until the oxygen has fallen to between 12 and 9 per cent, (from 14,500 to 22,000 feet), after which it increases in amount during the further reduction in oxygen.'^ The main function of the nitrogen of the atmosphere seems to be to act as a diluent and to prevent the too energetic action of the oxygen. We know now, however, that at least one family of plants-^the leguminosse — is able, by the aid of certain bacteria, to take nitrogen almost directly from the air and to store it in the form of pro- teids for future use as a food for animals. The ammonia ever present in the air is also a source of nitrogen food for some plants. The gaseous element argon, discovered in 1894 by Lord Rayleigh and Prof. Ramsay, comprises about 1 per cent, of what was previously considered atmospheric nitrogen. Thus far little is known concerning it except that its atomic weight is probably somewhat less than 40, its density about 20, and that it is very inert, though Berthelot has succeeded in making it combine with nas- cent vapors of benzene under the influence of an elec- trical discharge. That it is a constant component of the atmosphere for some definite purpose is more than prob- able, but what this purpose may be is as yet unknown. The carbon dioxide^ present in the atmosphere is of no direct use to animals, but is essential to the support of vegetable life, furnishing part of the carbon necessary for ^ Medical Studies in Aviation, Jour. Am. Med. Assn., October 26, 1918, No. 17, vol. Ixxi. 2 Carbon dioxide = carbonic acid gas = carbonic anhydride = CO2. Carbon monoxide = carbonous oxide = CO. CARBON DIOXIDE IN AIR 73 the formation of the carbohydrates and proteids, which are, next to water, the main constituents of plants. The proportion of carbon dioxide in the out-door air varies somewhat from time to time, owing to the changing conditions. It is washed out of the air by rain, and there is therefore less after a heavy storm; plants absorb it by day, and some give off a slight quantity by night; the strata of the atmosphere near the ground receive an excess of it from the soil-air; it is a constant product of combus- tion and of the decomposition of organic matter by sapro- phytic bacteria, etc. Though heavier than air, it is com- paratively evenly distributed through the atmosphere by the force of diffusion. The normal proportion in the atmosphere varies from 0.02 per cent, to 0.05 per cent., but we may take the average to be about 0.04 per cent. Should, however, any important tests of the amount in-doors be required, the percentage in the out-door air at that particular time and place should for the sake of accuracy also be determined. Within the limits just given, the carbon dioxide cannot be considered as an impurity of the atmosphere, for it is ever present in the air, and is as necessary to plant-life as oxygen is to animals. It is derived from the combus- tion of carbonaceous materials, from the exhalations and excretions of animals and men, and, as was indicated, in large measure by the action of the saprophytic bacteria and also of the budding fungi upon organic matter. Moreover, any excess above the hormal percentage as given is to be regarded not so much an impurity of the atmosphere as an indication that certain processes are at work, which by their other products may make the air impure and unsafe for human use. The amount of aqueous vapor in the atmosphere varies from time to time because the factors governing it — con- densation and evaporation — are continuously in action, these depending, of course, mainly upon the continual variations in temperature. There is probably never a perfectly dry air unless it is made so artificially, and 74 THE ATMOSPHERE— AIR precipitation occurs the moment complete saturation is reached. The usual range of relative humidity is probably from 30 to 100 per cent., this being equivalent, according to the temperature, to a water-content of from 1 to 12 or 14 grains to the cubic foot of air. The most satisfactory proportion for health has not been experimentally deter- mined, but is generally considered to be from 40 to 70 per cent, when the temperature is moderate.^ In the outdoor air there is at least a trace of ammonia either free or combined, a small amount of the salts of sodium (especially near the sea) and of other metals, ^nd a trace of organic matter. This last is part of the animal and vegetable debris of the earth; when above a trace, it is to be treated as an impurity, as should any excess of ammonia. Minute particles of innumerable substances are being constantly thrown off into the atmosphere, and it is only the unceasing action of nature's purifying powers that keeps the proportion within the limits of safety to the human race. Solid particles, lifted up by the winds, fall to the earth again, or, if organic, are partially oxi- dized and decomposed by the oxygen and ozone. The gases are diluted and diffused so as to be no longer harm- ful, or are decomposed, or are washed back to the earth by rain or snow. The great volume of carbon dioxide is kept within bounds by the action of the vegetable world. The natural purifiers of the atmosphere, therefore, are the force of gravity, diffusion, dilution by the air itself, winds, oxidation, rain, and the action of plant-life; and so exactly are these adjusted to their work that never, when they have fair opportunity to act, does the com- position of the air vary much from the normal for any great length of time. The impurities in the atmosphere that are especially 1 When the temperature is upward of 80° F. a humidity of but little more than 70 per cent, may be very uncomfortable and depressing if the air is still and evaporation from the body surface thus impeded. A breeze makes such humidity or even a higher one less noticeable. ATMOSPHERIC IMPURITIES 75 likely to have a deleterious influence upon health may be classed as follows: (1) Suspended matters. (2) Gaseous and semigaseous substances, including: (3) Those espe- cially due to combustion and decomposition processes, and which are particularly likely to contaminate the air of dwellings or inhabited apartments. The most important suspended matters are sand, dust, soot, pollen of various plants, microorganisms of all kinds, particles of epithelia and other excreta thrown off from animal bodies, and finely divided substances characteristic of certain trades or industries. These may do harm by clogging the air-vesicles of the lungs and thus obstructing respiration, though it is doubtful whether their action is ever only so mild or simple; by their irritant action upon the respiratory passages;^ by being in themselves poisonous or hostile to the system, or, as in the case of microorganisms, by the influence they have in the causation of disease. Disease germs may lodge in the respiratory passages and do harm, or may be swal- lowed and so cause maladies, such as typhoid fever or cholera, which primarily affect the digestive tract. It is, however, questionable whether pathogenic organ- isms, especially the bacteria, are commonly to be found dissociated from other substances floating in the air. Ex- periments by Cornet, Tyndall and others seem to show that such microbes are more apt to be adherent to dust particles, particularly those of organic nature, and it is probable that free bacteria in the out-door atmosphere could not long maintain their vitality deprived of nutriment and exposed to the action of light and oxygen. Besides, they are so quickly dispersed and reduced in numbers in any reasonable volume of unconfined air that the occa- sions must be rare indeed when they could thus cause 1 The pollen from certain varieties or species of plants is thought by many to have a specific influence in the causation of hay fever and similar ills, and there seems to be no doubt that it is frequently an aggravating and predisposing factor in the development or course of such disturbances. 76 THE ATMOSPHERE— AIR disease. In-doors, especially where ventilation is neg- lected, the case is different, and there is no doubt that the air may thus occasionally become the carrier of dangerous pathogens." We must also make a distinction as to whether the other solid impurities are found in the out-door air or in enclosed spaces; and if in the latter, whether in healthful dwellings, in sick-rooms and hospitals, or in workshops and factories. Out-of-doors, dust, sand, soot, pollen, waste dirt from dwellings, street refuse, and the remains of plant and animal life will predominate; in-doors the par- ticles will be more limited in variety, but not in impor- tance. Among them will be epithelial and other cells, possibly pus-corpuscles, hair, bits of clothing, food, etc. One may also find arsenical or other poisonous dust from wall-paper or paint. In sick-rooms and hospitals there will probably be pus-cells, mycelia, bacteria, etc. Mills, factories, and mines have their special atmospheres laden with particles peculiar to the occupation, which in many cases have a marked influence for harm on the health of the workers. The gaseous and semigaseous impurities of most im- portance are not so much those resulting from human respiration and cutaneous exhalations, but rather the prod- ucts of combustion, peculiar gases in sewer-air or soil-air, organic emanations and vapors from decomposing animal and vegetable matter, and the volatile substances that characterize the various atmospheres in and about gas- works, factories, and other places of industry. Chemically, they may be classified as the compounds of carbon and of sulphur with oxygen and hydrogen, ammonia compounds, volatilized minerals and mineral acids, and many gaseous and semigaseous matters of organic nature but indeter- minate composition. Inasmuch as certain of these impurities, viz., human exhalations, combustion-products, and not infrequently the so-called sewer-gas, are particularly liable to be found together as contaminants of the atmosphere of inhabited IMPURITIES IN DWELLINGS 77 rooms and dwellings, it will be advisable to consider them in a class by themselves, and to study their effect upon health both collectively and singly. The volatile excreta from the body are carbon dioxide, aqueous vapor, and a considerable amount of nitrog- enous organic matter, to which the term "crowd- poison" is sometimes given. As products of combustion from the ordinary lighting and heating apparatus of dwellings we may have carbon dioxide, carbon monoxide, sulphur dioxide, ammonia (with possibly its sulphide), and aqueous vapor. Of sewer-gas and soil-air we shall speak later. Carbon dioxide, contrary to the general opinion, cannot be said to be directly harmful to health in the propor- tions in which it is likely to be found in any dwelling or inhabited apartment. Although present to the ex- tent of not more than 0.05 per cent, in normal out-door air, numerous experiments indicate that both men and animals may inhale much larger proportions than this without apparent harm provided the percentage of oxygen in the air be maintained at or above the normal; an increase of the carbon dioxide from other sources than respiration and combustion seems to have no appreciable effect upon health until it amounts to at least 1 or 2 per cent., and some men work daily in atmospheres contain- ing almost this amount as a result of their peculiar occu- pations. Dyspnea does not begin to occur, and then only in some, until the percentage goes above 3 or 4. In quantities above these figures there is much difference of opinion as to the effect of the gas upon the human economy, and the writer is not aware that it has ever been determined just what percentage is fatal. Parkes states the lethal proportion to be from 5 to 10 per cent.; while another authority states that animals may be kept for a long time in an atmosphere in which there is a high percentage of carbon dioxide provided the percentage of oxygen be increased at the same time. Hime says that " it may be assumed that 10 or 20 per cent, is a dangerous 78 THE ATMOSPHERE— AIR amount" ;i but Wilson^ shows that air having from 25 to 30 per cent, may be inhaled with impunity. It is to be understood that the above percentages are all hy volume. According to his weight, an adult man at rest absorbs from 15 to 18 cubic feet of oxygen and exhales from 12 to 14 cubic feet of carbon dioxide in twenty-four hours. Reichert^ says: "The amount of O varies from 600 to 1200 grammes (15 to 30 cubic feet) per diem, and that of CO2 from 700 to 1400 grammes (12.5 to 25 cubic feet) — approximate averages being about 750 grammes of O and 875 grammes of CO2." According to Ott,^ "The amount of water thrown off daily is about a pound; of oxygen taken in, about a pound and one-half; and of carbonic acid thrown off, a little more than a pound and one-half." The minimum excretion per hour may there- fore fairly be taken to be about 0.7 cubic foot of carbon dioxide for adult men and 0.6 cubic foot for women or for each person of a mixed assemblage. Now, granting the presence of a single adult occupant, it is evident that it would require many hours before a room of, say, 1000 cubic feet capacity would lose sufficient oxygen or gain sufficient carbon dioxide to produce the slightest apparent harmful results, even though ingress of fresh air were prevented; and yet experience tells us that the atmos- phere of such a room will become exceedingly foul and actually detrimental to health long before the lapse of time necessary to exhale sufficient carbon dioxide to induce serious effects. Moreover, carbon dioxide is odor- less, while the air of inhabited, unventilated rooms is characterized by a decidedly offensive smell that remains for some time even after adequate ventilation has been secured and when chemical tests show the percentage of carbon dioxide to have been reduced to nearly the 1 Stevenson and Murphy, vol. i, p, 945. 2 American Journal of Pharmacy, 1893, p. 561. 3 American Text-book of Physiology, p. 536. ^ Text-book of Physiology, 4th ed., p. 392. CARBON DIOXIDE IN DWELLINGS 79 normal. "The chemical analyses of the air of over- crowded rooms, and the experiments upon animals made by many investigators, indicate that the evil effects ob- served are probably not due to the comparatively small proportions of carbonic acid usually found under such cir- cumstances. . . . The proportion of increase of CO2 and of diminution of oxygen which has been found to exist in badly ventilated churches, schools, theatres, etc., is not sufficiently great to account satisfactorily for the great dis- comfort which such conditions produce in many persons, and there is no evidence that such an amount of change in the normal proportion of these gases has any influence upon the increase of disease and death-rates which statisti- cal evidence has shown to exist among persons living in crowded and un ventilated rooms. "^ Therefore it must be something other than carbon dioxide that vitiates the air of dwellings and necessitates the provision of some system of ventilation. However, with our present knowl- edge we cannot say that a diminution of oxygen and an increase of carbon dioxide in the atmosphere which one breathes habitually do not tend to lower the general tone and perhaps the bactericidal powers of the body and thus to render it more susceptible to deleterious influences, and, since there is some evidence that as the carbon dioxide in the atmosphere increases there is a lessening of the amount of this gas excreted from the body, it will on general principles always be wiser to use every reason- able means to maintain the normal proportion of the various gases in the atmosphere. Moreover, the fact that tuberculous patients usually improve if they live contin- uously out of doors would seem to indicate that the full quota of oxygen in the air is essential to the best interests of health, and also that in-door air, though apparently but slightly impure, favors the development and progress of this disease. 1 The Composition of Expired Air and Its Effect upon Animal Life Mitchell, Billings, and Bergey, No. 989, vol. xxix, Smithaonian Con- tributions to Knowledge. 80 THE ATMOSPHERE— AIR Aqueous vapor is another of the substances excreted continually from both the lungs and the skin; but it is obvious that in itself it cannot be directly harmful to the system, for we find it ever present in all natural atmos- pheres, and are continually replacing by imbibition its loss from our bodies. The quantity daily thrown off from the lungs and skin will depend on the temperature and humidity of the atmosphere, the quantity of air inspired and water imbibed, and many other factors; but under ordinary conditions the average excretion will be from 100 to 1700 grammes (about 3.5 to 60 fluidounces), though increased exertion might cause even the latter amount tx) be greatly exceeded. It is accordingly possible that this large quantity of moisture, tending to saturate an atmos- phere already humid, and thus preventing evaporation from the skin, might indirectly and reflexly check the loss of heat from the body and the excretion of waste matters by the sweat-glands and that the retention of excessive heat and of such wastes in the system may help to produce the depression, headache, and other symptoms experi- enced by those in foul and humid air. It has been noticed that the symptoms due to foul air are more readily mani- fested when the temperature of the atmosphere is much below or much above the usual room-temperature of 65° to 70° F. At low temperatures the air is readily saturated, and beside, the excreting action of the skin is much lessened by the cold; at high temperatures the humidity is often already near the saturation-point, while the external heat tends to increase the quantity of water given off by the lungs and skin. "At high tempera- tures the respiratory centers are affected where evapora- tion from the skin and mucous surfaces is checked by the air being saturated with moisture — at low tempera- tures the consumption of oxygen increases and the demand for it^becomes more urgent."^ At 70° F. the aqueous ex- halation from an adult body would in an hour or less com- ^ Mitchell, Billings, and Bergey, loc. cit. HUMIDITY— CROWD-POISON 81 pletely saturate from 350 to 600 cubic feet of air wh ich already has the not unusual relative humidity of 75 per cent., while at 80° F. an equal or even greater volume of air would doubtless gain its maximum of moisture from the increase of perspiration due to the extra heat. Moreover, as evapo- ration of the perspiration is one of the most important means for maintaining the balance between heat-produc- tion and heat-dissipation, interference with this process naturally tends to raise the body-temperature rapidly and to produce the consequent effects upon the nervous mechanism. A stagnant atmosphere, therefore, is more depressing than one in motion, even though temperature and humidity be unaltered, since the movement of the air favors evaporation and likewise probably acts as a gentle stimulant to the skin. Crowd-poison. — The third contaminant given to air from human bodies is an indefinite volume of offensive organic matter, and for a time this was looked upon as by far the most harmful part of animal exhalations. But recently experiments by various investigators have seemed to indicate that this organic effluvium is not so dangerous as it has hitherto been considered, and that some, at least, of the symptoms due to air vitiated by respira- tion are to be attributed to the conditions already men- tioned, viz., increase of heat and moisture, together with lack of sufficient air movement. It is also doubtful whether much, if any, of this organic matter comes from the lungs of healthy persons.^ '* In ordinary quiet respira- tion no bacteria, epithelial scales, or particles of dead tissue are contained in the expired air. . . . The cause of unpleasant, musty odors in rooms may in part be due to volatile products of decomposition from decayed teeth, foul mouths, or disorders of the digestive apparatus, and * Fliigge, Hill, and others have found that the evil of close atmospheres is largely a result of elevated temperature, humidity, and absence of air currents. Tests were made on men who sat in impure air, but breathed pure air through tubes, and they presented all the symptoms usually resulting from bad ventilation. Report on Human ViUlity, Fisher, p. 85. 6 82 THE ATMOSPHERE— AIR in part to volatile iatty acids given off with or produced from the excretions of the skin, and from clothing soiled with such excretions."^ However, whatever may be the exact source of this contamination, we know this concern- ing it — that it is decidedly offensive to the sense of smell, that it is organic and nitrogenous, yielding ammonia, darkening sulphuric acid, decolorizing potassium perman- ganate, and rendering obnoxious pure water through which the vitiated air has been drawn. While it seemed to such careful observers as Brown-Sequard, d'Arsonval, Merkel, and others to be directly poisonous to lower animals, modern scientific evidence of this effect is lack ing. In general, it is given off proportionately with the carbon dioxide from the body, though this rule is not infallible; it is apt to be unevenly distributed through- out the atmosphere of the apartment, and is probably therefore not truly gaseous, but more like an impalpable dust; it oxidizes but slowly, being evident for some time after fresh air has been admitted and the carbon dioxide has been reduced almost to the normal, and, while neither condensed nor dissolved in the aqueous vapor from the body, it is especially attracted and retained by hygroscopic substances such as wool, paper, feathers, etc. Its smell is generally perceptible when the respiratory carbon dioxide reaches 0.03 or 0.04 per cent., sometimes before this point is reached, especially in sick-rooms or hospital wards, and is decidedly offensive when the total carbon dioxide approaches 0.1 per cent. The most important of the impurities resulting from the combustion of coal, the principal fuel substance used in towns and cities, are soot and tarry matters (to the ex- tent of about 1 per cent, of the coal consumed), carbon monoxide and dioxide, aqueous vapor, and more or less ammonium sulphide, carbon disulphide, hydrogen sul- phide, sulphur, sulphur dioxide, and sulphuric acid. The relative amounts of the oxides of carbon — as well as 1 Mitchell, Billings, and Bergey, loc, cit. COMBUSTION-PRODUCTS 83 of the oth^r gases — will depend upon the perfection of combustion; "but it has been calculated that for every ton of coal burnt in London something like three tons of carbon dioxide are produced," and as the coal consump- tion of that city is over 30,000 tons per diem, we can readily see that its atmosphere must receive the enor- mous daily contamination of about 300 tons of soot and 90,000 tons of carbonic acid. No wonder they have an occasional fog there! The combustion-products of wood are in the main carbon monoxide and dioxide and water, while those of coke and of gas are practically the same as those of coal. From the heating apparatus, if properly con- structed and arranged, these products pass almost directly to the exterior of dwellings and are rapidly dissipated in spite of their excessive volume, for "diffusion and the ever-moving air rapidly purify the atmosphere from carbon dioxide," and in fact from the other combustion-products also, with the exception of the soot and tarry products. Should, however, combustion be incomplete, or should the stoves or other heating apparatus be imperfect, the gases may seriously or even dangerously contaminate the house-air, the deadly carbon monoxide being particularly liable to leak not only through the crevices, but actually through the heated cast-iron plates, etc., of stoves and furnaces. Theoretically, a pound of coal requires 160 cubic feet of air for its perfect combustion, but actually from one-half to as much more must be supplied to the ordinary heating apparatus to secure complete oxidation of the fuel. Practically all the devices for artificial illumination, with the exception of the incandescent electric light, give off directly to the surrounding air combustion-products which are much the same as those from coal, and this contamination is consequently a positive factor in the vitiation of in-door air. "Every cubic foot of coal-gas yields, on combustion, roughly, half its own volume, or 0.52 cubic foot, of carbon dioxide, and 1.34 cubic foot of 84 THE ATMOSPHERE— AIR water vapor," besides some little carbon moi^oxide when ordinary burners are used. "Speaking generally, it may be said that each cubic foot of gas burnt per hour from the ordinary burners vitiates as much air as would be rendered impure by the respiration of an individual; it at the same time will raise the temperature of 31,290 cubic feet of air 1 degree F., and yields 217 calories (a kilogramme of water heated 1 degree C.) or 860 British heat-units (a pound of water heated 1 degree F.)."^ But inasmuch as the products of combustion are superheated, they rise at once to the top of the room and usually, for the most part, quickly escape to the outer air through the combined influence of negative gravity and diffusion; so that comparatively little air is needed to dilute the small proportion of such products that eventually cool and fall to the breathing-level. The accompanying table^ shows the influence of various lighting agents with respect to the condition of the room-air. From this table it will be learned that the incandes- cent electric light is the most satisfactory from a hygienic point of view, and there is no doubt that its very general introduction has done much toward obviating a constant source of vitiation, especially in rooms which require much artificial light, and are at the same time diffi- cult to ventilate. It is said that in a bank in London, in which several hundred persons are employed, the absences on account of illness have been so far reduced, apparently by the introduction of the incandescent electric light alone, that the extra labor gained has more than compensated for the increased cost of lighting. The general use of tungsten instead of carbon filaments for incandes- cent electric lamps is a recent improvement that provides a whiter, steadier and more brilliant light, and at a reduced cost for current. The electric arc light is said to form nitric acid; but even so, its effects are not so 1 Notter and Firth, Treatise on Hygiene, p. 140. « Ibid., p. 141. APPARATUS FOR LIGHTING 85 harmful as are those of the products of combustion of the ordinary candle, lamp, or gas-jet. Quantity consumed. i 1 1 il it It ?3 II :|5 Tallow candles . . . 2200 grains 16 Cu. ft. 10.7 Cu. ft. 7.3 Cu. ft. 8.2 1400 12. Sperm candles 1740 " 16 9.6 6.5 6.5 1137 11.0 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 No. 5 batwing burner 5.5 cu. 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, regeneration (Siemens) burner) 3.2 " 32 3.6 1.7 4.2 760 2.8 Coal-gas (Welsbach in- candescent) . . . 3.5 " 50 4.1 1.8 4.7 763 3.0 Electric incandescent light 0.3 1b. coal 16 0.0 0.0 0.0 37 0,0 Next to the incandescent electric lijjht in importance are the Welsbach and Siemens gas-lights; but of these the latter has not the illuminating power, nor is it so well adapted to house use as is the former. The Welsbach light makes use of the Bunsen flame (in which, by the way, the carbon of the gaseous fuel is completely oxi- dized and converted into carbon dioxide) to render incandescent a non-combustible mantle or network, com- posed of vegetable fiber saturated with the oxides of certain metals which have the property of becoming intensely luminous when sufficiently heated. It gives a white light of great illuminating and considerable actinic power, and of practically unvarying intensity. In fact, this quality of steadiness, in which it even surpasses the earlier types of incandescent electric light, is by no means 86 THE ATMOSPHERE— AIR the least of its hygienic advantages, since such steadiness is an important factor in the conservation of the eyesight. Recently hydrocarbon (kerosene and gasoline) lamps, making use of an incandescent mantle similar to the Welsbach, have been placed on the market, and are said to be safe and free from odor or danger of explosion. If Chimney. fra — Shade Support. Mantle. ^^ Mantle Support. Chimney Support. Gauze Tip. Gas Spreader. Corrugated Cap. antle Carrier. Centre Tube. Bobesche Support. Gallery. Bunsen Tube. Air Shutter. Adjustable Check. Fig. 14.— Welsbach light. these claims can be sustained, such lamps are of value, since they furnish a powerful and steady incandescent light at very low cost. A comparatively new illuminant, not mentioned in the foregoing table, is acetylene gas. This gives a very white and powerfully actinic light, and, on account of ease of SEWER-GAS AND SOIL-AIR 87 production and the small amount needed for ordinary lighting, is cheap and does not greatly vitiate the atmos- phere. But a mixture of the unburned acetylene with air in proportions of from 4 to 25 per cent, is highly explosive, and consequently the gas is not yet much used for interior lighting. SEWER-GAS AND SOIL-AIR. What is commonly called sewer-gas is a mixture of a number of gases, such as carbon dioxide, carburetted hydrogen, ammonium and hydrogen sulphide, nitrogen, etc., together with a considerable amount of fetid organic matters, the volatile or semivolatile products of animal and vegetable decomposition, all varying according to the condition of the sewer, the kind of matter received therein, the amount of surface-water, etc. The air from a closed cesspool may be extremely foul and poisonous, so much so that the emanations have not infrequently caused death in those who inhaled them in full concen- tration; on the other hand, the atmosphere of a properly constructed and well-flushed sewer may be almost as pure as that above the surface of the ground. Bacteria are present in varying numbers, with the possibility of some of them being the germs of specific diseases. But fresh sewage is not so likely to contaminate the air above it with microbes as that in which decomposition has begun, since Frankland has shown that solid or liquid particles are not liable to be scattered into the air by any disturb- ance to which the sewage may be subjected until gases of decomposition are produced. According to some writers, the bursting of bubbles of gas on the surface may dis- charge the bacteria into the sewer-air. It has also been shown that " bacteria can undoubtedly grow up the sides or walls of damp, nutrient sewers, and if these latter become at all dry, air currents readily detach and dis- perse them." It is, however, questionable whether many disease germs can withstand the natural antagonism of 88 THE ATMOSPHERE— AIR the saprophytic bacteria that predominate in sewage and on sewer walls. Another class of impurities that may at times be found in the air of dwellings comprises those coming from the soil and soil-air. The soil, in hygiene, refers to all that ..^•'i;, -0 , <;> Fig. 15. — Apparatus for determination of carbon dioxide in soil-air. (Harrington.) portion of the earth's crust that can in any way affect the health. All soils contain more or less air — soft sandstones from 20 to 40 per cent., loose sand from 40 to 50 per cent., and loose soils often very much more. As the soil is the recipient of most of the solid and COMPOSITION OF SOIL-AIR 89 liquid waste of all animal- and vegetable-life, and as the myriads of saprophytic bacteria that inhabit its upper strata are constantly working to convert this dead organic matter into simpler compounds suited to the nourishment of plant-life, the soil-air, taking the atmosphere above as a standard, will usually be far from pure.^ It is rich in carbon dioxide and in organic vapors and gases, while the proportion of oxygen is probably always less than that of the air above ground. Moreover, the carbon dioxide increases and the oxygen decreases the deeper below the surface the sample is taken. As much of the carbon dioxide is evidently derived from organic pollutions, it might be supposed that this gas could be taken as an index of the degree of the latter, and so it might if other condi- tions, such as permeability of soil, rate of circulation, etc., were always the same. But they are not, and the composi- tion of the soil-air is practically not the same at any two places, nor for the same place at different times. The underground-air is constantly in circulation, even to a considerable depth; but there is a hindrance to its free movement and diffusibility, and this, together with the great variation in the distribution of oxidizable and other contaminating matters, causes the variations in its com- position. The carbon dioxide therefore cannot be taken as an index of the relative purity. The forces that maintain the circulation of the ground- air are the wind, the daily change of surface temperature, the fall of rain, and especially in winter the local and arti- ficial conditions of civilization. A very slight wind will drive air through the soil for long distances, the rise and fall of the ground-water has its obvious effect, and the movement due even to slight changes of temperature is likely to be quite extensive and positive. Owing to evaporation from the ground-water, the soil- > Too much importance cannot be attributed to this saprophytic action in the upper soil, for it is one of nature's wonderful methods of securing and conserving not only the purity of our environment, but also the perpetuation of organic life. 90 THE ATMOSPHERE— AIR air is always quite humid, and, according to some writers, may also be laden with bacteria and other very light sub- stances lifted up by the ascensional power of evaporation. As sewage, house-wastes, and dirt of all kinds are par- ticularly liable to contaminate the soil about any inhabited dwelling, the air of that soil will more than likely be very impure, and care must be taken that it is not drawn into the house. This is especially apt to happen in cold weather, when house-fires are lighted and the in-door air is thus made warmer than that without, the tendency then being for the soil-air to pass, if possible, through the cellar walls and floors. These should be made as nearly air-tight as possible, and special attention should be given to the space underneath and about the furnaces or basement heating apparatus. As an instance of the importance of these precautions, Hime^ gives an account of the death of four persons. Enough illuminating- (coal-) gas was drawn from a broken pipe fifteen feet distant from the foundation walls of the dwelling to cause the fatality, although there were only eight or ten inches of tramped earth above the pipe and the only aspirating force was the difference of temperature within and without the house. A number of explosions have occurred, due to a similar leakage of gas from street mains through basement walls or into drains and sewers, since the admixture of illumi- nating-gas with air forms a most powerful and dangerous explosive. There is no direct evidence that the emanations from piggeries, bone-yards, soap-factories, garbage-incinerators, etc., are actually harmful to health; but they may be very decided nuisances to those living near by, and may also foster the excessive multiplication of flies, rats, etc., therefore, all such places should be strictly controlled by the proper sanitary authorities. The atmosphere of mines and other excavations is sub- ject to contamination by the excess of carbon dioxide in 1 Stevenson and Murphy, Treatise on Hygiene, vol. i, p. 949. DISEASES CAUSED BY IMPURE AIR 91 the soil-air, by gases from blasting agents and from fis- sures in rock, and by the products of respiration from men and animals working in the mines, etc. The air in deep cellars or basements, or in the holds of ships is also likely to be foul, owing to the difficulty of changing it sufficiently often, and frequently also to the insanitary character of stored contents or cargoes. In such situa- tions proper ventilation should be secured by all means available, and special care taken that the impure air does not affect the laborers in the one case or the passengers and crew in the other. DISEASES CAUSED BY IMPURE AIR. As a rule, the human system has the power of accom- modating itself, through habit, to withstand influences which, in one unaccustomed to them, would soon produce serious results. But in spite of this, if the body be ex- posed for any considerable length of time to conditions of impurity or deterioration in its supply of air, water, or food, such conditions will always tend to undermine health and increase the susceptibility to disease, even though they cause no more serious results. "Statistical inquiries on mortality prove beyond a doubt that of the causes of death which are usually in action, impurity of. the air is most important. No one who has paid any attention to the condition of health and the recovery from disease of those persons who fall under his observation, can doubt that impurity of the air marvellously afl'ects the first, and influences and sometimes even regulates the second. . . . The air may affect health by variations in the amount or conditions of its normal constituents, by differences in physical properties, or by the presence of impurities. While the immense effect of impure air cannot be for a moment doubted, it is not always easy to assign to each impurity its definite action. The evidences of injury to health from impure air are found in a larger proportion of ill health — i. <*., of days 92 THE ATMOSPHERE— AIR lost from sickness in the year — than under other circum- stances; an increase in the severity of many diseases, which, though not caused, are influenced by impure air, and a higher rate of mortality, especially among children, whose delicate frames always give us the best test of food and air."i These facts are now so well recognized that an abundant supply of fresh, clean air is regarded as essen- tial in the treatment of many diseases, and the practise of living as much as possible and even sleeping out-of-doors is widely advocated. The definite diseases caused by the solid impurities in the atmosphere are almost all such as affect the res- piratory passages and organs, with the possible excep- tion of those engendered by specific bacteria and other microbes. Much therefore depends upon the physical character of the solid impurities. Soft particles and those with edges smooth and rounded, like soot and coal-dust, may apparently do nothing more than coat or clog the air-vesicles and finer bronchial tubes, and in this way diminish the area of lung tissue exposed to the inspired air, although it is questionable whether any foreign matter in the lungs does not cause more or less irritation. With most of us, however, such impurities are of little account if care be taken to develop the full respiratory capacity of the chest; but where the air is heavily charged with such dust it has a positive effect upon health and duration of life. In 1862 Sir John Simon stated that with one exception "the 300,000 (coal) miners of England and Wales break down as a class prematurely from bronchitis and pneu- monia, caused by the atmosphere in which they live. The exception is important. The colliers of Durham and Northumberland, where the mines are well ventilated, do not appear to suffer from an excess of pulmonary diseases, or do so in a slight degree only." Happily, since this was written satisfactory ventilation systems have been placed in most of the collieries of England, and the condition of 1 Stevenson and Murphy, vol. i , pp. 121 and 122. EFFECT OF DUST IN AIR 93 the laborers correspondingly improved; but coal-miners are still, as a class, particularly liable to bronchitis, pneu- monia, asthma, emphysema, and fibrosis (fibroid phthisis), though they seem to be but slightly subject to primary tuberculosis of the lungs or other organs. On the other hand, if the particles of dust in the air are hard, angular, and sharp, the lung tissues are readily lacerated, inflammatory processes are quickly set up, and the opportunity for the inoculation of tubercle bacilli and other disease germs is very great. The mortality from tubercular phthisis among metal-miners, needle-cutters, steel-grinders and tool-grinders, etc., is remarkable, and they are also especially subject to asthma and emphysema. Among Cornish tin-miners, 68 per cent, of all sick are consumptive; of needle-makers, over 60 per cent. ; of flint-cutters, glass-cutters and -polishers, and of grindstone-makers, from 80 to 90 per cent., etc. It is said that a mixture of mineral and metallic dust seems to be more harmful than metallic dust alone, perhaps because of the greater clogging of the air- vesicles by the mineral matter. Likewise, with other occupations where there is much irritative dust floating in the air, the effect upon the health of the worker is marked, and we find lung troubles prevalent and many suffering and dying from phthisis, as, for instance, among cotton-spinners, flax-dressers, hemp-dressers, pottery-makers, etc. Defective ventila- tion, accumulations of noxious gases, improper habits, insufficient disinfection of sputa, and often the excessive humidity of the air necessary' in some of these pursuits, have doubtless something to do with the high sick-rates and death-rates; but withal, the marked effect of the solid atmospheric impurities cannot be denied. Again, workers in poisonous metals, compounds, or gases, such as paint-makers and painters, type-setters, gilders (using mercury), brass-founders, coppersmiths, etc., are subject to the influence of the respective poisons and the symptoms produced by them, with a correspond- ingly increased mortality. 94 THE ATMOSPHERE— AIR Among the diseases that may be caused by the inhalation or swallowing of specific microorganisms floating in the atmosphere are erysipelas, measles, scarlet fever, diphtheria, whooping-cough, infectious pneumonia, phthisis and other forms of tuberculosis, and epidemic influenza ; and although the germs of cholera and typhoid fever are usually car- ried by the drinking-water or food, they doubtless do sometimes find their way into the system from a con- taminated atmosphere.^ Only recently has the importance of "droplet infec- tion "been sufficiently appreciated.' By this term is meant the transmission of disease by the germ-carrying spray or moisture discharged from the mouths and and respiratory apparatus of sick persons or disease "carriers" into the surrounding atmosphere by cough- ing, sneezing, cheering or forcible speaking. It is more than probable that a very large, if not the greater, part of the infection of the disastrous and widespread influenzal epidemic in the autumn of 1918 was due to this mode of transmission. Lastly, the spores of certain fungi which have been found in the air of hospitals and elsewhere are known to cause certain skin diseases, such as tinea and favus; and it is almost as certain that the irritating or poisonous pollen of certain grasses and other plants have much to do with the causation or aggravation of such maladies as hay-fever or rose-cold. From what has been said, it will be surmised that it is scarcely possible at present to specify the exact effect upon the health of each of the impurities and influences communicated to the air by the human body, and that the symptoms observed to be due to air thus vitiated are very probably an evidence and result of the combined 1 The report of the commission appointed to inquire into the preva- lence and causes of typhoid fever in the late Spanish- American War shows that in some cases infection was probably due to the dust in the atmos- phere which had been raised by many passing feet from the roads over which leaking sewage wagons had been hauled. EFFECTS OF HUMAN EXHALATIONS 95 action of these factors rather than of any one of them singly. However, the writer feels that the oppression so commonly experienced in an unventilated room is often fairly attributable to the increase in the temperature and humidity and to air-stagnation or lack of sufficient movement; that the headache, disturbed nutrition, and febrile condition, lasting for hours and sometimes days after exposure to air thus vitiated, are probably due to the same factors together with the reflex influence of the organic matter upon the system, and possibly also, in part, to the suppression of cutaneous excretion dependent upon the high content of moisture in the air; and that the respiratory carbon dioxide by itself can but rarely have much influence upon comfort or health. If the respiratory and cutaneous vitiation be sufficient to produce acute effects, the immediate symptoms will be discomfort and a sense of oppression, followed by head- ache and not rarely nausea, and a rather decided rise of temperature, all of which may last for some time even after the individual goes into perfectly pure air. Those who habitually live in such an atmosphere are almost uni- formly languid, pallid and anemic, subject to headaches, nausea and loss of appetite, and often to skin disorders, and are undoubtedly markedly predisposed to phthisis, pneumonia, bronchitis, scrofula, rhachitis, etc. Moreover, such an atmosphere apparently favors the rapid spread of, increases the severity of, and retards the convalescence from, such diseases as diphtheria, scarlet fever, measles, typhus, smallpox, etc. This may be due rather to the vitiated atmosphere causing a decrease of bodily resis- tance and an increase in predisposition to* such maladies, than to the accumulation or the actual multiplication by growth of the disease germs in the foul air. When the condition of the air is very bad, the results may be serious and even fatal, as in the well-known cases of the "Black Hole of Calcutta"; of the prison in which 300 captives of war were crowded after the battle of Austerlitz (260 dying very soon after being placed therein) ; 96 THE ATMOSPHERE— AIR and of the steamer "Londonderry," in which, of 200 steerage passengers who were temporarily crowded into a cabin (18x11x7 feet) during a storm of only a few hours' duration, 72 were dead and others dying when the cabin was opened: but in these instances the lack of oxygen may have also been a very important factor in the results. As regards the influence of combustion-products on health, it will suffice to detail the symptoms resulting from inhalation of the various gases. It will be difficult to show that these gases, together with the coincident soot, have any general effect upon health when escaping into the out-door atmosphere, even when produced in such enormous quantities in cities as has been already indicated. It is possible that the sulphur dioxide and other sulphur gases may predispose to, or aggravate attacks of, bron- chitis or asthma in those living in the vicinity of gas-works, chemical factories, etc., but too little comes from the chimneys of dwelling-houses to do much, if any, harm. In-doors the case is different, for the gases from lights and fires become more and more concentrated if the ven- tilation be insufficient. The possible effects of varying percentages of carbon dioxide have been noted. We have no evidence of cases of chronic poisoning by this gas, although, as Parkes says: "The presence of a very large amount of CO2 in the air may lessen its elimination from the lungs, and thus retain the gas in the blood, and thus in time possibly produce serious alterations in nutrition." In cases of acute poisoning by this gas — i. e., where it is in great excess in the atmosphere — there is an almost immediate loss of muscular power, and the person may consequently be unable to remove himself from the place of danger, while others who go to help him may also suc- cumb and more than one be asphyxiated. Accordingly,^ volunteer rescuers should always remember to act with coolness and great rapidity, and to provide means for the prompt removal not only of the ones they would save, but of themselves as well. Fortunately, when one who has INFLUENCE OF COMBUSTION-PRODUCTS 97 been overcome by carbon dioxide is brought into an atmos- phere of pure air before life is extinct and is aided by artificial respiration, he usually recovers quickly and com- pletely because of the rapid escape of the excess of the gas from the blood and its replacement by the necessary oxygen. Death from carbon dioxide poisoning is prob- ably mainly due to asphyxia, partly from lack of oxygen and partly from paralysis of the respiratory muscles, although the latter, as well as the general motor palsy, would seem to indicate that the gas itself had also a posi- tive physiological and toxic effect upon the nerve-centers. Cases of poisoning by carbon monoxide are much more serious. Recovery from its effects is slow and uncertain, because this gas tenaciously unites with the hemoglobin of the red blood-corpuscles, paralyzing them as it were, and rendering them unable longer to act as oxygen- carriers to the tissues; while the union of carbon dioxide with the blood is always a much less stable one and is readily dissolved as soon as interchange with a normal atmosphere is available. Less than 0.5 per cent, of carbon monoxide in the air has caused s\Tnptoms of poisoning, and Roseman states that "air containing 0.4 per cent, may, in one hour, prove fatal." It appears that the gas, volume for volume, completely rsplaces the oxygen in the blood, and cannot again be displaced by oxygen, so that the person dies asph^Tciated; but Pokrowsky has shown that it may be gradually con- verted into carbon dioxide and be got rid of," if life be maintained sufficiently long. The symptoms of carbonous oxide (monoxide) poisoning are feebleness, oppressed breathing, trembling, and ina- bility to swallow; then "loss of consciousness, destruction of reflex action, and finally paralysis of the heart." " Hirt says that at high temperatures (25° to. 32° C. = 77° to 90° F.) it produces convulsions, but not at low tempera- tures (8° to 12° C. = 46° to 54° F.)." The blood and muscles are made a brilliant red by this gas; darkened by carbon dioxide. Claude Bernard says that a mixture of 7 98 THE ATMOSPHERE— AIR these gases is more destructive than either separately, probably because the excess of the acid-gas interferes with the conversion of the monoxide and its elimination from the blood, a process that is always slow and uncer- tain under the best of conditions. Illuminating- or coal-gas — composed of hydrogen, light and heavy carburetted hydrogens, a little nitrogen, and carbon dioxide, and from 5 to 7 per cent., or even more, of carbon monoxide — rapidly causes, when inhaled, giddi- ness, headache, nausea and vomiting (occasionally), confu- sion of intellect, loss of consciousness, general weakness and depression, partial paralysis, convulsions, and the usual symptoms of asphyxia. Mixed in large proportions with the air, death may ensue comparatively quickly, probably because of the large content of carbon monoxide. It is well to remember that the so-called water-gas, now so extensively manufactured for fuel purposes and also for diluting coal-gas, contains a much larger percentage of carbon monoxide (sometimes from 30 to 40 per cent.) than coal-gas, and that the effects resulting from inhala- tion of a mixture of the two will in all likelihood be more marked, more rapid, and more deadly than with undi- luted coal-gas. Much harm may likewise occur when even small quantities of this mixed gas are breathed from day to day, and there can scarcely be a doubt that the cause of many of the troublesome anemias might be traced to unnoticed or uncared-for leaks in the gas-pipes of dwellings. "The effects of constantly inhaling the products of gas combustion may be seen in the case of workmen whose shops are dark and who are compelled to burn gas during a large part of the day; the pallor, or even anemia and general want of tone, which such men show, are owing to the constant inhalation of an atmosphere so impure." Sulphurous acid-gas (S2O) and hydrogen sulphide (H2S) are each fatal to life, the latter when in a compara- tively concentrated state; but they are offensive to the senses and thus give warning of their presence, so that EFFECTS OF ILLUMINATING GAS 99 there is less danger of their causing serious results. Men can accustom themselves to much larger proportions of hydrogen sulphide in the atmosphere than can animals, but continued exposure to it is liable to give rise to ver- tigo, headache, slow and weak pulse, sweating, and loss of strength. When sewer-gas or soil-air escapes into the outer air they are usually soon diluted beyond power for harm; )but if either gains access to closed rooms or unventilated dwellings, its effects upon the inmates are depressing and decidedly harmful. In either case, concentration of the impurities may cause acute symptoms, such as vomiting, purging, severe headache and prostration. Their influence, however, is usually insidious, owing to dilution with the house-air; and the more common symptoms attributable to them will probably be pallor, languor, frequent head- ache, loss of appetite, diarrhea, impaired health, and often chronic anemia. Children especially suffer in nutrition, and with them febrile attacks may be frequent; but with all, the power of resisting such diseases as typhoid fever, diphtheria, etc., is lessened and the sus- ceptibility to them is increased, the sickness more severe, and the convalescence more prolonged. Indeed, sewer- gas and soil-air probably aggravate all diseases. In this connection Alessi has shown that when small animals, such as rabbits, rats, and guinea-pigs, have been exposed to sewer-air for some days, by far the larger majority when inoculated with only a small quantity of a slightly virulent typhoid culture contract the disease and die, while almost none succumb of those treated similarly in every way excepting by the exposure to sewer-air. He also showed that the inoculations were more deadly when the previous exposure to the noxious gas had been less than two weeks than when it exceeded that period, indi- cating that animals, as well as persons accustomed to such contamination, are not apt to manifest the symptoms due to it so rapidly or so seriously as are those who experience it for the first time — a fact well known to all observers. 100 THE ATMOSPHERE— AIR It is only fair to say that these experiments of Alessi have apparently been controverted by other observers; but, whichever may be correct, the truth of the following quotation doubtless still holds good: "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. "^ 1 Notter and Firth, p. 159. CHAPTER IV. VENTILATION AND HEATING. As we are not usually able to destroy the impurities of the atmosphere within ojir dwellings as rapidly as they are produced, we have recourse to ventilation as a means for their dilution and prompt removal. We must not think, however, that we do all that is necessary if we only renew the in-door air, for unless the source and supply from which we take that which is to replace or dilute the vitiated air be pure and clean, any system of ventilation which we may adopt will be of little value. External Ventilation. — External ventilation of buildings, streets, and cities is of importance, then, as well as that which relates only to the interiorof dwellings, workshops, and places of assembly. Numerous investigations and statistics, both here and abroad, show that "the health of a town largely depends upon the width of the streets, the general height of the buildings, and the amount of yard-space at the rear of each which separates it from its opposite neighbor." It is also difficult to overestimate the value of wide streets, numerous diagonal ones and frequent parks or open spaces, especially in the more thickly inhabited portions of a city. In this connection we may refer with advantage to some work of Dr. H. S. Anders, of Philadelphia, in which he shows that " the number of deaths from phthisis on a very wide street is proportionately small compared with those on almost any one narrow street," and "that there is plainly and generally a high mortality-rate from consump- tion associated with street narrowness in not a small part of Philadelphia, and that the relation between a high mortality and narrow streets is a positive and vital one." His statistics, covering a period of fifteen years, show that (101) 102 VENTILA7I0N AND HEATING in one city ward, certainly favored as to location, the ratio of deaths from phthisis per square or block on streets over those on streets under forty feet in width was approximately as 3 is to 5. Internal Ventilation. — As regards internal ventilation, it will be well to determine at the outset the meaning and limi- tations of the term. Parkes says: "It will be desirable to restrict the term ventilation to the removal or dilution, by a supply of pure air, of the pulmonary and cutaneous exha- lations of men, and of the products of combustion of lights in ordinary dwellings, to which must be added, in hospitals, the additional effluvia which proceed from the persons and discharges of the sick. All other causes of impurity of air ought to be excluded by cleanliness, proper removal of solid or liquid excreta, and attention to the conditions surrounding dwellings." With the function of ventilation thus limited, it will not be necessary to make provision for such an abundant supply of pure air as might other- wise seem advisable. It is evident also that the purity of in-door air must almost always be relative and not absolute, especially in a climate like ours, which for a considerable portion of the year necessitates warming of the air and some consequent economy in its use. Since the importance of excessive humidity, high tem- perature and air-stagnation as factors in causing much of the discomfort and depression in unventilated places is now appreciated, any proper definition or system of ventilation must also include the alteration or obviation of such conditions and the adjustment of the atmosphere to a state most favorable for physiological comfort and well- being. Wherefore, the present tendency is to consider the condition as well as the composition of the atmos- phere as of prime importance, and to give special atten- tion to the former in planning modern ventilation systems or equipment. Considering the problems of atmospheric improvement, however, from the standpoint of composition or content, two factors must be determined in order to discover the INTERNAL VENTILATION 103 quantity of air desirable and consistent with the require- ments of good ventilation and the maintenance of health : (a) the extent to which the air of a room is contaminated in a given time by the impurity it receives, and (b) the limit of permissible impurity beyond which there will be a possible risk or detriment to health. In accordance with the above-mentioned limitations of Parkes, the contamin- ating substances will usually be comparatively few in number, but the same factors are to be sought in the case of any detrimental substances in the atmosphere at any time, provided their source or cause cannot be directly removed. Although it is extremely difficult to determine quanti- tatively the organic matter given off by human exhala- tion in any given time, the carbon dioxide, as has been stated, is usually exhaled in a reasonably constant ratio with it, and can therefore be used as an index of the amount of it contaminating the air. Taking Pettenkofer's figures, which have been substantially confirmed by other investigators, viz., 0.6 cubic foot of carbon dioxide per hour per head for a mixed assemblage at rest, 0.7 cubic foot for adult males, and increasing amounts according to the physical work done, we have the first factor (a) of our problem determined for all cases where the products of human respiration and exhalation are the only contam- inants. In establishing the limit of permissible impurity — the second factor (b) — it will naturally be advisable to require that the supply of air from without shall be sufficient not only to be thoroughly consistent with health, but also that there may be no perception of impurity by the senses, the air of the room remaining apparently as fresh and pure as that out-of-doors. To this end de Chaumont made a large number of observations (over 450), and found that as long as the carbon dioxide due solely to respiratory impurity did not exceed 0.02 per cent., the in-door air did not differ sensibly from that without, but that when the respiratory CO2 reached 0.04 per cent, the air was rather *' close" 104 VENTILATION AND HEATING and the organic matter was becoming perceptible to the sense of smell. Subsequent investigations have shown that as long as the respiratory CO2 does not exceed 0.02 per cent, the atmospheric conditions have no perceptible effect upon health.^ Consequently, we may take this amount of carbon dioxide, over and above the amount normally present at the time in the outer atmosphere, as the index of the limit of organic atmospheric impurity from human bodies permissible in ordinary inhabited apartments. Having now the two factors of our problem, and pro- vided there are no other sources of contamination, it becomes a simple matter of proportion to determine the quantity of fresh air to be supplied to each individual. The equivalent of 0.02 per cent, is 0.0002 cubic foot of carbon dioxide in each cubic foot of air, or 2 parts in 10,000. In a mixed assembly at rest each person exhales 0.6 cubic foot of carbon dioxide per hour. Consequently, to dilute properly this respiratory CO2 and its coincident O fK organic effluvia, each person will need r^T^KF^or 3000 cubic feet of fresh air per hour. If the individuals are all adult males, or if they are working, there must be a correspond- ing increase in the air supplied, running up to 6000 or even 9000 cubic feet or more per head in certain laborious occupations. This is the theoretical amount of pure air necessary for good ventilation; but in practice we find that we can get along in safety and comfort with some- what less, because some of the bodily impurities are almost at once carried away and out of the room by the draughts through the exits, or through the cracks and crevices in the walls and ceiling which act as exits, and the incoming air does not, therefore, have to mix with and dilute that portion of the impurities that is so imme- 1 This may simply mean that the air movement is sufficient not only to obviate the concomitant factors of excessive heat, humidity and stagnation, but also to reduce the organic matter to an amount or pro- portion entirely innocuous to the human economy. FACTORS IN VENTILATION PROBLEMS 105 d lately removed, and also because the currents of air stimulate the skin, favor evaporation, cool the body and obviate stagnation, which is one of the depressing factors already mentioned. In other words, if 10 per cent, of the vitiation is thus directly taken away, 10 per cent, less of pure air is needed to dilute the remaining contami- nants to the limit of permissible impurity; but as the quantity and the consequent velocity of the incoming or of the outgoing air diminishes, less and less of the impurities are thus directly removed, there is lessened physiological reaction. So experience teaches that almost the entire theoretical supply of fresh air is actually needed in practice to secure satisfactory results. Provision must also be made for sufficiently diluting the impurities from other sources of vitiation whenever they are present. Although combustion-products generally accumulate near the top of the room on account of their high temperature, which also facilitates their escape, we should provide at least 1800 cubic feet of air for each cubic foot of gas burned, and ten times as much for each pound of oil consumed. In sick-rooms and hospitals an exception must also be taken to the assumption that 0.02 per cent, of carbon dioxide be taken as the permissible respiratory^ impurity, for it is found that the organic matter exhaled from the sick is much more offensive than that from the well, and is noticeable to the senses when the respiratory COj is less than the amount permissible for those in normal health. So, at least one-fourth or more must be added to the quantity of clean air necessary for the healthy, and a good rule is to give the sick as much as possible, provided it be properly warmed and distributed. This is independent of the modem fresh-air treatment of many diseases which is to be looked upon as a thera- peutic rather than hygienic measure; nevertheless, it is difficult to make a sharp distinction between the ti^^o and good ventilation of hospitals is always essential and most desirable. 106 VENTILATION AND HEATING The use of the following formula will often be of ad- vantage in solving problems relating to ventilation, viz. : ~=d, where e represents the amount of carbonic acid or other impurity added to the atmosphere in the given time, r the relative ratio of the impurity in parts per cubic foot, and d the delivery or volume of fresh air in cubic feet.^ Example: What will be the respiratory impurity in the air of a room of 3000 cubic feet capacity which has been occupied by three men for two hours, supposing that there has been an ingress of 9000 cubic feet of fresh air in that time? Here 6=0.7 X 3 X2=4.2, and d =3000+9000 = 12,000. 0.035 per cent, of carbon dioxide. Before considering the means by which a sufficient quantity of pure air may be supplied to buildings and apartments, it will be well to note the following restric- tions as to the size and height of the rooms. If a room be too small, the air therein will have to be changed often, the velocity at the inlets will be increased, uncomfortable draughts will be created, and the air will not diffuse itself so thoroughly throughout the room. Experience shows that even when the air is properly warmed, it cannot be changed much oftener than three times an hour without discomfort to the occupants of the room, unless the ven- tilating apparatus be very perfect in its workings and therefore expensive. Consequently, as we take 3000 cubic feet of fresh air to be the average amount required per person per hour, the cuhic space per individual should be at least 1000 cubic feet, with a corresponding increase where the occupants are all adult males, are all at work, or are in hospitals. 1 By allowing e to represent the total contamination per hour, and r to represent the limit or extent of impurity in any given case, this formula can be used for almost any other ventilation problem, whatever may be the contaminants or source of impurity. NECESSARY QUANTITY OF AIR 107 Again, it must be remembered that the difficulty of securing equable heating and ventilation increases with the height of the room above a certain limit, and that with the sick especially a certain amount of floor-space is necessary, both for the separation of patients and conve- nience of attendance. Ten or twelve feet will usually be found to be the safe limit of height for all apartments intended for continuous rather than temporary occupation, and consequently there should be a minimum allowance of from 85 to 100 or more square feet of floor-space per head, and even an increase above this in w^orkshops, hospitals, etc. However, there is no objection to high ceilings if one is not limited as to floor-space, pure air- supply, and heat; and they are even advisable in rooms where many lights are to be burned. Again, these restric- tions regarding cubic- and floor-space do not necessarily apply to such buildings as churches, theatres, etc., which are occupied for only a comparatively limited time, which can be thoroughly flushed out after use, and in which it is evidently impracticable to allot to each person the above floor-area. Yet pains must be taken in such assemblies to keep the atmosphere pure by whatever means are necessary; while for school-rooms and the like there must be extreme care that the pupils are not over- crowded, and that they have a full supply of properly warmed air. Any correct system of ventilation, in addition to the above considerations, must take into account the source of the air supplied, the distribution, the heating or cool- ing of the air when necessary, and its relative humidity. The air supplied to any house should be taken from well aboye the level of the ground, where it is free from contamination and is constantly changing, and not from cellars or closed areas, where the atmosphere is stagnant and full of impurities. The conduits leading to the heat- ing or ventilating apparatus should also be so arranged that they may be frequently and readily cleaned. It is well to have them covered with gratings to prevent 108 VENTILATION AND HEATING objects being thrust into them, and in some cases it may even be advisable to filter the air through coarse cloth or fine wire gauze to free it from dust and other impurities. In the mechanical system of ventilation adopted in the chemical laboratory of University College, Dundee, the air is filtered by being passed through jute cloth (light Hessian) stretched on frames seventeen feet long by four feet wide. In this case the presence of the screen actually increased the delivery of the air by nearly 10 per cent., probably by preventing eddies. The screens collected two and one-half pounds of dirt in seven weeks. They last about a year, and the cost is about 2d (four cents) a yard.^ The air may be kept in motion and efficient ventila- tion secured (1) by those forces more or less continually acting in nature, producing natural ventilation, and (2) by these in combination with other forces set in action by man, giving artificial ventilation. Natural Ventilation. — The three main forces of natural ventilation are diffusion, the winds, and the motion caused by the difference in weight of volumes of air of different temperatures. Diffusion is constantly taking place between all the gaseous constituents and impurities of the air, and even effects a change through brick and stone walls, but it alone is insufficient to keep the air pure, although it does much to further this. Moreover, as suspended matters are solid, not gaseous, they are not changed or removed by it. However, the action of this force should not be ignored in our calculations as being insignificant, for it is not only continuous, but it also affects the whole volume of the atmosphere in maintaining its uniformity of composition. "Roscoe found that when he evolved carbon dioxide in a room, the amount had decreased one-half from that cause (diffusion) in ninety minutes. "^ As the rate of diffusion is inversely as the square ^ Stevenson and Murphy, vol. i, p. 51. 2 Notter and Firth, p. 194. NATURAL VENTILATION 109 roots of the densities of the gases concerned, the inter- change goes on rapidly when there is much difference of temperature between the in-door and outer air, and also at the top of rooms, where the warm impurities tend to accumulate. Fig. 16. — Cowl or ventilator for aspiration. Winds are powerful agents for ventilation, and a slight breeze passing through a room changes the air therein many times in the course of an hour, and carries out by its force many of the solid impurities not affected by dif- fusion. Wind will pass through walls of wood, brick, or stone, although its progress is markedly arrested by much moisture in the walls and by paper or plaster. The aver- age rate of movement of the wind is considerable, but the disadvantages in utilizing it in ventilation are the no VENTILATION AND HEATING uncertainty of its direction and velocity, the difficulty of regulating it, and the fact that it may fail us at a time when we most need its action. In winter it usually has to be excluded directly from our houses, because a velocity of five or six feet per second is not comfortable unless the air be previously warmed. We may, however, take advan- tage of the facts that a small current with a high velocity will set in motion a larger volume of air, and that wind blowing across the top of a tube will cause an upward movement of air in the tube. This is one reason why there is almost always a draught up an unused chimney and why it usually acts as a good ventilating outlet. To utilize these perflating and aspirating powers of the wind, and to prevent back-draughts down chimneys and ventilating pipes, we make use of so-called ventilators or cowls J either movable or fixed. We can so arrange these that the force of the wind either drives air into the building (perflation) or draws air out of it (aspiration) . Very good systems employing these have been put in operation, the incoming air being warmed, when necessary, by passing it over stoves, steam coils, etc., and they are especially useful where the inner air is colder than that externally, and where artificial methods of ventilation dependent upon heat cannot be employed, as in the holds of ships, deep basements, etc. The most important agent in natural ventilation is, however, the movement produced by variations in the specific gravity of air. Although the wind might be included under this head, being produced by the same force, the air is moved independently of the wind, espe- cially in closed buildings. As the air expands when heated, it becomes lighter, volume for volume, and rises because the colder, heavier air pushes in beneath to occupy the space. Now in all inhabited apartments a warming of the atmosphere is continually taking place, not only by means of the lights and heating apparatus, but also by the bodies of the occupants. The consequent movement is therefore a continual though not necessarily an equable one, vary- WINDS AS VENTILATING AGENTS 111 Ing as it does with the temperature of the out-door air and the riumber and intensity of the heating agents within. There being such a warming and movement of the air, it follows that, unless a room be perfectly air-tight, some of the apertures will act as inlets and others as outlets, and the quantity flowing out of the room will be prac- tically equivalent to that flowing into it. Therefore, though this force may not be so powerful or efficient as strong winds at certain times, yet being more constant, more readily determined or calculated, and more controll- able, it is the one most to be considered in arranging a system of ventilation. To determine the velocity of the influx or outgo of air, we make use of the law that a fluid passes through an opening in a partition between two volumes of the fluid with the velocity which a body would acquire in falling from a height equal to the difference in level'of the fluid on the two sides of the partition. In the case of a current of air we substitute for the difference of level the differ- ence in pressure on the two sides of the partition or open- ing, and this is expressed by the difference in temperature multiplied by the difference in height of the openings of entrance and exit, and divided by 491, ^ir representing the expansion of the atmosphere in volume and the les- sening of density for each degree (Fahrenheit) of rise in temperature. The velocity will therefore equal V (diff. in temp.) X (diff. in height) . 491 Example: What is the velocity of the current in a chim- ney 40 feet high, the out-door temperature being 20° F. and in-doors 70° F.? Answer: -v ^?^-^ii? = 8 X 2 +, or about 16 feet per aecond. 491 In actual practice use is made of a table derived from this formula, or else the velocity is determined directly 112 VENTILATION AND HEATING by means of the anemometer. Allowance must be made for the friction of the air against the sides of the ducts and against itself, amounting to from one-fourth to one- half of the theoretical delivery, according to the length, size, straightness, etc., of the inlets and outlets. The friction will be inversely as the diameter of the openings and directly as the length of the tubes; the shape of the openings also affects it, and right angles diminish the current one-half. Accumulations of dust and dirt in air conduits greatly lessen the velocity. Fig. 17. — Anemometer, used for measuring the velocity of air-currents directly; A, slide for releasing or stopping the dial hands; E, support for attaching the instrument to a staff or cane. The average velocity multiplied by the total area of the inlets or outlets, with a proper allowance for friction, will give the quantity of air passing through the rooms or series of rooms in any given time. One of the most difficult problems in natural ventilation is to secure a uniform distribution of pure air through the rooms, and to remove the impure air as fast as the pure air is supplied, thus preventing its mixing with the latter. Certain circumstances always make the question compli- cated: the size and number of inlets and outlets, the rate VOLOCITY OF AIR-CURRENTS 113 and direction of motion, and the forces acting to produce the movement must always be subject to constant change, and must thus constantly alter the result. In fact, it is practically impossible to devise a plan that will satisfy all conditions at all times, and the best that can be done is to select that one which will give the greatest efficiency and most satisfactory results under all ordinary circumstances. The force of diffusion will always act as long as there is any difference of temperature and any communication between the exterior and interior, and no special attention need be given to it. For reasons already given, we cannot use the wind continually, but we should employ it when- ever possible by opening doors and windows, on account of its great power for sweeping out solid impurities and "crowd-poison" and thoroughly changing the air. In cold weather, currents from windows, etc., should be directed toward the ceiling, so that they may be diffused and par- tially warmed before reaching the inmates of the room. Numerous devices have been suggested for introducing unwarmed out-door air without discomfort, or for diffus- ing it through the room: among these may be mentioned perforated bricks, or double-paned windows, valves, screws, etc. A cheap and satisfactory temporary arrange- ment is to place a board about four inches wide and as long as the width of the lower window-sash beneath the latter. Or, better, have a light frame covered with fine netting or wire-gauze, four or five inches wide, made to fit above the upper sash: the fresh air from without can now enter freely between the upper and lower sash, being reflected upward by the inner surface of the glass in the upper sash, and thus mixing with warm air before reaching the occupants of the room; while the frame at the top of the window becomes an outlet for the foul air, the inter- ference of the netting or gauze preventing too rapid an outgo and consequent loss of heat. Another excellent and inexpensive device is a board as long as the width of the window and eight or ten inches wide which is placed so that its lower edge rests on the window sill and it slants 8 114 VENTILATION AND HEATING inwardly, being held in place by V-shaped pieces attached to the window frame at each end. When the window sash is raised the cool, incoming air is deflected upward by the sloping board so that it is practically unnotice- able a short distance from the window. By making suitable grooves in the end pieces, a sheet of clear or translucent glass may be substituted for the board, thus admitting a full supply of light and improving the appearance of the device. (Fig. 18.) Fig. 18. — Window ventilator with translucent glass instead of board. But in a climate such as our own, and in all cold coun- tries, special measures must be taken during a large part of the year for warming the out-door air before introduc- ing it into occupied rooms. Where we intend to depend most upon the third force of natural ventilation, viz., the movement caused by unequal weights of air, we must provide other openings for the entrance and exit of the air than the windows and doors, so that there will be a practically constant movement through the rooms in a given direction, that we may be sure the air is from a pure source, and that we may get the utmost service from our appliances. VENTILATORS 115 There is considerable difference of opinion as to the best locations for inlets and outlets, and as the conditions are necessarily different in every case and so many factors are to be considered, it is difficult to lay down general rules. It should be an aim, however, to have the air well distributed throughout the room or rooms and to have no direct draughts from the inlets either upon the occupants or to the outlets. It is the writer's opinion Fig. 19. — Direction of air-currents in room lighted by gas and heated by open grate. that usually the outlets should be located near the top of the room, owing to the tendency of the used air to rise, and because in unventilated rooms the foulest air for some time after its contamination will be found nearest the ceiling. The products of combustion from lights, etc., will also practically all be in the upper strata of air. (Fig. 19.) If, however, provision is or can be made for a constant and sufficiently strong aspirating force in the outlet ducts, it may be advisable to withdraw the used 116 VENTILATION AND HEATING air from near the floor level and below the inlet openings, though not in too close proximity to them, since in this way a more thorough distribution of the incoming air. and a greater dispersion of its contained heat are secured. This is aptly shown in the illustration depicting the cur- rents in a room heated by a ventilating grate. (Fig. 20.) This principle is also involved in the well-known Smead system of ventilation and heating, which still further serves economy by carrying the foul air beneath the floor of the room from which it is taken, thus warming the Fig. 20. — Direction of air-currents in room heated by a ventilating grate. floor with some of the heat the waste air yet contains and securing the utmost benefit and service from the fuel. (Fig. 21.) The location of the inlets should depend on the tem- perature of the incoming air; if it is cold, it should be admitted some considerable distance above the floor, so that it may diffuse and be partially warmed before reaching the inmates of the room; if it is warmed, it may come in near the floor or below the middle level of the room. DISTRIBUTION OF AIR 117 Where much fresh air is required, it is better to have a number of inlets and outlets than one large one of each, as the distribution is then more certain. The total area of the outlets may be the same as that of the inlets, as the expansion of the air is scarcely sufficiently great to require a difference. The outlets should all be on the same level; otherwise the highest one will be the one of greatest dis- charge, and often the only one, the others possibly acting as inlets and drawing air from an impure source. As the temperature varies from time to time, and with it the cur- Fio. 21. — Illustrating the Smead system of ventilation. rent, some arrangement is needed for regulating the size of the openings of the inlets or outlets to suit the varying conditions. To supply 3000 cubic feet of air per head per hour a velocity of 5 feet per second will require an inlet opening of 24 square inches for each person; but practi- cally it is better to have a larger opening than this, as the above velocity is uncomfortable unless the air be well warmed. Outlet tubes should always be protected from cold and kept as warm as possible. As long as there is a fire in a grate or stove connected 118 VENTILATION AND HEATING with a chimney there will be a constant upward current in the latter; and the area of the chimney's cross-section being known, and the velocity determined by the ane- FiG. 22 Fig. 23 Outlet ducts warmed by stove-pipes. mometer or by calculation, as already indicated, the amount of air passing out of the room in this way may readily be determined. In this connection it may be stated that a chimney may thus act as the only outlet, and LOCATION OF INLETS AND OUTLETS 119 all other openings into the room may serve as inlets, especially when the fire is brisk, the outgoing current, of course, being practically equivalent to the amount of Fig. 24. — Waterbury ventilating stove, showing encircling drum, inlet for out-door air, and outlet for impure air into chimney. incoming air. Moreover, the outgoing current may be so strong as to overtax the capacity of the inlets, in which case more or less of a vacuum will be created within, so that the outside pressure may cause down draughts in the 120 VENTILATION AND HEATING chimney from time to time and a driving back of the smoke and gases from the fire into the room. The obvious remedy is to efnlarge the inlet area by opening a door or window, or to lessen the exit draught by means of a damper in the chimney. On the other hand, the inlets may be so large and the current so strong that the air coming into the room cannot be properly warmed, in which case, again, the size of the outlet should be les- sened by a damper, or there should be an increase in the efficiency of the heating apparatus. When we wish to draw air from distant and non-com- municating rooms, the ducts may be led into a chimney below or just above a fire, or, better, into a flue or shaft alongside or encircling the heated chimney. When the exit ducts open into a chimney or smoke-stack the draught is greater just above a fire than below it, but the conduits should not enter near the top of the chimney, for there the extracting power is not so great and there is danger of high winds blowing smoke and foul air back into the rooms. Outlet flues may be constructed alongside chim- neys that are being constantly used; they should be as smooth as possible interiorly, and should be as high as the adjoining chimney, to avoid down draughts. The open- ings from the rooms into these ducts should be as near the ceiling as possible, to get the benefit of the higher temperature of the upper strata of air, unless, as previously indicated, there is certainty of the extracting force being constant and sufficiently strong, when the air may be taken from a lower level. (Fig. 24.) Artificial Ventilation. — Artificial ventilation is that which is brought about by the intentional application of the above- mentioned and other forces, and by means of special mechan- ical apparatus and devices, in contradistinction to natural ventilation, which may act independently of human cogniz- ance and intention. It consists in either extracting air from, or forcing it into, a room or building, or in both together. The object may be attained by heating the air by special apparatus in the outlet, or by warming the outlet itself ARTIFICIAL VENTILATION 121 or by the use of a fan, a screw, or a steam- or water-jet in either the inlet or outlet. In hospitals and other places where a constant and inde- pendent supply of heat can be afforded, extraction shafts apart from chimneys may be used. These extraction shafts may be heated by fires, steam pipes, or steam-jets at the bottom, or by steam or hot-water pipes coiled around the sides. Some system like the following is some- times used in mines where large quantities of air must be extracted. There are an entrance and an extraction shaft; large fires are constantly maintained at the bottom of the latter, the air is drawn down the former, diverted through all parts of the mine by partitions, and finally heated and carried up the extraction shaft. We may also use a jet of steam or water in place of heat to extract air through a shaft, the openings of the foul- air ducts being just behind the jet. It is said that a steam- jet may thus set in motion over two hundred times its own bulk of air. Lastly, fans driven by electricity, steam- or water-power are employed to extract the air, though these are usually more efficient in forcing in air. One of 36 inches diameter at 600 revolutions per minute will propel or extract over 18,000 cubic feet of air per minute. In ventilation by propulsion or driving in air, these large revolving fans are generally used. The advantages of this, the plenum, system of ventilating are the certainty as to the direction of current and amount of air supplied and the ease with which the quantity can be altered or measured as well as warmed; also, by maintaining a slight excess of supply, leakage into the rooms of cold or foul air from without is prevented. The disadvantages are the high cost of power in most cases, the inconveni- ence or danger from prolonged stoppage from accidents to the apparatus, and some difficulty in distributing the air. For instance, if it be forced in through small openings or at too great a velocity, it will not mix properly with the air of the room. This last objection can usually be obviated by giving special attention to the size, direction. 122 VENTILATION AND HEATING and arrangement of the inlet flues, and the relative loca- tion, size, etc., of both the inlet and outlet openings. The increased use of electric motors and lowered cost of run- ning them will doubtless serve to make this system of ventilation more common in the near future. Fig. 25. — Air propeller, with electric motor attached. In very large buildings it may be advisable or neces- sary to combine the plenum or propulsion with the exhaust or vacuum system, using power fans both to drive in and to force out large volumes of air. In this way an almost ideal ventilation may be secured, provided the incoming air be clean and be sufficiently warmed by means of steam or hot-water coils or radiators (see pages 144 and 145). Parkes and Kenwood summarize the essential and practical points of ventilation as follows: PLENUM AND VACUUM SYSTEMS 123 "1. When air is heated, it expands and tends to rise; when air is cooled, it contracts and tends to fall. "2. Cold air tends to enter a room and to move about very much as water would ; and this holds true so long as the temperature of the fresh air remains lower than that in the room. "3. The extent of inlet provision is not quite of the same importance as that for the exit of foul air; for if foul air is extracted in sufficient quantities, fresh air will enter somehow to replace it, as by skirtings, crevices in doors or windows, or even through brick-work in walls. "4. While the inlet provision for fresh air should aver- age 24 square inches for each individual, several small inlets not too near each other are preferable to one large one; and the provision of inlet areas somewhat larger than those of exit tends to minimize draughts. "5. Inlets should be as low in the room as possible — i. e.f just above the floor (so as not to raise the dust) — if the outside air is warm or has been warmed prior to entry; but at a height of five feet or more if the outside air is cold: otherwise unpleasant draughts are experienced. As a further protection against unpleasant draughts when cold air is admitted, the incoming air should be directed upward; while hot air, since it tends to rise, should be directed downward. "6. Outlets should be as high as possible, and prefer- ably close to or in the ceiling; and they should have their extractive powers maintained by means of heat or of an exhaust fan, or they are liable to act as inlets. " 7. If possible, outlets should be so placed that vitiated air is drawn toward them before mixing with the general air of the room. "8. The tendency for fresh air to take a direct course to the outlets must be overcome by judicious selection of the positions of inlets and outlets. "9. Methods of ventilation devised to ventilate crowded premises are generally inefficient unless the incoming air can be warmed in winter to about 60° F.; for efficient 124 VENTILATION AND HEATING ventilation by cold air cannot be tolerated, and there is a great tendency among workers to close all ventilating inlets. "10. With less than 250 cubic feet of space for each person, ventilation can never be satisfactory without the aid of mechanical force. "11. The source of the incoming air should be consid- ered. It should not be borrowed from adjoining rooms, but taken directly from the outside. One great advantage of the more expensive mechanical system of ventilation is the fact that sufficient air can always be obtained from a source that is known and selected. "12. Ventilation dependent on the extraction of foul air is more convenient and satisfactory than that in which propulsion is mainly relied upon; but the purity of the air is not provided for so easily. "13. Warmed air forced into a room should be raised only to a temperature sufficient to prevent a feeling of cold (about 60° F.). More highly heated air is often felt to be overdry and unpleasant." HOUSE-WARMING. In cold countries there must be some resort to artificial heat in the winter season, and as this subject is more or less inseparably and closely connected with ventilation, it may be appropriately considered at this time. Cold is depressing, uncomfortable, and sometimes dangerous to the young and aged and to women whose habits of life keep them much in-doors, though well-fed, healthy adult men may not be much affected if accustomed to it. In this country we seem to need a higher temperature in our houses than in Great Britain, on account of our drier climate and especially because we keep the atmosphere of our dwellings much too dry; evaporation and conse- quent cooling of the body take place more rapidly here, and so, while they are accustomed to a temperature of from 60° to 65° F., we find from 65° to 75° F. to be no HOUSE-WARMING 125 more than comfortable. If, however, the relative humidity is maintained at from 50 to 60 per cent., a temperature of 68° F. or even lower will usually be found quite as com- fortable and more healthful than a much higher one in a dry atmosphere. A low relative humidity is as unhygienic as one too high. It needs but slight investigation to determine that we practically make use of but two kinds of heat — radiant and convected — in the warming of houses, and that of these the latter is by far the more generally employed and the more economical. Radiant heat, although it is con- sidered to be the more healthful as it warms an object directly without raising the temperature of the intervening air, has the disadvantages of utilizing but a small propor- tion of the fuel-value, of decreasing directly as the square of the distance of the object from the source of heat, and of thus being available only in comparatively small apartments. Our best example of radiant heat is that which comes from open fires, though any highly heated object, as a stove, gives off more or less of it. Heat that is carried from one place to another by warmed masses of air, water, or steam is said to be con- vected, and because of the economy in its use and the ease of distribution, especially in large spaces, it is the kind most generally used. Conducted heat, which passes frond molecule to molecule of the conducting substance, acts too slowly to be available to any extent in house-heating and may therefore be omitted from this discussion. Just here it may be remarked that under present con- ditions there are three things, any two of which we may have in cold climates or weather, but not all three together except in rare instances: they are, good ventilation, efficient heating, and low expense. The reason for this is that any good system of ventilation necessarily and con- tinually carries off a large quantity of air, and the heat it contains, which latter is lost for warming purposes, must be replaced at the expense of more fuel. A. heat- unit cannot be used at the same time to produce ventila- 126 VENTILATION AND HEATING tion and to warm objects other than the air it keeps in motion. The principal aim, then, in estabHshing any system of combined ventilation and heating must be to introduce, warm and carry off no more air than is neces- sary for the requirements of good ventilation and health, and to produce the heat for warming this air and the house itself as economically as possible, though care must also be had to secure evenness of distribution, absence of uncomfortable draughts, etc. The usual appliances for house-heating are open grates or fireplaces, stoves, and hot-air, steam, and hot-water furnaces. To these may now be added electrical heaters, but the cost of maintaining the latter prevents their use at present by any but the wealthy. Ordinary grates and open fireplaces give practically only radiant heat, and render available only from 7 to 12 per cent, of the fuel efficiency. They also heat directly only the surfaces facing them of objects in the room, leav- ing the remainder cold, and by reason of the strong cur- rent up the chimney are also apt to bring in large quantities of air from without that has not been properly warmed, and thus to cause chilling and injurious draughts. Where there is some additional means of heating the air before it enters the apartment and where the chimney current is controlled by a damper, they are valuable, not only for the good ventilation they thus produce, but for the pleas- ing effect of the exposed fire as well. But if there be no additional or accessory heating apparatus, such a fireplace cannot be said to give good ventilation, even though large volumes of air pass up the chimney, for this air, entering unwarmed from without, sweeps across the floor of the room as a shallow, cold layer much below the level of the breathing apparatus of the inmates; while the more or less contaminated air above this cold stratum remains undiluted and unchanged. (See Fig. 19.) To make open grates more effective for heating, the sides and top should be inclined to the back at an angle OPEN GRATES AND FIREPLACES 127 of 135 degrees, so as to throw as many heat-rays as possi- ble into the room; the fuel surface should be concentrated, and there should be a damper to prevent too rapid com- bustion and too much heat and air escaping up the chimney. It is to be understood, of course, that the objects warmed by the radiant heat of the open fire do in turn give convected heat by warming the air surround- ing them. ^'S^CA^/^^ Fig. 26. — Jackson's ventilating grate. The outer casing is cut away to show space and surface for warming the incoming air. The air enters through the oblong inlet (a) and passes to the register opening (6) (in front) between and around the five smoke-pipes (c) above. If, however, the back and sides of these grates be sur- rounded by a space through which air can pass and be warmed by the heat that would otherwise be wasted, we shall have a much more satisfactory apparatus, since we thus get both radiant and convected heat and may obtain from 25 to 35 per cent, of the fuel efficiency. (Fig. 26.) And if clean out-door air be led into this air-space and thus warmed before entering the room, the ventilation will be greatly improved (see Fig. 20), other inlets will be unnec- essary, uncomfortable draughts will be avoided, and there will be sufficient heat provided for one or more apartments of moderate size. The air-chamber at the 128 VENTILATION AND HEATING back should not be too small, and there should be as much heated surface to warm the incoming air as possible. Stoves utilize a considerable percentage of the fuel — 75 to 80 per cent, or more — but do not remove much air; so ventilation has to be provided for in some other way and is apt to be neglected. Stoves may also give off dan- gerous gases and products of combustion if not properly cared for or if the damper in the stove-pipe be entirely closed. There should be as much surface exposed as is / Wh-e gauze X Da mper ...Jac/iet -w-n \ k ffesfv A if M M Fig. 27. — Jacketed ventilating stove. (Harrington.) possible without diminishing the combustion, so that there may be increased radiation and that much air may be warmed moderately rather than a little excessively. It is often advisable, especially in assembly- or school- rooms and the like, to surround the stove with a sheet- iron cylinder extending from the floor toward the ceiling and to bring in between this and the stove a supply of fresh air from without. This air becomes heated, and, passing out over the top of the cylinder or drum, gives a plentiful supply of convected heat and greatly improves STOVES 129 the ventilation. (Figs. 24 and 27.) A suitable outlet must, of course, be provided. Carbon monoxide and other gases are known to leak through cast iron when it is highly heated, so that stoves should not be allowed to become too hot. The produc- tion of carbon monoxide is most abundant soon after fresh fuel is added to the fire, and is evidenced by the characteristic blue flame above the coals. , If at this time the escape of this gas into the outer air is prevented by the careless or accidental closing of a damper in . the stove-pipe or chimney, it is prone to pass through the top and sides of the stove in the manner indicated, and to cause the serious and fatal results so often reported. Therefore it should not be possible to cut off com- pletely the draught from any coal-burning stove, nor should it be materially lessened until combustion is well under way. Other objections to stoves that are allowed to become too hot are the excessive dryness of the atmosphere which they cause and the unpleasant odor due to the scorching of floating organic substances that come in contact with the hot iron. The fuel most commonly used in both grates and stoves is either wood or some kind of coal (bituminous, anthra- cite, or lignite) ; but gas or oil may often be advantageously and more satisfactorily employed instead of any of these, since the heat can be had from them practically instanta- neously, can be closely regulated in quantity, and can be promptly checked when no longer desired, and since there is no production of dust or ashes in the room. The main objection to gas is that for large rooms or prolonged or continuous heating, it is usually more expensive than the other fuels; but this does not hold good for small rooms, nor sometimes for isolated apartments or where warmth is needed only temporarily; and it is very probable that before long fuel-gas will be — it can be now — supplied at rates which will justify a much more extended use of such fuel. 130 VENTILATION AND HEATING The ordinary kinds of gas-grates and gas-stoves, espe- cially those which consume the gas incompletely, should all be constructed with flues to carry off directly the products of combustion, and this particularly when any large quantity of gas is used. Theoretically, when the gas is burned in a properly adjusted Bunsen or "atmospheric" burner, the only combustion-products will be carbon dioxide and water, the former of which is rapidly dif- FiG. 28. — Section of Backus's portable steam radiator for use with gas. fused into the outer air, as has been shown, and is not likely to be harmful in any quantities thus produced, while the aqueous vapor is usually beneficial to the atmosphere rather than otherwise. However, it seems that in practice even these Bunsen burners may some- times give to the air a disagreeable odor (said to be due to the formation of acetylene), and so occasionally need flue connections. In this connection it may be interesting to describe one GAS GRATES AND STOVES 131 form of gas-heater which, so far as the writer knows, is unique. It is intended not only to consume perfectly the gas it uses, giving nothing to the air but carbon dioxide and water; but also to destroy by fire the impurities of the atmosphere of the room, thus doing away with chim- neys or flues and the necessity of excessive ventilation. By a peculiar arrangement a continuous and large current of air is made to pass through the flame, thus consuming the impurities whether gaseous or solid. The heat of the burning gas is also used to convert a quantity of water into steam, which, by heating the containing chamber or coils of pipe and, in turn, the atmosphere surround- ing these, warms many times the volume of air possible to heat by the flame alone. In addition, the humidity of the atmosphere is maintained by the evaporation of water from an open basin beneath the fire. The ordinary openings of any room are amply sufficient to allow diffusion of the excess of carbon dioxide — one- half escaping in this way, according to Roscoe, within ninety minutes — and to permit the ingress of enough air to supply all the oxygen-needs of the inmates and of the fire itself. Experience and careful experiments seem to show that the claims of the inventor are well founded, and that the apparatus is healthful in its operation and produces no harmful effects even after continued use for several months. At any rate, there seems to be no reason why we may not purify the air by fire instead of by dilu- tion and removal, the methods employed in the hitherto described systems of ventilation. Oil-stoves are now used quite extensively, and, beside being portable, have the same advantages as gas-stoves, viz., that a considerable quantity of heat may be had quickly and just as long as it is desired, and at a fairly moderate cost. The combustion-products necessarily mix directly with the atmosphere of the room and, where reasonably perfect burning is had, doubtless consist ol little else than carbon dioxide and water. One pound of oil, the hourly consumption of a rather large stove, will 132 VENTILATION AND HEATING require about 150 cubic feet of air for its complete com- bustion, and will produce about 25 cubic feet of carbon dioxide. "We do not think that the experience has yet been accumulated which would fenable us to speak positively of the innocuousness of a considerable admixture of car- bonic acid with the air we breathe; but the knowledge that in hundreds of cases oil-stoves are used for heating living-rooms and even bed-rooms, without apparent injury to the occupants, makes one feel fairly confident that the products of the complete combustion of hydrocarbons are not injurious when mixed with such an amount of air as is sufficient to dilute to a proper degree the respiratory products. . . . 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 day-rooms and sleeping-rooms. The efficacy 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."^ The above remarks, as far as they apply to the healthful use of oil-stoves, may probably be used with equal justice in regard to gas-stoves, provided that with such dilution their products give no obviously harmful or disagreeable results. CENTRALIZED HEATING. The heating apparatus thus far described is such as we are accustomed to employ for warming the air of a single, or possibly of adjoining rooms. Where a whole dwell- ing or other large building is to be heated, it will usually be of advantage to do this from one point, and that not 1 Notter and Firth, p. 228. HOT-AIR FURNACES 133 in any of the living apartments. In this way we shall have a centralization of fuel, both unburned and burning, and the ability to derive more heat from it; a lessening of the labor and attention bestowed on the fires; the obvi- ation of much dust, dirt, and combustion-products in living-rooms, and, presumably, a more equable and satis- factory warming of the whole building. From such a central point the heat is distributed by hot air, hot water, or steam, or by hot air in combination with either of the other two. Fig. 29. — Spear's hot-air furnace (without casing). Hot-air Furnaces. — Hot-air furnaces supply a large amount of convected but no radiant heat. There is a very prevalent opinion that they are not healthful, and that wherever possible they should be replaced by some other means of heating. But when properly constructed and 134 VENTILATION AND HEATING cared for, a hot-air furnace of the proper size is not only a good heater but also a powerful ventilating agent, for the large supply of air passing through it into the rooms above must in turn find an exit either through specially devised outlets or through the innumerable cracks and crevices around all doors and windows, and the ventilation will be accordingly. One frequent source of trouble is too small a fire-box, giving insufficient heating surface and necessitating too rapid and too intense combustion of fuel. There should be a considerable expanse of surface, never too highly heated, so that large volumes of air will be moderately warmed rather than small quantities overheated and " burned. '^ Air too highly heated is very dry and offen- sive to the senses ; also, by taking excessive moisture from the body through the skin and mucous membranes and by exciting glandular activity, it increases the liability to frequent "colds" and congestions. Moreover, a large quantity of air moderately warmed will perforce be car- ried to all the rooms of the house, warming them equably and driving before it the air already there : whereas a much smaller volume, excessively heated by the same or even a greater amount of fuel, will make its way along the conduits of least resistance to a few favorably located rooms, overheating them while the rest of the house is unwarmed, and any satisfactory natural ventilation is thus prevented. All joints in the furnace must be as nearly gas-tight as possible to prevent the combustion-products passing from the fire-box or smoke-flues into the air-chambers and thence into the rooms above. The furnace should be located near the cold side of the house — that is, the side on which the prevailing cold winds impinge — for it is said to be as difficult to drive the air ten feet against the wind as forty or fifty feet with it. It may also be well, if the basement ceiling is low, to place the ash-pit below the level of the basement floor, in order to give sufficient slope to the air-ducts; but in every case the HOT-AIR PURNACES 135 space beneath the furnace should be made impervious with cement or asphalt to prevent the drawing in of soil-air. The air-supply should not be taken from the cellar, even though the latter be apparently clean and free from Fig. 30. — llut-air furnace, ahuwiag culd-uir iuluL and huL-air lluea. Only one of the lateral branches of the main inlet {A) above is shown. contamination with soil-air, but should come from a clean source out-of-doors, well above the ground-level and from the direction of the prevailing winds. The cold-air duct or ducts should be screened at the entrance 136 VENTILATION AND HEATING to prevent the admission of refuse or vermin, should be ar- ranged to permit of regular cleaning, should have a damper to regulate the supply of air, and should have a cross-section equivalent to at least two-thirds of the combined sectional areas of the hot-air flues leading from the furnace. The importance of a large air-inlet cannot be too strongly em- phasized, for upon this feature may most depend the satis- factory action of the furnace. It may be desirable to provide for filtration of the air through coarse cloth or fine wire- gauze, especially if there be much dust in the incoming air.^ To lessen friction, the hot-air flues or ducts should be preferably round or square and not too small or narrow in cross-section; and for the same reason they should be as direct in their course and as nearly vertical as possible. They should be covered from the furnace to the register- openings with asbestos or other non-conducting material to prevent the loss of heat that otherwise escapes. from them into the cellar and between the partitions. Lastly, their register-openings into the rooms should not face the windows or prevailing winds, unless it be unavoidable, for if they do the passage of warm air into the rooms will often be almost, if not completely, checked. The following table, from Coplin and Bevan, gives the proper size for hot-air flues and registers: FIRST FLOOR. Size of room in cubic Size of pipe. Size of register. feet. If round. If oblong. If round, j If oblong. Less than 1500 7 nches 4X9 inches 1 9 inches | 7 X 10 inches 1500 to 2000 . 8 " 4 X 12 " 10 « 8 X 10 " 2000 to 3000 . 9 « 4 X 16 " 12 " 8 X 12 " 3000 to 4000 . 10 4 X 18 " 12 " 9 X 14 " 1 See page 108. COLD- AND HOT-AIR FLUES 137 Economy will be subserved in most eases by taking care to burn the fuel in hot-air furnaces quite slowly, since in this way larger quantities of air are warmed and more satisfactorily, and there. is also less waste of heat through the smoke-flues and up the chimney. Moreover, it is the experience of the writer that by working the furnace in this way at low pressure, so to speak, the air from it will be less likely to become too dry, nor will it need the addition of so much moisture, something essen- tially necessary and yet most often neglected where com- paratively little air is excessively heated. The amount of water to be added also depends upon the humidity and temperature of the out-door atmosphere. When the latter is but little, if at all, below the freezing- point and is almost saturated, and when the in-door air is but moderately warmed, as suggested, the lack of added moisture may scarcely be noticed ; while if the air without be at the same time dry and very cold, its actual content of water will be very little, and much added moisture will be needed to make it either comfortable or healthful, even though warmed to only a moderate degree.^ "Concerning the need of insuring a normal amount of moisture in the air of heated buildings, there is more or less difference of opinion, but the weight of evidence from a medical stand-point, and from our own sensations, points to the advisability of introducing an amount of moisture sufficient to bring the relative humidity of the air to 50 or 55 per cent. . . . Air at 25° F., saturated with moisture and then heated to 70°, would need over a half- pint of water in every thousand cubic feet to give it a humidity of 65 per cent., and this is far in excess of the * Most modern furnaces have a water-pan from which evaporation may take place into the warmed air, but the filling of this, when left to servants, is so often neglected that connection with the water-supply of the house by means of a float-valve or automatic cut-off would better serve to secure a constant supply. Even then, these water-pans as ordi- narily constructed are probably inadequate, especially in cold climates, to maintain the degree of humidity desired, and additional moisture should be provided from other sources, if possible. 138 VENTILATION AND HEATING capacity of the ordinary water-pan of the furnace, as is seen when we reckon what half a pint per thousand cubic feet means in the course of a day."^ Some recent tests by H. M. Smith, of Brooklyn, show that a relative humidity above 50 per cent, and a tempera- ture of about 65° F. is most healthful and comfortable. " With a temperature of 72 or 74 degrees and a relative humidity of 30 per cent, as compared with a room at 65 to 68 degrees and a relative humidity of about 60 per cent., the latter seemed the warmer and more comfortable." On the other hand, Ingersoll*'^ believes that in cold climates Fig. 31. — Humidifier. The cotton wicking shown absorbs water from a reservoir below. (Harrington.) the ideal in-door humidity for a temperature of about 70° is from 40 to 45 per cent., and that when above 50 per cent, the condensation in cold weather is unbearable. Prof. Wilson, of Milwaukee, says further: "About 25 per cent, of the cost of heating is expended in raising the tem- perature from 60 to 70 degrees; so if we can keep com- fortable at a temperature of 65 degrees, we shall have saved at least 12.5 per cent, of the total cost of heating." * Harrington, pp. 420 and 421. 2 Journal of Home Economics, April, 1915. HOT-WATER AND STEAM-HEATING 139 Hot-water and Steam-heating.— When it is necessary to carry heat for a considerable distance or to warm large buildings or blocks of buildings from a central point, it will be better and more economical to employ hot water or steam as the heat-transmitting agent, on account of the high specific heat of the former and the great amount of latent heat held by the latter. "It is uneconomical to convey heated air any long distance, as the amount of heat conveyed per cubic foot of air raised to any practical temperature is so small and so easily lost in transit. On this account Morin considers the availability (of hot-air furnaces) to be limited to a horizontal range of 40 to 45 feet from the heating apparatus."^ An equal quantity of heat, viz., 1 thermal unit, is required to raise 1 pound of water or 50 cubic feet of air 1 degree F., and accordingly water will carry more than four (4.21) times as much heat as an equal weight of air at the same temperature. "Further, a greater effect is produced when water, in the form of steam, is made the carrier of heat, because 1 pound of water vapor at 100° C. (212° F.) will, in condensing to form boiling water, give off suffi- cient heat to raise the temperature of 5.36 pounds of water (or 4.21 X 5.36 = 22.5 pounds of air) from 0° to 100° C. (32°to212°F.)."2 Hot-water heating may be by either the low-pressure or the high-pressure system. In the former, large pipes are used, and, the system being open to the air at its highest point, the temperature of the water can never be much above 212° F. at any part of the system. The water circu- lates comparatively slowly, but owing to the large volume, conveys much heat from the furnace to the places where it is needed. The high-pressure system employs small but very strong pipes, the water being completely enclosed from the outer air, wherefore it attains a high temperature and circulates rapidly. The necessary expansion is pro- ' Stevenson and Murphy, vol. i, p. 117. ' Notter and Firth, Treatise on Hygiene, p. 231. 140 VENTILATION AND HEATING vided for by larger pipes partly filled with air at the top of the circuit. The maximum temperature is regulated by the proportion of pipe, usually one-tenth, exposed to the fire. Either of the hot-water systems, but especially the low-pressure one, requires careful planning and setting to maintain evenness of circulation; and when the latter is complicated, as by many radiators at various levels, or where a number of circulations have to be supplied from the same boiler, it may be very difficult to maintain an • even head and an equable distribution of heat in all. "If properly constructed and the heating planned for when the house-plans are made, this hot-water system is probably the most economical, both in fuel used and repairs demanded."^ Steam-heating methods are usually quite satisfactory, not only because of the large quantity of heat carried, but also since a rapid circulation is readily maintained even under adverse circumstances. The size of pipe used will depend on the extent of the distribution, but the caliber of the radiator should always be considerably larger than that of the supply-pipes in order to favor condensation and the consequent liberation of latent heat, and every facility should be provided for the speedy return of the condensed vapor to the boiler. Care must also be taken to prevent the condensation occurring in such a way as to cause obstruction to the flow of the steam and the dis- agreeable thumping and noise that result. With either steam-heating or hot-water heating the direct, the indirect, or the direct-indirect method of radiation may be used. Of these, the direct method — that is, where the radiators are placed in the rooms to be warmed — is mdst commonly employed in dwellings and other buildings of moderate size; but it is open to the objections that in itself it does not bring about a sufficient change of air, that the necessary inlets and outlets for the latter are rarely provided, and that when present they 1 Coplin and Bevan, p. 325. METHODS OF DISTRIBUTING HEAT 141 are independent of the heating system of the house. Of course, these objections are wanting when the direct is combined with the indirect method, or when a plentiful supply of pure air is brought from without and is warmed by being made to pass through the radiators (either open or enclosed in boxing) before diffusing through the room. In the indirect method the radiators are placed outside of the room in suitable and convenient enclosures, into which fresh air is brought from out-of-doors, and from which the warmed air is conveyed by suitable conduits Fig. 32. — Indirect radiation. to the respective rooms above. The direct-indirect method locates the radiators in the room, but encloses them and provides inlets to the boxing from without, so that the entering air must pass over the heating surface and be warmed before entering the room. If properly arranged, both the indirect and the direct-indirect methods should furnish good and ample ventilation, the incoming warm air pushing the used air of the room ahead of it through the various openings in the walls of the room. Safety- 1 Figs. 32, 33, and 34 are used by courtesy of The American Radiator Co. 142 VENTILATION AND HEATING valves on steam boilers lessen the risk of explosions, and automatic thermo-regulators make it possible to maintain a practically even temperature throughout the house or building at all times. But there must be some arrange- ment for supplying additional moisture to the warmed air, just as with hot-air furnaces, for, contrary to the opinion of many, neither the steam nor hot-water systems increase the atmospheric humidity. In the clinical amphitheatre of the Medico-Chirurgical College of Philadelphia the indirect system is employed, Fig. 33. — This illustration shows a good method for incasing indirect radiation and also suggests a simple way to secure rotary circulation of the air in the room when it becomes desirable to shut off the out-door supply. The registers in the floor, however, are not advisable, as they readily collect dust and dirt. the details being as follows: The out-door air is brought from near the roof-level through a large shaft into the cold-air room, where it is moistened by a spray and whence it passes through a dust-filter, consisting of a double layer of fine wire-gauze. Thence it passes through tempering radiators (to raise the temperature partially) into the revolving fan, driven by its own engine, whence part passes through a second and larger radiator to be further warmed, and part below the latter, the two cur- rents again uniting and, after mixing, passing through the flues into the amphitheatre above. In this the tempera- AREA OF RADIATORS 143 ture is regulated by a thermostat, the latter governing a damper (not shown in Fig. 35) which always permits the same volume of air to pass into the flues, but controls the respective proportions of heated and tempered air, so that the mixture practically does not vary in temperature. In this way 900,000 cubic feet of air at a fixed tempera- FiG. 34. — Direct-indirect radiation. ture can be supplied per hour. For the private operating- rooms the system is the same except that the tempered and the heated air are not mixed, but each is carried by separate flues to double registers in the operating-rooms. In this way each operator can have the temperature that he desires in his room at any time. 144 VENTILATION AND HEATING Another excellent method is to use the plenum system, and to warm or "temper" the incoming air, either before or after it passes through the driving fan, to a temperature somewhat below that desired in the rooms, in which steam or hot-water radiators are suitably located. The air will then pass from the inlets more or less directly to the radia- FiG. 35. — Steam radiators and blower used in warming the clinical amphitheatre of the Medico-Chirurgical College of Philadelphia by the indirect system. (The casing of the radiators is not yet applied.) Tem- pering radiator at left; warming radiator at right; casing of fan between. tors and be additionally warmed by them before rising above the lower levels of the room. In this way the regulation of heat and the circulation and distribution of the fresh air are much improved, and there is less like- lihood of the latter going directly from inlets to outlets. To determine the amount of radiating surface needed for any room, we must multiply the volume of air to be AREA OF RADIATORS 145 heated per hour by the difference betweeji its temperature in degrees Fahrenheit before and after warming, and divide this product by 50, the quantity of air in cubic feet raised 1 degree F. by 1 thermal unit. This will give the number of heat-units required to warm the air. Then this quotient must be divided by the dift'erence between the temperature of the radiating surface and that of the air when finally warmed multiplied by 1.75 — the number of thermal units given off per hour by 1 square foot of hot-water or steam-pipe for each Fahrenheit degree of heat it loses. This will give the area of hot-water or steam-pipe required to w^arm the given volume of air. Thus, to warm 6000 cubic feet of air per hour from 20° to 70° F. will require 6000 X (70 - 20) ^„„^ ^ ^-- = 6000 heat-units. 50 and if the temperature of the surface of the radiator be 200° F., 6000 (200° - 70°) X 1.75 26,37 square feet, which will be the area of radiating surface required. To this must be added at least one-half square foot for each square foot of window-glass and for each square yard of outer wall exposed. 10 CHAPTER V. WATER. Next to air, water is the most important of all sub- stances necessary to human life. While it has been often demonstrated that man may do without food for a con- siderable length of time, even for several weeks, he can probably not survive much more than ten days without water. Not only must one have sufficient to supply the internal wants of the body and to replace that lost by excretion, evaporation and respiration, but from a sanitary point of view a plentiful supply is also needed to maintain cleanliness of bodies, clothing and dwellings, and oftentimes to remove sewage, excreta, etc., from the vicinity of inhabi- ted places. The care of furnishing water in abundance and of maintaining its purity is therefore entirely within the domain of the physician and the sanitarian. Before inquiring into the sources whence we obtain the water that we use, it will be well to know what amount is required by the body for its daily needs and how much for other necessary purposes, so that we may be able to judge not only whether a given source furnishes pure water, but also whether it gives a sufficient supply of it. The average adult should take from 70 to 100 fluid- ounces per day for nutrition and internal needs of the body alone — about one-third of this being a component part of the food and the rest being taken in as drink. The writer is of the opinion that the average person does not imbibe enough water for the most healthful action of his tissues and organs. Certain it is that in most cases the plentiful use of a good drinking-water not only greatly favors the body metabolism, but also materially assists in (146) AMOUNT NEEDED DAILY 147 the flushing out and carrying away of the various wastes and excreta of the system. In addition to this we must supply a sufficiency for cooking and for washing the food, body, clothing, house- hold utensils and parts of the house itself, and to remove the household waste and sewage through the drains and sewers provided for that purpose. Cleanliness is an essen- tial requisite for the preservation of health, and cleanly habits should be inculcated among all classes of people and every facility provided"'for removing filth of all kinds from persons, clothes and dwellings. This, of course, can- not be done without an abundant supply of water. Experience shows that about 25 gallons per head per day should be furnished for the above purposes, and as the quantity used by domestic animals, manufacturing establishments, municipal needs, etc., must be added to this, 50 gallons or even more per capita should be the daily quota for a community wherever it is at all possible to secure it. And though a supply that permits of excessive waste may be inadvisable and expensive, both in its pro- vision and on account of increasing the cost of carrying it away after use, it is always better to have too much than too little, and the disadvantages of too scanty an amount are much greater than those of one too large. It should be stated, however, that most foreign cities are supplied with much less water per capita than is apparently needed by the municipalities of this country, and yet they seem to have an abundance for all necessary purposes and the requirements of public health. For instance, London has an average daily supply of about two-thirds that of Philadelphia with one-third the number of inhabitants; while Berlin, which has about the same population as Philadelphia, had in 1905 an average daily supply of filtered water of only 22 gallons per head, all of which was sold to consumers by meter, but to which must be added considerably more that was from wells and other sources and was exclusively used for manufacturing purposes, running machinery, etc. Undoubtedly the quan- 148 WATER tity wasted in many of the cities in this country is exces- sive, and the cost of supplying that part of the total quota would go a long way toward improving and rendering pure and safe the remaining part that is absolutely needed. Whether the compulsory use of water-meters is the best way of bringing about an improvement in this respect remains to be determined; but it is also a question whether our larger cities, with rapidly increasing populations, can afford to continue to expend the money necessary to purify the enormous and increasing quantities of water daily supplied to their respective consumers. With the obser- vance of due care and conservation, a daily average of 100 gallons per capita would probably be found to be a reason- able maximum for almost any community. As only a small portion of the quantity indicated above is required for the internal needs of the body, it has been suggested that two kinds of water be furnished to each dwelling — one for drinking and cooking purposes and for the washing of the body, to which especial attention as to purity should be given; and another kind for all other purposes, its composition and purity being disregarded, excepting possibly as concerns the hardness. This would enable the authorities to furnish a water purer than usual for those needs wherein purity is of the greatest impor- tance, and would obviate the necessity of furnishing pure water abundantly for all purposes; but the plan would necessitate a double set of reservoirs, mains, distributing apparatus, etc., thus materially increasing the cost; and there would always be present the danger of the careless or ignorant using the impure water for bodily needs, thus increasing the risks and bad results that we wish to avoid. Therefore, wherever there may be an abundance of pure water for all personal and domestic purposes, if the authorities but take pains to furnish it, it will be best to have but one supply in dwellings, and this as pure and abundant as money and the ablest sanitary skill can make it, though there may be little or no objection to using a different water for factories, stables, city functions, etc. As to the question of supply through meters, it may be SOURCES OF WAT Eli 149 added that the suggestion has been made that the regular charge for water begin only after a certain specified amount per month per capita or per household has been furnished free or at the lowest possible cost, thus doing away with the objection that those who need the w^ater most for per- sonal and sanitary uses would be tempted to economize too much if they had to pay for all they consumed. To com- pensate for this it might be wise to arrange a sliding or increasing price scale for larger quantities. Whether a city could afford to do this, would have to be carefully considered, and would probably depend largely upon local conditions. Another method is "to assess every owner of premises where water is used (and measured by meter) a certain moderate, but fixed, sum yearly, even though w^ater used at the regular rate per thousand gallons does not call for so much charge." This initial sum should be considerably less than the rate necessary under the old method, and in itself would be an inducement to the introduction and use of meters. Any water used in excess of the volume repre- sented by this primary charge is, of course, to be paid for at the regular meter rate. Experience shows that meters greatly reduce the total consumption of water, since it is to the direct advantage of each consumer to check reckless waste on his own premises, which duty is otherwise neglected because it does not affect the yearly charge and cost of water to him. Meters, wherever used, seem to have materially reduced both the cost of water to the consumer and the cost of supplying it on the part of the city or other owners of the water- works, and, so far as the writer knows, no city or community that has once installed a meter system has discontinued their use. SOURCES OF WATER. Practically, all drinking-water has at some time or other fallen upon the earth from the atmosphere in the form of rain, hail, snow, or dew; but when we speak 150 WATER of its source we have reference rather to the immediate place or locality from which we collect it for use. The Fig, 36. — Cistern and filter installation. Approximate cost, S150. A, Hogshead or large tank; B, tight-cover; C, wire screen; D, |-inch 2-way rain cock; E, |-inch union; F, |-inch brass or galvanized pipe, perforated; G, tight overhanging cover; filter box may be wood, iron, brick, concrete, or 4 feet of large-size vitrified pipe; H, 24-inch layer fine sand; /, 6-inch layer well- burned wood charcoal size of wheat grains; J, 2-inch layer of gravel size of a small pea to give support and drain- age; K, 1-inch 2-way rain cock with 1 branch piped to waste; L, suction pipe; M, cistern, side walls 6 to 10 inches thick; A'', 1-inch overflow; O, sump or catch basin; P, emergency overflow; Q, screw cap (remove cap and attach hand pump when cleaning cistern); R, waste pipe; S, swing check valve; T, screened ventilator. When starting operation, waste the first water filtered; throttle cocks D and K to give the desired low rate of filtration; maintain water level above sand layer, thus protecting the surface film of mud. (Water System for Farm Homes, U. S. Depart- ment of Agriculture, Farmers' Bulletin, p. 941.) rain on reaching the earth is disposed of in three ways: part at once evaporates and goes back to the atmosphere, part flows off according to the slope of the ground and RAIN-WATER 151 collects in pools and streams, and part sinks into the soil. The ratio which these three portions bear to one another depends on the time, place, character of soil, amount of rainfall, etc. Consequently, we may classify the sources of potable waters — as Leffmann does — as follows: rain-water, collected immediately as it falls in the form of rain, dew, snow, etc.; surface-water, collected in ponds, lakes, streams, etc., and in free contact with the air; subsoil- or ground-water, derived mainly from the rain- or surface-water of the district, but which percolates and flows through the subsoil and is therefore not exposed directly to the atmosphere; deep- or artesian-water, which is separated from the ground-water of the district by one or more practically impermeable strata, and which accu- mulates at a considerable depth below the surface. Springs are the result of the out-cropping of water-rbearing strata below the level of the water-line in them, and furnish either subsoil- or artesian-water, according to the kind contained in the respective strata. Rain-water is theoretically the purest at our command, but in reality it takes up many impurities from the air in its fall, especially in the neighborhood of human habita- tions and communities, and by the time it reaches the earth contains ammonia, nitrous and nitric acids, and, in towns, sulphurous acid, soot, many bacteria and other microscopic plants. Moreover, and especially after con- tinued dry weather, the collecting surface upon which it falls is apt to be covered with dust and impurities of all kinds, which, being taken up by the rain-water, tend to make it unfit for use. But if there be some arrangement for turning aside the first portion of the rain, it contain- ing the most of the impurities, and if the remainder be filtered and stored in proper receptacles, the water may be of excellent quality. The main objection, however, to the sole use of rain- water is that dependence is placed upon a very uncertain source, and one which is especially apt to fail when an increased supply is most needed. The average rainfall 152 WATER in Philadelphia is about 39 inches per year; in very wet years it is about one-third more, and in very dry years about one-third less than the annual average. Each inch of rainfall gives 4.67 gallons per square yard of area on which it falls, equivalent to 22,617 gallons per acre. Allowing 60 square feet of collecting surface per head and estimating the loss by evaporation, etc., at 20 per cent., an annual rainfall of 30 inches would give only about 2 gallons per head per day, or just about sufficient for Movable covering stone. Paving. Level of ground. W/7Z!^>///////////y////////////////^^?i^:=r^^ Fig. 37. — A simple filter for rain-water. (Notter and Firth.) ^ drinking and cooking purposes, and none for the other needs of the household. Rain-water may be collected from roofs or from a plot of ground paved for the purpose with slate or cement, and be led by proper conduits to a cistern. It should be filtered before passing into the cistern (Figs. 37 and 38), while the cistern itself should be such as to give no unpleasant taste ^ Fig. 37 illustrates a filter for an underground cistern. One of similar construction can be readily made for cisterns above ground, the latter being always preferable. RAIN-WATEH 153 or injurious substance to the water, should be so situated that it will receive no rubbish or impurities and that the water may be kept cool, and should be cleaned regularly and sufficiently often to keep the water sweet and whole- some. As rain-water contains considerable carbon dioxide and other gases, its solvent powers are increased, and cisterns should not be lined with lead, copper, zinc, or iron, lest these metals be taken up by the water and produce harmful results. These remarks do not apply to the so- 1 L. 13Z TOP V/£kV LONGITUDINAL SECTION. Fig. 38. — Cistern filter of concrete and stone. (Bulletin No. 57 of the U. S. Department of Agriculture.) called rustless iron now much used; but galvanized iron should not be used, as it may give up zinc to the water. Cement should also be used in lining brick or stone cisterns instead of ordinary mortar, as the latter may add lime to the water and render it hard. Underground cisterns for storing rain-water should be avoided where possible, since they are liable to soil-air or sewage contamination unless absolutely air- and water- tight. Nor should the overflow pipe from a cistern open into a soil-pipe or sewer-pipe or drain, but always into 154 WATER the open air, since water is very prone to absorb the vari- ous gases with which it. comes in contact and the sewer- air may readily contaminate the entire contents of the cistern. Rain-water is especially valuable for cooking and wash- ing on account of its softness, water being called "hard" when it contains an excess of the salts of calcium or magnesium in solution. Hardness due to the presence of calcium bicarbonate is said to be temporary, because it disappears when the water is boiled, one molecule of carbon dioxide being driven off by the heat and leaving the insoluble calcium carbonate behind. Hardness due to many of the other salts of calcium and magnesium is called per- manent, because it is not removed by boiling. In cooking with water temporarily hard the chalk is precipitated upon the sides and bottom of the vessel, and, being a non-con- ductor, prevents the passage of heat and thus wastes fuel. Hard water may also prevent the proper softening of certain foods, such as peas and beans, in cooking. In washing and laundry work the calcium and magnesium salts unite with the fatty acids of the soap and prevent the formation of a lather; for instance, one grain of chalk destroys the efficiency of about eight grains of soap. As we do not call a water hard unless it contains more than ten grains of chalk or its equivalent per gallon, and as rain-water rarely contains more than one-half grain per gallon, it is easily understood why the latter is so valuable in the kitchen and laundry. Surface-waters. — A water-supply taken from rivers or smaller streams not polluted by the refuse and sewage from towns, factories, or cultivated farm-lands higher up the stream, may be fairly pure and safe to use. The best water of this kind will be from hilly and uninhabited, uncultivated tracts, with many small streams fed by con- stant springs and uniting to form rapid creeks and rivers. Such water may be tinged slightly with vegetable or mineral matters, but in general such coloration is harm- less. For storage, dams may be thrown across convenient SURFACE-WATERS 155 valleys, thus impounding the water and at the same time exposing it to the oxidizing and aerating influence of the atmosphere and allowing the solid impurities to settle to the bottom. Small lakes or ponds may be util- ized to add to supplies of this kind, provided they be not stagnant nor have much decaying matter along their baiiks. On the other hand, water from a stream which has received the sew^age from a village or town of any con- siderable size, or the refuse of factories, or the drainage from large tracts of cultivated land, should be considered as at least suspicious. River-waters are generally hard and may contain any of the minerals in the soils which they drain or over which they pass; but the great danger is from impurities of animal origin poured into them along their course. It is not safe to depend altogether on the self-purifica- tion of sewage-contaminated rivers, as was formerly done, though a considerable portion of the sewage and filth undoubtedly is removed, part by oxidation by the air in the water, especially in streams flowing over dams, rapids, etc.; part by subsidence or deposition along the banks; part by fish and animalculse, and much by the myriads of saprophytic bacteria which such waters contain. If no additional pollution is added, what is left unchanged by the above purifying agencies is still further diluted by the supplies of pure water that every stream receives from springs along its banks and in its bed and from tributary streamlets, so that, though the water may never be so pure as it was originally, it may possibly become or, by proper filtration or other treatment, be made a safe and usable water. But where the proportion of filth exceeds a certain percentage, and especially where sewage is being constantly added, the contained oxygen is rapidly used up and oxidation ceases, fish and animalculse cannot live in the water for lack of sufficient oxygen, and though the heavier and larger particles of the sewage sink to the bottom or stick to the sides, they are stirred up and set 156 WATER in motion by any increase in the velocity of the current. The only remaining agents active in the destruction of the foul matter are the bacteria, but in themselves they are often insufficient for the task, and the water thus polluted is unsafe for use.^ (See Figs. 39, 40, and 42.) The greatest danger from sewage contamination, how- ever, is that it may at any time add to the water the germs of infectious disease, which multiplying rapidly and not being surely removed or destroyed by the ordinary agents or methods of water-purification, greatly increase the risks to health. It often fortunately happens that. Fig. 39. — Outcropping of water-table. (Harrington.) owing to the hostility of the saprophytic bacteria of the water, or to the presence of certain chemical substances, or to other unfavorable conditions, as of temperature and the like, these pathogenic organisms do not multiply so rapidly as they otherwise would, and are therefore not plentiful enough to do much harm. But, as it never can be cer- tainly told when a water so contaminated becomes safe for 1 According to the report of the Rivers Pollution Commission some years ago, no stream in England is of sufficient length to purify itself satisfactorily of the sewage contamination it is liable to receive. On the other hand, according to a report (April, 1903) of the Commissioner of Health of Chicago, very careful and extensive investigation shows that the large quantity of sewage from that city discharged into the Illinois River has entirely disappeared long before the latter empties into the Mississippi at a point over 250 miles from Chicago. SUBSOIL- OK GROUND-WATERS 157 use again, and as the population of most towns and their consequent sewage production are constantly increasing, while the quantity of water in the receiving streams remains about the same or is diminishing from year to year, the use of such water should be avoided if possible; or, if it must be used, it should be purified and made reasonably safe by the most scientific and efficient means and methods available. Water from large fresh-water lakes will be of the best quality, provided it be taken from a point sufficiently distant from the shore to escape all danger of sewage contamination. Chicago apparently lowered the mortality percentage from typhoid fever from 7.2 in 1891 to an average of 2.1 for the decade 1896-1905, and to 1.1 for 1908, by preventing as far as possible the discharge of sewage into Lake Michigan and by taking the water- . supply from the lake at a minimum distance of two miles instead of 1400 feet from shore as formerly.^ Water from small lakes or ponds, and even from storage reservoirs, may become offensive to taste and smell through the growth in them of minute vegetable organisms, such as the algae, though it is not known that these are prejudicial to health. Subsoil- or Ground-waters. — Ordinarily, water loses much organic matter as it percolates through the soil, but takes up considerable carbon dioxide from the soil-air, which increases its solvent powers so that it may also dissolve some of the mineral constituents of the soil through which it passes. When these mineral substances become so great in amount as to give the water a decided taste or medicinal properties, we call it a mineral water; but when the inorganic matter does not render it ob- jectionable to the taste or too hard, the water, whether subsoil or artesian, will usually be quite safe and usable in so far as the mineral matters are concerned. Attention has already been called to the pollution of 1 One water-supply extends only 3300 feet out into the lake, but this supplies not more than 12,500 persons in the extreme north end of the city, and the water is sand-filtered. 158 - WATER the soil. How, then, can the water in passing through it lose its organic contents and become pure? Partly by mechanical filtration, but mainly through the combined action of the saprophytic soil-bacteria and the oxygen of the soil-air, which rapidly convert the organic impurities, both suspended and dissolved, into simpler and harmless end-products. The substances of vegetable nature are ultimately resolved by these agencies into carbon dioxide, water, etc., while those of animal origin and containing nitrogen give rise to the various ammonia compounds, or may be further oxidized into nitrous and nitric acids and their salts, all entirely harmless in the proportions in which they are found in the percolating ground-water. River Flood plain Fig. 40. — Section showing relation of water table to surface irregu- larities. (U. S. Geological Survey, Water-supply Paper 255.) but all of great value as nutrients for the higher plant- life of the soil. The rate of percolation has much to do with the com- pleteness and perfection of this action, for ample time ,^ must be had for the organic decompositions to occur. Therefore, anything that retards the downward flow of water favors its purification, and anything that increases ^ its movement decidedly affects for the worse its ultimate quality and character. The importance of this biological soil action can scarcely be overestimated, and the student should endeavor to appreciate not only the bearing which it has in the great scheme of nature's adaptation of means to ends, but also FLOW OF SUBSOIL-WATER 159 the importance of our utilization of it in the artificial purification of our environment and in the disposal of waste matters. We must understand, however, that for every soil only a definite amount of work can be ac- complished by the agencies mentioned and under the Fig. 41. — Diagram showing how wells and springs may be affected by geologic conditions, surface elevation and by differences in location and depth. A, limestone showing both small and large passageways; B, jointed crystalline rock; C, solid crystalline rock; D, alluvial soil; E, comparatively impervious stratum, as clay; F, stratum composed of sand, gravel, bowlders, clay and mixtures of them; G, comparatively impervious stratum, as clay or hardpan; H, porous sandstone; J, fissure spring (may be contaminated easily by campers or others) ; K, water table or line below which ground is saturated; L, flowing well (strikes joints carrying water) ; M, non-flowing well (strikes no joints) ; A^, shallow well (strikes a pocket of sand) ; O, seepage spring (yield small and perhaps during wet weather only); P, shallow and poor well; Q, artesian well (strong flow); R, artesian well (bottom in sand, flow mod- erate) ; »S, T, non-flowing artesian wells (head insufficient to force water to the surface of the high ground) ; U, well in clay (no yield) ; V, shallow well in sand ; W, hillside spring (both V and W are liable to contami- nation from the house wastes above) ; X, shallow and dry well (bottom in clay and against a bowlder) ; Y, flowing well (bottom in sand) ; Z, dry well (same depth as well Y but sunk where the water-bearing bed thins out). (Water Systems for Farm Homes, U. S. Department of Agriculture, Farmers' Bulletin, p. 941.) conditions existing at any given time. In other words, there is here also a limit of permissible impurity, and if this limit is exceeded, the conditions become unnatural, the bacterial and chemical action is inadequate, and the descending water is not thoroughly purified as it perco- lates through the overcharged soil. 160 WATER The subsoil-water slowly sinks through the ground until at some level or other it reaches an impermeable stratum, where it is retained in natural basins or escapes at some outcropping of the stratum below the water-level, thus forming a spring. (Figs. 39, 40, and 42). The level of the water in these undergound reservoirs is constantly changing according to the season, rainfall, discharge from springs, etc., though ordinarily the variation for any given place differs little from year to year. It is from wells sunk to these water-bearing strata and from springs that water is obtained for the majority of people who do not live in towns or cities supplied by water-works (Fig. 40). These Fig. 42. — Representing the difference between shallow and deep wells, and between the high-water and low-water level of the ground-water: a, soil and gravel ; b, clay or rock ; c, c, high-water, and d, d, low-water level. underground bodies of water are in constant motion toward one or more outlets at more or less distant points, but the currents are usually quite sluggish owing to the friction and capillary force of the particles of soil through which they pass. For the same reasons the surface of the water is not horizontal but curved, the curve being sharpest near the outlet, and the difference in level between high and low water is least near the outlet; also, the higher the level the greater the fall to the outlet and the greater the discharge. (Fig. 42.) The outflow from most continuously flowing springs represents the percolation through and drainage of such CONTAMINATION OF SUBSOIL-WATER 161 a comparatively large area that it is not probable that any considerable proportion of this area will be exces- sively polluted, nor that the percolate from any and all overpolluted parts of it will be so concentrated and charged with harmful impurities that the thoroughly puri- fied water from the remainder of the area will not be sufficient to dilute it sufficiently to eliminate all danger to health from its use. Consequently, springs are to be Fig. 43. — Map showing position of water-table by contours (contin- uous lines), lines of motion of ground- water (arrows), and surface- streams. (U. S. Geological Survey, Water-supply Paper 255.) ranked among the best and safest sources of natural waters, and general experience sustains the judgment. But the remarks regarding the purity of spring-water do not hold good for water from ordinary shallow wells — provided they do not pass through an impermeable stratum — or from springs where the water passes almost directly from surface to outlet, for in both cases the filtering action of the soil and the removal of organic 11 162 WATER matter by the prolonged action of the saprophytic bacteria are Ukely to be incomplete and imperfect. Likewise, water from springs that drain a limited and extensively polluted area may be seriously contaminated, and unsafe to use. Especially about human dwellings, where wells are com- monly located for the sake of convenience, are filth and pollution likely to be carried into the water, for sewage and dirt of almost every kind accumulate in constantly increasing quantity in the soil about a house, and always tend to exceed the limit of permissible impurity. There is also the ever-present danger of the water receiving the specific germs of disease from the human wastes of the household, no matter in what condition the surrounding soil may be. In this connection it is well to call attention to the fact that the visit of a transient and possibly unsuspected typhoid- or other "carrier" to a house or locality may be the source of an infection through the well-water and thus serve to explain the occurrence of a given disease where it has not occurred for a long time previously, if ever. Owing to the lessening of lateral resistance the surface- water passes rapidly and almost directly into the well (unless the wall of the latter be made water-tight to almost the full depth), and may carry with it solutions of all the impurities polluting the soil about the mouth ; and as wells drain a very considerable area — Parkes says one, in ordinary soils, whose radius is equal to four times the depth of the well — there are few wells about which such an area is not subject to dangerous pollution. (Fig. 44.) Moreover, the influence of pumping or other sudden with- drawal of water from the well is even more important, since it extends a distance from 15 to 150 times the tem- porary depression of the water-level, and impurities may thus be drawn into the well which ordinarily would tend to flow away from it. (Fig. 45.) Excepting the bacteria, which pass freely through almost all soils when resistance to the water-current is DEEP WATERS 163 markedly diminished, only such portions of the pollution as can be dissolved may reach the water in the well; and it is a fact that many waters thus polluted are sparkling and clear, with a pleasant taste and no bad odor, so that any suspicion as to their real character may be wanting. Moreover, even though specific disease germs be absent, there is always danger that the contamination may become so concentrated as to produce serious results, and this may occur in various ways: (a) the well may be so deep or the character of the soil such that in ordinary weather the liquid passing through the soil is so purified Fig. 44. — Representing the difference of percolation about cased (d) and uncased (e) wells: a, soil and gravel; b, clay or rock; c, cesspool. that it imparts no harmful properties to the water; but if the soil is being continually infiltrated with dangerous impurities and if, at length, heavy rains or continued wet weather supervene, there may be more and more of these impurities dissolved and carried into the well until the proportion of harmful matter in the water passes the safety-line, and as a result there is marked illness or increased predisposition to disease among those using the water; or (6) in continued dry weather the ground-water may be lessened to such an extent that the impurities that were formerly well diluted become sufficiently concen- 164 WATER trated to cause sickness, even though there be no unusual pollution of the soil about the well; or (c) the water-level in the well being suddenly or persistently lowered, a greater area is drained and additional collections of sewage may flow into the well. (Fig. 44.) Deep Waters. — Deep wells are those which pass through an impermeable stratum, and so do not get their supply from the subsoil-water. The relative depth of two wells is no exact criterion as to their classification, as the shal- lower one may really be a "deep" one and the deeper a "shallow" one, according to the presence or absence of Fig. 45. — Showing depression of water in shallow well caused by pumping: A, well; B, cesspool; C, underground water-curve. (After Field and Peggs.) the impermeable stratum. Artesian wells are very deep wells, piercing one or more impermeable strata. Sometimes the water rises and flows out of the mouth of a deep well, in which case the supply is drawn from a water-bearing stratum between two impermeable ones, and which has its only outcroppings higher than the top of the well. (Fig. 46.) The water accumulates in this natural reservoir above the level of the well-mouth, and is forced out when an opening is made through the uppermost impermeable stratum. Deep well-water is apt to be of much better quality than that frona shallow wells, since it PURITY OF DEEP WELL-WATER 165 usually represents the total percolation from a very large extent of ground surface, within the limits of which the combined areas and amount of pollution are insignificant in comparison, any possible impurities in the water being consequently reduced by dilution to much below the danger-point. It is for the same reason that there is such a difference in the quality of spring-water and of that from most shallow wells. Though the two waters seem to have a common source, one is the composite water of a large district, in which the average impurity or con- tamination per unit of surface may be infinitesimal; the other is mainly the special percolate from a limited area, which is, for the reasons given, particularly liable to be highly and dangerously polluted.^ Fig. 46. — Representing the spontaneous flow of deep or artesian wells, B and C: a, a, water-level in deep pervious strata, F, F; A, intermittent spring at out-cropping of F, F above impermeable stratum, E, E; D, shallow well in upper pervious strata. (Wilson.) It is also to be remembered that in many of the strata or beds supplying deep or artesian wells the water has been collecting for a very long time, possibly even for centuries, and it is incredible that organic pollution should persist with power for harm through periods of such duration. Artesian or deep well-water will also likely be very free from organic matters, but possibly heavily charged with ' Of course, the water in shallow wells, as in others, is being continu- ally changed by the onward movement of the underground current; but where this is slow in comparison with the percolation from the surface, the impurities of the latter will be in excess in the well-water. 166 WATER mineral salts. Should these latter not be present, the water will probably be of excellent quality; though if the well be very deep, it may be too warm for immediate use as a potable water. Frequently well-water, and that most often from shallow wells, is the only kind available, especially in country districts. In such cases care must be taken that impurities are kept out of the well by all possible means. If this be done, water may often be had of excellent quality. The area about all wells should be kept clean, and the well should be as distant as possible from any source of con- tamination, especially if the latter be a constant one. Wells should be walled or cased, shallow wells to below Fig. 47. -Diagram showing ordinary location of farm well. (U. S. Geological Survey, Water-supply Paper 255.) the water-level and deep wells to the first impermeable stratum, if possible, in order to cause the water to percolate through as much soil as possible before entering the well, in this way checking the rapidity of its descent and prolonging the biological action of the top-soil.^ Wells 1 As the saprophytic and nitrifying bacteria are only found normally in the first few feet of top-soil, where the conditions are favorable to their existence and growth, we cannot expect to have any further action by them after the water reaches its underground level and begins to move toward its outlets. Nor will there be any filtration in this on- ward progress, for that has been accomplished in the upper layers. It is for this reason that the filtrate from cesspools and similar pits is not organically purified, but is especially obnoxious and dangerous as it traverses the soil, for the bottoms of such pits are usually below the biological level, and there is also in them a lack of the oxygen necessary to maintain the action of the nitrifying bacteria. TESTING OF WELL-WATER 167 should also have a properly constructed covering and curb, to keep out splashings and drippings of muddy or dirty water. (Fig. 48.) In this connection Sedgwick says: "Excepting those cases in which cracks or fissures in the earth allow direct communication between polluting sources and wells of drinking-water, the author is strongly of the opinion that in most cases in which infection exists in wells, the pollut- ing material has found its way in from the top." "When one reflects on the carelessness with which wells used as sources of drinking-water are exposed to the access of filth from the top, such wells often being only loosely covered by planks, it is easy to see that from the boots of work- FiG. 48. — Well protection. (Bulletin 57 of the U. S. Dept. of Agriculture.) men, or from children playing on the planks, or from poultry walking about and carrying infection on their feet, pollution may take place. "^ We must not forget that wells drain a large area. As the ground-water has a constant movement in the direc- tion of natural outlets, the well should be so located that the current flows from it toward any near-by cesspool or other source of pollution. (Fig. 47.) The direction of the underground current can generally be determined by not- ing the location of the nearest spring or water-course, by Principles of Sanitary Science and the Public Health, 1902, p. 351. 168 WATER observing the dip of the underlying strata, or by digging holes at equal distances about the well and dissolving salt or an aniline dye in them in turn, and testing the water from the well after a time for the salt or color. If a well be much deeper than a neighboring cesspool, it may drain from the latter, even in opposition to the ground- water current, especially if the water in the well be sud- denly lowered. Again, dangerous impurities have been carried into wells from long distances through fissures or Fig. 49. — Diagram showing danger of pollution where casing is carried only to rock. (U. S. Geological Survey, Water-supply Paper 255.) crevices in rock. Harrington cites the case of a well which, "bored 500 feet into red sandstone, drained, through fis- sures, all the shallow wells in the vicinity. These being of no use as wells, were then utilized as cesspools, and draining again through the fissures, caused the well to become so foul that it had to be abandoned." (Figs. 49 and 50.) The water from the well should be frequently tested for chlorides and nitrates, these usually indicating sewage con- tamination, and this should be done especially after heavy WATER-SUPPLY AND TYPHOID FEVER 169 rains and also when the water in the well becomes low. The taste and odor of the water should also be noted after standing for a time or on being heated. Some other sources should be sought whenever such tests show con- tamination or when there are cases of infectious disease near at hand. Boiling the water and filtration are always to be recommended whenever there is the least suspicion as to impurity or infection. Fig. 50, — Pollution of subsurface-water in limestone. (Bulletin 57 of the U. S. Dept. of Agriculture. Shallow or subsoil wells in thickly settled towns should not be used to supply drinking-water or cooking-water, as the soil is always more or less saturated with filth and sewage, and it is practically impossible in such places to locate a well w^hich will not be in constant danger of receiving harmful impurities from some source or another. In an investigation^ made by the author in 1904 he discovered that the incidence of typhoid fever is greater in districts essentially rural, and not in those which include the great cities, many of which latter are known to have had high death-rates from this disease, and all of which have water-supplies which may, if not properly cared for, serve as common carriers of infection to their enormous populations. As the data from which this study was made were taken from the Report on Vital * Typhoid Fever in Relation to the Urban and Rural Population of the United States, American Medicine, April 22, 1905, pp. 649-652. 170 WATER Statistics of the U. S. Census of 1900, it must be remem- bered that all cities and towns of less than 8000 popula- tion were classified with, and that they collectively made up a large, if not the greater part of the so-called rural population. Now, in the smaller towns and villages it is more than probable that the inhabitants are supplied from private and shallow wells and cisterns, rather than from common sources, such as reservoirs, springs, arte- sian wells or modern filter plants, and, consequently, there is continual danger in such communities of the water being contaminated by neighboring cesspools and other sources of pollution, this danger rapidly increasing as the villages grow in size, for these wells and cesspools are brought closer together, and the entire body of ground- water supplying the wells is correspondingly more liable to be polluted beyond the limit of safety or to become at any time the common carrier of infection. Hence it is easy to understand how the so-called rural populations actually have, as a rule, a relatively higher sick- and death-rate from typhoid fever than do the dwellers in large cities; and it should be equally evident that it will be the part of wisdom for small communities to employ every possible means to secure improved and non-polluted water-supplies for the common use of their respective populations. The decision as to the quality of any water must in each case be determined by all the circumstances available which relate to it, and these should all be thoroughly in- vestigated before rendering an opinion, as some of them may counteract the others. However, other things being equal, the value of a water will probably be in accord with the following table: 1. Spring-water, 1 Very Wholesome ■ 2. Deep well-water, / palatable 3. Water from unpolluted streams, \ Moderately Q . . f 4. Stored rain-water, / palatable, buspicious < g_ Surface-water from cultivated land. j^ f 6. Sewage-polluted river-water, \ 7. Shallow well-water. Palatable. CLASSIFICATION OF WATERS 171 Fig. ol. — Showing death-rates from typhoid fever in 1894 in sixty-six cities, grouped according to the quality of their drinking-water. (Re- produced with the permission of the author, Mr. James H. Fuertes, and of the Association of Civil Engineers of Cornell University.) 172 WATER We may also classify waters as follows: (1) Pure and wholesome water; (2) usable water; (3) suspicious water; (4) dangerous water. (See chart on page 171 and table on page 228.) Pure waters and usable waters may be used without filtration; those of the third class should be fil- tered before distribution, and also at the house before use, if possible, and a purer source sought or all sewage- pollution prevented. Those of the fourth class should not be used at all except when absolutely unavoidable, and then only after purification by all the means at command. Inasmuch as most large cities must from necessity fur- nish a water of the second or third, and occasionally even of the fourth class, such water should be purified as much as possible before distribution by storage for a time in settling reservoirs and by some effective system of filtra- tion, combining these with chemical treatment if necessary. As much of the organic matter is oxidized, and many of the pathogenic bacteria are destroyed by saprophytes and other causes while the water is standing in the settling reservoirs, and as properly constructed and well-managed filters are even more efficacious to this end, a water origin- ally suspicious or worse may often be made usable by the above means properly employed. Not only must the storage reservoirs and filtering apparatus be kept clean and in good working order, but care must also be had that the distributing apparatus does not permit soil-air or sewer-gas or sewage to be drawn in through leaks in the mains at times when the flow is intermittent, and that lead pipes are not used for conveying drinking-water if the character of the water is such that it acts on that metal. A good potable water should be perfectly clear, free from odor or taste, cool, well aerated and, if possible, soft or with only a mild degree of hardness. Circumstances must determine the amount of dissolved matters permis- sible; what is an excess in one case might not be so in another. DISEASES DUE TO IMPURE WATER 173 DISEASES CAUSED BY IMPURE DRINKING WATER. A polluted water may carry the organisms of infectious diseases, or it may cause or favor the development of dis- eases which are not due to specific germs. In addition to these, and of at least equal importance from a sanitary point of view, is the depressed state of the system that the habitual use of impure drinking-water causes, and the predisposition to disease that ensues. By the faculty of accommodation and through long habit a community may become so protected against an impure water as to mani- fest no striking symptoms, while strangers may be seri- ously affected by it; but even in such a case the condition of those habitually using the water will probably be more or less depressed and not that of perfect health. The non-infectious diseases likely to be caused by im- purities in the drinking-water are primarily those affecting the alimentary tract, as dyspepsias, diarrheas, and other disturbances having their origin in severe or chronic gastric or intestinal irritation. So, also, impure water, even though it does not contain the actual germs, may have much to do in bringing on an attack of typhoid fever, specific dysentery or other infectious disease by so lowering the resistance of the body as to make it espe- cially receptive to the cause of the malady when introduced from another source. Large quantities of the sulphates of calcium and mag- nesium are thought to have special influence in causing dyspepsias, with loss of appetite, pain at the epigastrium, etc. An excess of iron in water is also prone to produce con- stipation, headache, loss of appetite and malaise. Goitre and the formation of vesical calculi are each supposed to be due to mineral or inorganic impurities, although the true relation of impure drinking-water to these dis- eases is still unsettled. "It has long been a popular opinion that drinking lime-waters gives rise to calculi of the oxalate and phosphate of calcium," and the "opinion that impure water is the cause of goitre is as old as Hip- 174 WATER pocrates and Aristotle.'' Further study of the principles underlying the treatment of goitre with glandular extracts may make it easier to determine whether impure water has a causative influence in the production of this disease. Diarrhea may be caused by any of the following im- purities in water: suspended substances of any kind, but especially those of fecal origin; dissolved animal, vege- table, or mineral matters, and fetid gases. The diarrhea produced by any of these contaminants may be so severe as to simulate true dysentery and cause doubt as to the diagnosis. Certain metals may be taken up from the earth's strata, or from the lining of cisterns, pipes, etc., and may produce their characteristic toxic symptoms in the system. Lead is one of these metals, and it will be well to note here the waters that are especially apt to take up this metal. Pure waters and those containing much oxygen act powerfully on lead, as do those containing organic nitrates and nitrites, especially ammonium nitrate. Waters containing carbon dioxide and the salts of calcium and magnesium and those free from absorbed gases act least on lead, and carbon dioxide seems even to protect lead by forming an insolu- ble carbonate on leaden surfaces, but water containing car- bon dioxide may take up lead for a time from new pipes until the insoluble carbonate is deposited within them. It has also been shown that in some cases wherein cold water does not act upon the metal hot water will dissolve a small but appreciable quantity of it. Copper, zinc, and arsenic are also metals that may be taken up by certain waters, and that may cause serious results from the use of the latter. Lead is more easily dissolved if other metals are in contact with it, probably owing to electrolytic action. Lead should not be used for pipes nor to line cisterns unless suitable tests show that the water does not affect it, nor should any water be used in which the tests show more than one-thirtieth of a grain of lead per gallon. Of the infectious diseases, germs of typhoid fever, cholera, and dysentery are usually carried into the system TRANSMISSION OF INFECTION BY WATER 175 by the drinking-water, while the same is sometimes true of scarlet fever, diphtheria, and kindred diseases. For a long time the belief that malaria is very frequently, if not most often, transmitted by the drinking-water, was held by many sanitarians, and there has seemed to be much circumstantial evidence to substantiate this opinion. However, careful scientific investigation has proved that this disease can be, and usually is, due to direct inoculation by at least one species of mosquito, which acts as an intermediary host in the life-cycle or development of the malarial organism (Plasmodium H^Jalariae), and almost all authorities believe that the disease is only transmitted in this way. But, as with the impurities causing non-infectious dis- turbances, water containing disease germs may some- times be used for a long time by those accustomed to it without the development of the specific malady, and it may only be after the system is weakened by excesses or other predisposing conditions that the disease manifests itself; or it may happen that only strangers and non- immunized inhabitants incur the disease. It has been suggested that this immunity is probably brought about by the very gradual introduction into the body of the dis- ease germs and their poisons, so that residents of the locality are not susceptible to the small numbers or quan- tities of these which are sufficient to give rise to the symptoms of the particular diseases in newcomers. It is sometimes difficult to determine just when or how a water-supply has been infected with pathogenic organ- isms, but recently it has been shown that a person who has recovered from a transmissible malady may continue to carry about in his body and to excrete the disease germs for a long time. Thus the bacteria of typhoid fever may be found for months in the urinary or fecal excre- tions of a considerable proportion of those who have had that disease and, in some, for even years thereafter; many such cases having been reported by numerous investi- gators. It is therefore easy to comprehend how such a 176 WATER person, going from place to place, might infect not one, but many sources of water-supply. The following table gives data relating to some notable epidemics of typhoid fever: Location. Date. Lausen, Switzerland Caterham, England Plymouth, Pa. ' , Ithaca, N. Y. Butler, Pa. . . 1872 1879 1885 1903 1903-04 Population. Cases. 780 144 5,800 352 8,000 1,104 13,000 1,300 18,000 1,348 Deaths. 21 114 78 111 Many instances have been recorded which practically prove the transmissibility of infectious diseases by means of drinking-water, and of these, reference may be made to the epidemics of typhoid fever at Lausen^ in Switzer- land, at Plymouth, Pa.,^ Butler, Pa., and Ithaca, N. Y.; and of cholera in London.^ The writer himself had an opportunity of investigating an epidemic of typhoid fever in a small village in North Carolina.^ In this there were only four or five in about sixty cases which were not undoubtedly due to contamination of the subsoil-water by the infected excreta from the first case; and of four of the exceptions (which were in one family), the first was in all probability infected by using the water while in attendance upon sick neighbors, and the others by direct contagion from the first. It was also shown that, with the exception of these four, the cases all developed directly along the lines of natural drainage leading from the residence of the original case — a boy who came to the village sick with the disease— and that the latest cases to develop were those most remote from the starting-point of the infection. Moreover, in most large cities of this and other countries 1 Pepper's System of Medicine, vol. i, p. 250. 2 Roh6's Text-book of Hygiene, 2d edition, p. 63. 3 Ibid., p. 64. * University Medical Magazine, May, 1892. PARASITIC DISEASES 177 the typhoid fever death-rate is accepted as the direct index of the character of the water-supply, and it seems to be a fact almost without exception that any marked improve- ment in the latter will be followed by an immediate and positive reduction in the former. (See chart on page 171.) The same may also be said to hold good in regard to diar- rheal diseases; while in eastern North Carolina there has been a marked reduction in the prevalence of so-called malarial fevers — which are probably paratyphoid in reality — as a result of the efforts of the State Board of Health, to persuade the people to substitute rain-water or deep well-water for the subsoil-water which was almost universally used a few years ago.^ The ova of certain parasites, such as tape-worms or round-worms, may often be taken into the system with the drinking-water, and these upon developing may cause disturbances that may require more than the slight atten- tion usually given to them. Any attack of convulsions in a child or other severe manifestation of reflex action should lead to the inquiry as to whether these parasites may not be present, and whether the water-supply has not been the source of invasion. It is now known that the parasite of ankylostomiasis or hook-worm disease may also be carried by and intro- duced into the human body by the drinking-water. Regarding the foregoing remarks, Parkes makes the following statements: "(1) An epidemic of diarrhea in a community is almost always owing to either impure air, impure water, or bad food. If it affects a number of persons suddenly, it is probably owing to one of the last two causes, and if it extends over many families, almost certainly to water. But as the cause of the impurity may be transient, it is not easy to find experimental proof. (2) Diarrhea or dysentery constantly affecting a com- 1 According to Hazen, for every death from typhoid fever prevented by the purification of a polluted water-supply, two or three deaths are prevented from other causes. This statement, Sedgwick says, he has been able to confirm and to establish as conservative. 12 178 WATER munity, or returning periodically at certain times of the year, is far more likely to be produced by bad water than by any other cause. (3) A very sudden and localized outbreak of typhoid fever or cholera is almost certainly owing to the introduction of the poison by water. (4) The same fact holds good in malarial fevers, and, especially if the cases are very grave, a possible introduction by water should be inquired into. (5) The introduction of the ova of certain entozoa by means of water is proved in some places, probable in others. (6) Although it is not at pres- ent possible to assign to every impurity in water its exact share in the production of disease, or to prove the precise influence on public health of water which is not extremely impure, it appears certain that the health of a community always improves when an abundant and pure water-supply is given; and, apart from this actual evidence, we are entitled to conclude from other considerations that abun- dant and good water is a prime sanitary necessity." The statistics already given and those to come in later pages are confirmatory of the correctness of this last assertion, and sanitary authorities now realize that, in addition to the mortality from typhoid fever, the main cause of an increase in the death-rate from diarrheal diseases is more often to be fairly attributed to a contaminated water- supply than to improper food or untoward temperatures. Even with respect to cholera infantum (which is generally supposed to be principally due to the influence of excessive heat upon the infant and its food) a number of epidemics show a closer relation to impure water-supply than to temperature-changes. THE PURIFICATION OF WATER. Impurities in water may be either solid matters in suspension or dissolved substances, and may be organic or inorganic. Any turbidity is due to solid particles, and water free from these is clear, though it may be colored more or less deeply by dissolved matters. But a THE PURIFICATION OF WATER 179 clear water may contain such solid bodies as bacteria, animalculae, ova of parasites, etc., which are too minute to be seen with the naked eye. Whether harmful or not, all impurities should be removed in so far as it is possible from all supplies of drinking-water. This may be done to a considerable extent with large volumes of water before distribution to consumers, and should always be attended to by the latter if the water is not already clean and within the limits of safety when they receive it. In fact, a large city at the present time can scarcely have a more important subject for consideration than that of obtaining and supplying the purest possible water-supply to its people. There will always be a tendency among many to allow matters to continue as they are or as they have been in the past, and a decided objection by others to incurring additional expense for what may seem to them only esthetic reasons; but no matter what may be the cost of providing a reasonable supply of pure water for any city's personal and domestic uses, a very little consideration will show that such expenditure is true economy from solely a financial point of view, even though we ignore the misery and sorrow of the sickness and deaths that are due to the use of a polluted water. As has been stated by the excellent authority quoted above, "the health of a community always improves when an abundant and pure water-supply is given. The death of 3400 persons from cholera followed the temporary supply of unfiltered water by the East London Water Company in 1866, while the rest of London re- mained nearly free from the disease;" and in 1892 "Ham- burg lost 8605 citizens from the same disease alone," regarding which "the health authorities found that the principal cause of this epidemic was the polluted water- supply,"^ while the neighboring city of Altona, which used filtered water, was comparatively free from the disease. Again, after the scourge of typhoid fever in Plymouth, 1 Hazen, Filtration of Public Water-supplies, 1895. 180 WATER Pa., in 1885, when there were, within a few weeks, 1104 cases and 114 deaths in a population of less than 8000 as a result of pollution of the water-supply by a single person, great care was taken to determine the exact cost of the ''visitation," as some would term it. It was found that the actual expenditure for the care of the sick was $67,100.17; loss of wages by those recovering, $30,020.08; a total of $97,120.25, to which should be added a number of times the $18,419.52 that those who died were earning per annum when taken sick. How much cheaper in com- FiG. 52. — Portion of the boundary line between Hamburg and Altona. The dots indicate cases of cholera. (Harrington.) parison would a protecting filter-plant have been! But overlooking special epidemics, and considering the average annual typhoid death-rates of our cities, we find that experience, both here and abroad, shows that with a pure water-supply a maximum death-rate from this disease is 25 per 100,000, and that any city may reasonably expect to secure even a lower rate by observing proper pre- cautions. And yet thirty-one cities of over 25,000 population, including three of over 100,000 and seven others of over 50,000, whose mortality returns were FINANCIAL LOSS DUE TO DISEASE 181 given in the United States Census Reports of 191() had a higher rate than this, seven being more than twice as high. Lawrence, Mass., with a population of 44,654 in 1890, built a filter at a cost of $67,000, saved enough lives, at $5000 per head, to pay for it within the first four months that it was in use, and had a reduction of almost 60 per cent, in the typhoid death-rate within a year. In Chicago, when the similarly estimated loss from typhoid deaths in the city and suburbs amounted to over $10,000,000 in 1891, the abandoning of a shore inlet near the mouth of the sewage-polluted Chicago River in 1892 resulted in a reduction of 60 per cent, in the typhoid mortality during the following year. But it is only when one realizes that an increase in the mortality from any cause of only 1 in 1000 of population means 1000 additional deaths per annum in a city of a 1,000,000, that he can appreciate the meaning and the loss in capitalization to the municipality of the exceedingly high typhoid mortality that obtains in some of our large cities. Philadelphia's death-rate from this disease has dropped from an average of 61.3 per 100,000 of population foreach of thefive years, 1903-1907 inclusive, to7.6 for 1916, the installation of filter-plants for the entire water-supply of the city having been begun in 1902 and completed in 1911. This represents a saving of 918 typhoid deaths per annum based on the population of the city in 1916, and probably as many more from other diseases due to impure water. At the valuation of $5000 per capita — not an excessive estimate according to the finding of courts in cases of death by accident, and, inasmuch as most typhoid cases occur during the working age of from fifteen to fifty years — in one municipality, with an average population of about one-third of a million, the excessive typhoid deaths above a 25-per- 100,000 rate amounted in five years (1900-1904) to the astounding total of 1888, represent- ing in capitalization at the above life valuation the sum of $9,440,000. Nor must it be forgotten that these 182 WATER figures do not include the cost of medical attention and nursing for the thousands who were sick, nor the loss of time and employment by those who recovered, nor do they consider the financial loss due to sickness and deaths from diseases other than typhoid fever that may be fairly attributed to polluted water-supplies. Can anyone doubt where true municipal economy lies, and is there not abundant opportunity for sanitary education and work in this direction alone for many years to come?^ Purification before distribution may be by either or all of three methods: subsidence, chemical treatment, and filtration. Subsidence. — This method consists in allowing the water to stand in large reservoirs until the greater part of the suspended matters have fallen to the bottom. If sufficient time be given, much of the organic matter, whether solid or dissolved, will be decomposed or reduced to simpler compounds by the action of the sunlight, oxy- gen, animalculse, saprophytes, etc. Most of the bacteria also, especially the pathogenic species, will disappear either by sedimentation, by death from lack of favorable conditions, or on account of the germicidal effect of the sunlight. "The great source of ultra-violet radiations and 'the cheapest disinfectant known,' as Duclaux puts it, is the sun. Rivers and lakes are freed from a great part of their bacterial contents by the bactericidal powers contained in the sun's rays."^ Consequently, a water originally quite impure may be much improved by this method alone, while if it is used in conjunction with, and preliminary to, filtration it will be additionally advantage- 1 According to the Report on Mortality Statistics of the U. S. Census Office for 1916, the deaths from typhoid fever in the "registration-area" in that year numbered 9,510. The typhoid death-rate for the entire "registration- area" dropped from 35.9 per 100,000 in 1900 to 13.3 in 1916, and the average for the last five years (1912-1916) Was 14.75. This is higher than that of most European countries, the rate for Eng- land and Wales for 1905 being 8.9; for Germany, 6.3, and for Norway, 3.8 per 100,000. ^ Von Recklinghausen, Journal of the Franklin Institute, December, 1914, p. 683. I PURIFICATION IN RESERVOIRS 183 ous in that it reduces the cost of the latter by lessening the frequency and expense of cleaning the filters. What the capacity of the reservoirs and the time of storage should be, depend on circumstances. If it is the only method of purification employed, and especially if the water is very foul, the longer the time of storage the better. Again, if the source of supply is variable in out- put or if it is liable to excessive pollution for limited 1^ 100 80 60 PHILADELPHIA, PA.-TYPHOID DEATHS I 20 * r U ^ % ■3 ■S € ■3 € ■3 J % % ^ ■§■ -3 % 5 •3 •3 - 't' •♦-1 M +1 c4 +1 * ■H 3 -H ^ H 5 1 1 4 1 '. 1 1 1 1 1 ^ 4 4 ' 4 ■3 Fatefed P f\ he red^ + 63 )— 13- M "Z. ^ 1 i rrr 1 1 1 i r - j U U_ 1 1 . L- • ' ! "ri ,,,.,.. ,,,.,.. .j__ -^ h - ' ' "^ ' ' Ih'lau-itrc and xnii>ikitlKui.rs j i ; ■• fuliltered ■: , : . : - - !_^_,.^_>.....__i4— J "1 ' 'tillered; | | lO ?o «- CO cs o — ' '^» cc "^ «fl g ^ ^ ^ -, ^ Fig. 53. — Chart showing the influence of filtered water upon the typhoid death-rate in Philadelphia.* periods, the capacity should be such, if possible, that water need not be collected during the emergency. On the other hand, if the water is to be subsequently filtered, the capacity of the reservoirs and time of storage need not be so great. Most German authorities on filtration hold that preliminary sedimentation for twenty-four hours or even less is sufficient, most of the solid matters being pre- * Figs. 53, 54, 55, and 62 are available through the courtesy of the Bureau of Water of the City of Philadelphia. 184 WATER cipitated within that time, if at all, and the filters being relied upon to remove the remainder, especially the finer particles and the bacteria. The English practise is to store the water for a longer time, though local causes related to the source of supply are the reason for this. Thus the Lea and Thames, from which the London companies take much of their water, are subject to extra pollution in times of flood, which are usually of short duration, and a sufficient reserve for such periods is of obvious value. 400 PHILADELPHIA, PA, TYPHOID CASES PER WEEK 1904, 1913 AND 1914 'f^d Jr A t^ - 1 ^n -f- ^ " 4 4= - , \ :: Jl : n.t __ __ 5 s- \.% wj 1 t ± A X - U t zt : : 1 s. --i ' i -_ _:__ i z* Ca* : : '^ fc : ; \ j» ^ X - ^^i S »5 a^ L Z-t i - - ^^ ^' : _ . § ^ 9- ^* t 28^5 54 ^o Rq ^„ , \^ 55 ^^^X ^S. ttS^^i ^a^ - I Zhez^^^^S, t.^.lL^ a-S, 5^ ■ S^ 5 a'^ uiL 1^ 5 K fi^^ =t ^.-'•o't^ ^. ^' o -^^l Ficker, Archives of Hygiene, 1903, xlvi, 274. 262 FOOD Good milk in bulk should be opaque, of clear ivory- white color, should have no peculiar smell or taste nor leave any deposit on standing. Nor should it show any change in taste or appearance upon boiling, excepting the formation of the slight skin of coagulated albumin due to the heating. Details regarding the composition of milk and the methods for its examination will be found in the final chapter of this volume. The addition of preservatives to milk is very common, and should be discountenanced, not only because they are usually added in quantities harmful or prejudicial to health, but also, and almost more important, because milk should be supplied to consumers in such a condition and state as not to need the preservative, the presence of the latter being therefore suspicious. The same reasons also justify the condemnation of the use of artificial coloring-matters. The chemicals commonly used as pre- servatives are boric acid, salicylic acid, and formalde- hyde. Of these, the salicylic acid is probably most harm- ful, as the habitual ingestion of even a moderate quantity is apt to be deleterious to the kidneys. (See Chapter XIV.) Cheese is a most valuable foodstuff, and, as a milk- product, may be considered at this time. Good cheese usually contains twice as much nitrogen and three times as much fat as the same weight of meat, but many persons apparently find it difficult of digestion and can eat but little of it. This is perhaps because the nutri- ment is so concentrated and because, as usually eaten, it forms in the stomach a tough or pasty solid lump into which the gastric secretion cannot penetrate. Mattieu Williams has remarked that we habitually use cheese in the conditions in which it is most indigestible — either in its raw state or cooked into a leathery mass — and he asserts that if the cooking is such that it is thoroughly mixed with other articles of food, or if it be masticated with other food, so that this commingling of particles takes place, it will be found to be quite digestible by almost EGGS 263 every one. He also advises the addition of a small amount of potassium carbonate in the cooking, as this favors solution of the casein and replaces that salt which is removed in the whey. As a food, only cheese made from whole milk, or from that to which extra cream has been added, satisfies all requirements, and skim-milk cheeses are decidedly less nutritious than those having the full proportion of fat. Butter, consisting as it does largely of the fat of milk, is a highly nutritious article of food and one of the most digestible of its class. It should be pure, sweet, and free from rancidity, and while some of the substitutes offered in its stead are entirely wholesome, they should never be sold as butter or used to adulterate it. Neither should butter contain an excess of water nor of casein, as its food-value, weight for weight, is thereby accordingly lessened. EGGS. Eggs yield almost their full weight of food in a con- centrated and very digestible condition, and are valuable on this account, as well as for their palatability and their value in the preparation of many dishes. Although con- taining practically no carbohydrates, they have sufficient food-material in themselves for the complete develop- ment of the living chick with the aid of nothing external except the oxygen which passes through the shell: the lack of the carbohydrate element, ordinarily one of the essential food-principles, is supplied by the heat from the mother hen or incubator which is sufficient for the development and maintenance of the vital processes, since the unhatched creature wastes almost no energy in physical activity. The white of ^gg is almost pure albumin with a little water and some salts; the yolk contains about 30 per cent, of fat and some albumin. The albumin coagulates at about 170° F., but if it is exposed to a still higher 264 FOOD temperature for any but a very short period of time, it becomes hard and difficult of digestion. A so-called "soft-boiled" egg is scarcely more difficult of digestion than an uncooked one, and is certainly more palatable to almost every one. Eggs, milk, and cheese may be made into many nutri- tious and palatable combinations which furnish food especially agreeable to the sick, as well as to those whose appetite and digestive functions have not been impaired. MEAT. Good meat, when deprived of its contained water, is a concentrated food, and is used not only on account of the large amount of nutriment it contains, but also for its rich and agreeable flavor. It represents much veg- etable matter converted into its present palatable and more digestible form by the metabolic activity of the animals from which it came. It contains all the essential food-principles, the carbohydrates, however, being present as muscle-sugar or inosite and, as in milk, in very small proportion. In all fresh meat there is much water, but more in lean than in fat meat; fat bacon contains 60 per cent.; lean beef, from 75 to 78 per cent, of water. As the proportion of fat increases, the quantity of albuminoids or proteids decreases : thus, lean beef may have only 2 per cent, of fat to from 20 to 24 per cent, of proteids, while bacon has about 24 per cent, of fat to 15 per cent, of proteids. Of the varieties of meat commonly used, beef is the most nutritious. Good beef should not be too pale nor too dark, should show no blood-clots, have almost no odor, be elastic and not soggy to the touch, be well marbled with clean, white fat, and have compact flesh. Dark beef indicates that the animal was not properly bled, or has had some febrile disease; wet and flabby meat, that it is approaching decomposition. The flesh of young RELATION OF MEAT TO DISEASE 265 animals is more tender than that of older ones, but not so digestible, partly because the young flesh cannot be so thoroughly masticated and the fibres so well separated. Therefore, veal is not so digestible as beef, nor lamb as mutton. "Young flesh is less stimulating and nutritious and more gelatinous than that of the adult." (Vaughan.) Veal should not be too pale, as that indicates antemortem bleeding or too young an animal. The calf should be at least one month old before the killing. Mutton is more digestible than beef, but not so nutri- tious. Its flavor is objectionable to some. Pork is an economical food for the poor man, as pigs of good stock store up three times as much of the food they eat as does the ox. The flesh is also easily preserved by drying or smoking, and ham and bacon are exceptions to the rule that dried meats are more indigestible than fresh ones. Again, pork fat furnishes much heat for cold weather by its oxidation and combustion in the body. But it must be remembered that it requires good digestive power to dis- pose of it, and that much pork is not to be advised for those of sedentary habits; also that certain parasites are especially liable to infest the tissues of the pig and to be transmitted thence to man. The flesh of poultry is acceptable to most palates, if not too old and tough. White meat is more digestible than the dark, but not so nutritious or rich in flavor, since the latter is more highly nitrogenous. Chicken broth is more nutritious and more laxative than that made from mutton. Fish is not sufficiently stimulating to constitute the chief flesh diet of a people, but it furnishes variety, and on account of its contained phosphorus should be used largely by those subject to neurosal affections. White- meated fish are more delicate in flavor and more easily digested, but not so stimulating as those of red flesh. Some fish are poisonous, either by nature or from inhabit- ing foul waters; while any fish may become so if under- going decomposition. Shell-fish are particularly liable to develop poisonous ptomains in the process of decom- 266 FOOD position, and, consequently, only such as are absolutely fresh should be used. Oysters and clams which have been taken from a water contaminated by sewage may also convey the germs of infectious diseases, such as typhoid fever; an instance of this having been demonstrated in the investigation of an epidemic of the latter disease in Connecticut, which was reported by Prof. Conn, of Wesleyan University, and another in a similar epidemic at Atlantic City, N. J., in 1903. "The following meats should not be eaten: (1) The flesh of all animals dead of internal diseases, or which have been killed while suffering from such diseases, or animals killed by overdriving. (2) The flesh of animals with contagious diseases that may be transmitted to man. (3) The flesh of animals that have been poisoned. (4) The flesh of animals with severe infectious diseases, as pyemia, etc. (5) Flesh that contains parasites that may be trans- mitted to man. (6) All putrid flesh. "^ Competent inspectors are appointed by governmental and state authorities to examine the various meats offered for sale in large cities, and undoubtedly do much good in preventing the sale of meat that is unfit for use. Unfor- tunately, from false ideas of economy in many communi- ties, the authorized inspectors have been too few in number. to be able to attend to all the work that should be done by them. Coplin and Bevan give the following as diseases which are to be specially guarded against: In cattle, epidemic pleuropneumonia, foot-and-mouth disease, contagious typhus, anthrax, tuberculosis, actinomycosis, Texas fever, dropsical affections, and indigestion. In sheep, braxy, variola ovina, black quarter, phthisis, fluke disease, and gid. In swine, anthrax, hog cholera, measles, and trichini- asis.2 It should also be remembered that the intestinal parasites, such as tape-worms and round-worms, often, if 1 Gerlach. 2 Manual of Practical Hygiene, 1st edition, p. 132 et seq. THE COOKING OF MEAT 267 not usually, gain entrance into the system through the ingestion of meat containing them in their embryonal or larval stages. Therefore, in cooking meat, every part should be heated to at least 160° F. sufficiently long to destroy any disease germs or parasites it may contain, as very rare meat may still harbor these organisms in a living state. Tubercu- losis, for instance, may be incurred by eating flesh imper- fectly cooked, since its germs are quite resistant; though it must be said that this disease is not so likely to affect the muscular tissues of an animal as are others of the maladies mentioned. The development of ptomains in flesh may also make it quite poisonous, and this is especially likely to take place in meats that have been kept for a long time after killing or in those preserved in cans or other packages that have been imperfectly heated or sealed. Meat is also cooked to improve it in appearance and to make it more agreeable to the palate and to aid digestion. As already stated, the effect of cooking upon muscle-tissue is " to loosen the bundles of fibrillse from each other so that they are readily torn asunder or crushed by the teeth." Perfectly cooked flesh is more savory than that which is either underdone or overdone. Meat cooked before rigor mortis sets in may be tender; cooked during the rigor, it is tough and is masticated with difficulty; after the rigor it is more likely to be tender when cooked than at any previous time. In cooking meat, the ultimate condition in which we wish it to be should always be kept in mind, and pains should also be taken not to overcook or use too high a temperature. The processes pursued in making a palat- able soup or broth, and in cooking meat so that it may retain all its juices, salts, and flavors, are radically dif- ferent. In the first case, it is desired to extract as much of the soluble constituents of the flesh as possible, and to do this the meat should be cut into small pieces and allowed to remain for a time in cold water, this afterward being very gradually raised to a temperature of about 160° F. 268 FOOD In this way the juices exude and the salts and soluble parts of the meat are dissolved before the pores are closed by the coagulation of the albumin. On the other hand, if it is desired to retain the juices and savor in the meat, the piece should be as large as possible that the surface exposed will be small in proportion to the volume. The meat is to be first subjected to a temperature as high as possible that the surface may be cooked at once and the albumin coagulated, the juices being thus prevented from escaping by the sealing of the pores. In boiling, this end is attained by plunging the meat at once into boiling water; in roasting, by having the fire or oven very hot. After this first heating it is best to lessen the degree of heat somewhat, that the subsequent cooking of the interior may go on more slowly and the temperature within may not rise above the coagulating-point and make the fibres hard and stringy. Meat cooked in this way should be tender, juicy, and rich in flavor. Broiling or grilling is, of course, but a modified roasting. Soups and broths made of meat-juices alone and with- out the addition of other substances are stimulating rather than nutritious, as they contain little albumin, carbo- hydrates, or fat. However, if certain vegetables be added to the soup, the latter will gain sufficient of these food- principles and be highly nutritious and such vegetable soups are of great value in all schemes of economic cook- ing. Bones are also of value on account of the salts, gelatin, and other soluble organic matter which they con- tain, and used with vegetables they make especially nutri- tious and easily digested soups. The meat from which soup has been made, on the other hand, is not all that is desirable, for though it still con- tains albumin and fat, it has lost its salts and savoriness and is unpalatable, and therefore not easily digested. It needs something — a sauce or condiment, or preferably a meat-extract, for meat-extracts are nothing but thin soups evaporated to dryness or condensed. Or, if both soup and the meat be taken at the same meal, the things CEREALS 269 lacking in each are supplied by the other, and the needs of digestion and nutrition are supplied. Frying meat, as it is commonly practised, should not be tolerated, as it renders the albumin of the flesh extremely tough, besides soaking it with fat or grease and thus greatly increasing the difficulty of its digestion. But frying by total immersion in boiling fat is an excel- lent way of cooking meats containing much water, and especially fish, for the boiling-point of fat or oil is very high and the meat is instantly cooked on the outside, while* the water in the interior, being converted into steam, prevents the ingress of fat by its expansion, cooks the albumin, and leaves the flesh in a light, flaky condi- tion. But the fat must be boiling hot when the meat is immersed, and the latter should not be allowed to remain in the former longer than lust suffices for perfect cooking. Beef-tea as ordinarily made is only a thin extract of beef, the stimulating properties of which will be consid- ered hereafter. To make a beef-tea containing any con- siderable amount of nutriment, the meat from which the juices have been extracted should be dried, pounded fine, and all fibrous and tendinous portions removed. This pounded beef should then be added to the liquid extract, as then only is it really a food. Moreover, the mixture should always be seasoned, even for the sick, that it may be thoroughly acceptable to both palate and stomach. In making the extract, it should be remembered that the meat should be cut into very small pieces and added to cold water in about the proportion of one pound of lean meat to one pint of water, and that the whole should be brought to the boiling-point very slowly. CEREALS. The cereals form one of the most valuable kinds of food. All but rice contain considerable proteid matter — from 10 to 20 per cent. — beside carbohydrates, which predominate, some fat, and a goodly proportion of phos- 270 FOOD phates. Rice has only 5 per cent, of proteids to 75 per cent, of starch, but it is easily digested, and is therefore a valuable food for the young and the sick; it is also well fitted as a chief food for dwellers in hot climates on account of its low heat-production. Wheat is the most nutritious cereal, and bread made from it is aptly called "the staff of life," since it is a food which, with the addition of a little extra fat and albumin, furnishes the essentials in proper proportion for the support of life. Barley closely resembles wheat in composition, and rye also is rich in nutriment, though perhaps a little more difficult of digestion than wheat. Oats are valuable on account of the large amount of fat they contain — over 5 per cent. — beside a full share of proteids, starch, and salts. But ordinary oatmeal needs vigorous digestive functions, and where the latter are lacking it is often productive of intestinal disturbance and irritation. Corn or maize, thoilgh not a true cereal, furnishes a valuable food with considerable fat; it also contains a vegetable fibrin. The proteid constituents of the cereals are vegetable albumin, casein, and gluten, the last of these being most abundant in wheat and perhaps of the highest food-value. Grinding breaks up the grain and the starch granules of the cereals, aids in separating indigestible parts, and renders the starch much more suitable for cooking. Wheat flour ground by the old method should be soft and smooth, but that made by the new roller-process is more apt to be slightly granular. It should not be too white, as that indicates a lack of the proper proportion of gluten, and should contain everything but the outer husk of the grain. The inner coats should be retained in the flour, as they hold a considerable part of the gluten and practi- cally all of the grain salts and possibly the vitamines.^ Cornmeal should be dry and powdery, or at least not too 1 The influence of polished rice as a factor in the causation of the dis- ease beriberi has been shown to be due to the loss of the vitamines in the germ and outer coating of the rice grains. CEREALS 271 granular. Flour of any kind should be kept well covered in a dry place, and should contain no living organisms nor any adulterants. Bread is practically made of flour, water, and salt, though sugar, milk, etc., may be added to improve the flavor. As flour and water alone make a tough and indi- gestible mass, bread is leavened to make it easier of mas- tication and digestion, and for this purpose either yeast, baking-powder, or aeration is employed. Yeast at the proper temperature rapidly converts some of the starch or sugar into carbon dioxide and alcohol, the former of which in escaping makes the dough porous and light, the walls of the cavities it produces being kept from collaps- ing by the tenacity of the gluten until the heat fixes them permanently. As the heat of baking dissipates both the gas and alcohol, from 10 to 12 per cent, of the weight of the flour used is lost by this method. Moreover, if the fermentation goes beyond a certain point, lactic and acetic acids are formed and the bread becomes "sour." Con- sequently, it has been advised that the yeast method be discarded, and that the leavening be done by means of baking-powders or aeration. Carbon dioxide is evolved from the baking-powders upon the application of heat and moisture, and the bread is made light by the gas, with no loss of food-substance, and, if the powders are pure, with nothing harmful added to the bread. There should be no alum or other adulterants in baking-powders nor in the flour itself. Alum unites with the phosphates of the flour, rendering them insoluble and preventing their absorption from the alimentary tract. Bread may also be leavened on a large scale by forcing air or carbon dioxide under high pressure into the dough, or by mixing the flour with cold water heavily charged with the latter gas. In this method, also, there can be no loss of food- material nor any detriment to the bread, provided cleanly precautions are observed. Good wheat bread should be almost white, light, sweet, spongy, and with a crust easily broken and equal in bulk 272 . FOOD to about one-quarter of the loaf. As considerable of the starch has been converted into dextrine in the crust, the latter is more easily digested than the interior of the loaf. Fresh bread is not nearly so digestible as that which is a day or two old. As stated, bread needs only a little added fat and albumin to make it a perfect food, the former of which, at least, is almost if not quite sufficiently supplied in the butter which is commonly used upon it. VEGETABLES. The vegetables in common use are valuable articles of food in that they give us the larger portion of carbohy- drates and also furnish an agreeable variety from day to day. In the fresh state they contain considerable water — from 75 to 90 or 95 per cent. — the residue being mainly one or another of the carbohydrates. Potatoes exemplify this well, since they contain but little proteids and fat, and practically all of their solid matter is starch. On account of their customary cheapness and ease of growth and storage they are usually considered to be a valuable article of food for the poor man, but it should not be for- gotten that other foods which are apparently more expen- sive may at times be actually cheaper than potatoes, both on account of containing those principles which the latter lack and because they require less expenditure of digestive energy. (See chart, page 276.) Beets contain much sugar and are nutritious, palatable, and easily digested. Onions have considerable sulphur, and should be used freely when its need is indicated. Cabbage, cress and other greens are especially valuable for the organic salts which they contain, and because they serve so well as relishes. Spinach is said to contain more assimilable iron than any other article of food commonly used. Celery and lettuce are nerve sedatives, and asparagus acts as a diuretic and is thought to be of special benefit to the kidneys. A caution should be introduced here concerning the VEGETABLES 273 use of raw vegetables which may carry from the soil the germs of certain infectious diseases derived from the fertihzers used in the field or from other sources. There can be no doubt that these have been the cause of infec- tion in certain cases, as of typhoid fever, and Metchnikoff has pointed out that while such germs are probably de- stroyed by the normal bacteria and reactions of the diges- tive tract, an abnormal condition of the latter may permit their introduction and the development of their specific maladies. The seeds of the leguminous group of plants, such as peas, beans, lentils, etc., contain from 22 to 25 per cent, of proteid matter in the form of vegetable casein, and almost 50 per cent, of starch. It is on account of this abundance of food-matter that they make such a valuable addition to soups and the like, and for the same reason they should also be used in any dietary where economy of expense is a factor. Green peas and beans are much more digestible than those that have ripened and dried, though, of course, they do not yield so much nutriment, weight for weight, as the latter. All vegetables should be so cooked as to retain their salts, or else the water in which they are cooked and which contains these salts should be used in making soup or broth, to be served at the same meal with the vege- tables. This is especially advisable with regard to pota- toes and sweet potatoes, as their soluble salts have much to do with their digestibility. It is for this reason that a properly roasted potato is always better than a boiled one, and that steamed vegetables are both more palatable and more digestible than those which have been cooked under water. In fact, Mattieu Williams has even sug- gested that possibly one reason why gout is so prevalent among Englishmen is because they habitually eat boiled vegetables and throw away the water in which these have been cooked. The salts not only help in the digestion of the starches, but they furnish bases to unite with and render soluble the irritating acids that produce the gouty 18 274 FOOD symptoms. It should also be remembered that the dried legumes should always be softened by soaking in water before cooking, and that they as well as other vegetables should be cooked, whenever possible, in soft water. Prepared starches, such as arrow-root, tapioca, sago, etc., are easily digestible, and therefore useful especially in the preparation of food for the young and the sick. Fruits are especially valuable on account of their flavor, acceptability to the palate, benefit to the diges- tion, and for their laxative action. Ripe fruits may be eaten freely: in most cases preferably early in the day. Fresh fruits are usually better than those dried or other- wise preserved; but where the former cannot be had, the latter should be used freely, and all should be used throughout the year whenever possible. For obvious reasons, green fruit, or that which has begun to decay, should not be eaten. Nuts are nutritious on account of the high percentage of fat that most of them contain, but are difficult of diges- tion unless thoroughly masticated. Recently pastes made from various nuts have been placed on the market, and are to be considered as an agreeable addition to our dietaries. ADULTERANTS AND PRESERVATIVES. Much might be written concerning the adulteration and sophistication of foodstuffs and of the addition of more or less harmful preservatives to food of a perishable nature. That the first is carried on to an enormous extent seems certain. The remedy appears to be in the passage and enforcement of stringent laws and the maintenance of frequent and rigid inspection by both state and govern- mental authorities, in the dissemination of information as to the adulterations practised and the means of detect- ing them, and in the utmost publicity and exposure in the case of transgressors, all of which is now being effected by the provisions of the Pure Food and Drugs Act and the means employed for its enforcement. ADULTERANTS AND PRESERVATIVES 275 This law, which became effective on January 1, 1907, provides "That for the purposes of the act, an article shall be deemed to be adulterated in the case of food: First. If any substance has been mixed and packed with it so as to reduce, or lower, or injuriously affect its quality or strength. Second. If any substance has been substi- tuted wholly or in part for the article. Third. If any valuable constituent of the article has been wholly or in part abstracted. Fourth. If it be mixed, colored, pow- dered, coated, or stained in a manner whereby damage or inferiority is concealed. Fifth. If it contain any added poisonous or other added deleterious ingredient which may render such article injurious to health. Sixth. If it con- sists in whole or in part of a filthy, decomposed, or putrid animal or vegetable substance or any portion of an animal unfit for food, whether manufactured or not, or if it is the product of a diseased animal, or one that has died other- wise than by slaughter." As to the use of preservatives, the very extensive sale, heretofore, of these in localities where they would be most likely to be added to food indicates their employment, as does their continual discovery by direct analysis. In Bir- mingham, England, such preservatives were found in 20 per cent, of 2300 samples of food examined, and boric acid in 5 per cent, of 1360 samples of milk. Such substances as boric acid, salicylic acid, and formaldehyde are commonly used, though it is frequently stated that more dangerous ones, such as hydrofluoric acid, are occasionally employed. And though it should in fairness be stated that it is pos- sible that, if only the minimum of such substances as boric acid and formaldehyde necessary to prevent putrefactive or fermentative changes in food be used, no harm to the human economy will result,^ yet it is undoubtedly wiser » Rideal and Fullerton (Public Health, May, 1899) arrive at the following conclusions: (1) Boric acid (1 to 2000) and formaldehyde (1 to 50,000) are effective preservatives for milk for twenty- four hours. (2) These quantities have no appreciable effect upon the digestion. (3) These quantities have no appreciable effect upon the digestibility of foods prepared with them. (4) Formaldehyde in the proportion given above, so far as their investigations have extended, does not appear to have any injurious action upon animal tissues or nutrition. 276 FOOD to condemn the practise of adding chemical preservatives of any kind to food. There are two reasons for this: (1) There is no surety and very Httle probabiHty that the minimum quantity of preservative consistent with safety to health will not be exceeded in most cases through care- lessness or recklessness. (2) That foods that apparently require such preservatives should be supplied to the consumer before the deterioration in them has begun, or else they should be sterilized by the more costly but safer employment of heat. The following diagram may be of service in deter- mining the value of certain foodstuffs. Fig. 78 CHAPTER VII. STIMULANTS AND BEVERAGES. The essential function and property of stimulants is to liberate some of the latent force of the body ; hence they are of use and value in sudden emergencies, to tide the system over important crises, to hasten a tardy convalescence, or perchance to whip up a flagging digestion so that it may more thoroughly prepare food for the repair of waste or the supplying of body-fuel. Those stimulants, excluding drugs, with which we are most concerned are of three classes, viz., nitrogenized vegetable stimulants, such as tea and coffee; nitrogenized animal stimulants, as beef- tea and meat-extracts; and alcohol. All these are "force- liberators," and though alcohol may sometimes act the part, in more moderate measure, of a "force-producer," it is well to remember that they give scarcely anything at all to renew or replace the energy which they set free. This being so, care should always be taken that some food be supplied during or shortly after the stimulation produced by the agents in question, in order that the body may have a new store of force to replace that which has been liberated. Especially is this necessary in cases of sickness; and as the soluble carbohydrates furnish fuel and consequent heat and energy to carry on the vital pro- cesses, these even more than other kinds of food are to be supplied, and will generally be well received and utilized by patients or others in need of stimulation. Again, just as we must not depend on stimulants alone to the exclu- sion of food, so also must we take care not to continue their use any longer than is necessary to attain our object, and likewise must not overstimulate or carry the action (277) 278 STIMULANTS AND BEVERAGES so far that the body is left poorer and weaker in force than before the use of the stimulants began. For example, beef-tea constantly stimulates the vital and nervous functions to greater activity, this requiring that either tissue or food be oxidized to produce the neces- sary energy. The stimulating factors in ordinary beef-tea are the meat-extractives, such as kreatin and kreatinin, which are products of the wear and tear of life, inter- mediate between living, active tissue and the final excre- tory mattei's, such as urea and uric acid; hence they can have little, if any, real food-value. Beside these the beef- tea contains only the salts of the meat, which, though valu- able, are not force-producers. Therefore, unless food be otherwise supplied, the body tissue must be consumed, and the result must eventually be disastrous; and yet this is what occurs to many patients through the mis- taken idea that beef-tea is both nourishing and stimu- lating. When "whole beef-tea" (the recipe for which is given on page 269) is used, these remarks do not apply, since it contains some true food, though even here soluble or readily digestible carbohydrates may wisely be added. The active principles of the nitrogenized vegetable stimulants resemble very closely in chemical composi- tion not only the meat-extractives, but also those drugs, like strychnine, which are used in medicine as tonics and cerebrospinal stimulants, and they act physiologically in a similar though milder manner. As beverages, tea, coffee, and cocoa supply fluid for the system and that stimulation of the assimilative functions that causes a sense of comfort after their use, cocoa and chocolate having also the advantage of supplying some food. But these beverages may all be abused in their use as readity as may beef-tea or alcohol, and "tea-drunkards" and "coffee-drunkards" are not uncommon in hospitals and in private life. The teacup is not always the one that "cheers but does not inebriate." Women especially who drink much tea are apt to be nervous and dyspeptic, to have the "tea-drinker's heart," and to suffer from ALCOHOL 279 headaches and neuralgias. They depend upon tea to take the place of nutriment, and soon use up what little store of force they may have had, since they fail to replenish it with fuel-food. Men are more addicted to the use and abuse of coffee, and often manifest symptoms directly traceable to such intemperance. While caffeine increases heart action, and may be used to advantage in cases of cardiac debility, for the same reason it should be taken with caution and in moderation where the cardiac action is already too vigorous. Vogel has advised the use of strong coffee with sugar and cream as a tonic and food in debility accompanying the acute diseases of children. It is interesting to note that among all nervous, ener- getic people the use of some one or other of these stimu- lant beverages is common, and that "total abstainers" from alcohol seem instinctively to resort to tea or coffee. And while it is probably theoretically true that the healthy person would better abstain entirely from the use of stimulants, except in emergencies or at rare intervals, yet the almost universal desire for and use of them prob- ably indicate that under our present high tension of living there is a real physiological demand and need for them that perhaps should be satisfied in a measure, but with moderation and judgment. ALCOHOL. Liebig says that "alcohol stands only second to fat as a respiratory material," but adds that "the same effect could be produced in the body by means of saccharine and farinaceous articles of food at one-fourth or one- fifth the cost." Fothergill also holds "that the chief portion of the alcohol ingested undergoes consumption in the body," but insists that "the question of * alcohol as a food' can never be separated or divorced from that of 'alcohol as a stimulant' or as a force-liberator." Much undue importance has certain been given to 280 STIMULANTS AND BEVERAGES scientific investigations that served to establish the fact that alcohol can be, and often is, almost completely oxidized in the body, and that it produces therein prac- tically the same number of heat-units as when it is con- sumed outside. But the inference that it can therefore be substituted for, and used with impunity in place of the usual carbonaceous foods is not justifiable, because the powerful physiological and ultimate pathological effect of the alcohol upon the higher nerve-centres and active tissues is ignored, because of the liberation of the body's latent force in excess of the energy which the alcohol sup- plies, and because even the above-mentioned investiga- tions and experiments went to show that there was an actual detriment to the nitrogen-bearing tissues of the body during its use. Again, Liebig writes that "the use of spirits is not the cause but the effect of poverty. It is the exception to the rule when the well-fed man becomes a spirit-drinker. On the other hand, when the laborer earns by his work less than is required to provide the amount of food which is indispensable in order to restore fully his working power, an unyielding, inexorable law or necessity compels him to have recourse to spirits. He must work; but in consequence of insufficient food a certain portion of his working power is daily wasting. Spirits, by their action on the nerves, enable him to make up the deficient power at the expense of his body; to consume today that quan- tity which naturally ought to have been employed a day later." This may also be the case where there is an abundance of food, but where it is improperly chosen for the needs of the individual or ruined by bad cook- ing. Education in the principles of the scientific and economical selection of food and its preparation may thus become a means of preventing those diseases that depend on, or are aggravated by, insufficient or improper food and consequent alcoholic excesses. The effect of alcohol upbn the weak and savage races is much more marked and disastrous than upon the civilized and strong ; RULES GOVERNING THE USE OF ALCOHOL 281 so it harms the health of the underfed and overworked mucli more than it does that of the well-fed man of means and leisure, and affects women and children more than adult men. This latter point is to be remembered in practice. Remember also that, while alcohol is partially a respi- ratory stimulant, it is a force-liberator and consumes the body-store, and unless given with other readily oxidizable food the risk is run of putting a patient "in a grave never dug by Nature," especially where there is already danger of the patient sinking from exhaustion. But it is just in these cases, when given with other food, that we find alcohol a valuable therapeutic agent. Give it with foods that produce heat and force — i. e., some form of the soluble carbohydrates, as maltose, malt-extracts, milk, milk-whey, or even sugar. Where the assimilative powers are weak it may be advantageous or necessary partially or wholly to predigest these foods; but above all, remember to replace what alcohol takes from the body, or physio- logical bankruptcy will ensue. Note also that, though alcohol may be in one sense a food, it is a very costly one, and that intoxication must occur long before a man could get the equivalent of a full meal. Alcohol is to be used in sickness practically to sustain the vital powers, to meet emergencies, and to lift the patient over obstructions in the road to health; and such use requires a thorough knowledge of its action coupled with the highest judgment. It should also be noted that there is an increasing tendency on the part of the medical profession to prescribe alcohol much less frequently and more sparingly than was formerly the practice. In malt liquors there is usually considerable maltose, thus combining with the alcohol a soluble carbohydrate of the highest value, and these brewed ales, etc., may some- times be used with benefit as tonics, especially where con- valescence is protracted. The stronger distilled liquors are diffusible cardiac stimulants, and are possibly valu- able in emergencies, but the continued use of them must only be advised with great caution. 282 STIMULANTS AND BEVERAGES Fothergill gives two excellent rules for the use of alcohol by the healthy: "First, never have alcohol in the brain when it has work to do; second, a little alcohol betwixt a a man and past trouble is permissible; but it is not well to put a little alcohol in front of a coming trouble." Murchi- son, in his work on Fevers, lays down these rules for practice, which it would be well for all to adopt: "What are the conditions of the animal economy in which alcohol may be of positive use? That there are such conditions, I believe cannot be denied by anyone who has honestly studied the subject; but they are not the conditions of perfect health. It is especially when the circulation is weak or sluggish that a daily allowance of alcohol may do good. Thus: (1) Alcohol is useful in the course of most acute diseases when the organs of circulation begin to fail, as they are apt to do. A moderate quantity usually suffices. The large quantity still sometimes administered may do harm by inducing congestion of internal organs. (2) In con- valescence from acute diseases or from weakening ail- ments, when the circulation remains feeble and the tem- perature is often subnormal, alcohol is useful in promoting the circulation and assisting the digestion. (3) In persons of advanced life the circulation is also often feeble, and a moderate allowance of alcohol often appears to be bene- ficial. All other conditions of the system marked by weakness of the muscular wall of the heart, whether permanent or transient, are usually benefited by alcohol." Alcohol may thus be of value in forestalling or overcom- ing the depressing influences of the toxins produced in certain of the infectious diseases, and in shock. In the latter, however, especially when due to accident or to some sudden cause, much harm rather than good may be done by the administration of excessive doses of alcohol, on account of their effect upon the depressed vital centres, and it is well to remember that better and speedier results will probably follow small doses sufficiently frequently repeated. Alcohol is a good servant, but a bad master. King MV£!HAGJSS 283 Chambers says: "Let alcohol be taken never as a stimu- lant or preparative for work, but as a defence against injury done by work, whether of mind or body. For example, it is best taken with the evening meal or after toil. Let the increase in the desire for, and the power of, digesting food be the guide and limit to the consumption of all alcoholic liquids. Let the forms be such as contain the least proportion of fusel oil. Let all with an heredi- tary tendency to hysteria or other functional diseases of the nervous system refrain from its use altogether, even though as yet in good health." BEVERAGES. To comment individually upon the multitude of non- alcoholic and non-stimulating beverages that are now more or less generally used, is both impracticable and unnecessary, nor will any attempt to classify them be of much value. For the most part they serve only to please the palate; though if in this way they bring about a greater ingestion of fluids when these are needed, their service cannot be considered a vain one. For it has already been stated that an ample supply of drinking-water or other fluids taken daily and habitually is essential to the satisfactory removal of the various waste matters from the body, and that without it the latter may readily develop conditions favoring disease. Moreover, it is true that certain gases and salts held in solution in some beverages, such as mineral waters, increase this excretory action, and may be highly bene- ficial in appropriate cases; but it should be a matter of caution that where such therapeutic results are thought to be necessary, competent medical advice should be the guide as to the kind and quantity of the agents used. This comment is justified by the fact that of late many substances capable of influencing the body functions have been advertised and sold in the form of one beverage or another directly to the laity, who, being incompetent 284 STIMULANTS AND BEVERAGES to judge as to whether or not such substances are actually needed in their individual cases, may in this way do them- selves much harm. Only such beverages, then, as are quite simple in their nature or as are advised by competent medical authority should be used. If they are artificially made and water is the solvent fluid, as it will be in most cases, there should also be a certainty that it comes from a clean and safe source, lest it carry the germs of disease. There is no doubt that frequently the cheaper bottled drinks which are dispensed so generally are made from water that has been liable to more or less dangerous pollution, and there is the additional risk that arises from the imperfect cleans- ing of the bottles for these liquids which have been returned to be refilled. A little thought as to the dangers which do exist in relation to this matter will be convinc- ing as to their gravity. Many of the most popular beverages are charged with carbon dioxide under compression, and the fact that so much of this gas can be taken into the system in this way without apparent harm, and its free elimination, would seem to be additional evidence that it cannot in itself be so very harmful in the atmosphere, even when in propor- tions considerably greater than the normal. In conclusion, it may be said that a free use of all such beverages as are known to be clean, safe, and wholesome will probably be found to be entirely favorable to health unless there be some contra-indicating reasons peculiar to the individual himself; and that their substitution, when- ever possible, in place of the alkaloidal and alcoholic stimulants is to be commended on hygienic as well as other grounds. CHAPTER VIII. PERSONAL HYGIENE. The proper consideration of this subject demands an ample volume rather than the limits of a single chapter, for the ultimate aim of all sanitary work is the preserva- tion and betterment of the health of the individual, and beside, the factors that affect the well-being of the person are so multitudinous in their number and in their phases that no brief discussion can comprehend them all. However, much that pertains to personal hygiene and that requires no repetition for its application has already been given in the preceding pages; so that it is hoped that if the reader will exercise that virtue of common- sense and reflection that is so essential in this study, the remarks to be added will be helpful in suggestion and in answering many questions, even though they may not be considered in any way as complete discussions of the respective themes. Each age has its own requirements, and that which may be entirely satisfactory or permissible at one time may not be so at another. To attain the best results it will often be necessary even to anticipate with prophyl- actic measures the birth of the child; and, broadly speak- ing, much of the welfare of future generations lies in the care of those now living. One of the gravest sociological problems of the day is as to how far the State is justified in restricting or prevent- ing the propagation of the defective or degenerate of the human race; and though the time may not be ripe for the law to take positive action in these matters, it is the duty of every sanitarian to use his utmost efforts to the end that only the healthy and the normal may continue. (285) 286 PERSONAL HYGIENE The advances in physiological and biological science in recent years have done much for all humanity, but in no respect, perhaps, have they been of more service than in determining the great influences of heredity and environ- ment and in establishing the fact that the presence or absence of disease is oftentimes, if not always, due as much to predisposing conditions and the physical status of the individual as to external and exciting causes. What may cause only a trifling ill in one may bring about most serious evils in another whose estate is not so fortunate. Life has been defined as the power of an organism to adjust continually its internal conditions to its external conditions, and as long as this is satisfactorily done life persists. The secret of personal hygiene and health, then, must lie in determining the relationship between the in- ternal and external conditions of the individual's organism. "Know thyself" is advice good for the body as well as for the mind or soul, and knowledge of the right kind can do no harm. He who knows his personal and physical nature and acts accordingly is well equipped to fight against the ills of life, and the study of the relationship above referred to will help the thinking man so to care for himself that in all probability his days will be pro- longed. But a caution or two must be interpolated here. It is well known that "expectant attention" too persistently directed toward a particular organ may lead to decided alterations or disturbances in the functions of that organ; and again, unless one well understands the mysteries of human physiology, a little imperfect or insufficient infor- mation in this respect may lead to the assumption or pur- suit of habits and practises actually dangerous to health. Too much ill-advised care and attention may be just as full of risk as too little, and physiological egotism without a sound basis may have a bitter reward. What is needed is that each one should study care- fully the phenomena of his daily life, should determine accurately the purpose and reason of each of the respec- IMPORTANCE OF SELF-STUDY 287 tive functions, and then, not forgetting their interde- pendence upon one another and that all should work in harmony, should endeavor to do that which will best facilitate the functional activity with the least expenditure of energy. There are a number of ways in which the study of per- sonal hygiene may be advantageously pursued, but for practical purposes one of the best is to consider it with respect to the main groups of organs and functions of the body, keeping always in mind, however, the correlation of these, and that no part of the body can be entirely independent of the rest.^ Nevertheless, the hygiene of infancy is a study by itself, for it is in that epoch of life that the plastic constitution can be and is molded most readily by all the influences of the environment, whether for good or evil, and it is at that time that salutary efforts are to be made with greatest hope of success and eventual good. Moreover, th'e principles of personal hygiene may be more readily taught to, and inculcated in, the young, but with much greater difficulty can we affect the mature or aged; for we are all creatures of many habits, and in the mature adult the impress of these may resist to the utmost any and all endeavors to modify or remove them. Too much stress cannot be laid upon the fact that it is the constitution, the nature of the inherent tissue, that controls or modifies the inception, development, and pro- gress of many of the ills of life, and that whether this in its normal and highest vigor be a bequest of heredity or be attained only by the most careful attention to details in the practise of the art of hygiene, it should always be looked upon as the most valuable physical possession of the individual. > This method has been followed in Pyle's Manual of Personal Hygiene, to which the reader is referred for an admirable discussion of the sub- ject, which must be treated all too briefly here. The writer would also recommead Starr's Hygiene of the Nursery to all who desire specific and authoritative information concerning the young. 288 PERSONAL HYGIENE To state again what has already been written: "The essence of sanitation is to secure perfect health, to increase the inherent power to resist noxious and harmful influ- ences, and to make all the surroundings and environments of the body pure and free from depressing factors." With this preface, the following discussions are added in the hope that they may be of assistance in determining the way of right living and in securing the welfare and health of each individual. HEREDITY. In the broad biologic sense, heredity is the transmission of a series of characteristics to and by a fused cell, formed from two cells furnished by respective parents, which carries on its evolution under certain governing impressions indelibly stamped by the two parental lines of descent; but, in the ordinary use of the term, it may be defined as the transmission to the offspring from parent or ancestor of any trait, type, temperament, characteristic, or predis- position which has a governing or influencing effect upon the growth or nature of that offspring. These transmitted impressions may be either for good or for evil. " It shows an incorrect conception of the law of heredity to look for a return of identical phenomena in each new generation."^ Also, "we do not mean exclusively by heredity the very complaint of the parent transmitted to the children, with the identical symptoms, both physi- cal and moral, observed in the progenitors. By the term heredity we understand the transmission of organic dis- positions from parents to children. "^ In true hereditary disease the faulty conditions must be transmitted in the germ-plasm, and not be due simply to accidental factors affecting the embryo during its fetal development, the results of the latter being congeniial rather than inherited. 1 Moreau, Psychologie morbide, 2 Morel, Traite des D6g6n6rescence8. MARRIAGE 289 Consequently, as hygienists, we must use the influence and power that we have to further the transmission of only beneficial or elevating characteristics, and to prevent the bequest of harmful influences and hereditary diseases to the generations to come. "The germ of the unborn infant must be complete and untainted in all its nature, otherwise we cannot hope for a vigorous and perfect growth or development." As the family is the foundation of the State, and society is a congregation of men for the purpose of acquiring greater power and more comforts through mutual co- operation, the latter, whether domestic or civil, has some right to make men understand that they must care for the health of the generations to follow, and to enact reasonable laws looking to the prevention or obliteration of transmis- sible infirmities. And history seems to show that no great nation has ever been destroyed or overwhelmed until its people had first neglected or abused the laws of hygiene, heredity, and sociology. MARRIAGE. We find that a married couple have generally, beside themselves, the welfare of from three to five human beings within their keeping. To produce healthy children and ones not prone to disease, both parents should possess good constitutions, and they should take great care not to weaken these by excesses of any kind, physical or mental, nor, as far as lies in their power, by any chronic disease. It is evident that children of parents that have been con- scientious observers and followers of Nature's laws must have a better chance for health and superiority all their lives. In this climate the proper age for marriage is consid- ered to be about twenty-four or twenty-five for the man, , and nineteen or twenty for the woman, though this must vary with the state of development of the parties con- cerned. Some of both sexes mature at a considerably earlier period than do others, and it would be unjust to 19 290 PERSONAL HYGIENE say that they were not fit for the duties of marriage till they reached the age of the maturing of slower-growing ones. Usually, however, before the ages given, develop- ment is not complete and the whole organism is in a transition state. We know that the use of any organ before it has attained its complete growth or development is very apt to cause exhaustion or, perhaps, premature degeneration of that organ, and we cannot but believe that children developed in immature sexual organs must be deficient in vital force and energy. It is often notice- able that a child apparently strong and vigorous may have but little power to resist disease or may even be strongly predisposed to some infirmity; in such cases there will likely be some defect or taint in the parent stock. Distinguishing characteristics are more likely to be transmitted in the early married life of parents, because their organs and forces are then more vigorous; but if a couple marry when quite young and before their own organs are fully developed, their elder children may be more deficient, mentally and physically, than their later ones. Late marriages are not likely to be so fruitful as earlier ones, possibly owing to the increased difficulty of parturi- tion on the part of the mother and her consequent unwill- ingness to undergo the ordeal more than a few times. But healthy middle-aged persons, who have married late, may have even healthier children than those who have married too early. In features, constitution, sense-organs, shape of head, etc., the child is most apt to resemble the father; while it will likely follow the mother in the shape of the trunk and in the formation of internal organs. The character and mental qualities of the child may come from either parent or from both. Maternal impressions, habits, or conditions during pregnancy, especially if continuous or persistent, undoubtedly often have a marked effect upon the coming infant. So also do maternal toxemias or INHERITED AND CONGENITAL DISEASES 291 other depraved conditions of the mother's system, though occasionally such influences apparently do not do as much harm as we would anticipate. There may, however, even be actual and direct infection of the child through the placenta. In fact, " intra-uterine infections and modifica- tions of the fetus are more frequent and more important than conditions of true inheritance of disease."^ INHERITED AND CONGENITAL DISEASES. Hereditary influences are generally transmitted directly from parent to child, but w^e occasionally find a cessation of a trait or predisposition for one or more generations and then a recurrence. To such a peculiarity we give the term atavism. "A family history of less than four genera- tions has only a limited value." An hereditary malady may be actually existent at birth and be transmitted directly from parent to offspring — as syphilis, structural deformity, mental or nervous defect, etc.; or there may only be an inherited predisposition to the disease, as toward tuberculosis, etc. Physicians have thus a twofold duty: first, to do all they can to guard against the transmission of such diseases; second, to combat the disease or any tendency to it as soon as the first symptoms thereof are discovered or it is suspected in the child. The first duty can be accomplished, theoret- ically, by preventing generation and production on the part of those, unfit to produce healthy offspring, and practically, within certain limits, by fighting the causes and their effects in the parent individual, especially at the ages or times when these have the greatest force or are most apt to manifest themselves. For the second, the child must be immediately placed in the most favorable hygienic surroundings, and everything possible done to prevent the further development of the disease or predis- position. In many cases such early interference will 1 McFarland. 292 PERSONAL HYGIENE accomplish much good, and the disease may be averted entirely. Especially is this true of those inheriting the tuberculous diathesis. Too often the child of a tuberculous parent is exposed after birth to the same conditions that served to develop the disease in the parent, and its inherited predisposition to the malady is intensified by the environment of a damp and undrained soil, a dark and un ventilated house, etc., and by insufficient or improper food, until infection is all too easily acquired, and the child that might have f 6^m niDi^ooii Fig. 79. — Eighteen feeble-minded children and grandchildren. A feeble-minded woman married an alcoholic man. Seven of their chil- dren were feeble-minded, two were alcoholic and one boy died in infancy. Two of the children (both feeble-minded) have children. All eleven were feeble-minded. Squares are males, circles are females.^ been saved becomes an early victim of the ignorance, carelessness or neglect of those who should have fostered it with extremest care and solicitude. On the other hand, the apparently complete eradication of the transmitted predisposition from many children whose inheritance has been as bad, but who were promptly removed from the unsanitary environment of their birth, shows how much this one influence may work for good. The most important of the supposedly hereditary or transmissible affections are syphilis, tuberculosis, scrofula, ^ Figs. 79 and 80 are from a Bulletin on The Transmission of Feeble- mind, issued by the Department of Public Health and Charities of Philadelphia, 1910. INHERITED AND CONGENITAL DISEASES 293 cancer, gout, hysteria, epilepsy, certain physical deform- ities, certain skin diseases, insanity, feeble-mindedness, and criminal tendencies of various kinds. But do not forget that what may appear to be a direct and actual inheritance of a disease may only be the production of the disease in that person by the same agents, environments, and morbid conditions as caused or favored the disease in the parent. However, even here there is very possibly a transmitted predisposition to the acquirement of the 00 4 .n%. i B B Q m B B B B Fig. 80. — Second generation apparently normal (six feeble-minded appear in the third generation). A feeble-minded woman, possessing a tuberculous brother, married an alcoholic man. Result, three (appar- ently) normal girls, one normal boy and one alcoholic son. One of the girls married an alcoholic man. Three feeble-minded sons, two normal sons (twins), two miscarriages and a child dying in infancy resulted. The other two, apparently normal girls, each produced feeble-minded ofT- spring; one a boy, the other, two boys. Squares are males, circles are females. Small black circle indicates miscarriage. This chart also illustrates atavism in its relation to feeble-mindedness. disease, rendering it all the more easy for it to develop and to manifest its symptoms upon slight provocation. Therefore there should be no marriage between persons inheriting predispositions to the same disease, especially if they be relatives, and "a person affected with heredi- tary or well-marked constitutional syphilis, or having a strong consumptive taint, or tendency to mental unsound- ness (or weakness) should not marry at all." Defective eyesight is very apt to be transmitted to 294 PERSONAL HYGIENE children, and the latter should be carefully examined and, if necessary, fitted with proper glasses beiFore being placed at school or at any work requiring much use of the eyes. Infirmities which do not prevent marriage from being fully accomplished, or which do not tend to the degenera- tion of the offspring, are not good reasons alone for for- bidding marriage, but all that have such a tendency are. A man should not marry a woman too far advanced in life, nor one that is very feeble, delicate, or deformed, especially as to the chest or pelvis. Hysteria, convul- sions, and epilepsy due to organic disease should prevent a woman from marrying, though some extremely nervous and hysterical women are much benefited by marriage and have healthy children. So with many women who have uterine congestions and displacements before marriage. Evidence seems to indicate that marriage between rela- tives is reprehensible, and that the danger increases with the nearness of the relationship, since the children of such marriages are prone to disease and to defects in the sense- organs, especially the eye and ear, or in mental qualities. But upon closer investigation it is probably more nearly true that "the objection to consanguineous marriages lies not in the bare fact of the relationship (of the parties con- cerned), but in the fear of their having similar vitiations of constitution." Few families or persons are absolutely healthy or free from taint, and "it may safely be asserted that when both parents are possessed of a physiological or pathological congenital characteristic, that characteristic is almost certain to be repeated in an aggravated form in the offspring."^ We can, accordingly, easily understand that "in consanguineous marriages the real danger is in the strong probability that both parents have some distinct taint of degeneration, which is liable to be increased in their children, but which might possibly disappear if each 1 Lawrence Irwell, Philadelphia Medical Journal, July 21, 1900. EXERCISE 295 married a person not bearing the same or some closely allied character. The marriage of two individuals of the phthisical type, whose families were strangers to each other, would be as productive of evil as the marriage of first cousins who were phthisically inclined."^ However, any advice on the subject must depend upon the special circumstances in each case, but chiefly on the health and degree of relationship between the parties. EXERCISE. Exercise is generally considered to mean simply the action of the voluntary muscles, but it has a wider mean- ing than this. Every organ in the body is capable of being exercised in some way or other; and if not properly exercised, an abnormal stdte is almost certain to ensue. "Life is organization in action." Each organ has its own special st'mulus, and if this be normal in amount and character, we should have health. Also, the trained use of an organ makes it more effective in the performance of its functions. But deficiency in exercise favors a lack of nutrition, wasting in size, and eventually degeneration of tissue; while, on the other hand, too much work may favor hypertrophy and tissue degeneration. Proper muscular exercise is highly beneficial to health, and in the end actually necessary to the proper perform- ance of functions in other organs; it is consistent with and necessary to health. But, to be of value, the exercise must not only be regular, but must also consist of move- ments of sufficient force to necessitate energetic contrac- tion of the muscles; we must do work. This necessitates resistance as an element, and we may define physical exercise as voluntary labor. We need the resistance to obtain the proper contraction of the muscles, the contrac- tion for their disintegration, the disintegration for their renewal, etc.; for we know that upon the constant ' Lawrence Iswell. Philadelphia Medical Journal, July 28, 1900. 296 PERSONAL HYGIENE destruction and disintegration of tissues depends their subsequent renovation, and that the strength and vigor of all parts of the body and of the whole body depend upon its newness. Beside the fact that proper physical exercise makes the voluntary muscles larger, harder, stronger, and more quickly responsive to the will, and that it increases the functional capacity of the involuntary muscles employed, it largely promotes health and strength by quickening the circulation and increasing the respiratory powers. Dur- ing muscular action (contraction) there is a conversion of potential energy into motion, a call for more food, an increased demand for and consumption of oxygen, and an increased production of and elimination of carbon dioxide and other waste matters. This increased demand for oxygen and elimination of carbon dioxide necessitate increased action of the respira- tory organs — the lungs, and this is one of the greatest advantages of physical exercise. The respirations are increased in frequency and depth, the lungs expanded, the air vessels flushed out and refilled with each inspiration. Doubtless many cases of pulmonary tuberculosis could be prevented or cured if only people could be taught to take sufficient and suitable exercise and to breathe properly, for we rarely find the lungs fully expanded except in the out- door worker or athlete. Consequently, the movements of any given exercise should be with speed and force sufficient to quicken and deepen the respiration; and, conversely, if any severe exercise is to be undertaken or a course of training begun, special care must be had to develop the lung capacity.^ A man exercising, even moderately in any manner, inspires considerably more air than when reclining at rest, ^ The caution, however, should be given here that persons with incip- ient tuberculosis, or with a marked tendency thereto, should not take up exercises involving deep and rapid breathing, except under the advice of a competent physician, as much harm may result in some cases from such unwonted excitement of the pulmonary tissue. EXERCISE 297 which latter amount is, for an adult, about 480 cubic inches per minute. Or, as Pettenkofer has shown, a man on a day of rest absorbs 25 ounces of oxygen and throws off 32 ounces of carbon dioxide and 29 ounces of water; on a day of work he absorbs 33.6 ounces of oxygen and throws off 45 ounces of carbon dioxide and 72 ounces of water. In other words, the elimination of carbon on a work-day is more than three-fourths of a pound. Muscular exercise is necessary, therefore, for the proper elimination of waste carbon from the body, and, as the action of the muscles is checked and lessened if the carbon dioxide produced by their action is not immediately carried off by the blood and eliminated by the lungs, it follows that during exercise there should be nothing to impede the circulation or the action of the chest and lungs, and that all tightness of clothing, especially about the waist, neck, and chest, should be avoided. Moreover, inasmuch as the amount of carbon dioxide and other waste matters eliminated is so very much increased during exercise, a much larger amount of pure air is needed, and all rooms and buildings wherein exercise is to be taken should be well ventilated. After exercise an increased amount of carbonaceous food and of water must be supplied to replenish the sys- tem for what has been eliminated. The increase of carbon food is probably best given in the form of fat rather than of the carbohydrates, though there is some difference of opinion on this point; and of all fluids, water is doubt- less the best in ordinary cases for training. As a general rule, alcohol is harmful, because it benumbs and deadens the nerves and will, and because, as every voluntary impulse must originate in the brain, anything that inter- feres with the communication between it and the muscles must lessen the promptness with which they respond and the consequent efficacy of their work. The advanced opinion of today seems to discountenance the use of alcohol in any form or at any time by those in training for contests of skill, endurance and strength. 298 PERSONAL HYGIENE By exercise the action of the heart is increased in force and frequency, the pulse is made full and strong, if the work be not too excessive or sudden, and the flow of blood and other fluids is increased throughout the whole body. As long as the heart is not overtaxed the pulse- beats are regular and even, though suddenly increased exertion may make the rate very rapid. Ordinarily exer- cise increases the rate from ten to thirty beats per minute. Excessive exercise leads to palpitation and hypertrophy of the heart (one reason why any extensive training should be under a competent trainer); but, on the other hand, deficient exercise leads to a weakening of the heart muscle and heart action, and probably to dilatation and fatty degeneration. If at the beginning of a new exercise the heart action becomes irregular, rest should be taken, and the exercise then begun in a more moderate and gradual way. The heart stimulus is largely due to the increased amount of blood in its cavities, but it should be remembered that the venous circulation is chiefly due to the muscles. "Every muscle is a little heart," and these, by their contraction, constantly tend to drive the blood onward to the true heart and lungs. Exercise greatly increases the amount of perspiration from the skin, this perspiration containing water, salt, and considerable waste matter. The evaporation of the water tends to keep the body cool, but on account of the great heat-production there is not much danger of chilling the body during exercise. As soon as work is stopped heat-production is checked, the body cools off rapidly, especially in a strong draught or a current of air, and then there is danger of chilling unless more clothing be added. Flannel is best for this purpose because it is a non-conductor of heat and hygroscopic and so prevents too rapid cooling of the body. Keep the skin clean so that the sweat-glands may be unobstructed in the per- formance of their functions. Exercise increases the appetite, partly because of the increased demand of the muscles for food, and partly on EXERCISE 299 account of the increased circulation of the blood through the vessels of the alimentary tract, digestive glands and the liver, this causing a more perfect digestion of food. If exercise be taken too soon before meals, either the stomach, by calling the blood from the exhausted muscles, will prevent their proper repair and rest; or the muscles, calling the blood from the stomach, will prevent the proper formation of the gastric juice when food is intro- duced. If exercise be taken too soon after eating, it is apt to prevent the flow of blood to the organs of digestion and the formation of the digestive juices; or, by forcing the contents of the stomach into the intestines before gastric digestion is completed and before the food has reached a condition in which the intestines can make use of it, to cause intestinal irritation and indigestion. Proper physical exercise favors a symmetrical brain development, for it not only sends more blood containing food and oxygen to this organ, but exercise of the func- tions of the centres governing the action of the muscles must also favor the growth and development of those centres. "Hand culture, apart from its value per se, is a means toward more perfect brain culture," and exer- cise by itself alone is truly educational, although this feature of it may be more fully developed and empha- sized by proper systems and methods. The great trouble is that it is extremely liable to be misapplied, misunder- stood, or neglected. The aim of training should be to increase the capacity of the lungs and the breathing power, to strengthen the heart and the circulation, to invigorate the brain and nerve-centres, to improve digestion and nutrition, to make the muscles more powerful, more responsive to the will and their capacity for endurance greater, and to lessen the amount of adipose tissue. Systematic exercise also helps one to resist disease, because by it waste mat- ters are carried off; pores, glands, and organs are kept at work and healthy, and active tissues take the place of weak and sluggish ones. 300 PERSONAL HYGIENE Fatigue is due to lack of contractile material in the muscles to continue work, to the exhaustion of nerve-force and motor impulses from the brain, and to accumulation of waste products, possibly leucomains, in the muscle. Active exercise is that brought about by one's own movements; passive, that produced by something outside or collateral to one's own power. It is hard to determine how much exercise any given person ought to take, as the personal equation varies so much. The average healthy man should probably do work equivalent to 150 foot-tons daily. The work of walking on a level at the rate of three miles per hour is said to be equal to that of raising one-twentieth of the body-weight through the distance walked. According to this, a man of 150 pounds in walking one mile does work equal to 17.67 foot-tons, and his total daily physical labor should be equivalent to walking about nine miles at the above rate to get the proper amount of daily exercise. This seems like an excessive amount, but if the actual physical work of one's customary vocation be taken from this, it will probably not leave so very much for the daily health-task. The natural disinclination of many to exercise grows stronger by indulgence, and while urgent reminders are wanting and the evils arising from the neglect, abuse, or misuse of exercise are not so very immediate or apparent, the latter are still certain to result, and are not at all consistent with good and perfect health. BATHING. In health we make use of baths and bathing for the cleansing of the body, the stimulating of the functions of the skin, and as a tonic to the whole system. A suitable bath properly taken is exhilarating and thoroughly enjoy- able. Baths are also to be employed in sickness as a means of cure, but such use of them is foreign to the present discussion. H. C. Wood says: "Cleanliness and the maintenance BATHING 301 of the proper condition of the skin require the use of the bath at least twice a week. In some very deHcate persons the general bath produces marked depression, but this can almost always be avoided by the use of very hot water. If the hot or warm bath be employed habitually, it should be preferably taken at night, and, unless under very exceptional circumstances, the hot bath should always be followed by cold sponging or the cold shower-bath, or by a plunge into cold water." The temperature of a cold bath may be from 40° to 75° F.; a tepid bath, 75° to 85° F.- a warm one, 85° to 100° F ; a hot one, from 100° to 110° F. A cold bath is taken not so much for its cleansing as for its tonic and stimulating effects; the others are used mainly for their cleansing properties, though if followed by the cold sponge, shower, or dip, the sense of exhilaration produced will be marked. Cold baths taken immediately after physical exercise while the body is still w^arm, but after perspiration has ceased, and followed by a good rubbing and friction of the skin, dispel fatigue and give a sense of buoyancy and lightness. The shock of the first contact of the water with the skin is but momentary, and can be withstood by most persons unless there be serious organic disease; and the reaction produced certainly compensates for the primary discomfort. If the bath be taken in the open air^ there is the additional benefit of a plentiful supply of fresh air for the lungs, of the physical exercise and the increased circulation induced by swimming or combating the surf, and, if in the sea, of the stimulation of the skin by the salt water. In fact, sea-bathing may be advan- tageous to a marked degree where the circulation and action of the skin are sluggish. Those who are subject to organic heart disease should not indulge in sea-bathing nor in deep fresh-water bath- ing, since a sudden tax may be made upon the strength and the heart action be disturbed or checked. Women who are menstruating or who are in the later months of pregnancy should not take cold baths. 302 PERSONAL HYGIENE Baths should not be taken too soon after meals, because digestion may be lessened or entirely stopped by the blood being called from the stomach to the skin and muscles, and nausea and vomiting thus induced. "There can be no doubt that many of the cases that are called 'cramps,' and which frequently result in drowning, are due to this cause."^ In cold baths the head should be immersed first, "to avoid increasing the blood-pressure in the brain too greatly, which might result if the body were gradually immersed from the feet upward."^ The following rules, issued by the English Royal Humane Society, are worth noting: "Avoid bathing within two hours after a meal, or when exhausted by fatigue, or when the body is cooling after perspiration. Avoid bathing altogether in the open air, if, after having been a short time in the water, there is a sense of chilli- ness, with numbness of the hands and feet; but bathe when the body is warm, provided no time is lost in get- ting into the water. Avoid chilling the body by sitting or standing undressed on the banks or in boats after having been in the water. Avoid remaining too long in the water, but leave the water immediately if there is the slightest feeling of chilliness. The vigorous and strong may bathe early in the morning on an empty stomach; the young and those who are weak had better bathe two or three hours after breakfast. Those who are subject to giddiness or fainting, or who suffer from palpitation or other sense of discomfort of the heart, should not bathe (out-of-doors) without first consulting their physician. "^ After any kind of a bath the body should be thor- oughly dried, not only to restore and accelerate the cir- culation of the skin by the friction and to prevent cooling by the evaporation of the water, but also to prevent chafing and eczematous eruptions where the skin is subject to the friction of clothing. Warm or hot baths 1 Rohe's Text-book on Hygiene. 2 Ibid. 3 See also Sea Air and Sea Bathing, by John H, Packard. BATHING 303 should not be taken if the person is to be exposed to the cold within several hours, and the same rule applies to Turkish, Russian, or vapor baths; so the former had best be taken in the evening, and the latter should not be taken away from home, especially in cold weather, unless the bather rests for a time after the bath, and then wraps up well before going into the open air. In all warm baths in health the principal object is to secure the cleansing effects, and to be effective their use must be systematic. The pores of the skin are self- cleansing only to a certain degree, and the free use of warm w^ater is most beneficial in removing dry epithelium, sweat, dirt, and grease. If the pores of the skin are ob- structed, there are not only irritation and eruptions of the skin produced, but more work is thrown upon the kidneys, and these, if unsound, will break down the quicker. Soft water is to be preferred for ordinary bathing and washing, because it often prevents or lessens cutaneous irritation and because it saves soap. Public baths have become a marked feature in the scheme of municipal sanitation of a number of cities, and are of benefit not only directly, but as a means of incul- cating a habit of cleanliness in those who use them. Where possible, separate baths should be provided for the two sexes, and all should be at all times under competent and strict supervision. There is some danger, however, of the spread of infection, especially of skin diseases, in the use of swimming pools, or of individual bath-tubs, and shower booths should always be provided in preference to the latter. For the same reason the water in swimming pools should be frequently changed, and it is also well to attempt to render it aseptic by the addition of small quantities of certain chemicals, such as chlorinated lime or copper sulphate. A Turkish bath consists: (1) Of a dry, hot-air bath at a temperature of from 120° to 170° F., or even higher, for from ten to thirty minutes, which causes in most per- sons profuse perspiration with no sense of discomfort, 304 PERSONAL HYGIENE but rather a pleasant sensation. After this come: (2) A hot shower-bath to wash off the sweat. (3) Shampooing, massage, and scrubbing to remove thoroughly all dirt, loose epithelium, and perspiration from the skin. These take place in moist air at from 100° to 110° F. (4) A warm shower-bath gradually changing to a cold one, and then a thorough drying of the body and a rest for a quarter- or half-hour. A Russian bath differs from this only in that moist air at 150° F. or under is used instead of dry air for the first bath. It has been said "that a person ought never stay in either the hot-air or steam-room if in anywise oppressed, or to use very cold water afterward if one feels any shrinking from it." Nor should one who is very corpu- lent or who has organic heart disease take a Turkish or Russian bath without the advice of a physician. But for healthy persons they are quite pleasant and in most cases beneficial, provided they are not taken too often and that one does not indulge in them too long at a time. The terms sun-baths, mud-baths, sand-baths, and pine- needle baths are self-explanatory. These are used in treating certain diseases, and are supposed to be espe- cially beneficial in rheumatic affections. CLOTHING. There is scarcely anything that can be said on this subject with which almost every one of ordinary intelli- gence is not in some respects conversant. According to Poore, the main objects to be sought in clothing the body are : " ( 1 ) To maintain the temperature and, by preventing the loss of animal heat, to diminish to some extent the demands for food. (2) To allow the chief heat-regulating mechanism — i. e., the evaporation from the skin — to pro- ceed with as little hindrance as possible. (3) To allow all muscular acts the greatest possible freedom, and to avoid the compression of the body in so far as may be possible. (4) To protect the body from heat, cold, wind, and rain. CLOTHING 305 (5) To disguise as little as may be the natural beauties of the human figure."^ The substances from which articles of clothing are usually manufactured are wool, silk, cotton, linen, leather, and furs, although almost everything that can possibly be fashioned to suit the needs or fancies of the wearer is or has been utilized for the purpose. Goods of all manner and kind are woven from the first four substances men- tioned, either singly or in combination one with another, and felts are made from wool, hair, or fur, these latter being made, not by weaving, but by an interlacing and matting together of the fibres by pressure and rubbing. Wool. — In a general sense wool is probably the most valuable of clothing materials, since in a variable climate or where there are sudden changes of temperature it is the safest for the wearer to use. While, taking fibre for fibre, it probably does not vary so much from linen or cotton as a heat-conductor as is generally believed; it is usually woven in such a way as to entangle large quan- tities of air in its meshes, thus preventing either sudden lowering or raising of the body-temperature, since dry air is an especially good non-conductor of heat. Moreover, wool is very hygroscopic, readily taking up water and perspiration and giving them off slowly, thus reducing the cooling by evaporation to a minimum and regulating the heat-dissipation of the body. All who are subject to rheumatism or to such disturbances of health as to render them susceptible to sudden temperature-changes should wear woollen garments next the skin the year round, varying the thickness and weight, of course, to suit the season; and children and others subject to digestive disturbances will usually be greatly benefited by the constant use of a woollen (or, in case that is too heavy, a silken) band about the abdomen. As it is ordinarily woven, some persons cannot tolerate wool next the skin on account of its irritating properties. » Stevenson and Murphy, Treatise on Hygiene. 20 306 PERSONAL HYGIENE These latter are obviated, however, if the undergarments be made of pure wool woven by methods similar to that introduced by Jaeger, or of a mixture of wool or cotton, or by wearing a garment of linen or cotton net next the skin and underneath the woollen underclothing. The Jaeger method, by the way, is said to provide for the escape of moisture from the material and for the free per- meation of air through its interstices. Silk. — Silk is an excellent non-conductor of heat, and is almost as hygroscopic as wool, so that it is suitable material from which to make warm clothing. Its great natural beauty and the facility with which it takes coloring matter also make it desirable from an esthetic stand-point, while its great disadvantage is its high cost. For those who cannot wear wool next the skin and to whom cost is no objection, silk is an excellent material for under- garments. Cotton. — Of all the fibres, cotton is probably the most generally used for clothing. It is not so hygroscopic by far as wool, but it is hard and durable, and is, above all, cheap, so that it furnishes the bulk of the clothing for the masses. If smoothly woven and of a light color, it makes extremely cool garments for warm climates or seasons. On the other hand, if warm clothes are desired, the cotton must be woven so as to have large air-spaces in the fabric, thus making it resemble the ordinary woollen clothing in texture and partly in function, and should be of a dark color. Cotton should not be worn next the skin by those subject to disturbance by sudden tempera- ture-changes, nor during exercise, unless in the latter case it is changed immediately after the exercise or additional clothing is added to the body to prevent too rapid evapor- ation and cooling. Linen. — Linen is valued for its purity of color when bleached, and for its durability. It is more expensive than cotton, and its hygroscopic and heat-conducting properties are about the same as the latter. It is especially desirable for use in clothing for hot climates and for CLOTHING 307 articles of dress that are easily soiled and need frequent cleansing. Furs. — Furs provide extreme protection against the wind and cold, both on account of the impermeability of the skin and of the large quantity of air entangled in the fur itself. Leather. — Leather is utilized for foot-coverings, etc., on account of its durability, pliability, and practical imper- viousness to moisture, especially when oiled; and in cold countries is also used for body garments on account of its resistance to the wind and the efficacy with which it keeps the body surrounded wath a layer of warm air. Rubber. — With the possible exception of rubber, which is especially useful for the protection which it gives from wind and rain, other materials from which clothing is made need not be mentioned here, because of the comparative rarity of their use and their close resemblance to those already named. The value of any material for clothing purposes, however, may be said to depend upon the slow- ness with which it permits the passage of heat to or from the body and the evaporation of water, the amount of air its meshes contain, its impermeability to the wind, or else its special adaptability to some particular purpose. Certain materials are manufactured from combinations or mixtures of two or more of the four fibres first men- tioned, and it sometimes becomes necessary to distinguish these one from another and to determine the proportion of each in the goods. This is done by microscopic examination, each fibre having its own peculiar char- acteristics, and by chemical reactions. Some of these latter are as follows: Wool and silk dissolve in hot liquor potassae or sodse of a specific gravity of 1050, while cotton and linen are not affected. Wool and silk are stained yellow by strong nitric or picric acid; cotton and linen are not. Sulphuric acid affects wool but little, slowly dissolves silk, and changes cotton or linen into a gelati- nous substance that is colored blue by iodine. Hot concentrated zinc chloride dissolves silk, but not wool; 308 PERSONAL HYGIENE and copper dissolved in ammonia rapidly dissolves silk and cotton, linen more slowly, but only slightly swells wool. Cloths are often sophisticated in the process of manu- facture, and their value greatly lessened thereby. Wool is mixed with "shoddy,'' which is made from old and used woollen rags torn asunder and then respun with an addition of fresh wool; silk is heavily weighted with salts of tin, iron, or with other substances; and cotton and linen are stiffened and glossed with an excessive amount of starch, white earth or the like. Shoddy can be determined by the use of the microscope; the weighting of silk by chemical reactions and solutions; and over- starching, etc., of cotton and linen by washing and drying. It will not be advisable here to go fully into considera- tion of the influence which the shape and style of the individual garments of ordinary use have upon health, for that would require a much longer discussion than the present space permits; but the general rule may be laid down that each article of clothing should be adapted to the peculiar needs and occupation of the wearer, and that it should in nowise interfere with the proper develop- ment, use, or physiological functions of any part of the body. Trite and hackneyed as is the subject, the writer feels that he would be wanting in the performance of his duty if he failed to condemn the habits and fashions of dress that demand undue constriction of the trunk of the body. All sanitarians practically agree upon the importance of "vital capacity," as measured by the development and extent of expansion of the thorax, in determining the constitution and health of the individual. But not only may the corset harm by interfering with the func- tions of respiration and circulation, but it may also deform and induce even more serious troubles by its displacement of the abdominal and especially of the pelvic organs, and by the grave interference with the nutrition, tone, and CLOTHING 309 functions of all of these. It is a fair challenge to any woman who declares that she does not dress too tightly, to ask her to measure honestly her waist circumference and expansion both with and without the garment in question, and to make her decision accordingly. And it is certainly false doctrine to teach, as is so often done to young girls, that it is really necessary that the normal human body should have artificial support. The natural muscles kept in proper training, tone, and action are all- sufficient to give the most perfect and most beautiful human form. Another matter of serious moment is the harmful influ- ence of ill-fitting and improper shoes upon the structure and function of the foot. This was demonstrated, so far as men are concerned, by the unduly large number of men rejected for military service in the recent war because of defective feet, as well as by the remarkable improve- ment and benefit experienced by many others after wearing for a short time the army shoe made upon the normal last. How much more serious is the effect of the abnormal styles and high heels of women's shoes can be readily demonstrated and should be appreciated by thoughtful students of hygiene. When exposed to the sun's rays or to other sources of radiant and incandescent heat, fabrics absorb heat irre- spective of the constituent materials, but in the following order as regards color: white, light yellow, dark yellow, light green, Turkey red, dark green, light blue, and black, the latter color absorbing more than, and light blue almost twice as much as, white, the material in each case being the same. In the shade the degree of absorption depends more on the material than on the color. Lastly, it should be remembered that, as disease germs are readily conveyed from place to place and from one person to another by the clothing, and especially by that which is hygroscopic by nature, care should be taken to keep the garments in as cleanly and aseptic condition as possible, to disinfect them whenever they have been 310 PERSONAL HYGIENE exposed to infection, and, for those who are much among the sick or liable to infection, the use of smooth, closely woven, non-hygroscopic outer or overgarments that can be readily cleansed, such as those made of cotton or linen, is to be highly recommended. LIGHT. The important influence of sunlight in the development and maintenance of a healthful condition in all higher organisms, both animal and vegetable, is well known by everyone, but as yet there is a lack of information as to the exact physiological methods and processes which are due to this great force. We know that, for the plants, chlorophyll is the intermediary agent which largely assists in the conversion of carbon dioxide and the storage of carbon in various compounds, and that the presence and action of this chlorophyll are largely dependent upon the light-supply; while for the animal kingdom, and espe- cially for the human race, it is evident that the effect of sunlight is manifested more or less directly in the blood and skin, though the whole body quickly shows a marked appreciation of its presence or absence. But when this has been said, there is little else that can be added as a matter of positive information. No one knows just how the pallid and anemic child that has been reared in the shade and dark is converted into the tanned and ruddy picture of health in so short a time, but the results are unquestionable. The subject demands further study, and it may not be out of place to indicate one or two directions in which the investigation may, perchance, be wisely pursued. In the first place, there has doubtless been too little appreciation of the fact that sunlight in its totality has many other rays of force than those which manifest them- selves alone to our sense of sight. The existence of the ultra-violet rays and the fact that these are more powerful actinically than those of the ordinary spectrum have been satisfactorily demonstrated, and the only question LIGHT 311 is as to what the true physiological power and influence of these invisible rays may be. It is not certain at present that some of them, at least, are not closely related to the manifestation of force discovered by Rontgen, and there is good reason to believe that the penetrative powers of light as regards the human body are not fully known or appreciated.^ Nor can we tell how much of that power of the sun whose effects we feel and see is in nature on that border-land between light and electricity that is as yet so vague and unknown. Again, the destructive effect of sunlight, and of light from minor sources as well, upon the germs of disease and other low forms of life, and upon their toxic products, is now a matter of common knowledge, though many are not aware that it has been proved that this germicidal action of light is directly in relation to its actinic power. Especially has it been shown that the ultra-violet rays quickly destroy the vitality of micro-organisms and the toxins produced by them. Considering this, together with the statements in the preceding paragraph, may we not surmise that hostile organisms, even in the deeper tissues, are overcome both in this way and by the improved condition of the blood due to the light, and that this hypothesis helps to explain the good results that follow the open-air treatment of many diseases and abnormal conditions? The tubercle bacilli are especially susceptible to its influence, and everyone should know that an abun- dance of sunlight is just as essential to the tuberculous patient as are plenty of good food, pure air, or proper clothing. Bie, Finsen and others have done much to develop the treatment of disease by light, whether from the sun or artificial sources, and good results are frequently 1 Some experiments by the author and by numerous others seem clearly to indicate that some of the radiant energy from the sun, and in lesser degree from other sources of light, is able to penetrate substances hitherto considered opaque, and to produce phenomena similar to those due to the Rontgen rays. Consequently, if the experiments referred to are well founded, the penetrative ability of this energy, as regards the human tissues, would seem to be more than probable. 312 PERSONAL HYGIENE obtained from such treatment, especially in the case of cutaneous or superficial diseases. And although more might be said in reference to the possible and probable chemical activity of the light in and upon the metabolic processes of the animal body, as there is still the un- FiG. 81. — Heliotherapy, Sea Breeze Hospital, Sea Gate, New York, March 18, 1913. Cured case of tuberculosis of the knee. No sinus. (Hinsdale's Atmospheric Air in Relation to Tuberculosis.) certainty of hypothesis and theory, it may be wiser simply to leave the foregoing suggestions as food for thought and incentives to further research and investi- gation. The importance of an abundance of daylight in all rooms where much work is to be done should not be LIGHT 313 overlooked. Not only is it necessary for the conservation of the influences just mentioned, and as a destroyer of pathogenic organisms, but it is also more agreeable and safer for the eyesight than any form of artificial light yet devised. An important aid to the illumination of dark interiors has been the introduction of panes or plates of glass with a series of ridges or prisms, which refract and diffuse throughout a room light which would otherwise illuminate it but partially or not at all. The -" :«^ia-_i- ^^^^^if-. - — ^^t -z-^-. w— _ Fig. 82. — Action of prismatic glass in projecting light. (Harrington.) prisms are made with various angles, and may be placed either in the ordinary window sash or in projecting canopies, according to whether the direct light from the sky is obstructed or not. (Fig. 82.) The relation of artificial lighting to ventilation has been discussed. In addition to this point, the quantity of light supplied and its steadiness have an important bearing on the hygienic value of any artificial source of illumination that it may be necessary to employ. CHAPTER IX. SCHOOL HYGIENE. It was remarked in the chapter on Personal Hygiene that the best time for applying the laws of hygiene is in the days of childhood and youth, for then the whole organism is plastic and yields readily to both external and internal impressions and forces. This being so, the great influence of the factors common to school-life may be readily conceived, and inasmuch as the average child will be subject to them for a large part of from eight to ten or more years, the importance of a study of school hygiene will not be denied. It concerns the parent, the physician, and the citizen, and its inves- tigations must consider the personal hygiene of the scholar, the conditions of his health, his habits, the amount of work done, the sanitary environment and requirements of the school-room and building, the furniture, the venti- lation and heating, and the influence of all these upon the individual's state and development. Next to the scholar himself and his parents, these matters are of special interest to the physician, for, in addi- tion to being one who from his special training and educa- tion is often called to act upon school committees and boards of education, or as a medical inspector of schools, he has to treat many disturbances of health in the young which have their origin or cause in the harmful or insani- tary conditions of school-life. There are disorders to which all children are subject whether in school or out; but a special class are markedly influenced by school-life or work, and to these abnormal conditions we may give the term "School Pathology." Of some of these, overwork is the cause; others are set up by other factors. (314) INFLUENCE OF OVERWORK UPON HEALTH 315 Overwork, coupled with depressed vitality or other influ- ences, may'give rise in children to one or more of the follow- ing troubles: dyspepsia, headaches, nervous derangements, chorea, epilepsy, neurasthenia, backaches, menstrual dis- orders, and, in some cases, consumption. On the other hand, faulty arrangement of seats and desks, improper location of windows, blackboards, etc., may cause spinal and other physical deformities, defective eyesight, etc. Of the first class, even where the amount of work may not seem, or may not really be, too much for the capacity of the child, worry about rank or over an approaching examination may have a harmful effect upon a nervous temperament. This is especially so if the examina- tions come at the end of a spring term, when the scholars are all more or less worn-out and debilitated. The forcing process should be avoided as far as possible, and if grades are to be given at all, they should be as much as possible for the work and attendance during the term, and not so much for the actual work done at examination time. Moreover, young children should not be kept in school for too many hours in the day, nor should school be looked upon by parents as a place to which to send chil- dren to keep them out of the way and from mischief. Edwin Chadwick has shown that a child from five to seven years can only attend to one object for about fifteen minutes; one from seven to ten, for twenty minutes; from ten to twelve, for twenty-five minutes, etc., and that the length of individual lessons and likewise the total day's work should be arranged accordingly. The very early years of school-life should be given to inculcating correct habits of attention and of morals and to training the will and powers of concentration and observation, rather than to the teaching of any special knowledge. But apart from the physical conditions of the school- room and postural and other personal habits of the pupils, it is probably the work attempted outside after school hours, and not the actual work done in the school, that is most responsible for the breaking down of health, 316 SCHOOL HYGIENE especially in older scholars. In Cleveland, in 1881, of 186 girls in the high school, 29 per cent, of* those who studied less than two hours, 70 per cent, of those study- ing from two to four hours, 93 per cent, of those study- ing from four to six hours, and 100 per cent, of those studying over six hours daily out of school, had poorer health while at school. Of these same girls, the per- centages of those whose health was "very poor while at school," dividing them the same way as regards over- work, were respectively 14, 40, 66, and 100 per cent. This loss of health was attributed by the parents to stair- climbing, irregularity of meals, worry about rank and examinations, etc.; but Goodell says: *'So commonly do I find ill health associated with brilliant scholarship, that one of the first questions I put to a young lady seeking my advice is, 'Did you stand high at school?' " Another writer says: "The effects of anxiety are worse than carrying heavy loads." In fact, one of the leading educators of the country has suggested that children should not be required to study reading, writing, or drawing before the age of ten or eleven, as these bring into action and use the close appli- cation of the finer sense organs and faculties which are not as yet fully developed; but he advises that the instruction of the earlier years of school-life should consist mainly of language lessons, history, nature studies, and such others as may be taught orally and that will at the same time develop the child's powers of attention, obser- vation, and reasoning. There is more than a chance that such a plan of instruction would not only secure better results from the teacher's point of view, but that it would also be safer for the scholar's physical organism. While a child is at school its mind should not be wearied by outside tasks, as music or painting lessons, nor the body weakened by social dissipations, late hours, and indigestible food. Girls are more susceptible to dis- turbances of health, and are more subject to them, because they are more willing to undertake extra or double work ILL HEALTH DUE TO SCHOOL-LIFE 317 than boys, and because they are more ambitious and worry more about rank. In all children the obtaining of good health and a sound constitution is of the first importance. Youth is the time for gaining health, not for losing it; for building up sound bodies and constitutions, not for breaking them down, and school-life should always have the former as one of its greatest ends. Of what use is all the learning one may gain before the age of eighteen, if there be no strength to use it afterward in the battle of life? School-life is sometimes responsible for dyspepsia by interfering with the regularity of meals, the children missing the mid-day meal and having to depend upon a meagre lunch, often of sweets and indigestible food. This is especially important when the rest of the family dine at noon, and there is only a light meal served in the even- ing. Again, many habitually lose their breakfast through fear of being late, or else bolt the food without masticat- ing it and gulp down hot coffee or tea before starting on a run for school. But often the loss of appetite is due simply to lack of fresh air and proper exercise, or else to the nervous condition of the child, which is sometimes such as to interfere with almost all of the body functions. Such dyspepsias are to be treated by attention to the foregoing points rather than by medicine. Headache is a common disturbance among school-chil- dren, and may be due to any one of several causes, among which are overwork — producing irritability and disturb- ances of cerejiral circulation — indigestion, bad air, eye- strain, etc. /The eyes should always be examined when headaches are persistent, and any defects corrected by proper glasses^/ Associated with the headaches, frequent bleeding from the nose may occur and should not be over- look^, as it may indicate circulatory disturbance. ,^*NEye-strain is a particular evil of civilization, and makes its first appearance in school when the scholar tries to accommodate the eye to the short range which reading requires, but for which the eye mechanism is not well 318 SCHOOL HYGIENE adapted by nature." "In New York City 29.5 per cent, of 79,069 children examined suffered from defective vision. In London 26 per cent, of 20,000 children ex- amined by eight ophthalmologists had defective vision, and of this number 12.5 per cent, suffered from vision of one-half or less. In Philadelphia 34 per cent, of 1156 children had defective vision, and of this number 6 per cent, had vision of one-half or less. A small proportion of this number only is fitted with glasses. The rest suffer from real eye-strain."^ One of the most common symptoms of nervous derange- ment is sleeplessness or restless sleep, and this condition should give warning that something is wrong. Folsom says: "I doubt whether there is an exaggerated preva- lence of manifest or well-marked diseases of the nervous system among school -children. If due to the school-drill, my impression is that they come for the most part later in life, after the children have left school, and because of constitutions weakened during school years, instead of strengthened as they should be." Children subject to chorea or epilepsy should not attend school, not only for their own sake, but also for that of the other children, who may be unduly affected by their nervous manifestations. Such children should be educated quietly and cautiously, with proper treatment and plenty of out-door life. Neuras- thenia or general break-down may occur, usually from overwork, and especially among young women. It may come on unexpectedly after the examinations at the end of the term, when the strain and excitement are removed. Menstrual disorders are also apt to occur among girls that are being overworked mentally, and we ought to remember that the system is undergoing a heavy strain at the time this function is developing. Also, for certain young women rest from customary work is necessary at the time of the periodical recurrence, and excuses for absence at this time ought to be freely granted. It has 1 Report on National Vitality, Fisher, pp. 8, 74, and 75. INFLUENCE OF SCHOOL-FURNITURE 319 been well said that ** girls get through as much work as boys, working in their own way." The development of consumption may be due to the school-life, though it is hard to say how frequently this is the case. Bad air and overwork are both important factors in its production, and if these are forced on under- fed or predisposed children the disease may be provoked. Only recently have we realized that a large proportion of the cases of tubercular infection occur in early life. The greatest mortality from this disease is in the first two years, after which there is a quiescent period for about ten years. Then, at the age of twelve years in girls and approximately sixteen in boys there begins a new and marked increase in the mortality rate which apparently must be due to the lighting up of the disease from latent foci in the body rather than to a new infection from without. The notable recrudescence of the disease at these ages is most reasonably to be attributed to the stresses incident to pubertal development and should warn us that added burdens at this time, whether of the school or home, are positively inadvisable.^ "In a consumptive family the steadfast rule should be that the mind be wholly subservient to the body's welfare." The main cause of spinal and other deformities and defective eyesight is apt to be found in faulty construction of seats and desks, improper location of windows, etc., though excessive work or strain may maintain a low vitality and act as a predisposing condition. The latter point is shown by the fact that spinal curvatures are more prevalent in those especially prone to weakness of the muscles, as women and girls. But no desk or seat will remove original weakness of muscle as the one important predisposing condition, and children cannot be made strong by supports. "Spinal curvature is not only a product of low vitality, but does harm by permanently fixing vitality at a low standard." * See Hess: Tuberculosis in Children, Jour. Am. Med. Assn., January n, 1919, pp. 83-88. 320 SCHOOL HYGIENE If Fig. 83.-Position assumed in writing with the desk too high. (Pyle.) Fig. 84.— Position assumed in writing with the desk too low. (Pyle.] INFLUENCE OF SCHOOL-FURNITURE 321 Improperly arranged seats and desks not only often cause spinal deformities, but also help to develop defective eyesight by causing the scholar to hold the book too near the eyes and by making him bend his head so that the circulation of blood is impeded and ocular congestion favored. However, no seat can be devised in which a child will maintain a correct or "normal" position for any but a short time, as this is an impossibility for young children; but the aim should be to furnish a seat in which one will naturally assume the correct position after having temporarily taken any other. "Movement is a child's way of resting; rest is a kind of work, to be taught by degrees." Seats should have backs to prevent fatigue, but a comfortable back gives support to the lower part of the spine rather than to the shoulders and upper part of the spine. Many foreign authorities advise seats with backs only high enough to support the lower part of the spine, and low enough for the scholar to rest his elbows upon them while studying. The following points, suggested by Lincoln, are worth noting : " (1) The chair is often too high for young scholars. The most convenient plan may be to provide foot-stools. (2) The seat from back to front ought to be long enough to support the whole thigh. A more or less spoon-shaped hollow in the seat is commonly thought desirable. The curve of many settees is such as to produce pain at the point where the tuberosities of the ischium rest on the wood; the support is there not wide enough. (3) Seats must have backs. The straight, upright back reaching to the shoulders is bad; a straight back, slightly tilted, is not bad. American seats are commonly curved, with curved backs. (4) The edge of the desk should come up to, or overlap, the edge of the seat. The recognition of this fact is a recent discovery. (5) Most of our best desks are too high relatively to the seat, doubtless to prevent the pupil from stooping. Something is gained in con- venience of reading by this plan, but it interferes with correct positions in writing. The elbows, hanging freely, 21 322 SCHOOL HYGIENE ' should be only just below the level of the lid." For near-sighted children the higher desk may be a necessity in writing; if the desk is made low, a portable writing- stand may be placed on top of it when necessary. Windows on only one side of a large school-room may not give sufficient light for the desks most remote from them. Consequently there should be windows on two sides, preferably adjoining ones, of large school -rooms. The windows should be at the back and to the left of the scholar, thus giving the best light upon the desk for either reading or writing. They should not be placed in front of the scholars, as the continuous glare is very trying and injurious to the eyes. They should extend almost to the ceiling and have square tops, to admit as much light as possible. In some cases refraction prisms (Fig 82) may be used to advantage. Blackboards should have a dead-black surface, not a glossy one, and should be on the sides of the room on which there are no windows. Walls should be of a neutral tint, not glaringly white. In some cases considerable additional diffusion of light may be secured by installing a series of light-colored cur- tains corresponding in color to the walls of the room and that may be drawn to cover the blackboards when the latter are not in use. CONSTRUCTION OF SCHOOL-HOUSES. The principles already given as to ventilation, heating, water-supply, etc., apply here as elsewhere. From 1800 to 2500 cubic feet of fresh -air should be supplied to each scholar per hour. In cold weather this should, of course, be satisfactorily warmed. The air-ducts, both inlets and outlets, must be sufficiently large to change the air without causing injurious and uncomfortable draughts; and these ducts should be as short and free from bends as possible, or, better, the rooms should open into the supply and exhaust shafts directly. The air may be warmed either by steam or hot- water coils or by a furnace, CONSTRUCTION OF SCHOOL-HOUSES 323 though preferably by the former to avoid "baking" the, air, and also preferably by the indirect system. There is no objection to having additional heating apparatus in the school-room, provided it is guarded so that the scholars may not be accidentally burned. Any system that will give a sufficient supply of fresh air properly heated will of necessity be more expensive than the old way of not ventilating at all except by opening the windows at recess time, but experience shows that the increase in expense is not so very great, as so much heat is lost by opening the windows in this way, and the benefit to the chil- dren more than compensates for the additional outlay.^ Country schools may be heated by stoves surrounded by sheet-iron drums, and ventilated with fresh air from with- out brought in near the bottom of the stove. (See Figs. 24 and 27.) Passing up between the stove and drum the air is warmed and gives good ventilation without chilling or draught. As great a length as possible of stove-pipe should be exposed in order to get the full benefit of the heat from it. The Smead system of ventilation and heating has been used with satisfaction in many schools throughout the country. In this, the air being warmed and brought into the school -rooms at a level a few feet above the floor, circulates through them and is finally withdrawn through registers at the floor level, whence it is carried under- neath the floors to large outlet shafts in which a draught is constantly maintained. In this way thorough diffusion and changing of the air in the school-rooms are secured, and, moreover, the floors are kept warm by the heat from the air which is passing beneath them and which would otherwise be wasted. (Fig. 85.) '"Newton reports a case of an old, unhygienic school building in a small town being fitted up with a ventilating system, with the result that the cost of the improvement was saved in a short time in salaries that otherwise would have been paid to extra teachers for taking the place of those made sick by the foul air in the building." Report on Human Vitality, Fisher, p. 73. 324 SCHOOL HYGIENE The relative size of the school-room is of importance. Each pupil should have about twenty square feet of floor space, and as there should not be over forty pupils to the room, the total area of the room should approximate 800 square feet. The length of the room will depend not only upon the distance both teachers and pupils can be heard distinctly, but at which the scholars can see the blackboards, charts, etc., distinctly, and school manage- ment is undoubtedly easier in a room that is not too long. Experience shows that ordinary blackboard writing is Fig. 85. — Illustrating the Smead system of ventilation. visible at twenty-nine feet, so the maximum length of the room will be about thirty-two feet, this allowing for an aisle of sufficient width at the rear of the room. With the area of the room already determined as indi- cated above, this length necessitates a complementary width of twenty-five feet, a dimension that is also in a measure governed by the principle that the school-room should not be much more than twice the height of the top' of the windows, which in turn, should extend almost to the ceiling. And as it is agreed that the ceilings for rooms CONSTRUCTION OF SCHOOL-HOUSES 325 of this size and purpose should be about twelve or thirteen feet high, the width mentioned is a correct one. Ample cloak-rooms should be provided for every school; they should be warm and well ventilated in order to secure the rapid drying of the garments in wet weather, but they should not communicate directly with the school-rooms themselves, if it can be avoided. Provision should also be made for readily disinfecting them, and, in fact, the whole school building at intervals and when- ever necessary. In 1897 at Newcastle-upon-Tyne, "the experiment was tried of closing each school, where scholars were being taken ill, for a few hours only, long enough to allow of thorough purification and the sprinkling of the floors of class-rooms with disinfectants. This disinfection so far as measles was concerned, was followed by the extinction of the disease in question."^ The school-house should be on dry and well-drained soil, as dampness is not only depressing to all constitutions, but is also an important factor in the causation of phthisis and strumous diseases. There should not be too much shade about, and as many rooms as possible should have sunny exposures. If the sunlight is annoying during the session, it may be excluded by inside blinds or shutters, but we must not lose sight of its helpful influence in the destruction of bacteria and purification of organic matters. Where sunlight is scanty or it is difficult to illuminate the school-rooms, it may be advantageous to furnish one or more of the windows with some form of the diffusing and refracting prisms already described (page 313), thus giving an abundance of light where there was formerly a deficiency, and materially lessening the eye-strain of the scholars. Basements of school-houses should be well lighted and dry, and should be kept scrupulously clean that moisture » American Year-book of Medicine for 1900, pp. 54.3 and 544. '32G SCHOOL HYGIENE and noxious gases may not be drawn into the rooms above. If properly arranged and cared for, they may be used as play-rooms in stormy weather when it would be unwise to send the scholars out-of-doors. Open-air Schools. — A striking innovation of recent years is the open- or fresh-air school, the first being established in Germany in 1904, and in this country, in Providence, R. I., in 1908. Since then others have been opened in many American cities, and "there is but one reason against the very extensive adoption of the open-air school — its expense. The cost per capita (about $140 per annum) is four or five times that of the per capita cost in the regular school."^ As Cornell further says: "The fresh-air school is really a sanatorium. It provides not only free air, but also nourishing food, enforced rest, warm clothing, individual teaching, sympathetic care, and medical attention which corrects eye-strain, adenoids, decayed teeth, and anemia. Naturally, the health benefits of the open-air schools are due to other causes as well as the fresh air." Nevertheless, the results obtained are most striking and have served to increase the enthusiasm of the advo- cates of these schools, for it must be remembered that the pupils in them have been selected because they were poorly nourished, had a marked tubercular tendency, or were even in active stages of tuberculosis. The gain in weight, strength and health, increase in mental activity and progress in school work are marked, and all serve to justify these schools and the increased cost of main- taining them. The water-supply should be free from impurities and as good as can be had. In the country, if from a neighbor- ing farm-house spring or well, it may be contaminated by leakage from cesspools and barnyards. Or the school water may be taken from a neighboring spring or stream which is receiving contamination from the school-house ^ Cornell's Health and Medical Inspection of School Children, p. 115. CONSTRUCTION OP SCHOOL-HOUSES ,327 cesspool or other sources. For this reason, teachers should be taught the tests for chlorides and ammonia and the reason for making them, and should make these tests frequently. If cause for suspicion arises, the use of the water should be stopped at once. Fig. 86. — Type of sanitary drinking fountain installed in schools by placing bubbling-cups on old fixtures. (Newmayer.) Water-closets and urinals, where in use, should be kept clean by a competent janitor, and the principal or head- teacher should see that this is done. In the country, the 328 SCHOOL HYGIENE pail or earth-closet system should be substituted for the usual privy-vault or cesspool, and it should be the duty of some one apart from the teacher, regularly appointed and paid by the school directors of the district, to see that removals are made at proper intervals; the teacher should maintain supervision over the daily condition of affairs. If possible, the out-houses should be connected with the school-house by covered ways, that the children may not be exposed in inclement weather; but these ways should be open or else constantly ventilated by open windows on either side. Cesspools, if unavoidable, should be at least fifty feet distant, and should drain away from the school- house. Though approving the Smead system of warming and ventilation for school-rooms, the writer cannot say that he approves that modification of it wherein the foul air from the building is carried over the fecal excreta of the inmates before being discharged into the outlet shafts and carried to the outer air. Though the method rapidly desiccates the excreta and renders it inoffensive to the senses, there is danger of the dissemination of disease germs as well as a departure from sanitary principles in the method. Ample provision must be made for the rapid escape and for the safety of scholars and teachers in case of fire or panic. Fire-drills should be regularly practised in all schools of two stories or more, and presence of mind inculcated, that emergencies may be met with safety. The comfort of the child should not be forgotten in the construction of the school-house, though preservation of health is the main aim. The importance of ample and properly equipped school- and other playgrounds for children should also be em- phasized. Not only does active natural play in suitable surroundings do far more for the physical welfare of the body and the invigoration of the mind than formal gymnastics, even though it be admitted that the latter have a place in education, but the former also aids in < o J Dl, < a. u o X t, to ^ Pu 1- s: "5 « a I u. MEDICAL INSPECTION OF SCHOOLS 329 establishing a better social and moral status among the children by affording natural outlets for exuberant energy, developing self-restraint and consideration of others, keeping the boys off city streets, and preventing thoughtless or malicious mischief. Such playgrounds should, wherever possible, have competent supervisors in attendance to advise, encourage, and instruct those who make use of them, as well as to prevent disorder or abuse of privileges. MEDICAL INSPECTION OF SCHOOLS. As certain diseases are contagious, it is necessary that school authorities have the right to forbid the attendance of such persons as have been exposed to in- fection until all danger of transmitting the disease to others is passed. This power is usually, however, exerted only in the case of those diseases most dangerous to life and health, though the stringency of the regulations varies at different places. Smallpox, scarlet fever, diph- theria, measles, and even whooping-cough should always be quarantined, and it would be better to keep children who are afflicted with minor diseases of this class out of school till all danger of infection is over, as it is only by rigid measures like this that we may finally be able to eradicate those maladies. Considerable evidence now supports the view that there is a marked decrease in the prevalence of both scarlet fever and diphtheria during the summer holidays and an increase in the fall and winter due to school attendance. But Niven, of Manchester, England , thinks that ''the extreme measure of closing a school for scarlet fever is rarely called for, and is not so likely to be effectual as in the case of measles."^ Local boards of health should make and enforce rules looking to the prevention of the spread of the graver * See Public Health, February. June, and September, 1899; also American Year-book of Medicine for 1900, p. 538. 330 SCHOOL HYGIENE contagious diseases, and should, when necessary, close school-buildings till all danger is past. Lincoln gives the following as a system of general regulations: ^'(1) Persons affected with diphtheria, measles, scarlet fever, or smallpox (varioloid) must be excluded from the schools until official permission is given by the board of health for their readmission. (2) Persons living in a family or house where such a case occurs are also excluded until similar permission is given. (3) This permission is not to be given until sufficient time has elapsed since the occur- rence of the last case to insure safety, nor until the premises have been disinfected under the direction of the board of health. (4) If a child suffering from one of the above diseases attends school, the premises of the school must be disinfected under the direction of the board of health before they are used again. (5) Physicians, teachers, school-officers, and school-children knowing of such cases of disease should at once report them to the board of health. (6) The board should also notify the school authorities of all such cases. (7) Notice must be sent to the family by the school authorities, acting conjointly with the board of health." In some cities a card catalogue is kept of all the pupils in the public schools, each card representing a single pupil and giving full information concerning his or her home, parents, brothers and sisters, and where the same are employed, or are attending school. In case of the absence of any pupil for three days or more, the city board of health must be notified by the school authorities and the scholar is not permitted to return to school until the health officers are satisfied that there is no danger of infection and have so notified those in charge of the school. Competent and wide-awake truant officers are also frequently able to give early notice of the occurrence of infectious disease in the homes of school children so that prompt precautions against its spread may be instituted. The following table of the periods of incubation of the respective diseases is based on an experience of over MEDICAL INSPECTION OF SCHOOLS 331 twenty-eight years at the Rugby School, England, by Clement Dukes.^ AN ANALYSIS OF THE PERIODS OF INCUBATION. Name of disease. Scarlet fever Chicken-pox Mumps Rose-rash Measles . Short- Long- est est period period of incu- of incu- bation bation (days). (days). 1 9 13 19 14 25 12 22 8 14 The largest number occur on the following days. Second and fourth Fifteenth Nineteenth Sixteenth Eleventh The majority of the cases arise between the following days. Percentage re- ferring to pre- vious column, \ e. g.. 59 per ct. i occur between I the second and fourth days. Second and fourth Fourteenth and seventeenth Seventeenth and twentieth Fourteenth and seventeenth Ninth and twelfth 10 out of 17 » 59 per cent. 24 out of 36 = 66 per cent. 50 out of 69 = 72.46 per ct. 31 out of 40 =« 77.5 per cent. 18 out of 24 = 75 per cent. Another authority gives the following: TABLE OF THE ERUPTIVE FEVERS. Name. Chicken-pox Erysipelas Measles . Rotheln . Scarlatina' Smallpox Typhoid fever Incubation. Day of rash. 4 to 14 days 1 to 5 days 10 to 12 days 7 to 17 days 1 to 21 days 8 to 14 days 10 to 21 days Second or third First to third Fourth First or second Second Third or fourth Seventh to four- teenth Duration of eruption. 4 to 8 days 4 to 8 days 3 to 5 days 1 to 3 days 4 to 10 days j 16 to 25 days Duration of disease. 1 to 2 weeks 1 to 3 weeks 10 to 14 days 4 to 7 days 2 to 3 weeks 3 to 5 weeks 3 to 4 weeks Children having had one of the above-named diseases may return to school with safety after the following periods, provided there has been a thorough disinfection 1 Lancet, April 29, 1899. "^ In regard to the discrepancy in the above tables respecting the incubation of scarlet fever (from one to twenty-one days), the writer believes the shorter period to be more nearly correct; also that the incubation period of measles is frequently less than ten days, as is occa- sionally that of typhoid fever. Relapses may extend the duration of typhoid fever to much more than four weeks. 332 SCHOOL HYGIENE of their homes and clothing: "Scarlet fever, six weeks from the date of rash, provided desquamation and cough have ceased. Smallpox and chicken-pox, when every scab has fallen. Whooping-cough, after six weeks from com- mencement of whooping, providing the characteristic spasmodic cough and whooping have ceased, or earlier if all cough has passed away. Diphtheria, not less than three weeks, if convalescence is completed; there being no longer any form of sore throat nor any kind of dis- charge from the throat, nose, eyes, ears, etc., nor any albuminuria." Wherever possible, a bacteriological ex- amination of the nose and throat secretions of a scholar that has had diphtheria should be made from time to time, and his return to school should only be permitted when two successive examinations no longer show the pres- ence of the specific organism in the secretions mentioned. Rules and regulations like the above, when promulgated, "should have the force and authority of law, and should be enforced, if necessary, by the entire power, including school ofiicers, etc., of the State."^ Boarding-schools and similar institutions should have an infirmary where contagious diseases may be isolated, and those in charge should make that isolation from other scholars and inmates as complete as possible. At the beginning of a term it may be well to subject scholars who have been exposed to contagion to a postponement of attendance until the probable period of incubation for the special disease is passed, the period dating from the time of exposure and subsequent disinfection of clothing, etc. With the above precautions it will rarely be neces- sary to close a school unless a disease is markedly epi- demic and malignant. It is to be hoped that we shall soon have a means of inoculating persons against all contagious diseases, as we ^ Recent investigations have shown that the purulent discharge from the ear that so often follows attacks of measles and scarlet fever, and less frequently, of diphtheria, may be highly infectious and a positive agent in disseminating the respective maladies. Consequently children should be excluded from schools until this sequel of disease as well as others has entirely disappeared. MEDICAL INSPECTION OF SCHOOLS 333 ■§0 O Cod) 0*» E» «- o O •I C 2 Q 2 « te S a f^ W fi ea £ S — " ":3 o I i MO+J '-•2= S-9 o eoT3 3 a3..jQ u 3 «-as 5'-- •sill o 0-- 0) !gi§ 1 00 r C S^S ^'o 1^ c3 C 05^ 05 > 05— S 03-S -►i 0.213 6 « a o o-2-g IS." ©"o " w) :5 g o ^1=^ £§"..§ - fl 0,30 g d^ -tJ 08 3 « C 0-0.^ 2^'^'S ^ ^ « u c! •-sill a'O O O* ;2g- ^-fi ^ o _^— u S « 3 O £ 0*0 (u a o 3 pu-5 « 00 oj c ■'i « >.> c g > -0"S' c 3 o c 08 -e OS o a OT3 5 of • ^§ • o T * w a 5 OQ 334 SCHOOL HYGIENE now do against smallpox. At present, boards of health and school boards should insist on the vaccination of all school-children. In Illinois, from 1880 to 1883, the deaths from smallpox among unvaccinated children were 48 per cent, of those incurring the disease; among the vaccinated, only 0.9 per cent. In Philadelphia all who desire it are vaccinated free of charge by the vaccine physicians, and it is compulsory for all school-children. Lincoln has also suggested that further regulations similar to the following should be in force in every school district: "Every child entering the public schools must show a certificate from some reputable physician, giving name, age, residence, approximate date of vaccination, date of examination, result of examination; the last two to be of the physician's own knowledge. The fact of vaccination must be entered on the school record and on lists for promotion and transfer. The school authorities shall annually report the number of those not protected to the State Superintendent of Education. School authorities may order the exclusion of non-protected persons, after sufficient notice, where they think the measure required for the public health. Re vaccination at the age of fifteen may be required under similar cir- cumstances. Those unable to pay should be furnished with free vaccination by the school authorities. A phy- sician's certificate of protection by a previous attack of smallpox is equivalent to a certificate of vaccination." Contagious ophthalmia is a disease often prevalent in charitable and educational institutions and occasionally in primary schools, and requires great care to prevent its invasion and spreading, as well as to effect a cure. Those afflicted with it should be quarantined until there is no further discharge or till the granulations on the inner surface of the eyelids have disappeared. Enfeebled health and poor and insufficient food favor its development, but the chief means of contagion is by the use of the same wash-basins and towels by a number of children. Other diseases that may be transmitted in much the same way are chronic conjunctivitis ("granular lids") MEDICAL INSPECTION OF SCHOOLS 335 and those due to fungous and other parasites, as the tineas ("ringworm of the scalp or face")> pediculosis, etc., all of which may be transmitted by an interchange of hats or caps or other garments. School children should not be allowed to attend the funerals of companions dead of a contagious disease, nor should funerals be allowed to take place from school- houses under any circumstances, owing to the effect on the thoughts and sensibilities of nervous children. One of the most noteworthy developments in the line of modern public health work is that of school medical inspection. Not only are the troubles of ailing or defective pupils discovered, the attention of parents directed thereto, corrections of the same brought about and the spread of infectious diseases prevented; but the general welfare of the public at large is enhanced by the physical, mental and moral improvement in the youthful portion of the population that is an inevitable result of the work. As an indication of the importance and extent of such work in a large city, the records in Philadelphia for the calendar year 1913 show a total of 158,974 notices by school inspectors to parents concerning physical defects in the children, of which about 75,000 were for troubles requiring treatment by physicians, and about 64,000 were because of carious teeth requiring dentist's attention. In the same period almost 3,000 contagious and 14,000 parasitic diseases were reported. The following table indicates the nature of the physical defects recommended for treatment: Eye-strain 17,506 Other eye cases 7,595 Nose and throat defects 34,522 Ear defects and diseases 2,261 Diseases of teeth 64,238 Orthopedic defects 2,706 Poor nutrition 2,464 Functional nervous diseases 1,111 Heart disease 872 Skin disease (mostly unimportant) .... 19,833 Accidents, acute illness 2,208 Miscellaneous 3,608 336 SCHOOL HYGIENE The important part, however, of the report from which the above figures are taken is that in the first seven months of the year 43 per cent, of the defects then reported had been corrected subsequent to the issuance of the inspector's notices, the proportion of defects corrected, classified according to the nature of defect, being as follows: Per cent. Eye 36.0 Ear 61.0 Nutrition 52.3 Heart . ' . 53 . 8 Nose and throat 29 . 9 Teeth 27.5 Orthopedic 37.8 "Medical inspection in our schools returns large divi- dends on small investments. Jensen has shown that the cost of a school dental clinic in Germany is only one mark per year per child. The cost saved must be very many times this sum." "Cronin, of New York, main- tains that in a school population of 650,000, 30 per cent, of the children were from one to two years behind their proper class. Ninety-five per cent, of these children were so principally because of defects of eye, ear, nose, or throat, which could easily be detected and remedied through effective medical inspection. Experiments at home and abroad have proved beyond any doubt that the majority of children of this sort, when given proper medical treatment, improve markedly in intellect and general conduct. The State attempts to educate these children, but its efforts are, to a large extent, wasted. Osier calcu- lated that in the special city to which reference has been made there was, on account of a lack of medical super- vision of educational work, a yearly financial loss of $1,666,666; of course, the loss which came from moral deviation due to defective physical functioning was of far greater importance. He also said recently, in effect, that he considered it of greater importance to the nation that the question of sound teeth be intelligently considered MEDICAL INSPECTION OF SCHOOLS 337 than that the consumption of alcohol be restricted, im- portant as the latter problem is."^ 1 Report on National Vitality, Fisher, pp. 123 and 173. Readers especially interested in the many and various phases of School Hygiene are advised to consult Cornell's Health and Medical Inspection of School Children (F. A. Davis Co. New- mayer's Medical and Sanitary Inspection of Schools (Lea & Febiger), Terman's Hygiene of the School Chi'.d (Houghton, Mifflin & Co.); Dresslar's School Hygiene (Macmillan Co.) and Rowe's Physical Nature of the Child (Macmillan Co.) as sources of authoritative and abundant information, and for details that may not be included in the limits of a single chapter. 22 CHAPTER X. DISINFECTION. As has been stated, disinfection is that part of pro- phylaxis which has to do with the destruction or modifi- cation of the exciting causes of disease, and we may accordingly define a disinfectant as "an agent capable of destroying the infective power of infectious material," or, as "an agent which brings about the destruction of bacteria in general, and more particularly of those that act as the exciting causes of disease."^ Consequently, as with our present knowledge we are practically limited in the use of disinfection to the infectious diseases only, a disin- fectant must also be a germicide. Theoretically, it should, also have the power of destroying the poisonous properties of the toxins which the disease germs produce arfi'd which create the characteristic symptoms of the specific diseases, but whether all efficient disinfectants have this power is by no means proved; nor is it altogether essential that they do have it, since by killing the germs we check the further production of the toxins; and disinfectants are mainly used not so much to cure or arrest the progress of a disease in a patient as to prevent its incurrence by others. In a popular sense, the term disinfection is given a wider meaning than is indicated above, one including not only the use of antiseptics and deodorants, but often also the actual removal of filth and all matters favorable to the growth or spread of disease germs, which is, strictly speaking, a matter of sanitation. It is needless to say that the latter work may be part of the prescribed duties of a disinfector, but it is not one of the essential functions of a disinfectant. 1 Harrington, Practical Hygiene, p. 488. (338) DISINFECTANTS, ANTISEPTICS AND DEODORANTS 339 It will be well here to make the distinction between disinfectants and antiseptics and deodorants, as the terms are often erroneously used interchangeably, and as there is a common belief that whatever is a deodorant or an anti- septic is also a disinfectant. An antiseptic is an agent that retards or arrests bacterial grow^th and the conse- quent production of toxins or ptomains, though it does not necessarily kill the microorganisms themselves; and though some antiseptics are germicidal, others are not, and therefore as a class they cannot be considered or used as disinfectants. But, on the other hand, "agents which kill bacteria in a certain amount prevent the mul- tiplication of the latter in culture-fluids when present in quantities considerably less than are required to destroy vitality." So, a diluted germicide may act as an anti- septic and may be used therefor. For instance, chlorin- ated lime, which is a good disinfectant in solutions of proper strength, may arrest further bacterial grow^th or action in a mass of sew^age or filth and prevent the latter acting as a culture-medium for disease germs, even though the agent be totally inadequate in quantity to kill all the microorganisms present. In the same way, it may act as a deodorant — which, by the way, is an agent that simply removes or destroys offensive odors, and is not necessarily either a disinfectant or an antiseptic — both by checking the further action of saprophytic bacteria and the consequent formation of putrefactive odors, and by actually decomposing and oxidizing those of the latter already formed. In practical disinfection it is also w^ell to remember that while masses of dead organic matter may not in some cases contain disease germs, and may be even hostile to them, in general the reverse of this is more likely to be true, and decaying matter often furnishes a good field for the increase of pathogenic organisms. Moreover, the noxious gases given off to the air and the poisonous products added to a drinking-water from such masses may also do much harm by depressing the system, lower- 340 DISINFECTION ing the vitality, and acting as predisposing conditions to the incurrence of such filth-diseases as cholera, yellow fever, typhoid and typhus fever, diphtheria, etc.; so /yMRMOVfrr • S.AMiTj^Tioisr Good OFair 'gen that in turn acts powerfully upon the organic matter present, including living microorganisms. "Germs of all kinds, including the most resistant spores, are destroyed by this solution; but it must be remembered that the disinfectant itself is quickly decomposed and destroyed by contact with organic matter, and that if this is present in excess, disinfection may not be accomplished, especially w^hen the germs are embedded in masses of material which are left unacted upon after the hypochlorite of lime has been all exhausted in the solution." Labarraque's solution of chlorinated soda is also an effective mild dis- infectant, but does not keep well, and chlorinated lime is 348 DISINFECTION equally good and much cheaper. However, the soda solution has scarcely any disagreeable odor, and makes a pleasant disinfecting bath for the person. The official solution must contain at least 3 per cent, of available chlorine, but it may be diluted with from two to five parts of water before use, especially for bathing. ''Though probably effective against sporeless bacteria in somewhat less proportions, solutions of chlorinated lime should be of at least 1 per cent, strength by weight, and should be used in excess, to allow for both the dilution by the mass to be disinfected and the exhaustion of the hypochlorite by organic matter. "In the U. S. Army a 4 per cent, strength of chlorinated lime in solution is officially prescribed for use in disinfection of the excreta of the sick, it being specifically stated that the chlorinated lime so used shall be of good quality and not have under- gone decomposition.''^ Bichloride of Mercury. — Bichloride of mercury (corrosive sublimate) is one of the best germicides that we have, and is effective in comparatively weak solutions. It corrodes metal, and so cannot be used to disinfect waste-pipes, etc.; and it combines with and coagulates albumin, which inter- feres somewhat with its action. This coagulation is pre- vented to a degree by the addition of a small amount of citric or tartaric acid to the solution, which addition also favors the solution and, as was first shown by Laplace, increases the efficiency of the mercurial salt. The same result is said to be obtained if one part of hydrogen peroxide (15 per cent, solution), be added to three parts of a corrosive sublimate solution of any strength. Common salt (0.5 to 1 per cent.) or ammonium chloride when added to twice the quantity of corrosive sublimates increase its solubility, but they are said to diminish its efficiency somewhat. However, it is better not to use corrosive sublimate in disinfecting fecal excreta or sputum, as these always contain more or less albumin, and 1 Rosenau's Preventive Medicine and Hygiene, p. 1019. CHEMICAL DISINFECTANTS 349 also because the sulphur present in the excreta permits the formation of a sulphide of mercury, which has almost no power as a disinfectant. A lime solution is better and more certain. Bichloride of mercury should be used in solutions of from 1 in 1000 to 1 in 500 strength for ordinary disin- fection, though weaker preparations are sometimes used in surgical cases. It is especially valuable where a large amount of fluid is to be freely used, but on account of its poisonous properties and the consequent danger of accident from a lack of color, stock solutions should always be colored by adding a little aniline dye or copper sulphate. Ab- bott cautions that the stains of blood and feces on cloth- ing are rendered almost indelible by long soaking in bichloride solutions. Silver nitrate is almost, if not fully, as good a disinfectant as bichloride of mercury, and does not coagulate albumin so readily, but is much more expensive and has the objectionable property of perman- ently staining many things. Carbolic Acid. — Carbolic acid is effective in the absence of spores, and, according to Koch, should have first place in disinfection against the cholera germ. It is of doubtful value, however, in cases of typhoid fever, as it is said that the typhoid bacilli can be cultivated in a medium containing 0.5 per cent, of carbolic acid; nor is it reliably efficient against spore-forming organisms. Solutions should always be made by first dissolving the acid in hot water, and should contain from 2 to 5 per cent, of acid, the latter being practically a saturated solution. The addition of a small quantity of glycerin is said to facilitate the solution. The stronger solution is especially valuable for the direct disinfection of human excreta of all kinds, but must be thoroughly mixed with the same, as carbolic acid coagulates albumin, though not to the degree caused by bichloride of mercury; while the weaker fluid (2 or 3 per cent.) may be used freely for the disin- fection of clothing or the washing of walls, floors, furniture, etc. A 2 or 3 per cent, solution of a mixture of equal 350 DISINFECTION parts of carbolic and sulphuric acids is valuable for the disinfection of water-closets, urinals, etc., as the latter acid increases the effectiveness of the mixture; but it must not be kept too long in contact with metals on account of the corrosive action of the sulphuric acid. Rosenau states that the addition of 0.5 per cent, of hydrochloric acid to carbolic acid aids its activity. Solutions of the cresols (meta-, para-, and ortho-), which are derived from coal- or wood-tar, and much resemble carbolic acid, may be used for the same purposes and in about the same strength as solutions of the latter. In fact, tricresol, which is a refined combination of the three, is two or three times as powerful a disinfectant as carbolic acid, and, in solutions of from 0.5 to 1 per cent, strength, makes an agreeable and efficient disinfectant for use in surgery and obstetrics, especially as it does not coagulate albumin as readily as do carbolic acid and corrosive sublimate. As carbolic acid and cresol solutions are all poisonous, they should always be so labelled, although the characteristic odor serves as a partial safeguard to those accustomed to it. The cresols do not corrode metals and can be used with soaps and oils to form emulsions, both of which features increase their usefulness for surgical and other purposes. Creolin. — Creolin is another coal-tar product that has some germicidal power, but is not so efficient as was formerly credited. Being cheap, it may be used freely for disinfecting drains, stables, urinals, and such places where its rather strong odor is not objectionable. It should be made up in from 2 to 5 per cent, strength in water, and, being insoluble, the mixture must be thoroughly stirred or shaken each "time before use! As McClintock and Frey have shown that most of the coal-tar disinfectants, including carbolic acid and the cresols, do not destroy the virulence of vaccine virus in the strength and time in which they kill practically all non-spore-forming bacteria, "the inference is allow- able that this class of disinfectants is not safe to use for CHEMICAL DISINFECTANTS 351 such diseases as smallpox and the presumably protozoal diseases, such as syphilis, measles, scarlet fever, etc."^ Zinc Chloride. — Zinc chloride is a good antiseptic and deodorant, but not a very powerful disinfectant. A 5 to 10 per cent, solution will kill germs without spores. Calcium Hydrate. — Calcium hydrate, when mixed with water to make a thin whitewash (milk of lime), is said to be a good disinfectant, especially for excreta, etc., and is one of the cheapest and easiest to obtain. It should be added to the infectious matter in excess or until the mixture is decidedly alkaline and will require from one to two hours to disinfect thoroughly. The proportion of lime to water should be about as 1 to 4, equal parts being first taken to allow the slaking of the lime, and the rest of the water then added and the mass thoroughly mixed by stirring. Two quarts of this mixture per day for each person using a cesspool will keep the contents of the latter disinfected and free from putre- factive odors, provided its use commences with the use of the cesspool, or that the prior contents have been dis- infected by an excess of this or a chlorinated lime solu- tion, or by an abundance of the latter salt or quicklime in powder. Air-slaked lime should not be used to make up the "milk of lime," as it is practically worthless, but the lime should always be freshly slaked with water as indi- cated or else kept in an air-tight container after such slaking. Sulphate of Iron. — Sulphate of iron, which acts as an antiseptic to prevent putrefaction, rather than as a disinfectant, may also be added to the contents of an offensive cesspool or one that has received infected matter to the extent of about four pounds for each cubic yard of the mass. The sulphate should, of course, be thoroughly dissolved before using. Hydrogen Peroxide or Dioxide. — An extremely valuable disinfectant for local or topical applications to the person * Rosenau. loc. cit, p. 1012. 352 DISINFECTION is hydrogen peroxide or dioxide (H2O2). It is harmless, even when taken internally; is effective in comparatively weak solutions, and is especially active in the destruction of pus organisms. It is usually supplied in the form of a 15 per cent, solution in water and at present only its high cost prevents its more extended use. Chlorine and Sulphur Dioxide. — Until the discovery, in 1892, of the great disinfecting power of formaldehyde or formic aldehyde by Trillat and Aronson, about the only gaseous disinfectants of practical value were chlorine and sulphur dioxide. Of these, chlorine is the more powerful and efficient, but the distressing and oftentimes serious symptoms which it produces when accidentally inhaled, and the bleaching effect that it has upon many articles, have both tended to prevent its common employment. Like the sulphur dioxide, it acts best in the presence of moisture, and therefore steam should be simultaneously introduced and liberated in the room or enclosure in which either of these disinfectants is used. Sufficient chlorine for 1000 cubic feet of space may be generated by carefully pouring two fluidounces of strong sulphuric acid and three fluidounces of water, previously mixed and cooled, upon eight ounces of sodium chloride (common salt) and two ounces of man- ganese dioxide. The acid must be added to the water little by little and with care, and the salt and manganese should be in an earthen vessel upon a bed of sand, to prevent injury to the floor or carpet. Moreover, as the chlorine gas is very heavy, the generating apparatus should be at as high a level as possible in the room to get even fair diffusion. Sulphur dioxide (SO2), though not so positive in its ac- tion as chlorine, is more frequently employed on account of the lesser risk and trouble connected with it. It prob- ably kills germs not containing spores if sufficiently con- centrated and in the presence of moisture, and is therefore useful in the fumigation of rooms and of articles that cannot be subjected to steam-heat or chemical solu- CHEMICAL DISINFECTANTS 353 tions. But it will bleach or tarnish many articles, and for this reason and the fact that it is thought by some to be inferior to formaldehyde, its use has been in a measure supplanted by that of the latter whenever that could be obtained. To secure sufficient concentration at least three pounds of sulphur should be burned for every 1000 cubic feet of air-space. The sulphur should be well moistened with alcohol, unless the prepared sulphur candles now on the market are used, and allowance should be made for a considerable proportion that is usually not burned. Care must also be had to guard against setting fire to the room from the sputtering of the sulphur, and especially to have present in the atmosphere an abundance of aqueous vapor. Before the fumigation of a room with chlorine or sul- phur dioxide, or with formaldehyde, all apertures and crevices in the walls, ceiling, or floor should be carefully closed from the outside to maintain the gases in as con- centrated a state as possible during the process, which should continue for at least twenty-four hours in the case of chlorine or sulphur gas, and for not less than twelve hours with formaldehyde. After the fumigation the room should be thrown open and well ventilated, and then thoroughly cleansed with a corrosive sublimate, carbolic acid, or hot soda solution, a 4 per cent, solution of the latter being not only cleansing, but strongly disinfectant as well. Sulphur gas excels formaldehyde in the destruction of such vermin as roaches, bed-bugs, fleas, flies, and mos- quitoes, and may be preferred to the latter or used as an adjunct to it where there is danger of infection being transmitted by these agents. Likewise, it may be used to destroy larger animals, such as rats and mice, that we now know may be carriers of various disease germs. (See p. 364.) Hydrocyanic acid, which may be freely liberated as a gas by the addition of dilute sulphuric acid to cyanide of 23 354 DISINFECTION potassium, has been used both as a germicide and an in- secticide. Its high relative cost does not warrant its use as a substitute for sulphur-gas or formaldehyde, but the certainty with which it kills all kinds of small vermin, and even higher animals, such as rats and mice, that may carry infective organisms, renders it of high value for this purpose. Its poisonous nature, however, should always be remembered, and great care always observed in its use. Formaldehyde. — Formaldehyde (formic aldehyde), both in its gaseous state and in solution, is undoubtedly one of the best and most efficient disinfectants now in use. It has considerable penetrating power, although less than steam or than was claimed for it at first by its more enthusiastic advocates, while for surface disinfection it acts almost immediately. It is much better in this respect than chlorine or sulphur dioxide, already men- tioned, and where it is properly used, only such articles as bedding, mattresses and pillows, that can be better treated with steam, need be removed from an infected apartment. Clothing, rugs, hangings, etc., that can be freely exposed to it are quickly sterilized. Another important feature is that it does not bleach nor act destructively on either clothing or furniture, and that, although it is quite irritating to the conjunctivae of the eyes and to other mucous membranes when concentrated, it is virtually non-poisonous. Formaldehyde is readily absorbed and held in solution by water to the extent of 40 per cent, by weight of the latter, but as soon as this proportion is exceeded there is a polymerization of the gas and a solid (paraformalde- hyde or paraform) is precipitated, which is only resolved again into formaldehyde at a temperature of 275° F. The 40 per cent, solution is practically identical with the preparation which is commercially known as formalin, which has usually an addition of 10 per cent, of methyl alcohol as an additional safeguard against precipitation. Very weak solutions (1 or 2 per cent.) of the gas are still effectively disinfectant, while its virtue as an antiseptic CHEMICAL DISINFECTANTS 355 persists even when the dilution is carried to a remarkable degree. One peculiar effect of the solutions is that of rendering connective tissue and all gelatinous substances insoluble in either hot or cold water, and it is probably to this that its germicidal activity is largely due, since the food-supply of the bacteria, if not the substance of the latter them- selves, is partly of this nature. For the same reason it hardens and disagreeably roughens the skin, which tend to prevent its use for topical applications to the human body. Fig. 90. — Schering's lamps for volatilizing paraform. Several methods have been devised for the production or liberation of formaldehyde in rooms and buildings in such volume as positively to secure both surface and penetrative disinfection. One of the first devised and best methods involves the heating and vaporizing of a solution of gas, such as formalin or formochloral, the latter a mixture of the former with calcium chloride. For instance, in Trillat's apparatus the latter solution is used, the calcium chloride being added to insure against the precipitation of paraform. A simpler device, called a regenerator, allows formalin to flow in a fine stream through a copper coil heated to redness by a flame be- neath, the gas and vapor then passing directly into the 356 DISINFECTION room in a superheated and effective condition; and in other apparatus, hke the Novy-Waite and Trenner-Lee generators, there is special provision for the rapid evolution of the gas at high temperature and to prevent its poly- merization. Both of these methods have the advantage that the apparatus may be operated outside of the room to be disinfected, and the action accordingly controlled; Fig. 91. — Modified Novy-Waite formaldehyde generator. also that the amount of gas liberated depends directly upon the strength and quantity of the solution evaporated. In the Schering method the solid paraform is heated in a receptable over an alcohol lamp, the volume of resulting formaldehyde depending, of course, upon the amount of paraform used. This method has yielded some excellent results experimentally, and is of special value CHEMICAL DISINFECTANTS 357 in disinfecting small rooms, closets, and sterilizing cases for instruments, dressings, etc. The gas may also be liberated in a room by spraying formalin from a properly constructed compressed air or steam atomizer, or by evaporating it from saturated sheets hung about the room, but as this is not certain to liberate all the gas from the solution, more of the latter must be used. FiQ. 92. — The Trenner-Lee formaldehyde generator. Formerly a very common form of apparatus was that devised in the form of a portable lamp to develop the gas directly by the oxidation of methyl alcohol, the vapors of the latter being made to pass over or through tubes or coils of heated platinum, and to be thus converted into the disinfectant gas. Considerable formaldehyde can 358 DISINFECTION doubtless be produced in this way, but with most ap- paratus of this kind the amount at any time is uncertain and the results indefinite, since part of the alcohol vapors are polymerized and part are further oxidized into com- pounds such as carbon monoxide and carbon dioxide. Therefore, with such apparatus, this method is, as a rule, only to be advised for comparatively small apartments or enclosures, and not where certainty of disinfection is important. However, these objections have been over- come in the Kuhn generator, which is simple and positive in operation and manipulation, and has been proved efficient and reliable under severe tests. Abbott states that he has "obtained the most satis- factory results through the use of formalin to which 10 per cent, of glycerin has been added, as recommended by Schlossmann; and through the employment of a generator after the plan of that advised by Novy and Waite. In these tests we found that 80 per cent, of all exposed infected objects in a room could be disinfected when 500 c.c. of the formalin-glycerin mixture per 1000 cubic feet of air-space was completely evaporated and the room kept closed for three or four hours. "^ In the other apparatus one pound of formalin or fprmochloral, from 50 to 75 of Schering's paraform tablets, or a quart of methly alcohol are to be respectively used for each 1000 cubic iept of air-space to be disinfected.^ A very simple method of liberating formaldehyde-gas and one whose efficacy, it is asserted, has been thoroughly established by laboratory tests, is to pour one pound of formalin containing 40 per cent, of formaldehyde on eight ounces of permanganate of potash in a high vessel, this being the proper amount for 1000 cubic feet of space or less. The gas is liberated freely and speedily, and with but little risk of polymerization or of any remaining in solution. Of course the effectiveness of action will be 1 Hygiene of Transmissible Diseases, 1899, p. 269. 2 See also U. S. Quarantine Regulations, as quoted on p. 361. CHEMICAL DISINFECTANTS 359 enhanced by the previous or coincident vaporizing of water in the room. Whenever formaldehyde is employed as a gas, all the apertures in the room should be carefully and tightly closed, since, having the same specific gravity as the air, its diffusion takes place rapidly. Moreover, after a sufficient volume of the gas has been liberated, it should be allowed to act as long as possible, preferably for twelve hours at least, and better for twenty-four, since, though it is more rapid, the time element is just as important a factor with this as with other gaseous disinfectants. Fliigge thinks we obtain good results if 90 per cent, of the disease germs present are killed by the formaldehyde fumigation. Lastly, the gas is an excellent deodorant, combining as it does with the effluvia from decomposing substances to produce odorless compounds. Its odor, in turn, may be quickly dissipated from a room by evaporating a little ammonia therein. The following table of Koch and Jaeger is added to show the comparative disinfectant strength of some substances occasionally used for the purpose: Disinfectant. Strength. Bichloride of f 1 to 20,000 mercury . 1 to 1,000 1 to 12,000 Silver nitrate 1 to 4,000 1 to 2,500 Acid, hydrochloric 2to 100 Acid, sulphuric . < 2 to 15 to 100 100 Ferrum chlorate 5to 100 Calcium chloride 5to 100 Potas. perman. . . 5 to 100 caustic Ii„>e{°:°^«- 100 100 3t^ 1,000 Acid, carbolic ^ 10 to 100 1 to 100 Formaldehyde . 3 to 100 (K. Walter.) Objects submitted to experiments. Anthrax spores Anthrax spores Anthrax spores Cholera and typhoid Diphtheria Anthrax spores Anthrax spores Anthrax spores Anthrax spores Anthrax spores Anthrax spores Cholera Typhoid Staphylococcus and Streptococcus pyog Anthrax spores Nearly all patho- genic germs Anthrax spores All other pathogenic \ germs / Time required for destruction. 10 minutes. 1 minute. 70 hours. 2 hours. 2 hours. 10 days. 53 days. 8 days. 6 days. 5 days. 1 day. 6 hours. 6 hours. 8-11 sec- onds. 24 hours. Less than 30 minutes. 15 minutes. 1 minute. 360 DISINFECTION In any case of infectious disease special attention should be given to disinfecting the excretions and secretions which are known to be most likely to contain the disease germs, viz., the desquamating epithelium and likewise the renal secretion in measles, scarlet fever, and all the exan- themata; the dejecta and urine in typhoid fever, cholera, tropical or infectious dysentery, and in tuberculosis of the intestinal or genito-urinary tract; the sputum in tuberculosis of the lungs and air-passages, and in in- fluenza, pneumonia, and diphtheria; secretions from the throat and nose in diphtheria, scarlet fever, measles, infantile paralysis and cerebrospinal meningitis; discharges from abscesses, suppurating or gangrenous wounds, etc. During the course of the illness there should be no more communication than is absolutely necessary between the occupants of the sick-room and those in the rest of the house, and a sheet should be hung at the door and kept moist with some disinfecting solution, as this will largely prevent the escape of infective dust particles through the doorway. All articles going from the room, whether dishes, clothing, or food, should be submerged in a disinfectant or covered with a cloth wet with it, and should be burned, boiled, or otherwise disinfected as soon as possible thereafter. Excreta should be disinfected as soon as discharged from the body, but should not be emptied into a water-closet, sewer, or cesspool till the dis- infectant has had ample time to do its work, at least one hour being given for this action. Ventilation should be as perfect as possible; sunlight should be admitted when- ever it will not injure or annoy the patient, and, above all, cleanliness in every respect should be insisted upon as being most essential. Sick-rooms should be well screened to prevent the access of flies, as these may carry infection to others from sputum, excreta or even the body of the patient. The dress of the nurse or attendant should be such that dust and germs do not readily adhere to it and that it may readily be disinfected and cleaned, the cotton uni- CHEMICAL DISINFECTANTS 361 forms of a hospital training school being almost ideal in this respect. If this were in the form of an overgarment that could readily be slipped off when the nurse has to leave the sick-room, there would be an additional element of safety, just as there will be if there is provided some- thing like the long, old-fashioned linen "duster" for the casual visitor, whether physician or parent, to slip on when entering the room. The nurse should, of course, bathe not only the patient but herself as well with disin- fectant solutions, such as Labarraque's (diluted), carbolic acid, or tricresol; should destroy at once all possible infec- tion coming from the patient, and at least every other day should wipe with a cloth dampened in a disinfectant all window-sills, tables, and other surfaces upon which dust and the attached germs continually settle. A closet with a close-fitting door may be made to serve as a good disinfecting chamber for garments that are not in immediate use, as a few ounces of formalin sprinkled on the garments themselves or a few paraform tablets burned in one of the Schering lamps will quickly sterilize the contents of the closet without serious discomfort to the occupants of the adjoining room. It is taken for granted that, if possible, before the occu- pancy of the room by the sick, all upholstered furniture, heavy drapery and everything not absolutely necessary were removed from the room. Even the carpet should be taken up and rugs used temporarily in its place. If this is done, the work of disinfecting the room after it is no longer needed by the patient will be greatly facilitated. Since Chapin and others have shown the great pre- ponderance of infections by contact, or through intimate personal relationships, final disinfection after a case of illness may be deemed of less importance than it was formerly considered to be. Nevertheless, it should be looked upon as an additional factor in preventing the further spread of infection, and should be carried through with the same thoroughness that should be observed in other methods of disinfection. 362 DISINFECTION Where the use of formaldehyde is not available, the final disinfection should be carried out as follows: All bed-clothing, etc., should be either submerged in some disinfectant solution or in boiling water, or else covered with a sheet wet with a disinfectant, and boiled as soon as possible thereafter. No clothing should be sent away from the house to be laundered. Bed-quilts, blankets, mattresses, etc., should be subjected to steam sterilization if possible; if not, the blankets and quilts should be carefully sterilized by boiling, and the mattresses had better be burned, though they may be disinfected inter- nally by the introduction of formalin or formaldehyde gas, and externally by wiping and wetting with a strong solu- tion of corrosive sublimate. The carpet or rugs should be carefully taken up, carried to an open space, well beaten, and then hung in the open air for a time, provided they cannot be sent at once to some place where steam steriliza- tion is available. All furniture and the woodwork of the room should be washed with corrosive sublimate solution (1 to 1000 or 500), taking care to get the fluid into all crevices. The floor may be scrubbed with lye or hot soda solution (4 per cent.), and then mopped and flooded with the corrosive sublimate solution. The walls should also be wiped with cloths wrung out of this solution, and any paper upon them removed after fumigation, unless it be new and free from cracks. Or the walls may be rubbed down with crumbs of bread and the latter burned, as the bread contains much gluten to which the dust and bacteria adhere. Fumigation with sulphur dioxide is usually of somewhat doubtful efficiency unless considerable attention is given to the details. If it is employed, it should be done first, before the bedding, etc., is removed and the walls, floors, and woodwork are wiped or washed, and all open- ings from the room, cracks, crevices, etc., should be closed by sealing on the outside, and sufficient gas liberated by suitable means. The vessels containing the gas-generating substances should be placed in larger vessels containing water to avoid the danger of fire, and vapor of water PHYSICAL DISINFECTANTS 363 should be liberated in some way simultaneously with the gas, say by placing hot bricks or the like in the water, or else water should be sprayed freely from an atomizer over everything in the room, as sulphurous acid has little disinfecting value except in the presence of moisture, which also greatly enhances the effects of formaldehyde. The room should then remain closed for twenty-four hours, and, lastly, should be well ventilated for a day or two before being furnished and occupied again. Should it be possible to use formaldehyde, the disinfec- tion is much simplified, and is to be carried out in the way already indicated; but whatever the gaseous disin- fectant employed, it should always be followed by the washing or wiping of walls, ceilings, floor, and all exposed surfaces with a disinfectant solution, and by the steam sterilization or boiling of all removable articles where- ever possible. In fact, it should be remembered that no one of these processes will in any probability destroy all the infection, but that each must be carried out with conscientious thoroughness and strictest attention to detail in order to secure the greatest measure of success. Where flies, mosquitoes or other germ-carrying vermin are possibly present, it may be advisable to follow the fumigation by formaldehyde with another by sulphur dioxide, as the latter is much the more certain to kill both insects and rodents. The gas from 1 pound of burning sulphur per 1000 cubic feet of space should kill flies and mosquitoes within two hours ; that from 2 pounds should kill rats within four hours, and that from 5 pounds should kill bed-bugs, lice, etc., within six hours. The United States Quarantine Regulations, promul- gated October 20, 1910, authorize the following disin- fectants and the methods of generating and using them: PHYSICAL DISINFECTANTS. Burning. — Of unquestioned efficiency, but seldom re- quired. 364 DISINFECTION Boiling. — Very efficient and of wide range of applica- bility. The articles must be wholly immersed for not less than thirty minutes in water actually boiling (100° C). The addition of 1 per cent, of carbonate of soda renders the process applicable to polished steel, cutting instru- ments or tools. Steam. — (a) Flowing steam {not under pressure). Flowing steam (not under pressure) when applied under suitable conditions is an efficient disinfecting agent. The exposure must be continued thirty minutes after the tem- perature has reached 100° C. {h) Steam under pressure without vacuum. Steam under pressure will sterilize, provided that the process is continued twenty minutes after the pressure reaches 15 pounds per square inch. The air must be expelled from the apparatus at the beginning of the process. If im- practicable to obtain the designated pressure, a longer exposure will accomplish the same result. (c) Steam under pressure with vacuum. Steam in a special apparatus with vacuum attachment is the best method of applying steam under pressure, the object of the vacuum apparatus being to expel the air and to pro- mote the penetration of the steam. The process is to be continued for twenty minutes after the pressure reaches 10 pounds to the square inch. GASEOUS DISINFECTANTS. Sulphur Dioxide. — Sulphur dioxide is efficient, but re- quires the presence of moisture. It is only a surface disinfectant, and is lacking in penetrating properties. An atmosphere containing 4.5 per cent, can be obtained by burning 5 pounds of sulphur per 1000 cubic feet of space. This amount would require the evaporation or volatilization of about one pint of water. Under these conditions the time of exposure should not be less than twenty-four hours for bacterial infections. A shorter GASEOUS DISINFECTANTS 365 time will suffice for fumigation necessary to kill mosquitoes and other vermin. The sulphur may be burned in shallow iron ovens (Dutch ovens) containing not more than 30 pounds of sulphur for each pot, and the pots should stand in vessels of water. Quicker and better results can be obtained from burning the same total amount of sulphur in a number of small, shallow ovens (Dutch ovens), 5 to 10 pounds in each, than in a few large ovens. The sulphur ovens should be elevated from the bottom of the compartment to be disinfected in order to obtain the maximum possible percentage of combustion of sulphur. The sulphur should be in a state of fine division, and ignition is best accomplished by alcohol; special care to be taken with this method to prevent damage to cargo of vessel by fire; or the sulphur may be burned in a special furnace, the sulphur dioxide being distributed by a power fan. This method is peculiarly applicable to cargo vessels. Liquefied sulphur dioxide is now commercially available and may be used for disinfection in place of sulphur dioxide generated as above, it being borne in mind that this process will require two pounds of the liquefied gas for each pound of sulphur as indicated in the above paragraphs. Sulphur dioxide is especially applicable to the holds of vessels, or to freight cars and apartments that may be tightly closed and which do not contain objects injured by the gas. Sulphur dioxide bleaches fabrics or materials dyed with vegetable or aniline dyes. It destroys linen or cotton goods by rotting the fiber through the agency of the acids formed. It injures most metals. It is promptly destructive to all forms of animal life. This property renders it a valuable agent for the extermination of rats, insects, and other vermin. Formaldehyde-gas. — Formaldehyde-gas is effective if applied by one of the methods given below. Formal- dehyde-gas has the advantage as a disinfectant that it does not injure fabrics or most colors. It is not poisonous 366 DISINFECTION to the higher forms of animal Hfe. It fails to kill vermin such as rats, mice, roaches, bed-bugs, etc. The method is not applicable to the holds of large vessels. Formal- dehyde is applicable to the disinfection of rooms, cloth- ing, and fabrics, but should not be depended upon for bedding, upholstered furniture, and the like, when deep penetration is required.^ Many formaldehyde solutions do not contain 40 per cent, of formaldehyde, and all are apt to deteriorate with time. It is therefore necessary to use a quantity in excess of the amount prescribed in these regulations, unless the solution has been recently analyzed. The following methods of evolving the gas may be used : (a) Autoclave under pressure, 3 to 12 hours' exposure. (6) Lamp or generator, 6 to 18 hours' exposure. (c) Spraying, 12 to 24 hours' exposure. {d) Formaldehyde and dry heat in partial vacuum, 1 hour's exposure. {e) Chemical, as formalin-permanganate method of Russel, or formalin-aluminum sulphate-lime method of Walker, 6 to 18 hours' exposure. The minimum number of hours' exposure, as given above, applies to empty rooms of tight construction containing smooth, hard surfaces; the maximum number of hours' exposure applying in all cases to textiles and other articles of a similar kind requiring more or less penetration. Autoclave under pressure: This method has consider- able penetrating power when applied as detailed below. Rooms or apartments need no special preparation beyond the ordinary closing of doors and windows. Pasting, caulking, or chinking of ordinary cracks and crevices is not necessary. The doors of lockers and closets and the drawers of bureaus should be opened. In this apparatus use formalin (40 per cent.), with the addition of a neutral salt, such as calcium chloride (20 per cent.). The gas must be evolved under a pressure not less than 45 pounds. ^ It should be noted that formaldehyde disinfection is more efficient in warm, moist, or still weather than in cold, dry, and windy weather. GASEOUS DISINFECTANTS 367 After the gas is separated from its watery solution the pressure may be allowed to fall and steam projected into the compartment to supply the necessary moisture. Use not less than 10 ounces of formalin per 1000 cubic feet, and keep the room closed for three to twelve hours after the completion of the process. For large rooms the gas must be introduced at several points as far apart as pos- sible. It is applicable to the disinfection of clothing and fabrics suspended loosely in such a manner that every article is freely accessible to the gas from all directions. Lamp or generator: This method requires an apparatus producing formaldehyde by a partial oxidation of wood alcohol, and in using it the room or apartment should be rendered as tight as practicable. Oxidize 24 ounces of wood alcohol per 1000 cubic feet, and keep the room closed from six to eighteen hours, in accordance with the provisions in a previous paragraph. This method leaves little or no odor. When applied to clothing and textiles, the articles should be suspended in a tight room and so disposed as to permit free access of the gas. (See also previous paragraph.) The wood alcohol should be of 95 per cent, strength, and should not contain more than 5 per cent, of acetone. Spraying: The formalin (40 per cent.) should be sprayed on sheets suspended in the room in such a man- ner that the solution remains in small drops on the sheet. Spray not less than 10 ounces of formalin (40 per cent.) for each 1000 cubic feet. Used in this way a sheet will hold about 5 ounces without dripping or the drops run- ning together. The room must be very tightly sealed in disinfecting with this process, and kept closed not less than twelve hours. The method is limited to rooms or apartments not exceeding 2000 cubic feet. The formalin may also be sprayed upon the walls, floors, and objects in the rooms. This method is markedly interfered with by, and is not to be relied on at, low temperatures, say below 72°" F. At 43.5° F., very little formaldehyde is liberated, the formaldehyde being polymerized on the sheets. 368 DISINFECTION Formaldehyde with dry heat in partial vacuum: This method has superior penetrating powers and is especially applicable to clothing and baggage. The requirements of this method are (1) dry heat of 60° C. sustained for one hour; (2) a vacuum of 15 inches; (3) formaldehyde evolved from a mixture of formalin with a neutral salt, in an autoclave under pressure, using not less than 30 ounces of formalin (40 per cent.) for 1000 cubic feet; and (4) a total exposure, under these combined conditions, of one hour. Chemical, as (1) Formalin-permanganate method. When formalin is poured over crystals of permanganate of potash, a vigorous reaction takes place and a large quantity of formaldehyde-gas is liberated. Reaction is over in a short time, five minutes, and if a proper pro- portion of substances is used, the residue is almost dry. The proportion is 2 pints of formalin to 1 pound of perman- ganate of potash. One pint of formalin for 1000 cubic feet of space should be used if the temperature is 60° F. or less; a less amount may be used for higher temperatures, but not less than 10 ounces per 1000 cubic feet. This method is extremely efficient on account of the rapidity with which the gas is liberated, but the danger of fire should be guarded against, as the formaldehyde-gas being in a comparatively dry state, is inflammable in the presence of a light, such as lighted matches, lamp, etc. (2) Formalin-aluminum sulphate-lime method. Add 1 part sulphate of aluminum to 2 parts of hot water. One part of this solution is added to 2 parts of formalin (both by volume). One part of this second solution is poured on 2 parts of unslaked lime (quick lime), broken into small particles. The process of liberation of formaldehyde- gas is completed in about twenty minutes. This method is not as efficient as the previous one, as less than half the amount of formaldehyde-gas is yielded from the same amount of formalin. Two pints of formalin per 1000 cubic feet of space should be used, if the temperature is 60° F. or less. GASEOUS DISINFECTANTS 369 Fire should be guarded against, but this danger is decidedly less than in the permanganate process on account of the large amount of water vapor coming off with the gas. The stated times of exposure to sulphur dioxide and formaldehyde are sufficient to destroy bacterial infection due to non-spore-bearing organisms, providing that the infection is present on the surface. If the room is of peculiar, construction, so as to impede the diffusion of the gas, or if the room is a dirty one, or if on account of any other condition the germicidal action of the gas is rendered more difficult, the time of exposure should be proportion- ately increased, or supplanted by other methods. Chemical Solutions. — Bichloride of Mercury. — Bichloride of mercury is a disinfectant of undoubted potency and wide range of applicability. It cannot be depended upon to penetrate substances in the presence of albumin- ous matter. It should be used in solutions of 1 to 1000. The solubility of bichloride of mercury may be increased by using sea-water for the solution, or by adding 2 parts per 1000 of sodium or ammonium chloride to the water employed. Carbolic Acid. — Carbolic acid in the strength of 5 per cent, may be substituted for the bichloride of mercury, and should be employed in the disinfection of the cabins and living apartments of ships to obviate injurious action on polished metals, bright work, etc. Formalin. — Formalin containing 40 per cent, of for- maldehyde may be used in a 5 per cent, solution as a substitute for bichloride of mercury or carbolic acid, and is useful for the disinfection of surfaces, dejecta, fabrics, and a great variety of objects, owing to its non-injurious character. In the foregoing chapter the author is much indebted to A. C. Abbott's Hygiene of Transmissible Diseases, and Rosenau's Preventive Medicine and Hygiene for authoritative and up-to-date information as to the value of the agents and methods of infection, and the reader is referred to these works for an abundance of detail which the limits of the present volume do not permit. 24 CHAPTER XL QUARANTINE. Quarantine may be described as the methods and measures imposed by a government — local, State, or national — to prevent the introduction of infectious dis- ease into the country or from one locality to another. Although the term in itself is misleading, being derived from the Italian quarante (forty), and signifying the period of detention of the first Venetian quarantines, it is now generally taken to indicate the entire routine of inspec- tion, disinfection, and detention, without regard to the length of time involved. While all civilized nations have from the earliest times recognized the importance of separating those afflicted with epidemic disease from the well, the development of the idea and practise of quarantine has necessarily been consequent upon the growth of commerce; and while there has been isolation for leprosy for unknown ages, the first quarantine enactments, in our meaning of the term, were put in force in Venice about the beginning of the fifteenth century as a barrier to both the black and the Egyptian plague. Then it was realized that epidemic diseases were transmitted by those attacked, a bureau of health and a lazaretto were established, the effects of those who died of the plague w^ere destroyed, and the period of detention of incoming vessels, passengers, and cargoes were fixed at forty days, the idea being that this period was in itself more or less mystic and salutary. As time went on and the plague spread over the whole of Europe, the number of lazarettos was largely increased, especially in the eighteenth century. Of these, the one (370) HISTORY AND PURPOSE OF QUARANTINE 371 at Marseilles became the most noted, not only because it was located at one of the most important ports of the Mediterranean, but because of its excellent care and man- agement. Thanks to the increased efficacy of quarantine and other sanitary regulations as the knowledge concern- ing them developed, the plague rapidly subsided soon after the beginning of the last century, and interest in it was supplanted by that in relation to the frequent epi- demics of cholera and yellow fever that began to alarm the civilized world; and it is to prevent the ingress of these latter diseases, together with leprosy, smallpox, typhus fever, and plague, that the present quarantine regulations are in the main devised. With the knowledge already gained regarding the nature and causes of infectious diseases, their periods of incubation, etc., it is at once evident that it will be neither necessary nor wise to fix upon a prolonged and arbitrary time during which vessels or passengers must be detained in quarantine. All that is needed is that the proper inspecting officers shall be satisfied that there is no danger of infection entering the country, and, where any deten- tion is necessary, it is only for so long as will suffice for the disinfection of the vessel, cargo, and passengers' effects, and to cover the period of incubation of the sus- pected disease. The present quarantine laws of the United States, and the latest regulations of the Treasury Department based upon them, are especially designed to afi'ord the greatest possible protection to the country against the importation of disease with the least possible detention of incoming vessels and passengers. An important innovation that facilitates both these ends has been the establishment of an American quarantine in foreign lands, as it were, viz., the inspection and, if necessary, detention and disinfection by officers of this government of all vessels, passengers, and cargoes leaving a foreign port for any port of the United States. This undoubtedly greatly diminishes the danger of the introduction of anyjnfectious disease; but in addition, 372 QUARANTINE there is that section of the law that provides that the President may, whenever the condition of affairs shall seem to warrant it, "prohibit, in 'whole or in part, the introduction of persons and property from such countries or places as he shall designate and for such period of time as he shall deem necessary." Accordingly, every vessel clearing from a foreign port for this country must obtain from the United States con- sular officer of the port, or from the medical officer ap- pointed for the purpose, a bill of health, "setting forth the sanitary history and condition of said vessel, and that it has in all respects complied with the rules and regula- tions in such cases prescribed for securing the best sani- tary condition of the said vessel, its cargo, passengers, and crew." Before signing the bill of health the consular or medical officer must be satisfied that the conditions certified to therein are true, and must inspect "all vessels from ports at which cholera, yellow fever, or plague in men or rodents prevail, or at which smallpox or typhus fever prevails in epidemic form," and "all vessels carry- ing steerage passengers." Moreover the vessel must be clean in all parts, especially the hold, forecastle and steer- age, before stowing cargo or receiving passengers, and all parts liable to have been infected by any communicable disease must be disinfected before the bill of health is issued. "At ports where cholera prevails in epidemic form, special care should be taken to prevent the water- and food-supply from being infected. The drinking-water, unless of known purity, should be boiled and the food thoroughly cooked and protected against contamination by flies, etc. Where yellow fever prevails, precautions should be taken to prevent the introduction of mosquitoes (stegomyia) on board the vessel. At ports or places where plague prevails in men or rodents, every precaution must be taken to prevent rats, fleas, or other vermin from getting aboard." "So far as possible, passengers should avoid embarking at a port where quarantinable disease prevails, and com- QUARANTINE REGULATIONS 373 munication between the vessel and shore should be reduced to a minimum." The regulations also indicate what kind of cargo, com- ing from or through infected districts, may or may not be shipped, and what kinds must invariably be disinfected under any circumstances. As to the passengers, while they are divided into two classes, cabin and steerage, no person suffering from plague, leprosy, cholera, smallpox, yellow or typhus fever, scarlet fever, measles, or diphtheria or other com- municable disease in epidemic form is allowed to ship. Steerage passengers and members of the crew who have been exposed to smallpox must be vaccinated before embarking unless they can show proof of immunity by former attack or by satisfactory vaccination within one year. If the passengers or any of the crew have been ex- posed to typhus fever infection, they may not embark until twelve days, and for plague, seven days, after such expos- ure, while steerage passengers and sailors from cholera- infected districts must be detained for five days in suitable houses or barracks located where there is no danger from infection. Passengers and sailors, who, in the opinion of the inspecting officer, have been definitely exposed to the infection of yellow fever (i. e., as from a house or locality known to be infected), should not be allowed to embark for six days after said exposure. No alien who is a leper should be allowed to embark for the United States. The baggage of passengers or crew exposed to infection or from infected ports should be inspected and, if necessary, disinfected and, in the case of plague or typhus fever, treated to destroy vermin. The same rules as to detention and disinfection are to be applied to those coming from places where the plague, yellow fever, or smallpox is prevalent in an epidemic form, and if one of these diseases or cholera breaks out in the detention barracks, there must be a repetition of the previous isolation, disinfection, etc., dating from the removal of the last case. Cabin passengers from cholera 374 QUARANTINE or other infected ports or districts should produce satis- factory evidence as to their exact place of abode during the five days immediately preceding embarkation, and if there is any reason for the belief that any one of these or his baggage has been infected, such passenger is to be detained under medical inspection a sufficient time to cover the period of incubation since the last exposure, and his baggage is to be disinfected. Every steerage passenger must also have an inspection- card, stamped by the consular or medical officer, giving name and last permanent residence of passenger, and of ship and port with date of departure, etc. ; and all baggage of passengers must have a label bearing the seal or stamp of the United States consular or medical officer, the name of port and of the vessel carrying the baggage, and the statement and date of inspection or disinfection. It is evident that if these regulations at foreign ports, together with those required at sea — viz., rigorous clean- liness and free ventilation of the vessel, daily inspection by the ship's physician, isolation of the sick, disinfec- tion of their clothing, bedding and excreta, destruction of mosquitoes and vermin, etc. — be properly observed, there can be but little chance of the germs of quarantin- able disease gaining entrance to our country; and, since the duration of the voyage will in most cases exceed the period of incubation of most of the contagious diseases, if none of these manifest themselves on shipboard at sea there will be no need for any detention at the port of entry beyond that which the inspecting officer stationed there requires for the performance of his duties, viz., to inspect the vessel, bill of health, crew and passengers, and their lists and manifests, the ship physician's clinical record of all cases treated, and, when necessary, the ship's log. This inspection service is to be maintained at every domestic port throughout the year, and is in force not only with respect to all vessels from foreign ports, but also regarding any vessel with sickness on board, vessels from * ENTRY OF VESSELS 375 domestic ports where cholera or yellow fever prevails, or where smallpox or typhus fever prevails in epidemic form, vessels from foreign ports carrying passengers having entered a port of the United States without com- plete discharge of passengers or cargo, and vessels hav- ing been treated at national quarantine stations that are located a considerable distance from the port of entry of said vessels. Moreover, the duties of the inspecting officer above stated are only the required minimum stand- ard, and such other regulations may be added by legal State or local authorities as may, for special reasons, be necessary. If the inspecting or health officer is satisfied that the vessel is not infected and all the foregoing requirements have been complied with, he gives his certificate, to be delivered to the collector of customs of the port, and no vessel is permitted to land any of its passengers or cargo unless it have this certificate, together with the bill of health, etc., from the port of departure, as evidence that the regulations have been properly observed. On the other hand, if vessels arrive under the following conditions they are to be remanded by the authority of the Secretary of the Treasury to the nearest national or other quarantine station where proper accommodations and appliances are provided for the necessary disinfection and treatment of the vessel, passengers, and cargo; and only after treatment and after obtaining a certificate from the proper officer that the vessel, cargo, and passengers are each and all free from infectious disease and from danger of conveying the same, can a vessel be admitted to entry to the ports named in the certificate. The conditions under which arriving vessels are to be placed in quarantine are these: "(a) With quarantinable disease on board or having had such disease on board during the voyage," the quarantinable disease for the pur- poses of these regulations being cholera (cholerine), plague, yellow fever, smallpox, typhus fever, and leprosy. (6) Any vessel which the quarantine officer considers infected 376 QUARANTINE with quarantinable disease, (c) If arriving at a port south of the southern boundary of Virginia in the season of close quarantine (April 1 to November 1) from a tropical American port, unless said port is known to be free from yellow fever, (d) Vessels arriving at ports north of this line and south of the southern border of Maryland, be- tween May 15 and October 1, if from a tropical American port, unless said port is known to be free from yellow fever, (e) Vessels arriving at a southern port, referred to in paragraphs (c) and (d) during the season of close quarantine for such ports, via a northern port, when from a port known to be infected with yellow fever, unless six days have elapsed since the fumigation of the vessel in such northern port, and a certificate be presented from the quarantine officer at such northern port, or an ac- credited medical officer of the United States. (/) In the case of vessels arriving at a northern port without sickness on board from ports where yellow fever prevails, the personnel shall be detained under observation at quaran- tine to complete six days from the port of departure. (g) Towboats and other vessels having had communica- tion with vessels subject to quarantine shall themselves be quarantined if they have been exposed to infection." '^ Vessels engaged in the fruit trade may be admitted to entry without detention, provided they have complied in all respects with the special rules and regulations made by the Secretary of the Treasury with regard to vessels engaged in said trade. "^ There are ten national quarantine stations and a number of others under State or municipal control; those which have steam disinfection chambers and other efficient equipments are located at Portland, Me.; Boston, New York, Sandy Hook, Delaware Breakwater, Reedy Island in the Delaware River, Cape Charles, Baltimore; Wil- mington, N. C; Savannah, Blackbeard Island, Ga.; Charleston, Dry Tortugas, Key West, Mullet Keys, ^ Quarantine Laws and Regulations of the United States. ENTRY OF VESSELS 377 Pensacola, Mobile, Chandeleur Islands, New Orleans, Galveston, San Diego, San Francisco, and Port Townsend; the ten national ones being included in the list. The essential requisites for a properly equipped quar- antine station, after the selection of a proper location — which should be convenient, but not in the line of future city growth — are the following:^ (1) A boarding station, including boat-house and boatmen's quarters. (2) A board- ing-boat, preferably a steamer or motor launch. (3) An anchorage for the detention of infected vessels. It should be safely out of the track of commerce, convenient but not too close to the main quarantine establishment, sheltered, and with good holding ground for anchors. (4) A fumiga- tion steamer with appliances for generating and forcing sulphurous acid (or formaldehyde) gas into vessels, and with tanks and pumps for disinfecting solutions. (5) A wharf, in water at least twenty feet deep, and upon which are constructed a w^arehouse, tanks for disinfecting solu- tions, and a disinfecting house containing steam dis- infecting chambers. (6) A lazaretto or hospital for the treatment of contagious diseases. (7) A hospital for non- contagious diseases. (8) Barracks or quarters for the detention in groups for those who may have been exposed to contagion or infection. (9) Quarters for medical officers. (10) A cremation furnace. When a vessel is remanded to quarantine by the in- specting officers at a port of entry, its treatment and that of its cargo and passengers will depend largely upon the disease with which it is infected, being more severe if the latter is cholera or yellow fever. In case of infection by either of these diseases the vessel is at once sent to the anchorage, and must remain there until the passengers have been discharged and the vessel purified, and in any case there must be no direct communication allowed between quarantine or a vessel in quarantine and any person or place outside, except under supervision of the quarantine officer. 1 Roh6'8 Hygiene. 378 QUARANTINE Moreover, if cholera has occurred on board, all passen- gers and all of the crew, except such as are necessary to care for her, must be at once removed, the sick to be sent to the lazaretto or hospital, others specially suspected must be carefully isolated, and the remainder separated into small groups, between which there must be no com- munication. Those who are especially liable to convey infection must be bathed and furnished with sterile cloth- ing before entering the barracks, and no articles capable of carrying infective matter, especially food and water, should be taken into the barracks. All baggage or effects of passengers or crew that has been exposed to the infec- tion, all articles of the cargo likely to be infected, and all furniture, living apartments, and such other portions of the vessel as may possibly retain or convey infection must be disinfected. The water-supply must be changed at once, the tanks thoroughly disinfected by steam or potassium permanganate solution, and refilled with water from a pure source or with water recently boiled. The water-ballast of a cholera-infected vessel, or of one from a cholera-infected port, should never be discharged in fresh or brackish water without previous disinfection, and the ballast tanks should be refilled with sea-water or else be disinfected before refilling. Nothing is to be thrown overboard from a cholera-infected vessel in quarantine, but everything that is to be destroyed, even deck-sweep- ings, should be burned in the furnace. The special regulations on account of yellow fever involve a careful visual and thermometer inspection of all persons, the immediate disembarking and removal of the sick, screened against the access of stegomyia mos- quitoes, to a place of isolation, and a similar isolation in screened apartments of all persons with a temperature above 37.6° C. Other persons shall be disembarked, if possible, and shall be subjected to observation for six days, dating from the last possible exposure. The ship shall be moored at least 200 meters from an inhabited shore, and shall be fumigated for the destruction of mos- THEATMENT OF INFECTED VESSELS 379 quitoes before the discharge of the cargo, if possible. If this is not possible, the discharge of cargo shall be under the supervision of the quarantine officer, preferably by the employment of immune persons for the discharging. If non-immunes are employed, they must be kept under supervision during the discharging and for six days after the last day of exposure on board. For the destruction of mosquitoes there shall be a complete and simultaneous fumigation of all parts of the vessel, preferably by sulphur dioxide. With respect to plague, on board ships on which this disease has occurred, either in men or rats, there must be careful inspection, immediate disembarking and iso- lation of the sick, and the destruction of all rats on ship- board as soon as practicable, the cargo being partially or completely removed, if necessary to this end, and proper precautions being taken to prevent rats getting ashore. Seven days is considered as the incubation period of plague, and all persons shall be held under observation for at least five days. Soiled linen, personal effects and belong- ings of crew or passengers considered to be infected shall be disinfected and rendered free from vermin, and "in all cases the quarantine oflficer shall assure himself that the vessel is free from rats and vermin before granting "free pratique." For typhus fever twelve days is considered as the incu- bation period, and the efforts for disinfection are chiefly directed toward the destruction of vermin. The sick are, of course, to be removed and isolated, and those exposed to infection detained under observation for the incubation period. With regard to smallpox, all persons who have been exposed to infection on any vessel which arrives with, or has had, this disease on board during the voyage, must be vaccinated or detained in quarantine not less than fourteen days since the last exposure, unless they can show satisfactory evidence of successful vaccina- tion within one year or of having had smallpox. Living compartments and other parts of the vessel and baggage 380 • QUARANTINE and belongings of crew and passengers that have been exposed to infection must be disinfected; but if the dis- ease has been properly isolated and sufficient precautions taken to prevent the spread of the disease, the vessel is only detained in quarantine long enough for the removal of the sick, disinfection of compartments, baggage, etc., and the vaccination of exposed persons, as indicated above. "Vessels arriving at quarantine with leprosy on board shall not be granted "free pratique" until the leper with his or her baggage has been removed from the vessel to the quarantine station. No alien leper shall be landed. If the leper is an alien passenger and the vessel from a for- eign port, action will be taken as provided by the im- migration laws and regulations of the United States. If the leper is an alien and a member of the crew, and the vessel is from a foreign port, said leper shall be detained at quarantine at the vessel's expense, until taken aboard by the same vessel when outward bound." The disinfection of the holds of vessels is to be by mechanical cleansing, by an acid bichloride of mercury solution (1 to 800) applied under pressure, and by sul- phurous acid-gas (10 per cent, per volume strength) for from twenty-four to forty-eight hours. All ballast must be discharged or disinfected before the disinfection of the hold, and all solid ballast must be disinfected before being discharged into fresh water. The steerage and forecastle are to be disinfected by live steam, if possible, for at least half an hour, and, if not, by sulphur dioxide and bichlo- ride solution, as was the hold. Baggage, bedding, carpets, \ etc., are to be removed with caution and to be disinfected by steam or by boiling, and, finally, all woodwork of the vessel is to be thoroughly cleansed mechanically and then washed with an acid bichloride of mercury solution (1 to 1000). The following Rules for the application of disinfectants in quarantine work were issued as part of the quarantine regulations of the United States Government on October 20, 1910: DISINFECTANTS IN QUARANTINE WORK 381 APPLICATION OF DISINFECTANTS IN QUARANTINE WORK. The holds of iron vessels, empty, shall be disinfected by either: (a) Sulphur dioxide generated by burning sulphur, 5 pounds per 1000 cubic feet of air space, or liberated from 10 pounds of liquid sulphur dioxide, sufficient moisture being present in both cases; time of exposure, twenty-four hours. (6) Washing with a solution of bichloride of mercury, 1 to 1000. Holds of wooden vessels, empty, shall be disinfected by: (a) Sulphur dioxide in the manner prescribed above, followed by: (6) Washing with a solution of bichloride of mer- cury. Holds of cargo vessels, when cargo cannot be removed, shall be disinfected in so far as possible by sulphur dioxide, not less than 4 per cent, per volume strength, and where possible this should be generated from a furnace to minimize danger of fire in cargo. Living apartments, cabins, and forecastles of vessels shall be disinfected by one or more of the following methods: (a) Sulphur dioxide; the destructive action of the gas on property being borne in mind. (6) Formaldehyde-gas. (c) Washing with solution of bichloride of mercury, 1 to 1000, or 5 per cent, solution of formalin, or 5 per cent', solution of carbolic acid, preference being given to carbolic acid for application to polished woods, bright metals, and other objects injured by metallic salts. The forecastle, steerage, and other living apartments in bad sanitary condition must be disinfected by method (a) followed by method (c). 382 QUARANTINE Mattresses, pillows, and heavy fabrics are to be disin- fected by: (a) Boiling. (6) Flowing steam, i. e., steam not under pressure. (c) Steam under pressure. (d) Steam in a special apparatus with vacuum attach- ment. Clothing, fabrics, textiles, curtains, hangings, etc., may be treated by either of the above methods from (a) to (d) inclusive, as circumstances may demand, or by formal- dehyde-gas or sulphur dioxide where the article is of a character which will not be damaged by sulphur dioxide. Articles injured by steam, such as leather, furs, skins, rubber, trunks, valises, hats and caps, bound books, silks, and fine woolens should not be disinfected by steam. Such articles should be disinfected by formaldehyde-gas or by any of the agents allowed in these regulations which may be applicable thereto. Those which will be injured by wetting should be disinfected by a gaseous agent. Clothing, textiles, and baggage, clean and in good con- dition, but suspected of infection, can be efficiently and least injuriously disinfected by formaldehyde-gas, gen- erated by one of the methods previously described. Textiles which are soiled with the discharges of the sick or presumably are deeply infected, must be disinfected by: (a) Boiling. , (6) Steam. (c) Immersion in one of the germicidal solutions. Cooking and eating utensils are always to be disinfected by immersion in boiling water or by steam. As to the passengers and others who have been isolated in groups, they are to be inspected twice daily by the physician and remain under his constant surveillance, and can have no communication with anyone in a differ- ent group or outside of quarantine, except through the quarantine officer. The water-supply and food-supply are to be strictly guarded, and are issued to each group separately. The latter is to be simple in character and DISINFECTION OF VESSELS 383 abundant in quantity, but no fruit is to be permitted. Strict cleanliness is to be enjoined, disinfection wherever necessary, and, in case quarantinable disease appears in any group, the sick will be immediately removed to the hospital, and the rest of the group bathed and their effects disinfected, and all of them removed to other quarters, if possible. None are to leave quarantine until the end of the incubation period of the disease in question, dating from the last exposure to infection and the final disinfection of such effects as were taken to barracks; and no convalescent may leave quarantine until a bac- teriological examination shows him to be free from infection. As has been stated, the treatment of vessels infected by some diseases is not necessarily so severe as that of others, but in each case every effort is made to allow no loop-hole for the entrance of infection into the country, and no vessel may leave quarantine until she has a certifi- cate from the health (quarantine) officer that she has in all respects complied with the quarantine regulations, and that, in his opinion, she will not convey quarantinable disease. She is then said to be granted free pratique. The law further provides that " when practicable, alien immigrants arriving at Canadian and Mexican ports, destined for the United States, shall be inspected at the port of arrival by the United States consular or medical officer, and be subjected to the same sanitary restrictions as are called for by the rules and regulations governing United States ports; that inspection-cards will be issued by the United States officer at the port of arrival to all such immigrants, and labels affixed to their baggage, as is required at foreign ports." Where such immigrants are not inspected at the port of arrival they shall enter the United States only at certain designated points on the frontier, and then only after such inspection, detention, disinfection, vaccination, etc., as may be necessary or required by the officers there stationed. There is also provision for the inspection of State or 384 QUARANTINE local quarantines from time to time by the Supervising Surgeon-General of the U.S. Public Health Service, or by any officer of that service detailed by him; and for the observance at all quarantines of such additional rules and regulations as may from time to time be promulgated by him. INLAND QUARANTINE. Under this heading may be considered the means that may be employed to prevent an epidemic extending from one locality or district to another, although the principle and aims are practically the same as those of maritime quarantines, viz., to define certain boundaries beyond which no person or thing capable of carrying infection may pass, and to establish certain points of ingress or egress on these boundaries where there may be the necessary detention, inspection, disinfection, etc. The sanitary cordon "consists of a line of guards, mili- tary or civil, thrown around a district or locality, either to protect the same from the surrounding country when infected, or to protect the surrounding country from the infected district or locality." "It is not intended to bottle up all the people who are caught within an infected district, but, on the contrary, is intended as a means of exit to those who will not carry with them contagious diseases to the people beyond. "^ It may be single or double; in the latter case the inner line closely encircles the well-defined infected locality, and the outer line the whole suspected territory. This latter may be removed as soon as it is evident that the space between it and the inner line is not infected. To be efficient the cordon must be so guarded that, even though it be many miles in length, no unauthorized person may pass through it, while at certain places upon it camps of probation or detention must be established, where all persons coming from the infected locality may be kept under observation ^ Roh6's Hygiene, "Quarantine." INLAND QUARANTINE 385 for a time equal to the period of incubation of the disease in question. These camps of probation or detention are to be distinguished from the camps of refuge, which were first suggested by Surgeon-General Woodward in 1878, and which are "simple residence camps established to receive the population of an infected community when it has been determined to depopulate the infected district." At these camps of detention provision must be made for inspecting every person and disinfecting all baggage before entering camp, for isolating the occupants and housing and feeding them in the most comfortable and sanitary manner during the detention, for inspections twice or thrice daily, for the isolation and care of the sick in hospitals at a safe distance from camp, and for the issuance of a certificate granting "free pratique" when the period of detention is over. A notable instance of the sanitary cordon was that about the city of Brownsville, Texas, and along the Rio Grande, in 1882; and of a detention camp, that at Camp Perry, Florida, in 1888. In addition to these measures it may be necessary or advisable to establish a railroad quarantine, as follows: "At certain convenient points, which will be the only points of egress by rail from the infected district, an inspection service and disinfecting station are to be maintained throughout the epidemic. Here all the baggage and freight are to be properly disinfe^cted and all passengers are to be examined by the official inspectors; if the latter are from the infected locality, or have not a certificate from some recognized health officer as to where they have been for the previous days corresponding to the incubative period of the disease, they are to be at once remanded to the nearest camp of probation, there to undergo the necessary detention. Moreover, it may seem advisable to prevent any passenger cars going beyond the infected district, and to disinfect all freight and baggage cars that do so." 25 386 QUARANTINE Local and House Quarantine. — There may also be local or house quarantines established by municipal boards of health or other authorities to prevent not only the family or attendants of the sick from mingling with the rest of the community, but also to keep injudicious outsiders from spreading the infection through unwise visitations. And though such isolation may appear at times a hard- ship to certain individuals and to be unduly severe, one should not forget the great cost to all concerned of epi- demics once inaugurated, nor that it is only by such stringent measures that we shall be able to eradicate the infectious maladies from our communities. Vaccination. — ^The foregoing remarks apply likewise to other prophylactic measures, such as, for example, vaccination. Within the last few years there have been many epidemics of smallpox throughout the whole country, the extent and spread of which were due to a very general neglect to secure the protection afforded by vaccination. -To controvert those who assert that this prophylactic measure is of no value, the following statistics are quoted from McFarland, from Welch and Schamberg, and from Harrington: Prior to the adoption, April 1, 1875, of the German law requiring vaccination at birth and at the tenth year, the annual mortality in Prussia, from 1816 to 1870 was from 7.32 to 66 per 100,000 of population; in 1871 it was 243.2, and in 1872 it was 262.67, owing to the introduction of French prisoners. Since then there has been no epidemic, but from 1875 to 1886 the average annual mortality was 1.91 per 100,000 and the lowest 0.36. On the other hand, from 1870 to 1895 over 20,000 died from smallpox in Paris alone, where vaccination is not compulsory. In the following table, note that vaccination was com- pulsory in the first five cities and not enforced in the other four: INLAND QUARANTINE 387 Death-rate for Smallpox. (in 100,000 of population— 1875-1889). < Berlin 1.16 Hamburg 0.74 Breslau 1.11 Munich 1 .45 Dresden 1.03 Paris 26.24 St. Petersburg 35 . 82 Vienna 64.90 Prague 147.90 According to Harrington, in the Sheffield epidemic of 1887-88, 1.55 per cent, of vaccinated and 9.7 per cent, of un vaccinated were attacked, the death-rate among the former being 0.7 and among the latter 48 per 1000. Among children under ten the rate of attack was 5 and 101 per 1000 respectively for vaccinated and unvaccinated, and the death-rate was 0.09 and 44 per 1000. From the statistics of this epidemic w^e have: Rates of Attack per 1000 Persons. Persons not vaccinated 94 . 00 Persons once vaccinated 19 . 00 Persons twice vaccinated 3 . 00 Death-rates per 1000 Persons. Persons not vaccinated 51.00 Persons once vaccinated 1 . 00 Persons twice vaccinated 0.08 The same authority states that a "successful primary vaccination within three days after exposure to existing cases of smallpox will prevent the development of the disease, and as late as the fifth or sixth day will either prevent or modify an attack." So that epidemics, even when well under way, can be checked by wholesale vacci- nation. However, vaccination should be repeated from time to time, especially when there is danger of infection. In Philadelphia, in 1901-04, not one of the 350Q smallpox patients treated at the Municipal Hospital had been sue- 388 QUARANTINE cessfully vaccinated, as evidenced by the scar, within four years of the attack, and this in spite of the fact that about 500,000 persons, or one-third of the city's popula- tion, were vaccinated during this epidemic. From the data of this hospital Welch and Schamberg compiled the following:^ Percentage Cases. Deaths. of deaths. Vaccinated in infancy, good scars . . 2335 152 6 . 50 Vaccinated in infancy, fair scars . 1105 135 12.21 Vaccinated in infancy, poor scars . . 1524 345 22.64 Postvaccinal cases 4964 632 12 . 53 Unvaccinated 3687 1542 41.82 Total 8651 2174 25.13 Again in the same hospital, "during a period of thirty- four years, in which time over 9000 cases of smallpox have been treated, not a physician, nurse, or attendant who had been successfully vaccinated or revaccinated prior to going on duty, contracted the disease." Surely, with modern statistics such as the foregoing at hand, it is not necessary to recall the excessively high mortalities of the eighteenth century prior to Jenner's discovery, amounting to half a million or more annually in Europe, to convince intelligent persons of the great value of this one method of prophylaxis, and yet legal compulsion seems to be necessary to secure its general employment. In the preceding pages the author has attempted to present briefly the principles and the regulations of quarantine as practised in the United States at the present time; but the reader is referred for further details to the extremely interesting and valuable chapter on the subject in Rohe's Text-book of Hygiene, by the late Dr. Walter Wyman, the former Supervising Surgeon-General of the Marine-Hospital and Public Health Service. 1 Acute Contagious Diseases, page 55. CHAPTER XII. THE REMOVAL AND DISPOSAL OF SEWAGE. The waste from dwellings is of three kinds: house- sweepings and the ashes from fires; the waste from kitchens, scraps of food, etc., commonly known as gar- bage, and sewage, the most important, consisting as it does of the solid and liquid excreta of the body together with waste w^ater from wash-tubs, bath-tubs, kitchens, laundries, etc. Ashes alone have little effect upon the health, except that they absorb moisture readily, and if allowed to accumulate in a cellar may do much to keep it damp and mouldy. For the same reason, if they be mixed with refuse vegetable matters, putrefaction is favored and noxious emanations given off. The dust from ash heaps may also be carried into the house and largely increase the solid impurities of the air therein. Consequently, ashes should be frequently and regularly removed from the premises. Kitchen garbage readily decays, and if allowed to remain in the vicinity of the house may pollute both the air and soil about it; but inasmuch as it has some value as a food for animals, there is usually no difficulty in the smaller communities in having it removed by scavengers without expense or delay. Care must be had, however, that this is done properly and that all receptacles are kept in as cleanly a condition as possible. Most large cities now find it safer to collect and cremate the garbage at the expense of the municipality, rather than to allow private individuals to keep for its consumption large numbers of animals within or near the city limits. Even though the (389) 390 THE REMOVAL AND DISPOSAL OF SEWAGE former plan be the more costly, experience shows that this garbage may and should be consumed in properly arranged crematories at convenient locations without annoyance to the residents of the vicinity, thus saving the expense and time necessary for conveying the garbage beyond the municipal limits. The kind of waste to which we give the name sewage is, however, of more importance to sanitarians, since it is always a possible factor in the production of disease, and since it presents the greater difficulties in respect to its removal from dwellings and the ultimate disposal of it. In addition to the substances already named and which usually come from dwelling-houses, sewage may contain the liquid excreta from stables, the refuse from factories of all kinds, the drainage from polluted soils, and the excess of rain-water not taken up by evaporation or retained in the soil. Its composition must therefore be always complex and variable, but there will be practi- cally always present in it sodium chloride, ammonia, carbon monoxide and dioxide, hydrogen and ammonium sulphide, fetid and decomposing organic matter, and myriads of bacteria. Fresh sewage will not be so offen- sive to the senses as that in which putrefaction has commenced, nor will the gases arising from it be so dan- gerous to health. Frankland has shown that "solid or liquid matter is not likely to be scattered into the air from the sewage itself by any agitation it is likely to undergo until gas begins to be generated in it;'^ and it is really doubtful whether the air of a properly constructed and well-ventilated sewer can be shown to contain a harmful excess of injurious gases and organisms. However, it is essential that sewage should be removed from the premises of a dwelling as soon as possible after its pro- duction and before decomposition begins. When the above-mentioned constituents of sewage are to be disposed of collectively, the water-carriage system is usually the best. Although the pneumatic system (wherein air-tight pipes extend from the dwellings, etc., SEWAGE 391 to resetvoirs from which the air is periodically exhausted and the sewage thus drawn into them) would seem to be advantageous where the topographical conditions do not permit of natural drainage, it is always subject to the danger of breaks occurring and destroying the action, and seems to have been practically successful in but few instances. A modification of the pneumatic system which seems to be more successful and practical is the Shone or ejector system. In this the sewage is conducted by gravity through suitable drains to convenient ejector stations or tanks, whence it is forced by means of compressed air to the irrigation fields or other places of ultimate disposal. The system has been in successful operation in Arad, Hungary, since 1896, the plant disposing of the sewage of 20,000 persons from five ejector stations at a working cost, excluding interest and sinking fund, of about 25s. ($6.25) per day.^ On the other hand, where house refuse only is to be considered, and where the waste- water can be kept from the other parts of the sewage, or where the water-supply, the physical conditions, or the cost of constructing the necessary sewers prevent the use of the water-carriage method, recourse should be had to the pail or earth-closet system. The use of primitive privy-vaults or cesspools is most insanitary and dangerous, and should be con- demned in almost every instance. Where the necessity for one of the latter seems imperative, it should be made absolutely water-tight, so that none of the contents may escape to pollute the surrounding soil and soil-air or to contaminate the ground-water in the neighborhood. Moreover, the pits should be properly ventilated and should be cleaned out regularly and often, which may be done without offence by some form of odorless excavat- ing apparatus, such as is now commonly used. The daily addition of a solution of chlorinated lime or » American Year-book of Medicine for 1900, pp. 549 and 550. 392 THE REMOVAL AND DISPOSAL OF SEWAGE milk of lime or of sulphate of iron, to the extent of about two quarts for each person using the cesspool, will do much in the way of checking bacterial growth, even though it does not actually disinfect the contents, and will largely prevent the offensive odors of putrefaction from such accumulations. It should be noted that the contents of such a vault, or of a simple pit in the earth, undergo putrefaction rather than natural decomposition, if no antiseptic be used, because of the lack of sufficient oxygen supply and of the adjunct action of the nitrifying bacteria which are found only in the uppermost layers of the soil. It is also probable that many disease germs, particularly those of diphtheria or typhoid fever, will survive and multiply better in the contents of such a vault than in sewage or refuse treated by the methods to be hereafter described. In the pail system the more solid waste matters, and especially human excreta, are collected in a suitable pail or tub, which, holding only a limited amount, must of necessity be removed and emptied regularly and often. If the outbuildings used for this purpose be kept clean and properly ventilated, such a system will be both economical and healthful. Advantage may here be taken of the great deodorizing, nitrifying, and oxidizing power of fine, dry earth, and various forms of earth-closets have been devised to be used in conjunction with the pail system. If a quantity of dry, sifted earth, in bulk about twice that of the dejecta, is thrown upon the latter after using the closet, they will be rendered inodorous and inoffensive. For this purpose loam and clay are best, though sifted ashes may be used with almost as good results, but sand or gravel will not be as efficient as the loam or ashes. Moreover, owing probably to the action of the nitrifying bacteria in the earth, all traces of the peculiar nature of the organic compounds are quickly destroyed, and the mixture soon becomes practically nothing but humus and is an excel- lent fertilizer. PAIL OR EARTH-CLOSET SYSTEM 393 Harrington^ says of peat used for this purpose that it "has not only remarkable power of absorption, but also very marked bactericidal properties. It will absorb and retain from nine to eighteen times its weight of water, it acts as a deodorant in the same manner as charcoal, and it retains ammonia in apparently unchanged condition. Experiment has shown that neither the typhoid nor cholera organisms can retain their vitality in contact with peat longer than a very few hours, and the same is true of many other varieties of bacteria." The pail or earth-closet must, of course, be separate and apart from the dwelling, as it is impossible to have the same means of keeping the gaseous emanations and effluvia out of the house as with the water-carriage system; and it is also important that the liquid house- slops, wash-water, etc., be kept separate from the fecal waste, which should be kept as dry as possible to lessen putrefaction and to increase its possible value as a fer- tilizer. Nor should this liquid waste be allowed to soak into and pollute the soil about the house. It should be collected in a water-tight reservoir, whence it can be removed at frequent intervals, or, better yet, carried by suitable drains to a kitchen garden or other land at a proper distance from the house, and be there disposed of by irrigation or sub-irrigation. As one can readily see, the pail or earth-closet system is especially well adapted to isolated houses and small communities, where each householder can take care that the necessary details are properly attended to, and where, as is likely, there is not a general water-supply, or where the expense of constructing the necessary sewers would be too great. But even in cities as large as Manchester, England, "where four-fifths of the people are obliged to have earth-closets," the system is said to have proved entirely advantageous and practicable. ^ Practical Hygiene, 1st edition, p. 470. 394 THE REMOVAL AND DISPOSAL OF SEWAGE Where there is a common and general supply of water throughout the house or to a number of houses there must be some provision for carrying off the waste-water, and as this latter will probably have become polluted in its use, it will be advantageous to employ it to remove the other sewage. In fact, where the conditions are favorable the water-carriage system will usually be found the best of all, because it is more 'nearly automatic and depends least on human interference and efficiency. The necessary apparatus comprises, on the one hand, that which belongs to the building and its premises, viz. : the house fixtures, pipes, and drains; and, on the other, the common or public sewers which receive the sewage from the house-drains and convey it to its place of ulti- mate disposal. SEWAGE-PLUMBING AND HOUSE-DRAINAGE. The essence of any good system for the removal of sewage from a dwelling or building is simplicity. There- fore, inasmuch as it has been stated that sewage should always be removed from the premises as soon as possible after its production and before fermentation or putrefac- tion begins in it, it is evident that in such a system we should have for our object and should provide for: ''(1) The speediest possible removal from the house to the public sewer of excretal and other refuse by means of water. (2) The prevention of the deposit of foul matter in any part of the drainage system and of percolation into the soil of polluting liquids. (3) The establishment of a current of air through every part of the soil-drains and pipes, in order to disperse any foul gases that may form and to allow them to escape with safety into the open air. (4) The prevention of any entry of air from soil-pipes, drains, and waste-pipes into the house. (5) The exclusion of the air of the common sewer from the house-drains and the house; the last being, perhaps, the most impor- tant, as the air of the public sewer may at any time con- SEWAGE-PLUMBING AND HOUSE-DRAINAGE 395 tain the active germs of specific disease."^ Some modern authorities, however, would omit this last requirement on the ground that the air of the street sewer is no worse than that in the house-drains and soil-pipes of dwellings and that the latter, because of their number and frequency, afford one of the best means of ventilating the common sewer. The attainment of the above requirements is to be secured in the manner to be described. The soil-pipe is that which receives the sewage from water-closets and, usually, from the waste-pipes of other fixtures, such as bath-tubs, wash-stands, sinks, etc., and which connects them with the house-drain; the latter is the conduit connecting the soil-pipe with the sewer. Waste-pipes convey the contents of wash-stands and other fixtures to the soil-pipes or to a branch of the house-drain. (See Fig. 93.) The soil-pipe is usually located almost entirely within the house, although, were it not for the danger of its con- tents freezing, it would be better to have it fastened to the wall outside. It is made of cast or wrought iron, should be at least four inches in diameter, should convey the sewage as directly as possible from the fixtures to the house-drain, and must extend unobstructed from the latter to several feet above the roof, ending where winds and currents from high walls and chimneys will not interfere with its free ventilation. Every branch of the soil-pipe more than eight feet in length, or to which two or more water-closets are connected, should also be extended above the roof, or else be extended and connected to the main soil-pipe above the highest fixture connected therewith, as there must be no closed ends wherein foul or stagnant air may collect. All joints must be absolutely air-tight, and the pipe must be so secured that any vibration or settling of the building will not be likely to destroy its continuity. In new buildings, especially, it would be well if * L. C. Parkes, Hygiene and Public Health, 2d edition, p. 139. 396 THE REMOVAL AND DISPOSAL OF SEWAGE all soil-pipes were exposed or else covered in with panels easily removable at any" time to permit of inspection or MAIN TRAP Fig. 93. — Illustrating sewage-plumbing of a house. The traps of the rain leaders at their junctions with the house drain have been accidentally omitted. repairs. Any hidden pipes or those difficult of access should be of extra heavy materials, and extra care should be given HOUSE-DRAIN 397 to the joints and supports. The soil-pipe and house-drain should both be as smooth as possible interiorly, and in the construction they must be carefully inspected to prevent any of the material used in caulking or cementing the joints from projecting within to obstruct the free flow of sewage. Outside of the house the house-drain may be of iron or of glazed and impervious earthenware, but no earthen pipe should be permitted within five feet of a foundation wall, and where any part of the house- drain is within the build- ing it should be of iron and securely fastened to the foundation-wall above the cellar floor. The connection Fig. 94. — Method of connecting soil-pipe with house-drain. between it and any soil-pipe should be by means of a rounded elbow, and not by an abrupt right angle. (Fig. 94.) The house-drain should not be less than four nor more than ten inches in diameter, should be laid on a firm foundation, should have air-tight joints, and should have a slope toward the sewer of at least one-half inch to the foot. If a house-drain empty into a sewer of the "combined" system, there should be a trap just before its junction with the sewer to .prevent the passage of sewer-air back into the house (Fig. 93) unless it is planned to use such 398 THE REMOVAL AND DISPOSAL OF SEWAGE house connections to ventilate the sewer, and there must also be an opening for fresh air between this trap and the house-drain, so that there may be a constant current through the house-drain and soil-pipes to the exit above the roof, and the air in the soil-pipes thus kept from becoming foul and stagnant. But if the house-drain empties into a sewer of the "separate" system, there need be no trap between the drain and sewer, because the air in the latter will probably be better than that in a "combined" sewer and because there is otherwise practically no adequate ventilation of the "separate" sewer. However, the fresh-air inlet between sewer and house-drain is always advisable, as it tends further to assist ventilation. A hduse-drain should not empty into a cesspool unless it is absolutely necessary, and in such case the cesspool must be well ventilated and also separated from the drain by a fresh-air inlet and trap, just as when the drain empties into a combined sewer.^ Nor should any cess- pool empty into a sewer. Where rain-water conductors empty into house-drains or sewers, they should be separated from the latter by traps having a seal of not less than five inches, to prevent sewer-air passing up through them to the vicinity of windows, etc. So, also, all waste-pipes, gutters, and other pipes opening into house-drains should be trapped. In the house all water-closets and other fixtures should be as near the soil-pipe as possible that there may be no long stretches of foul waste-pipe underneath the floors, and all connections with the soil-pipe should be made at an acute angle that the discharge into the latter may not interfere with its free ventilation. Each fixture must be separately trapped, and the trap must be located as near its fixture as possible. There must be no connection ^ The "septic tank" hereafter described must not be confused with the cesspool mentioned here, as it is permissible to connect the house-drain directly to a properly constructed septic tank, for reasons that are made apparent in the description of the latter. SEWAGE-TRAPS 399 between a fixture and the soil-pipe or house-drain which is not trapped. A little reflection will show that by observing the above rules of construction provision will have been made for each of the five specified requirements of the system, and the air in the soil-pipes will be almost as pure as that of the house itself. The absorption of foul gases by the water in the house-traps and their subsequent dispersion into the atmosphere of the house will also be almost impossible. But there must always be free communica- tion between the air inlet into the house-drain and the outlets from and at the top of the soil-pipes; otherwise Figs. 95 and 96. — These illustrations show how a uniform caliber prevents the accumulation of dirt in a trap, and how angles and corners favor such accumulations. (Gerhard.) the air in the soil-pipe cannot be changed and foul gases will accumulate which, by their pressure, would tend to force themselves into the house whenever an opportunity occurred, and might even overcome the seal of some of the traps. Sewage-traps are "appliances placed between house conveniences (fixtures) and soil-pipes and drains or sewers, to prevent sewer-gas gaining an entrance into the house.'* Many traps are too complicated. The simpler a trap the better, provided it have sufficient seal. The seal of a trap is the depth of water or the mechanical appliance which prevents the back-flow of gas. Mechanical appli- ances are liable to become clogged and not to fit tightly, 400 THE REMOVAL AND DISPOSAL OF SEWAGE thus allowing the passage of sewer-air; they also tend to check the free onward flow of the sewage, thus favoring deposition in, and preventing, the cleansing of the trap. The S or siphon trap is as simple as any, is of uniform Fig. 97. — S or siphon trap, with opening for ventilation pipe. (Gerhard.) Fig. 98.— Bell trap. (Gerhard.) diameter throughout, has no corners or projections to catch dirt, and is thoroughly cleansed by each fair flow of water through it. The value of a trap does not depend so much on the amount of water it contains as on the depth or strength of the seal. On account of evaporation Fig. 99. — Cudell's trap. (Gerhard.) Fig. 100. — Bower's trap. (Gerhard.) the water-seal of a trap may become lessened or destroyed unless the fixture to which it is attached be in frequent use; it is therefore advisable to have as few fixtures of any kind in the house as the comfort or convenience of PREVENTION OF SIPHONAGE 401 the inmates will allow. So, also, if a house is to be un- occupied for a time, it is well to cover the water in the traps with oil or glycerin to prevent evaporation of the former. Leakage or capillary action, the latter caused by accumulations of hair, thread, etc., in the trap, may likewise lower the water so that sewer-gas may pass through from the soil-pipe. Fig. 101. — Grease trap. C, cover; 7, inlet; V, vent: 0, outlet. (Harrington.) Lastly, the seal of a trap may be broken by siphonage, either by a strong rush of water through it from its own fixture, or by a rush down the soil-pipe from a fixture higher up, and this is especially liable to occur if the trap be some distance from the soil-pipe, or if the fixtures above discharge a large amount of water at once. To prevent this, openings are frequently made at the top of the traps on the side next the waste-pipe or soil-pipe and con- nected with vent-pipes, which should open into the soil- pipe above the entrance of the waste-pipe from the highest fixture, or be continued separately into the out-door air. (See Fig. lOL) But this increases the expense, and, as 26 402 THE REMOVAL AND DISPOSAL OF SEWAGE the vent-pipes, to be efficient, must be almost two inches in diameter, they also favor evaporation from the trap. If the trap is properly constructed, if the soil-pipe is of suitable size and height, and if the fixtures be placed as near the soil-pipe as possible, there will be much less danger of siphonage occurring. Where it does occur, McClellan's anti-siphon attachment (Fig. 102) is said to work advantageously, being inexpensive and permitting Fig. 102. — McClellan's anti-siphon attachment. Sectional view of vent with cup lifted out of the mercury by the inflowing current of air, indicated by the arrows. (Rohe.) a free ingress of air to the trap, but no egress of air from the soil-pipe into the house. In this device a small weighted and inverted cup rests with its edge immersed in a ring of mercury, from which it is raised by the atmospheric pressure only when the siphonage sufficiently reduces the pressure within the pipes. The mercury and the weight of the cup make a seal sufficient to prevent any outflow of gas, It is also said that if the waste- TESTING OF PIPES AND DRAINS 403 pipe be connected with the soil-pipe by a divergent open- ing, siphonage will be less likely to occur. Fig. 103.— a modern bath-room. (Courtesy of the Standard Sanitary Manufacturing Co.) All waste-pipes, soil-pipes, and house-drains, should be tested before use by closing all openings and forcing in air to a pressure of at least thirty pounds to the square inch. Leaks may also be detected by plugging the lower openings and filling the pipes with water, or by pouring an ounce of oil of peppermint into the highest fixture and 404 THE REMOVAL AND DISPOSAL OF SEWAGE quickly following this with several gallons of hot water, the heat volatilizing the oil, whose odor escapes at every opening in the pipes unprotected by a trap or water-seal. Fig. 104. — Old-fashioned wash-basin with overflow horn discharging beneath plug. (Harrington.) FiQ. 105. — Improved stand-pipe overflow. (Harrington.) WATER-CLOSETS 405 The heat imparted by the hot water will also help to trace out hidden soil-pipes. All fixtures should be exposed to the free ventilation of air underneath and about them, and water-closets and wash-stands should not be closed in with carpentry work. (See Fig. 103.) Traps should also, if possible, be where they may be opened and inspected at any time. Under each closed-in fixture, if there must be such, there should be a drip-safe to catch any leakage or overflow of water, but the pipes, if any, leading from these should never empty into waste-pipes or soil-pipes; they should lead preferably into the open air and not to the cellar, as the cellar-air, which is usually impure, thus gains access to the house. Even if these drip-safe pipes are trapped and open into the soil-pipe, ,the water in the trap is replenished so rarely that evaporation soon destroys the seal and allows the air tb pass from the soil-pipe into the house. The overflow pipe of old-fashioned wash-stands and bath-tubs is objectionable, as it collects dirt of all kinds, soap, epithelium, etc., and it is almost impossible to clean it. Beside, it will often be found opening into the waste- pipe below the trap, thus allowing the free passage of sewer-air into the room. When new fixtures are being put in they should preferably be such as make use of the stand-pipe or equally safe principle in the stoppers and that have no separate or concealed overflow pipe or outlet (Figs. 104 and 105). Water-closets. — ^The requisites for a good water-closet are : that it does not allow the escape of sewer-air from the soil-pipes into the house; that it is thoroughly and easily cleaned each time after use; that there are no hidden parts in which filth can collect, or which cannot be readily cleaned ; that the flushing or washing out of the closet be done in such a way that dirt or spray, be not thrown into the air of the room ; that there be sufficient water-supply to wash out the bowl and trap each time and to refill them to the proper level; that the trap itself is not siphoned or 406 THE REMOVAL AND DISPOSAL OF SEWAGE left empty by a discharge of water from this or another fixture. Of the different kinds of water-closets the pan and the valve closets are among the oldest and the worst, and should 1 ',^ff»*ftftfff^r^fTff\ /iffHTfiriimTrh" Fig. 106.— Pan closet. (Gerhard.) Fig. 107.— Valve closet. (Gerhard.) not be used anywhere. They consist of a receiving bowl, the bottom of which opens into a swinging pan or is closed by a valve . The pan or valve and the lower part of the receiving WATER-CLOSETS 407 bowl are enclosed in another bowl, the container, connected with the soil-pipe and trap. The depth of water in the receiving bowl in pan closets is regulated by the depth of the pan, and in valve closets by the location of an overflow outlet. In both kinds the contents of the receiving bowl are discharged into the container by the tipping of the pan or valve, and consequently the sides of the con- tainer, as well as the under side of the pan or valve, soon become thickly coated with filth. This, being hidden, accumulates, decomposes, and contaminates the air in the Fig. 108. — Plug or plunger closet, (Gerhard.) container, which air is of necessity discharged into the room as often as it is displaced by the contents of the receiving bowl. In valve closets the overflow-pipe from the receiver furnishes an additional way by which the foul air may pass from the container into the atmosphere of the room. It needs no argument to show that these closets are decidedly dangerous to health. Plug or plunger closets are those in which the outlet above the trap is stoppered by a plunger, this being usu- ally in a chamber at the side of the receiving bowl, and are almost as objectionable as pan or valve closets, 408 THE REMOVAL AND DISPOSAL OF SEWAGE modern plumbing wisely discarding all three. The bowl and side chamber holding a considerable quantity of water, the trap is well flushed out each time of use; but the side chamber and plunger, being hidden and not easily cleaned, soon become coated with filth and dangerous to health, as there is nothing to prevent the air from passing from' this chamber into the room. Moreover, the plug may not close the opening completely, thus allowing a continual waste of water. A trapped overflow-pipe in the plunger keeps the closet from overflowing. ^MM'A^*i^<.bi^ii^^^Sm Fig. 109. — Short-hopper closet. (Gerhard.) Hopper closets consist simply of a bowl connected below with an ordinary trap, and, as there is nothing to get out of order, this kind is theoretically one of the best. The objection to long hoppers is that dirt is apt to stick to the sides and become offensive, but this can be prevented if it is so arranged that water begins to flow down the sides as soon as the closet is put to use, thus preventing adhesion. Short hoppers have not this objection, as the feces fall directly into the water in the bowl and are carried out through the traps as the bowl is flushed. All water-closets should have a flushing rim encircling the top, so that all sides of the bowel may be washed down and cleansed each time the closet is used. Wash-out closets retain considerable water in the bowl, and are emptied by a strong flush of water from the WATER-CLOSETS 409 flushing rim. They are simple, do not readily get out of order, and have been much in favor up to the present time, but siphon closets are now tending to supplant Fig. 110. — Wash-out water- closet. (Parkes.) This bowl is too shallow. Fig. 111. — Dececo siphon closet. (Parkes.) them. As they are a modification of the short-hopper closet, so is the siphon closet a modification of the wash-out varietv. Fig. 1 12. — Sanitas siphon closet. (Harrington.) In the siphon closet the contents of the bowl and trap are lifted out by siphonic action, and then the bowl and trap are refilled, as in the case of wash-out closets, by an after-flush. In the Dececo closet — a siphon closet — use is made of the principle involved in the Field flush-tank. 410 TttE REMOVAL AND DISPOSAL OF SEWAGE Hopper, wash-out, and siphon closets should be sup- plied from water-closet tanks, which should give a cer- tain and sufficient volume of water with only a short pull on the chain or pressure on the rod or knob. The bowl and trap should also be automatically refilled from the tank after use. Water-closets should not be connected directly with the water-supply pipes of the house, as air from the closets may be sucked into them at times when the water-supply is cut off, and the water afterward contaminated by it. But this is difficult to avoid in pan, valve, or plug closets, and is another serious objection to their use. Vent-pipes from the bowl and seat of water-closets must be large, and must not open into the soil-pipe, but into the open-air; they must not open near a window nor any place from which air is taken into the house, but may open into a flue which is constantly heated, as a kitchen chimney, or may themselves be heated and have a current maintained in them by a small lamp or gas-jet. In this way the room in which a water-closet is located may be effectively ventilated. Water-closets should never be placed in dark closets nor in bed-rooms or living-rooms, but should always be in separate rooms that have free communication with the open air by means of a large window or by a ventilating shaft of at least four square feet sectional area throughout its length. It is also advisable that bed-rooms should not communicate directly with bath-rooms, etc., con- taining water-closets, unless there is every assurance that the closet and plumbing connected with it are first-class in every particular. It will not be out of place to suggest in this connection that apparatus for household conveniences, such as wash- stands, bath-tubs, water-closets, kitchen sinks, etc., which satisfies every practical sanitary requirement can now be had at prices that are quite reasonable when the necessary care and scientific experience in construction are taken into consideration. Much advance has been in the reduc- SEWERS 411 ing of the number of parts in an article, some being now made in a single piece, thus lessening or eliminating the crevices that would collect and hold dangerous filth; likewise concealed overflow pipes and corners and de- pressions difficult to clean have been done away with; and a third gain has been in the substitution of solid vitrified or enameled metal ware for articles that were made of comparatively soft substance and with a glazed surface that was liable to crack and thus permit the absorption of foul matters and possibly harmful organ- isms. That these advantages have also been accom- panied by an advance in esthetic appearances is well demonstrated by the illustration on page 93, or by what may be seen in almost any well-equipped modern dwelling. SEWERS. These are the conduits provided to receive and convey the contents of house-drains and other drains to the place of final disposal or discharge. They may be of either of two kinds — combined or separate. Sewers of the first class, which have heretofore been most commonly used in this country, are constructed to carry off all kinds of sewage, the waste liquids, etc., from factories, street- washings, and the surplus rain-water of the district drained by them. As this necessitates a size and capacity sufficient to receive the greatest probable rainfall upon the area drained in addition to the other sewage, it is evident that the depth of the usual daily volume of the latter in the sewer will be so shallow and the current so sluggish as greatly to favor the settling of the solid and semisolid constituents, the obstruction of the sewers, and the development of bacteria and sewer-gas. To obviate these faults and to insure a more rapid flow by keeping the depth of sewage as great as possible, the smaller conduits, at least, are generally made ovoid in section, the smaller end, of course, being downward. Combined sewers are not only more expensive to construct 412 THE REMOVAL AND DISPOSAL OF SEWAGE and to keep in repair than those of the separate system, but greater care must be had to see that they are at all times properly ventilated. The main advantage claimed for them is that the expense of constructing separate conduits for factory wastes, street-washings, and the excess of rain-water is avoided; but this is a doubtful one both in respect to economy and sanitation. Fig. 113. — Section of ovoid sewer of "combined" system. The ventilation of sewers of this kind is usually suffi- ciently provided for by the inlets for street-washings and rain-water located at street-corners, and by manholes but if these are not close enough together to keep the sewer atmosphere constantly changing and reasonably pure, other ventilation openings should be made. Heretofore the practice has been to exclude the air of combined sewers from house connections by means of the traps SEWERS 413 already described, but of late there is a tendency to utilize such house connections as efficient ventilators of the sewers because of their number and frequency, also because it is realized that the air of a properly con- structed and maintained sewer is quite as pure as that in the house connection. Only the sewage proper from dwellings, and occasionally from small factories, is admitted to the sewers of the separate system, the rain-waters, surface-waters and soil- waters being removed by other drains or channels. The advantages of this system, which is now indorsed by almost all sanitarians, are that the volume of sewage to be carried is comparatively small and constant, and that it can be calculated very approximately from the daily water-supply and population; that the cost of construc- tion is much less than that of sewers of the combined system, and that, while it is available and satisfactory for large cities, it is the only one that small communities would consider or can afford; that the sewage is more concentrated and uniform in composition, and can thus be better utilized as a fertilizer or disposed of in whatever manner may be most sanitary and advantageous; that the sewers, having smaller peripheries and smoother walls, are more frequently and effectually flushed, and that they are more completely ventilated and altogether better suited to the work to be performed. The disadvantages of sewers of this class are that a community must have two sets of drains, one for sewage and the other for rain, street, and factory waters, and that after a protracted dry season the street-washings, etc., may be very foul; but these are out- weighed by the advantages mentioned above. "No sewer of this system should be more than six inches in diameter until it and its branches have accumu- lated a sufficient flow at the hour of greatest use to fill this size half-full, because the use of a larger size is waste- ful and because ventilation becomes less complete as the size increases. The size should be increased gradually and only so rapidly as is necessary by the filling of the 414 THE REMOVAL AND DISPOSAL OF SEWAGE sewer half-full at the hour of greatest flow; and the upper end of each branch sewer should be provided with an automatic flush-tank (Fig. 114) of sufficient capacity to secure the thorough daily cleansing of so much of the conduit as from the limited flow is liable to deposit solid matters by the way." There should ordinarily be no traps between house- drains and sewers of the separate system, since, having no rain-water inlets, the latter would otherwise have no openings for ventilation. Moreover, since the "separate" sewers are so regularly and thoroughly flushed, the air in ^ Fig. 114. — Field's annular siphon flush-tank, (Parkes.) them is not likely to be impure, and there is not as much reason for excluding it from the house-drains, etc., as there is regarding the air from "combined" sewers. The junction of house-drains with sewers of the separate system should be by divergent openings, so that the air may pass freely into the drain as the sewage empties into the sewer. Should one desire, however, to separate his house-drain from the public sewer by means of a trap, and thus prevent the ingress of sewer-air into his premises, the ventilation of the sewer can be secured by providing a vent-pipe between the trap and the sewer. But in no DISPOSAL OF SEWAGE 415 case must the inlet-pipe for air on the other side of the trap, between it and the house, be omitted; nor should the two air-pipes be so near together that air from the former will be likely to be drawn into the latter. All sewers should be laid on a good foundation with sufficient fall to give at least a velocity of two feet per second to the flow. If made of brick, they should be laid in a mortar made of cement and sharp sand, and all sewers should be as smooth as possible inside to prevent the arrest of particles of sewage. Sewers of the com- bined system shpuld not be pervious to the soil-water, as the liquid sewage is just as apt to pass from them to the soil and to pollute it dangerously as the soil-water is to pass into the sewers. But the rain-water drains of the separate system may also be employed to drain the subsoil. DISPOSAL OF SEWAGE. The ultimate disposal of sewage is a matter of consider- able importance which commonly does not receive the attention it deserves. The method frequently employed in this country of discharging the sewage into a running stream is reprehensible, because the natural purification of a water thus contaminated must always be slow and more or less uncertain, and because the risk to those using the polluted water must be a constantly -increasing one. Where the district drained and supplied by the stream is a sparsely settled one, and where the volume of fresh or running water is very large in proportion to the quantity of pollution it receives, the objections to the disposal of sewage in this way may seem to be theo- retical rather than practical; but as the population in- creases and the ratio of pure water to filth decreases beyond certain limits, the question becomes more serious and pertinent. It is said that to dilute safely the sewage of 1000 persons requires from 2,000,000 to 4,000,000 gallons of unpolluted^ water per day; this, of course, not 416 THE REMOVAL AND DISPOSAL OF SEWAGE destroying the disease germs nor eliminating the danger of their multiplication. Other methods of sewage disposal resemble closely those already described for the purification of water, in that they make use of straining and subsidence, chemical and biological treatment, and filtration. In order that sewage may "lose permanently its power for evil" and not be a source of nuisance either to the community from which it comes or to others, it is necessary that it undergo certain changes or treatment after it reaches the end of the sewer system and before being discharged into a stream or body of water which, perforce, must practically always be the ultimate destination of the water content (over 99 per cent.) of all sewage. Such change or treatment con- sists essentially in the oxidation and mineralization of the putrescible organic constituents of the sewage into the simplest end-products, viz., carbonic and nitric acids and their salts, and water; the elimination or destruction of pathogenic organisms, and, incidentally or where necessary, the removal of insoluble inorganic matter or of certain harmful or objectionable factory wastes, acids, alkalies, etc. What method will be best suited and most satisfactory for a given locality can only be determined by a con- sideration of all the conditions and factors involved, including frequently careful preliminary experimental treatment over a reasonable period of time. The installa- tion of works for the proper conversion of the sewage of a community will relatively involve considerable expense, and it will be difficult or impossible in the near future to secure a change in method, if a wrong or unsatisfactory one be first put in use. Among the methods already successfully employed both in this country and abroad may be mentioned, straining by means of fixed or movable screens, sedimentation, liquefaction by so-called ''septic" action, the use of activated sludge, filtration and irriga- tion. The striking feature is that in almost all of these except sedimentation and mechanical straining, the essen- PLATE V FACTORS IN SEWAGE PURIFICATION BY DILUTION MAN BACTERIA ^ ^ HAVING FLAGELLA ALGA MICRRSTERIAS PROTOZOA CRUSTACEA FISH PERIDINIUM ■^ C'-^L.OPS — .^^, , NAUPLIU5 BUREAU OF SURVEYS DEPARTMENT OF PUBUC WOWCS CITY OF PHILADELPHIA AUGUST I9l3. DISPOSAL OF SEWAGE • 417 tial and greater part of the work is done by the living microorganisms normally present in the sewage itself and without the addition of extraneous substances. Two or more of the above methods may be and frequently are combined with much better results than would be possible if only one of them were used. Straining is accomplished by means of screens of various kinds or by coarse-grained filters made of coke (one-quarter inch), buckwheat coal or the like. The screens may be fixed or movable and be made of rods, wire gauze or perforated plates with openings of various sizes according to the material which it is desired to remove by this method and also according to the subsequent treatment of the sewage. The movable screens bring the collected matter above the surface of the sewage where they are cleaned by brushes, scrapers or an air blast. The simplest sedimentation treatment is to allow the sewage to flow slowly through a tank, this securing better deposition of the sludge than the alternate filling, and emptying of the settling basin, provided the addition of chemical precipitants is not to be madjg. Care should be had to secure an even flow through the whole cross- section of the tank above the sludge deposit on the bottom . With a rate of flow about fifty feet per hour and four hours or so for the time of settling, good results may be expected. The sewage may be collected in large tanks, with the addition of certain chemicals, such as lime, alum, or sulphate of iron, to increase the precipitation, and the suspended impurities allowed to settle to the bottom of the tanks, whence they can be removed, squeezed partially dry in hydraulic presses, and either disposed of as a fertilizer or cremated. The clear effluent or liquid part of the sewage may be allowed to flow at once from the settling tanks into a convenient watercourse, provided it is there well diluted, or it may better be filtered through an area of porous soil or through prepared filter-beds. If the filtration is properly done, the filtrate will contain nothing harmful, and may be allowed to flow where it will without danger. 27 418 THE REMOVAL AND DISPOSAL OF SEWAGE Chemical treatment will probably cost from thirty-five to fifty cents or more per annum per individual of the population supplying the sewage, but an even more im- portant question than cost is whether the addition of the chemicals may not interfere with the natural biological processes of purification constantly taking place in most sewage and interfere with the further purification of the effluent. Chemicals that are or have been used as pre- cipitants are lime, lime with sulphate of iron, alum, or alkali waste, sulphate of iron alone, and a combination of alum, charcoal, and clay. The precipitate obtained with the latter makes a fertilizer of some value, but it is not well to count too much upon a financial return from this as a by-product. The septic-tank system for the disposal of sewage par- ticularly aims to take advantage of the biological and saprophytic action occurring naturally in all polluted waters. The idea is to favor and not to hinder the purify- ing bacteria and other agencies by placing the sewage under the conditions most favorable to their growth and action, thus facilitating the conversion of organic matters, both solid and dissolved, into substances entirely harmless and unobjectionable. In other words, advantage is to be taken of the action of both the anaerobic and aerobic saprophytes which abound in all sewage that is not too strongly impregnated with antiseptic chemical wastes from factories or other sources. In the intermittent filtration and irrigation methods of sewage disposal the service of the anaerobic organisms is practically eliminated because the success of these methods depends largely upon a free and frequent aeration of the filtering material or the soil. On the other hand, the purpose of the septic tank is first to make use of the disintegrating and lique- fying action of the anaerobic bacteria upon the undissolved organic matter before subjecting the sewage to the action of the aerobic bacteria which it contains. Hence it is well to precede either intermittent filtration or irrigation by first passing the sewage through the septic tank, A THE SEPTIC TANK 419 similar action but not so complete may be had by the preliminary use of a contact filter. The septic tank for large volumes of sewage should be long and comparatively shallow, but should have such a capacity and cross-section that the sewage will pass through the tank in from six to twelve hours. At the upper end the fresh sewage should enter within a few inches of the bottom of the settling or "grit chamber," ^ct X) Caipocy// 320^a/. ©I ;;:^:^\:;:/^'::\;;/^^o^v/{v^:X:-.:/•v^<<;V^^•i^y^/^^•cr?^■i;:^y;^iy?gt^: ir ^^^■^l^:\■^-M'^^.^^:^:::^T^^.^:^^^^}>^^:-N^^,,Kl,:r^^^.^^^^ : \' .1 ±^ C •1) l^i- p;. . •.<-,••- 1.-./^< -A*.-, -.v.-i. L X v/. '-0 lu^^^^^^^^^jy c/ f ///€f C '\v% Fig. 115. — Double-chamber septic tank for family of six people, suitable to conditions where outlet fall is difficult to obtain.^ which is separated by a partition from the rest of the tank, and in which most of the street sand and other inorganic solids are collected. Thence it goes into the larger space, where the anaerobic bacteria carry on their work. The tank may be entirely covered in to exclude air and light, for though a thick scum or cake of sludge soon U. S. Bulletin. 420 THE REMOVAL AND DISPOSAL OF SEWAGE forms on top that would serve this purpose, there is some possibiHty of it being broken and air admitted by ice, snow, and other causes. However, experience has seemed to show that tanks without other covering than the sludge work fairly well and to give an effluent as good as that from tanks that were covered. As the sewage passes slowly through the tank the organic matter is decomposed with the evolution of considerable gas that DIAGRAM SHOWING TME CONSTRUCTION OF AN EM5CMER TANK CITY Of PH1LA0EI.DHI4 OEPARTMCNT OF Public wooks BUREAU OF SuRVEVS SfWAOE OliPOSAL DIVISION Fig. 116 might be collected and used for heating or lighting purposes, if the tank and volume of sewage were large enough to warrant it. An important variation of the septic tank is the so-called "digestion tank.'' Of these "the best known type is the Imhoff, or Emscher, tank. This is a deep septic tank divided by sloping partitions into an upper and a lower compartment, so arranged that the sewage flows slowly through the upper compartment while the sludge settles through openings in the partition DISPOSAL OF EFFLUENT 421 walls into the lower compartment, where digestion takes place. The advantage of this type of septic tank is that the sludge alone is submitted to septic action without allowing the products of decomposition to mix with the flowing sewage above, while more complete digestion improves the character of the sludge from the stand-point of subsequent disposal.^" This virtue of smaller bulk and quicker drying possessed by the sludge from Emscher tanks is of considerable importance when the volume of sewage to be treated is as great as that furnished by our larger American cities with their abundant water supplies. The author just quoted also states that septic sedi- mentation continued from twenty-four to forty-eight hours will remove from 40 to 50 per cent, of suspended matter in weak sewage and from 80 to 85 per cent, in strong sew^age. The following table prepared by Dr. Rideal indicates the changes in sewage due to biologic action in septic tanks, contact beds, trickling and intermittent filters, etc Substances dealt with. Characteristic products. Initial. Transient aerobic Urea, ammonia, and changes by the oxy- easily decomposable gen of the water sup- matters /- ply, rapidly passing to: First Stage. Anaerobic liquefaction Albuminous matters; Soluble nitrogenous and preparation by cellulose and fiber; compounds and fatty hydrolysis fats acids; phenol deriva- Second Stage. tives; gases, ammonia Semi-anaerobic break- Amido compounds; Ammonia, nitrites, ing down of the inter- fatty acids, dissolved gases. mediate dissolved residues, phenolic bodies bodies Third Stage. Complete atiration; ni- Ammonia and carbo- Carbonic acid, water trification naceous residues and nitrates. 1 Rosenau, Preventive Medicine and Hygiene, p. 853. 422 THE REMOVAL AND DISPOSAL OF SEWAGE The effluent from a septic tank may be carried into a shallow aerating trough over the sides of which the fluid flows in thin sheets, whence it may be conveyed to intermittent filters or irrigation fields; or it may be distributed through fixed or travelling sprinklers on aerobic or contact beds, or on trickling filters, the object in all being to enable the sewage to be thoroughly and speedily acted upon by the aerobic bacteria. Irrigation fields for our larger and rapidly growing cities are prac- FiG. 117. — Trickling or percolating filter, Pennypack Creek Works, Philadelphia. tically out of the question because of the great area of necessary land and its high cost, and for the same reason intermittent filters may also be inadvisable for cities of the largest size. For it must be remembered that the volume of sewage per capita is very much greater in American than in foreign cities, both because of our overgenerous supplies of water to dwellings and of the almost universal use of "combined" sewers, which add the rain-water, factory wastes and street washings to the sewage proper. TRICKLING OR PERCOLATING FILTERS 423 Aerobic or contact beds are large water-tight vats or tanks filled with porous materials, such as cinders or coke, etc., from i to J inch in size, the idea being that there should be as much capacity for the sewage as possible, and at the same time a ready aeration of the mass when the bed is drained, the beds becoming more efficient after being used some time, as they have thus become impregnated with the right kinds of bacteria. When a contact bed is filled with sewage and allowed to stand there is a rapid deposit of suspended and colloidal matter upon the myriads of surfaces of the solid material of which the filter is constructed, which deposit is rapidly acted upon by the ever present bacteria which increase in number from day to day. This action is partly anaerobic when the bed is filled with sewage, but becomes mainly aerobic as the fluid is drawTi off and air refills the inter- stices of the bed. After filling, the beds are left undis- turbed for a couple of hours, and are then drained, after which they remain empty for from two to four hours, it having been found possible by using auto- matic filling and emptying valves to repeat the process three or four times daily. It will usually be wise to carry the effluent from the septic tank through at least two of these beds, but if the process is properly accom- plished, "by this purification an effluent is obtained which is saturated with dissolved oxygen, which remains entirely inoffensive in smell for an indefinite period in an incubator at summer heat, and which therefore, when dis- charged into a water-course, would maintain the respira- tion of fish, and would never render the water offensive."^ "Trickling filters, otherwise called 'sprinkling filters' or 'percolating filters,' consist of beds of porous material such as broken stone, coke or clinkers upon which the sewage is sprinkled and through which it percolates to underdrains laid on a tight floor beneath. The entire bed is arranged with reference to complete aeration through- 1 Leffmann, Civic Hygiene, in Vol. V of Cohen's System of Physio- logic Therapeutics. 424 THE REMOVAL AND DISPOSAL OF SEWAGE out, in order that the organic matter of the sewage may be- come thoroughly oxidized. The suspended matter of the sewage is not permanently retained in the beds, but flakes off at intervals and is carried out in the effluent, which is turbid and requires subsequent clarification. The object of the trickling filter is to change the character of the organic matter so as to render it non-putrescible. The rate of application varies from 500,000 to 2,000,000 gallons per acre daily, one acre of trickling filter serving a popula- tion of 10,000 or more. Well-operated sprinkling filters receiving the effluent from plain sedimentation or septic tanks are capable of removing from 85 to 90 per cent, of the suspended matter and from 90 to 95 per cent, of bacteria, yielding an effluent that is non-putrescible. This method is useful when sandy areas of suitable size are not . available for intermittent filtration or are too expensive.^ The subsequent clarification of the effluent from trickling or sprinkling filters may be satisfactorily accomplished by the addition of chlorinated lime and passage through a settling basin of moderate size. Sewage may also be disposed of by intermittent down- ward filtration, either through specially constructed filter- beds or a prepared area of soil and by irrigation or sub irri- gation. *'The volume of sewage which may be success- fully purified upon a given filter area is inversely propor- tional to the amount of suspended matters in the sewage applied. In other words, if the whole or a part of the suspended matters are removed from the sewage by some treatment preliminary to filtration, the filters can be operated at much greater rates and a smaller area will be required for the treatment of a given volume of sewage.^" For sewage, intermittent filtration is superior to the continuous process — in fact, is almost essential, as the interruption in the percolation permits a renewal of the air-supply in the filtering medium or soil, and thus fur- 1 Rosenau, Preventive Medicine and Hygiene, p. 858. 2 Report of Massachusetts State Board of Health, 1908. INTERMITTENT FILTRATION— IRRIGATION 425 nishes a sufficient quota of oxygen for the use of the aerobic bacteria and for the oxidation and nitrification of the excessive amount of organic matter in the sew- age. With sufficiently frequent intermittence, fine sand, such as is used for building purposes, makes an excellent artificial filter, capable, it is stated, of purifying 50,000 gallons of crude sewage per acre per day and of removing all the solids, much of the dissolved matters, and 99 per cent, of the contained bacteria. Where the crude sewage is allowed to settle or is treated biologically in septic tanks, a much greater quantity of the clarified effluent can be filtered daily, as has been indicated. By intermittent soil filtration we mean "the concentra- tion of sewage at short intervals, on an area of specially chosen porous ground, as small as will absorb and cleanse it; not excluding vegetation, but making the produce of secondary importance. The intermittency of application is a sine qua non even in suitably constituted soils where- ever complete success is aimed at."^ The land should be levelled and underdrained with tile drains at the depth of five or six feet, and should be divided into four parts, no part to receive sewage for a longer time than that which comprises one-quarter of the daily flow. An acre of properly prepared soil wdll thus dispose of the crude sewage of 1000 to 2000, or the clarified sewage of 5000 people. The soil to be used for this purpose, as well as that for irrigation and subirrigation, should be porous and loamy; if clay, it should be well broken up and mixed with ashes; sand does not purify sewage well, especially at first, in these methods. The sewage impurities are removed partly by mechanical filtration, but especially by oxida- tion, the latter being due partly to the air in the interstices of the soil, but chiefly to the aerobic saprophytic bacteria, which rapidly convert the organic impurities into ammonia, nitrates, nitrites, and other simple compounds. » Metropolitan Sewage Commission; see Notter and Firth, p. 546. 426 THE REMOVAL AND DISPOSAL OF SEWAGE Irrigation means ''the distribution of sewage over a large surface of ordinary agricultural ground, having in view a maximum growth of vegetation, consistently with due purification, for the amount of sewage supplied."^ Subirrigation is a modification of this, the sewage being delivered through uncemented drains a few inches beneath the surface of the soil. Unless very porous, the land should be underdrained ; it should also be levelled to prevent the sewage flowing off the surface too rapidly. The under- drains need not be nearly so close together, however, as in the intermittent filtration system. The crops raised on irrigation farms are healthful in every respect, and there can be no reasonable objection to their use as food; there would be decided objection, however, to sprinkling the vegetables with sewage water. For example, an epidemic of typhoid fever in Prague, in 1903, was traced to the use of radishes which had been placed in polluted river water in order to freshen them and improve their appearance for marketing. It is ac- cordingly probable that many cases of this disease of ob- scure origin may arise in a similar way, since it is by no means uncommon for the "truck" gardeners in the neigh- borhood of cities to use the contents of privy vaults etc., as fertilizer, and Rullman has shown that typhoid bacilli may live for six months or even a year in human, and more especially in organic filth. Thus celery, banked for bleaching with such a soil, might readily become a carrier of the harmful germs. On the other hand, it is not likely that the latter are carried to and taken up by the rootlets of the plants growing on the sewage farms, for the records of the latter thus far tend to disprove this. On the large irrigation farms of the city of Berlin, which has a population of about two million, the cost of sewage disposal before the recent war w^as about covered by the returns from the crops raised upon them. The mortality 1 Metropolitan Sewage Commission; see Notter and Firth, p. 547. SEPTIC TANKS FOR PRIVATE DWELLINGS 427 of those employed upon them is very low, and there seems to be no particular tendency to illness that can be attributed to the sewage. It is even said that the employees use with impunity the clear water in the effluent canals for drinking and other purposes. Paris has also adopted the irrigation method, and the sewage of the entire city is treated in this way. The sewage of from 100 to 150 persons per acre may be satisfactorily disposed of by irrigation, Berlin's rate, with an especially favorable soil, being 142 per acre. It is to be especially recommended for isolated houses, for small communities, or for charitable or other State institutions. SURFACE OF GROUND "fOM Fig. 118. — Septic tank for private dwelling. For private suburban or country dwellings, the Illinois State Board of Health have recommended the small septic tank illustrated in Figs. 118 and 119, for which the follow- ing description is given. ^ "The plans shown here are for a tank suited to the uses of the ordinary household of from five to ten persons, and, ' See Bulletin, September, 1906, vol. ii, No. 5. 428 THE REMOVAL AND DISPOSAL OF SEWAGE FROM THE HOU^^t SEWAGE FI.FUD Fig. 119. — Septic tank for private dwelling. C././^ANHOLC ON LCreL GttOUNO use THtS OUTLET. TOP l/ZSkV. Fig. 120. — Single-chamber septic tank for six people.^ 1 U. S. Department of Agriculture, Bulletin on Water Supply, Plumb- ing, and Sewage Disposal for Country Homes. CONSTRUCTION OF SMALL SEPTIC TANKS 429 with a fair amount of intelligent attention, it will ac- complish its purpose excellently, removing from the rural or suburban home a factor which is gradually becoming a distinct menace to the public health." C / M/^NHOL£ y^ "^ C.f. /^ANHOLS ^ « a *1 -1.- Z ~-' Lo ■ <■■.■■■ ■ ». ,■■■ o .o ■ ■« . ■«.■»•■ ■■;.»;.■..■«■.■. .■ ' :4'--»X ~-~-~-~-~.t»75rr 01=32 'A^' RODS wAreR L/Ner. 6'6' SlOf=>£ SLfCHTLY- TOWARD /NLET S£TCr/OUAL v/£y/. t'O' yVAT^R LINE TOP V/SIV. Fig. 121. — Double-chamber septic tank for eight people.* "This plant consists of two tanks, the first the septic tank proper, the second, a discharging tank. The septic tank is, in construction, practically a cistern 4 feet in diameter and about 3 feet deep. The sewage from the house enters this tank through a lightly trapped pipe, the flow from the ordinary household preventing the back-flow of air. Across the center of the tank is a wall which 1 U. S. Department of Agriculture, Bulletin on Water Supply, Plumb- ing, and Sewage Disposal for Country Homes. 430 THE REMOVAL AND DISPOSAL OF SEWAGE divides it into two chambers of equal size. The height of this wall is exactly to the point of outflow. " The sewage from the house enters the first chamber of the septic tank with considerable force, causing some dis- turbance of the contents. The flow over the dividing wall into the second chamber, however, is even and slow, so that the contents of the second chamber are not dis- turbed and the flocculent matter settles readily to the bottom. "The bacterial action on the contents of this tank is often so complete that there is no appreciable residue or sludge, and in this case the tank will rarely, if ever, have to be cleaned out. In some instances, however, the tank will require occasional cleaning. The sludge from a well- constructed tank is not offensive, and may be disposed of without difficulty. "The sewage is carried into the discharging chamber (which is a cistern 6 feet in diameter and about 4 feet in depth), through a deeply trapped pipe. The second or discharging tank should be of sufficient size to hold the overflow from the septic tank for a period of 12 to 24 hours. At the bottom of the discharging tank is an auto- matic siphon which is opened automatically when the effluent reaches a certain height in the tank or chamber — a height of about 2 J feet. Through this siphon the con- tents of the chamber will pass in a very few moments, at which time the siphon will automatically close and the chamber will again refill. " From the siphon a pipe conducts the effluent, which is usually entirely without odor and is inoffensive in every way, to the place of discharge, usually on a lawn, provided it is well undertiled and drained, or in a pasture or field." According to the Bulletin of the U. S. Department of Agriculture on Water Supply, Plumbing and Sewage Disposal for Country Homes, "Single-chamber septic- tank systems may be made to give fair satisfaction if properly designed and operated. On such a system the DISPOSAL OF SEWAGE 431 sewage is received, settled, partially purified, and dis- charged by one chamber. CAST iRor^ coi^£:ff. ^•:o-.:.;;.;«3;-.: o/AMirTeff /2' ri^m))))m)^i)kwA /f/f!/fV>->///r/n. CAST IfPON CYUNDtf? ff^M SEPTIC TANK 'WMm ;'*:w r.2'^ 6 concrete h 3£CT/0N. TO DISTRIBUTION BOTTOM U i)mm)mm^^^^ ^^^^^^^^^^^^ PLAN. Fig. 122. — Plan and section of sewage-diverting gate. (U. S. Bulletin.) "There is necessarily considerable disturbance of the sewage in the tank and, in addition, the discharge is con- 432 THE REMOVAL AND DISPOSAL OF SEWAGE tinuous. This makes necessary two disposal systems, with a diverting gate to allow an occasional breathing spell for each system. If such an arrangement is not used, the disposal system must be of much larger capacity {?y^r£- C/f/)/^3£-/? fh:>rr7 /an/r \ ^"77'/c Fig. 123. — Ground plans of tile sewage-disposal systems. than for the double-chamber tank system in order to prevent the continuous discharge from waterlogging the system. " If a single chamber tank is used, it should be designed and constructed with elbows at inlet and outlet and THE ASHLEY SYSTEM 433 with baffle boards before these openings to break up the current." A somewhat similar provision for the disposal of the sewage of not only single dwellings, but even of large institutions, such as hospitals, schools, country clubs, etc., is the so-called Ashley system. In this the chief features are the "biological tank" and the "nitrification duct or subsoil bacteria bed." In the former, which is "so constructed as to induce rapid sedimentation of the solids and so gauged as to produce for the bacteria the most favorable conditions for growth possible, without consuming all the oxygen in the sewage before discharging the tank effluent into the nitri- fication bed," the anaerobic action takes place and about one-fourth to one-third of the purification of the sewage is effected. The latter, which "performs the final and real process of purification," by oxidizing and nitrifying the Hquefied organic compounds coming from the biological tank, is so built from common building materials as to " cause the liquids to be completely divided and scattered through its interior, and so contrived as to cause air to circulate constantly through the granular materials of which the duct is composed, thereby causing a very decided aerobic bacterial action therein by means of the trickling fluids coming in contact with the aerobic film covering the filtering media." The final product is practi- cally pure water, and is usually taken up by the surround- ing soil, making it unnecessary in most cases to discharge it into a neighboring stream or lake. This system has the advantages that the component parts and the whole are always planned and installed for the exact work which it has to do, that it is underground and so out of sight and inoffensive in every way, that it is not affected in its biological functions by frost, and that it practically requires no attention after being once prop- erly constructed and installed. A half-hour's time once a year is sufficient to care for an ordinary residential plant. 28 434 THE REMOVAL AND DISPOSAL OF SEWAGE "The septic tank, although air-tight and supposedly water-tight, should be located as far from the house and the RESULTS OF BIOLOGICAL TREATMENT 435 well or spring as convenience and local surroundings will permit, thus reducing the danger of pollution or nuisance in case of leakage or improper operation of the system. The sewer from the house should be of vitrified sewer pipe, usually of 4-inch size, with tightly cemented joints, and should be laid to a grade not less than 9 inches per 100 feet. Where the fall from the house to the tank is excessive, it is a good idea to lay the last 100 feet of tile to the minimum grade to break up entrance velocity."^ It should always be remembered that any sewage- disposal plant can only do a certain amount of work, and therefore must be designed to meet the conditions under which it must operate. Regarding these condi- tions, Frankland says: "The recent experimental work on the bacterial treatment of sewage . . . shows most conclusively that the best results are achieved by sepa- rating the phases in which the bacterial purification takes place, allotting distinct places to the anaerobic and the aerobic organisms respectively engaged on the work. "The anaerobic bacteria are supplied along with the sewage, and practically no difficulty arises in retaining their services on the works beyond that of providing them with space and time in which to carry on their labors. The aerobic bacteria, however, demand air in addition to space and time, and if this air be not provided in sufficient quantities they go on strike, and leave the works, their place being taken by their less exacting anaerobic brothers, who are, however, unable to finish the work of purifica- tion. " There is, then, the constant tendency for the overflow of the anaerobic bacteria into the aerobic department of the works, if there be any stinting of air in the latter. In order, therefore, to insure the services of the aerobic bacteria being retained on the premises, it is desirable to ' United States Department of Agriculture, Bulletin on Water Supply, Plumbing, and Sewage Disposal for Country Houses, p. 38. 436 THE REMOVAL AND DISPOSAL OF SEWAGE provide for the aerobic bacteria at least two workshops through which the sewage, on coming from the anaerobic department, is made to pass. "The first of these aerobic workshops it may be diffi- cult to provide with adequate ventilation, the result being that both anaerobic and aerobic bacteria will here be found competing with each other, and that the aerobic organ- isms will be unable to complete the work of purification. The sewage, however, on passing into the second and better ventilated workshop will there fall almost ex- clusively into the hands of aerobic bacteria, which it will, under proper management, leave as an inodorous, almost pellucid liquid incapable of putrefaction."^ Another writer summarizes as follows: "As compared with the process of chemical precipitation and sedimen- tation, the bacterial process presents the following advan- tages: (a) It requires no chemicals, (b) It produces no offensive sludge, but only a deposit of sand or vege- table tissue which is free from odor, (c) It removes the whole of the suspended matter, instead of only about 80 per cent, thereof, (d) It effects the removal of 51.3 per cent, of the dissolved oxidizable and putrescible matter, as compared with the removal of only 17 per cent, effected by the present chemical treatment, (e) The resultant liquid is entirely free from objectionable smell, and does not become foul when it is kept; it further maintains the life of fish."^ The following table of results is given as an example of what may be accomplished by a proper combination of the septic tank and aerobic filter-bed, and also serves to show that the reduction in total organic solids, free ammo- nia, etc., is not entirely completed by the anaerobes in the former, but is continued by the later action of the aerobic organisms when they are given opportunity to work: 1 See Francis Wood's Practical Sanitary Engineering, p. 216. 2 American Year-book of Medicine for 1900, p. 549. RESULTS OF BIOLOGICAL TREATMENT 437 Table Showing Changes in Sewage Under Biological Action. Parts per 100,000. Sample. Sewage . Septic tank Filter, 1 foot Filter, 2 feet Filter, 3 feet Number of records. Organic solids in Free Albumin- oid am- monia. suspen- sion. ammonia. 18 28.50 2.164 0.972 16 3.80 1.716 0.340 ! 16 0.16 0.036 0.052 16 0.05 0.020 0.037 i 16 1 0.06 0.009 0.031 1 Oxygen absorbed in 4 hours at 80° F. 5.019 2.184 0.328 0.286 0.244 Disinfection of crude or effluent sewage may at times be deemed necessary or advisable. For this purpose, various agents have been suggested and sometimes used, but on the basis of availabihty and expense, especially where considerable quantities of sewage are involved or the treatment is to be more or less continuous, experience has narrowed the selection to compounds of chlorine and of copper. Of these, chlorinated lime (often called chloride of lime or bleaching powder) and copper sulphate are the cheapest and most used, the former being more active, requiring less time and being less susceptible to organic matter. As in all other efforts at disinfection, sufficient of the germicidal agent must be used, there must be thorough mixing, and sufficient time for action must be given before the sewage is diluted further or discharged into a stream. The quantity of disinfectant needed per million gallons of sewage will depend upon the state or degree of clarification of the latter, but with a good effluent the cost of disinfection need not be excessive. Electricity has also been suggested as an agency for the purification of sewage, but in most localities is still too expensive for the purpose. In the Webster process iron electrodes are used, and the favorable results are supposed to be due partly to the hypochlorites which are formed from the chlorides always present in the sewage, and partly to the carbonates and oxides of iron, which not only 438 THE REMOVAL AND DISPOSAL OF SEWAGE deodorize but also help to oxidize rapidly the organic matters. By this method about 70 per cent, of the putres- cible matters and almost all the bacteria are removed from the sewage, but it is still rather costly on account of the large amount of iron consumed. The selection of the method of sewage disposal has in the past been made too hastily or without sufficient con- sideration by some communities, with correspondingly unsatisfactory results. In all cases, careful and scientific tests, covering the several seasons of the year, and taking into consideration local conditions and factors, should be made not only of various methods, but of different com- binations of methods, sufficient time being taken to deter- mine the value of each. A decision arrived at in this way will be most likely to prove satisfactory and to be the most economical and salutary to all concerned. For extended discussion of the problems relating to the removal, treatment and disposal of sewage, the reader is referred to the text-books on Sewerage by Folwell, and on Sewage Disposal by Kinnicut, Winslow and Pratt. CHAPTERXIII. ^ INDUSTRIAL HYGIENE AND OCCUPATIONAL DISEASES. The marked increase in recent years of social thought and consideration of all that pertains to human labor have given greater and wider importance to the subject of industrial hygiene than ever before. The question, ''Am I my brother's keeper?" has a novel insistence, and the intimate relationship between capital and labor, employer and employed, and the community and the worker are more clearly defined. Moreover, modern conditions present new problems. Complicated machinery has supplanted hand labor and complicated processes have developed from those that were essentially simple. Busy workshops with enlarged outputs add harmful dusts, vapors, moisture, etc., to the environment of the worker far beyond the safety limit. Specialization and fast speeding keep the nerve strain of the operatives at high tension for long hours. Over- crowding in factories and other places of employment favors insanitary conditions and increased danger from infection and injury. Transportation adds new perils, as electric roads are added to those of steam and as motor carriages, trucks and cycles and self-propelled devices of all kinds multiply beyond number on streets and roadways. Carelessness and ignorance jeopardize the safety of the new laborer or of him who does not continually appreciate his risks, and fatigue is a positive factor for disaster, as is shown by the greater proportion of accidents in the later part of the working day. That the field of opportunity and service is enormous is patent when we realize that there are approximately (439) 440 INDUSTRIAL HYGIENE 25,000,000 wage-earners in this country of whom more than one-half are engaged in manufactures, trade and transportation, and that, according to the Efficiency Society, "from one-third to one-half of the lives of all wage-earners are spent in their places of occupation, generally within doors, and subject not only to industrial accident but also to lowered vitality, illness, disorders and diseases arising in part, at least, from their conditions of employment." Another authority states that 30,000 wage-earners are killed and 1,500,000 wounded by indus- trial accidents annually; also that there are 13,000,000 cases of illness annually among industrial workers, all this representing an annual financial loss of nearly $750,000,000. Moreover, at least one-fourth of this great total is probably avoidable and almost one-half of the sickness is prevent- able. On the other hand, all the ills and disaster that befall wage-earners must not be attributed to, or blamed upon, their occupations. They are subject to the insanitary conditions of their homes and their communities, many of these under their tolerance and with which their employ- ment or employer has nothing to do. They are liable to the same infections that come to others by way of water or food or through contact. Some are vicious and dis- sipated and waste their health and lives as well as material substance in riotous living. Others are careless and perhaps ignorant of proper sanitary precautions about the home and concerning the person. AH these may have sickness and trouble in full measure, no matter what their occupations. Even in the factory or place of work, the harmful conditions may not be inherent or essential to the occupa- tion. Only one part or process of an industry may be dangerous, and this risk may possibly be minimized or elimi- nated by special safeguards and extra care. Perhaps the entire nature of the occupation from the health stand- point may be changed by proper attention to cleanliness, ventilation and proper humidity of the atmosphere. The OCCUPATIONAL MORBIDITY 441 removal of dust by readily installed blowers and conduits would remove the harmful feature of many trades. Per- haps the length of working day, time for rest, or the high tension due to speeding, rivalry, or even the temperament of an inconsidertae employer or foreman has more to do with causing poor health, especially among women, than the work itself. Thus due thought should be given before an occupation is clashed as necessarily dangerous or unheal thful. For the same reason, caution must be had regarding the inconsiderate use of what may be termed the vital statistics of occupations. Many statistical tables are fallacious because the influence of important and varying factors affecting their construction has been overlooked. Thus, age, sex, race, heredity, etc., all help to determine the healthfulness and the length of life of an individual perchance even more than does the nature of his vocation. Add to these the effects of personal habits, home sur- roundings, etc., upon the welfare of the individual, and it will be seen that the outside influences that actually modify the health or the longevity of a large proportion of the workers in a given occupation must be many and positive. That there are dangerous trades, harmful processes and devitalizing pursuits, no one denies. The caution is that we do not seek to find too much in hastily prepared or carelessly considered tables of occupational statistics, and that especial care be had in comparing the life data of various and possibly dissimilar industries. Rosenau^ well says that "in order to improve the hygienic conditions under which people work, and in order to prevent the diseases of occupation, five funda- mental conditions are essential: (1) investigations; (2) laws; (3) factory inspection; (4) penalties; (5) education. It is self-evident that before anything may be accom- plished a careful study must be made of the facts. These investigations must include not only scient'fic studies, 1 Preventive Medicine and Hygiene, p. 915. 442 INDUSTRIAL HYGIENE but economical and sociological factors. Suitable laws are necessary, for it has been found in practice that the conditions cannot be corrected by an appeal to voluntary reform. To be effective the laws must provide ample ways and means for their energetic enforcement. A systematic factory inspection is necessary in order not only to protect work people against preventable diseases of occupation and to correct sanitary defects, but also to enforce the laws concerning hours of occupation, child- labor and related subjects. These laws have little force unless they provide a penalty both against the employer and the employees. Either party to the contract should be held legally responsible in case of violation. Finally, education directed to the employer, the employee, and also to the public at large is necessary to obtain and sustain the laws and maintain the standards." A matter of much importance is the measure of the day's work. It is not practicable to have a period of fixed duration for all because of the varying conditions and circumstances in different employments and for the same employment in different localities. Necessity often demands long-continued and strenuous effort and this may be the routine from day to day, but wisdom indicates that the customary task should not demand the maximum physical or nervous effort of the worker. There should be a constant store of energy in reserve; in fact, where possible, an increase instead of a depletion of that store. While heavy physical labor is in itself exhausting and should limit the number of hours of work, even more so is work requiring fixed mental attention and activity or high nervous strain, and if both muscle and brain are heavily taxed, then safety demands short hours with intervening periods of rest sufficient for thorough repara- tion. On the other hand, where the demands upon the system are variable in their intensity and more or less routine and automatic, calling for no extreme or long- continued strain, the day's work may be long and yet WOMEN AND CHILDREN 443 satisfactory. Nevertheless, there should always be care that each worker should have his full quota of time for healthful sleep, eating and the proper enjoyment of life. In many trades and occupations the eight-hour day has been adopted or the tendency toward it is strong. This has meant a decided change in many instances from former custom where ten hours or even more represented the usual day's work. But from carefully collected reports it would seem that if due attention be given to details and essential efficiency, the shorter hours may be equally advantageous to both employer and employee, and without financial loss or detriment to either. In fact, in purchasing labor as well as selling it, the question of fatigue should be kept in mind. When the worker tires his work will drag and will not be as efficient as when he is rested. This loss coupled with the cost of power, light and other overhead charges for the extra time may, as has been proved in a number of establishments, more than counter-balance the apparent loss from shorter hours. Reference has already been made to the increase in factory accidents as the work-day lengthens. Work- men's compensation laws which provide for the recom- pense of injured employees may give an added interest to this and become another argument for shorter hours. Women and Children. — Of paramount importance in all discussions of industrial hygiene are the questions that pertain to the labor of women and children. So much depends upon the proper conservation of all the inherent vigor and vitality of these essential elements of the body politic that any abuse of them is a social crime involving harm not alone to the weaker members of the community mass but to all. The children of today are the adults of the next generation, and the women are the potential mothers of those w^ho are to follow. For our own sakes as well as theirs we cannot afford to permit practices or customs that tend to interfere with the education, stunt the full physical, mental and moral 444 INDUSTRIAL HYGIENE development, or prematurely age and weaken the vitality of the immature members of society. So, with equal wisdom, must provision be made that those who are to bear the children that are still to come shall have every reasonable protection against overtaxation of their energies and what- soever may tend toward the degeneration or suicide of the race. According to Rosenau, New York was the first State in this country to pass a factory act regulating child labor. This was in 1886, when thirteen years was fixed as the minimum age at which children might begin to work in factories. Since then many other States have passed similar laws and in almost all of them, as well as now in New York, the minimum age has been placed at fourteen. A number of the States regulate the number of hours per day and per week during which the child may work, and some prohibit work at night, especially by girls, and in certain dangerous trades and in occupations involving exposure to temptation. In Massachusetts in 1910 "the State Board of Health was given power to declare from time to time whether or not any particular trade, process, of manufacture, or operation, or any particular method of carrying on such trade, process of manufacture, or operation is sufficiently injurious to the health of minors under eighteen years of age employed therein to justify their exclusion therefrom. "^ The Board of Health has power of discretion, however, to determine whether such pro- cesses may not be carried on with reasonable safety when certain precautions are observed and guaranteed. A recent innovation, as in Pennsylvania in 1915, is the requirement that children at work between the ages of fourteen and sixteen shall attend continuation schools for a specified number of hours per week, the hours of labor being lim'ted accordingly. That the hours of women who labor at arduous or exacting trades or occupations should be regulated is evi- ^ Harrington, Preventive Hygiene, 5th edition, p. 678. - FACTORY SANITATION 445 dent to every student of the question, and also that reasonable allowances should be made for absence or lessened work at certain periods. Full provision for cessation from factory or similar employment with continuing pay both before and after child-birth is also essential. The Swiss law specifies a total of eight weeks for this interim, which is none too short for the mother's future health and safety. Of marked importance is the influence of strenuous labor outside of the home upon both the birth-rate and infant mortality. Statistics show that it is very much to society's selfish interest to study this question most carefully and to evolve necessary laws and regulations not only for the protection of the individual women who must work for a wage, but even more for the sake of its own ultimate welfare and safety. Even in occupations that are not considered extra hazardous or strenuous and that seem natural or appro- priate for women, there is much room for consideration for the workers. Factory Sanitation. — While certain occupations must necessarily be dangerous, in spite of reasonable precautions, because of poisonous minerals or chemicals or harmful dusts, gases or vapors involved, many trades or pursuits that have hitherto been classed as unhealthful have been so because of the failure to maintain ordinary sanitary precautions and to provide proper apparatus for adequate ventilation, removal of dust, regulation of humidity, etc. A dirty factory or shop in a dusty trade with no sanitary rules or orders against promiscuous expectoration needs only one tuberculous employee to scalter the germs that will start a series of cases that persist and increase in number from year to year until eventually the occupa- tion itself is looked upon as dangerous and all its workers as specially liable to consumption. And so with other infections; whereas a clean shop with abundant sunlight, good ventilation, careful removal of dust, and strict orders as to sanitary personal observances under penalty of loss of employment or heavy fines, would actually 446 INDUSTRIAL HYGIENE minimize the liability to infection for all of its employees. So novel and unusual is the absolutely clean and sanitary factory that even n those trades that have to do with the preparation or conservation of our food, we find that cleanliness is made a matter of advertisement and as worthy of attracting great attention instead of being taken as a matter of course. So common have been the faults and laxity in this respect in the past and so prone is human nature to sacrifice the welfare of both employees and public to apparent finan- cial profit, that competent and efficient factory inspection is essential in order that the rights of all may be protected. Such inspection must be conversant with the requirements of the law in all its details as it applies to the occupation and particular place in question, and must deal justly with the employer as well as the employee, and particularly with the community at large, which may have more at stake than either of the two. The inspector must note the provision or absence of all that makes for better work, better health and better living, and for such a sanitary state that, excepting what is unavoidably inherent in the nature of the occupation, disease and inipaired health can have no excuse for origin or persistence in that factory or shop. One particular duty of the inspector will be to note the ages and the hours of employment of working children; another, to advise and, where he has the authority, to insist upon such devices as will protect the workers against preventable accidents as well as harmful poisons, dusts and vapors; and still another, to collect and collate facts and data upon which improved legis- lation may be based and economic and social progress may be advanced. Harmful and Dangerous Occupations.— The limitations of the present work do not permit an extensive discussion of even the more important occupational diseases, but some suggestions as to their classification may enable the reader to appreciate their extent and their bearing upon public health in general. HARMFUL AND DANGEROUS OCCUPATIONS 447 Oliver makes the following general subdivision:^ 1. Diseases due to gases, vapors and high temperatures. 2. Diseases due to conditions of atmospheric pressure. 3. Diseases due to metallic poisons, dusts and fumes. 4. Diseases due to organic or inorganic dust and heated atmospheres. 5. Diseases due to fatigue. The above would seem to overlook the infectious diseases, such as anthrax, tetanus, glanders and hook- worm disease, one or another of which may have a close relation to an individual's occupation. Moreover, a disease may have such varying factors as to place it in more than one of the above divisions. Hanson^ classifies all occupations practically as follows: "1. Those which are intrinsically dangerous to health by reason of the nature of the materials involved, or by reason of the conditions which arise from the industry or by one or more processes of the industry. 2. Those which are carried on under conditions which are not indispensable to the industry or to any of its pro- cesses and which promote susceptibility to disease. 3. Those which involve exposure to mechanical violence and are dangerous to life and limb rather than to health.'* The difference between the first and second classes is that in the second the harmful conditions are essentially avoidable, while in the first class some of the factors are unavoidable while others may or may not be so. The third class scarcely comes in the domain of hygiene and need not be discussed further. " The line of division between these two (first and second) classes is not a sharp one, and some occupations may be said to belong to both classes. For the purpose of considering the specific factors in industries which are inimical to the health of the workers, occupations may be divided into the following groups: • Rosenau, loc. cit., p. 922. 'Harrington, loc. cit., p. 655. 448 INDUSTRIAL HYGIENE Group I. The occupations or processes which are of particular hygienic interest and give rise to the most clearly defined and wide-reaching occupational diseases or poisonings are those which involve exposure to — 1. Irritating and poisonous dusts. 2. Irritating and poisonous gases and fumes. 3. Infective or parasitical matter in dust. 4. Abnormal atmospheric pressure. Group II. Of distinct importance, though not always giving rise to definitely proved occupational diseases or poisonings, are occupations or processes which involve — 1. Prolonged use, strain, pressure, fatigue. 2. Excessive heat. 3. Dampness. 4. Offensive gases and vapors. Some occupations are conducted under such con- ditions that they may properly be regarded as belonging to a number of subgroups. Mining, for example, may be considered under Group I, 1, 2, and Group II, 1, 2, 3, 4; and cigar-making under Group 1, 1, 2, 3, and Group II, 1."^ From the foregoing it will be noted that dust, whether irritating, poisonous or infective, is an important factor in determining the healthfulness of many occupations, and that if its prevention or prompt removal can be provided for, what has been looked upon as a dangerous trade may become a comparatively innocuous one. And, as such prevention and removal oftentimes depends simply upon the installation of proper hoods and exhaust apparatus, healthfulness may be merely a matter of reasonable expenditure of money and strict enforcement of appropriate legal regulations. Likewise, a similar enforcement of sanitary provisions may do much to ameliorate the condition of the workers in those pursuits wherein heat, humidity or harmful gases and vapors are the harmful factors, and to develop a sane appreciation of the value of the health of the ^ Harrington, loc. cit., p. 656. POISONOUS METALS 449 laborer as contrasted with the comparatively small outlay necessary to bring about and maintain the improved conditions. Reference has been made in another chapter to the fact that dust made up of hard and sharp particles is more irritating and harmful than that in which they are soft and smooth. Thus, it has long been known that workers in metallic dusts had a high incidence of both pneumonia and phthisis, and that, other factors being equalized, the frequency of the latter disease decreased in various occupations accordingly as the dust particles became softer and less angular as well as less in quantity. To enumerate all occupations or processes in which dust is prevalent and harmful would be difficult. Among the most important of these, however, may be mentioned steel grinding of all kinds, glass grinding, pearl-button making, stone cutting, w^ork in tobacco factories, cotton or linen mills, and where chemical or poisonous dusts are prevalent. The poisonous metals most frequently used commercially are probably lead, arsenic, phosphorus, chromium and mer- cury. Of these the first two may be carried into the system in the form of dust, although they are also ingested in other ways; the other three are usually absorbed through the skin and mucous membrane of the mouth or are taken in as fumes and vapors. Lead is employed in a very large number of trades and processes — probably over 100 — so that cases of lead poisoning are by no means uncommon. Frequently the patient has only his own carelessness to blame for his ill-health, but it is also often due to the lack of proper precautions and hygienic control of con- ditions on the part of the employer. In many cases of lead poisoning, the metal has entered the system in the form of dust or fumes, and seems to be more dangerous in this way, the absorption probably occurring through the lungs as well as stomach. On the other hand, it is frequently ingested by the mouth, being carried thither on soiled hands or fingers; in these cases, attention to 29 450 INDUSTRIAL HYGIENE ordinary hygienic precautions on the part of the workers should prevent a large proportion of the cases, and the use of proper respirators should be equally efficacious with regard to those of the first class. In all places where the workers handle or come in contact with lead ample ^ Fig. 125. — Steel and iron workers at emery wheels. Showing effec- tive front and side guards for their protection against the inhalation of dust particles. (Illustration supplied by Dr. W. C. Hanson for Massa- chusetts State Board of Health.) provisions, including a supply of hot water and soap, should be made for washing and, in some cases, bathing, and those exposed to the metal should be required to make frequent and regular use of such provisions. Eating places should be entirely apart from the place of work. HARMFUL AND DANGEROUS OCCUPATIONS 451 The occurrence of phosphorus poisoning has been greatly lessened in recent years by the prohibition in a number Fig. 12G. — Lead working in the manufacture of storage batteries. In mixing peroxide of lead and litharge employees are exposed to lead poisoning. The employee shown was wearing a respirator, but was not willing to wear long gloves. (Illustration supplied by Dr. W. C. Hanson for Massachusetts State Board of Health.) 452 INDUSTRIAL HYGIENE of European countries of the use of white phosphorus in the manufacture of matches, and by a heavy tax upon their manufacture in the United States and federal laws forbidding their importation after January 1, 1913 and their exportation after January 1, 1914. So also processes in which mercury poisoning formerly occurred, such as gilding and mirror making, have been so changed that few, if any cases now occur in those trades. There is still some risk in the felting industry in which the fur or hair is sometimes treated with mercuric nitrate, and in occupations in which metallic mercury and amalgam is much handled. Arsenic is used in a large number of trade processes and in those in which much dust is preva- lent, there may be considerable risk to the workers. Chromium is used in the tanning, industry and is a cause of local inflammations of the skin and mucous membranes, causing severe and intractable ulcers. The list of occupations in which the prevalence of irritating or poisonous gases or fumes is a factor in causing ill-health among the workers is a long one. Carbon monoxide, from whatever source, is a very dangerous gas, and so is chlorin, Pettenkofer asserting that 60 parts of the latter gas in 100,000 of air will cause death. Fumes from the strong acids, nitric, sulphuric and hydro- chloric, are intensely irritating, as is ammonia, and may cause acute or chronic respiratory trouble. Other sub- stances used commercially and giving off dangerous or harmful gases or vapors are wood alcohol, naphtha, nitrobenzol, aniline and other nitro derivatives, carbon disulphide, etc., and anyone of these may be the cause of most serious or fatal results. The importance of frequent and thorough examinations of all who work in the pres- ence of poisonous metals or vapors should be emphasized and the duty impressed on those who are apt to develop a false sense of security through carelessness, habit and familiarity with the respective dangers. Tuberculosis can scarcely be considered an occupational disease but it is the chief cause of death in many occupa- GENERAL PROPHYLAXIS 453 tions where dust is excessive and irritating and where rules against expectoration and uncleanliness are not enforced. Maladies more truly related to occupation are anthrax, which may occur among those who handle hides, horse-hair and wool, and glanders and foot-and- mouth disease, to which hostlers and stockmen are exposed. Ankylostomiasis or hook-worm disease, while prevalent in the southern United States and in certain parts of Europe, frequently occurs among tunnel- and mine- workers, and hence is sometimes called miner's anemia. It is evident that the incidence of the foregoing and all other parasitic occupational diseases may be greatly lowered by disinfection and other prophylactic measures. So also the means of prevention, protection or improve- ment in diseases due to excessive heat or humidity, or to fatigue, strain, posture, etc., are obvious and the long list of such affections need not be detailed here. A peculiar malady is that to which workers in compressed air, as in caissons and under-river tunnels, are subject. It comes on after the worker returns to atmosphere under normal pressure, and is marked by headache and severe pains in the back, legs and abdomen, rapid pulse, sweating and more or less motor paralysis. Death may occur in a short time in some cases, but most cases recover com- pletely, especially under treatment, which consists mainly in subjecting the patient again to the high pressure and then reducing it very gradually. Regarding prophylaxis in general, the following by Hanson is most appropriate.^ " It will be noticed that the disastrous effects attributed to occupations are in very large part due to non-observ- ance of the principles of general hygiene, and chiefly to inattention to that most important sanitary measure, perfect ventilation. It will have been noted that the conditions which bring about impairment of health may be reduced very largely by a constant supply of fresh air. ' Harrington, loc. cit., p. 677. 454 INDUSTRIAL HYGIENE With proper attention to this matter and improvement in the home and home influences, greater attention to the character and preparation of food, and a more general observance of the beneflcial influence of active out-door exercise, no very great difference would be noted in the health of the various classes of work people, and the expression, occupational diseases, would lose whatever significance it now has." On the other hand, however, all that pertains to in- dustrial hygiene will be a matter of moment and real importance to all who are interested in the public welfare and the health of the body politic, and whether that interest be chiefly in the line of investigation, legislation, industrial supervision or popular education, much remains to be accomplished before conditions can be satisfactory and sanitary for the worker and conducive to the safety and common health of the general community in which he lives. Proper protection for the adult men as well as for the women and children, proper allotment of time for rest and recreation as well as for work, and proper attention to all details that affect the bodily health of each one who labors at a daily task are essential in order that the public at large may be safe and truly prosperous. CHAPTER XIV. MILITARY HYGIENE. This subject is one which has to do with active and presumably healthy men under conditions more or less abnormal and sometimes of a peculiar and unusual stress. Moreover, the actual financial value of the life and health of the individual to the State is more directly manifest than under ordinary circumstances, and, though at times the interests of the former must be sacrificed to those of the latter, it is of the highest economic and practical importance that a government should conserve as far as possible the health and welfare of each member of its army and navy. Consequently, much thought should be, and is, given to all those questions which rightly come under this head, and the effect of the efforts made in this direction is very marked, especially with reference to the regular or standing armed force of the country. Mer^ who have become accustomed to military service, and to whom it is a real and permanent business, have probably a better health status than the average citizen, owing to the regularity of their habits and work and to the oversight and care which are given to the details of their life. Conditions are much different, however, when men are suddenly called from many occupations and ways of living to active army or naval service. They do not accommodate themselves readily to the change, nor do they appreciate the importance of details that may seem trivial to them but that have great bearing on their future health. Often the utmost efforts on the part of those in authority and who are skilled in these matters are appar- ently of no avail and lead to undeserved censure. How (455) 456 MILITARY HYGIENE much more serious actual neglect of hygienic measures may be has been proved more than once in the past. The following quotation from the Report of the Sur- geon-General of the Army for 1899 is as pertinent to-day as when written: "Hygiene is one of the principal subjects of examina- tion for candidates desiring appointment in the medical corps of the army, and at the subsequent examinations for promotions to the grades of captain and major it is given a most prominent place. It is also the most prominent subject in the course of instruction at the Army Medical School, where the student officers spend five hours daily for a period of five months in practical laboratory work relating for the most part to the cause and prevention of infectious diseases; but the comparatively small number of medical officers of the regular army available for duty in the large camps occupied by our volunteer troops at the outset of the war (Spanish-American) proved to be entirely inadequate to control the sanitary situation in these camps." In a study of military hygiene, all phases of the routine life of the soldier should be discussed, for it is the combi- nation of these that make for good or ill. Unless the emergency is grave and large numbers of men are needed quickly, much attention should be paid to the selection of the men, and only those enlisted who satisfy certain physical requirements. They should be neither abnormally short nor tall; the weight should be in proper ratio to the height; the vision and general health good, and especially should the chest measurement and expansion or "vital capacity" be considered as of great importance. "It has also been observed that a close correlation exists between the physical and moral development of men; in fact, lowering the physical means lowering the moral standard of recruits."^ 1 Notter and Firth, p. 917. EXAMINATION AND SELECTION OF RECRUITS 457 Age is also a factor that should be considered. If recruits are too young, they are not able to withstand long-continued work or strain, nor will they be so likely to resist the incurrence of disease. On the other hand, men who are too old will be more liable to have habits of life or taints of chronic disease that will interfere with their military duty, and they will also not serve the maximum length of time that makes their work most economical to the government. It was chiefly for these reasons that the limits of age for those first called into the national selective army were fixed at twenty-one and thirty-one years, and it is fortunate that the war termin- ated before there was great and continued need for many men below^ the former or above the latter age. "The experience of the U. S. Army and of all other armies is that the admission rate to sick report is highest for young soldiers under twenty years of age. This is especially true of typhoid fever. The death-rate is highest in young soldiers, nineteen years and under, but declines after twenty and reaches its minimum between twenty- five and thirty years, rising again slowly up to forty years and rapidly thereafter. "^ " The medical officer's first duty is to rigorously examine his command, if it has been newly raised, and inexorably to eliminate all men unfit for full military duty. Upon the medical officer who examines recruits for enlistment lies a heavy responsibility, for it practically rests with him to determine the physical efficiency of the command. Unfortunately in time of war, when the necessity for effective men is the greatest, this selection is apt to devolve upon untrained civilians who have neither the special knowledge that fits them as judges nor the position that enables them in doubtful cases to withstand the con- stant importunities of still less informed recruiting officers. The careful examination of recruits is not practical hygiene, 1 Havard's Military Hygiene, Second edition, p. 16. 458 MILITARY HYGIENE but the successful application of hygiene requires carefully selected men to secure the best results."^ That this is so was shown by the rejection by the final examining boards of the Army of a large number of the men who had already been passed by the selective draft boards of their respective localities. At least one of each draft board was a physician, and while there is no question as to the purpose and desire of practically all of these to decide honestly and to the best interests J '*' '^.*S' •••■ J .-^1': ^^ ■ •'it-* .. ' *- -^c ■^ ^■- B^JjL^iL.:^ • .-,' ;^ .^^Ji » ^^m Mfe "' ' ' KT'".. .*.- -^^NHfes^^ IBHijBJ Fig. 127. — Settiu.w^/ 3P,0ffP. 10,000 . "itKR. Of MOBIUMTlOft CIVIL LIBBWY WAR WAR Fig. 132, — From the Report of the Surgeon-General, U. S. Army, for 1918. the Army in 1917 was about three times that of the Army of 1861, the actual number of cases in 1861 has been multiplied by three. "This table, represented graphically in Fig 132, speaks for itself. Aside from gonococcus infection (which is probably commoner now than formerly, and is almost certainly more carefully diagnosed) none of the diseases of the list show an important increase over 1861 . Measles MORBIDITY IN THE CIVIL AND WORLD WARS 473 and mumps ap})areiitly show a slight increase. The great reductions in disease are those brought about by improved sanitation. Diarrhea and dysentery are reduced from 244,(X)() to 11,000, due to treatment of feces and fighting the fly. Typhoid fever is reduced from 10,000 to 225 by keeping down the fly and especially by pro- tective inoculation; typhoid, the former great scourge of armies, has become as negligible as smallpox. Malaria has been reduced from 167,000 to less than 2000, due to elimination of mosquito breeding areas. , ADMISSIONS, FIRST SIX MONTHS CIVIL WAR AND PRESENT WAR COMPARED (WHITE TROOPS). United States enlisted men, First half- July-Dec, year of 1918 (first Civil half-year of Disease. WarXS. present war). Measles 41,815 46,428 Pneumonia 9,246 7,675 Mouth and throat infections .... 125,445 52,462 Mumps 6,336 7,843 Typhoid fever 10,068 225 Minor intestinal inflammation . . . . 244,107 10,985 Malaria 167,163 1,796 Tuberculosis and hemorrhage of lungs . 7,998 6,850 Syphilis 14.790 7,755 Gonococcus infection 18,849 45,027 Total 645,817 187,046 "Mouth and throat infections have been cut in third by better ventilation, preventing of crowding and spitting, and the isolation of carriers. The result for the various diseases amounts to a saving during this half year of mobilization of about half a million cases of sickness and the rescuing of the lives of 10,000 soldiers. Of deaths in 1917 there were 2984 in Army enlisted men in the United States. For the same strength in the Civil War there were 13,959. Thus the advance in sanitation and preventive medicine since 1861 has saved in the first half year of the war over 10,000 lives." As typhoid fever, dysentery and cholera are well known to be transmitted by drinking-water, sanitary precautions * Report of the Surgeon-General, U. S. Army, for 1918. 474 MILITARY HYGIENE as to the care of the water must be observed. Though the quotation above states that "infected water was not an important factor in the spread of typhoid fever, etc./' it must not be inferred that no cases were found to be due to such water. In fact, many cases were undoubtedly thus caused, as Vaughan clearly states; but the authorities, early realizing the dangers that might be due to a bad water, made such efforts to obtain pure supplies that other means of infection became relatively more important. Every effort should therefore be made to secure the purest water-supply possible in every military camp, and to have it thoroughly sterilized before use if there is any suspicion of its pollution. A full description of filtration methods and of the sterilizer (Forbes, p. 209) that was adopted by the Army has been given in the chapter on Water. The Darnall Filter. — Should the Lyster bag not be available this apparatus may be used. This is an adapta- tion of the principle of mechanical filtration to the needs of troops in the field. It consists of a galvanized iron tank, two water cans, and a siphon filter and cloth crated. The essential part is the cylindrical metal framework of the siphon, over which is wrapped the filtering material, a closely woven cotton fabric. This is placed in the tank filled with raw water to w^hich the precipitant has already been added, and the water after passing through the filtering cloth into the cylinder is discharged by siphonage into the water can. As matters in suspension deposit upon the cloth the flow diminishes, and the filter should be taken out and the cloth removed and cleaned by wash- ing and sterilizing by boiling water. The precipitant con- sists of alum and sodium carbonate in such proportions that they neutralize each other. This precipitant is furnished in a small tin can with a measure which holds 2 grams. The water cans when filled to the mark hold 3 gallons. One measure of the precipitant added to each can of raw water is sufficient for even grossly polluted waters. The crated filter weighs 52 pounds and will deliver about DRINKING-WATER AND FOOD 475 200 gallons of water iji four hours. It completely clarifies the water, and its bacterial efficiency is about 98 per cent. This apparatus cannot be depended upon for the certain elimination of all pathogenic bacteria, but it jjurifies or linary waters to a degree that renders them reasonably safe. It wil) furnish plenty of clear water unchanged in temperature and taste within an hour after getting into camp. One filter may be carried by each company in the field. For troops in the field and where water of reasonable clarity can be had, the so-called Lyster bag has come Fig. 133. — Tripods for Lyster bags, with one bag partly svispended from foremost tripod. into recent use. This is made of heavy canvas with several closing push-cocks near the bottom, holds about 40 gallons, has a removable canvas cover to exclude dust and dirt and can be slung from any convenient support by means of rope loops at the top. When hung and filled, a sealed tube containing 1 gram of fresh calcium hypochlorite is broken and its contents dissolved in the water, thus quickly sterilizing it. Any perceptible taste 476 MILITARY HYGIENE of chlorine which is in the strength of approximately 1 part per 1,000,000 soon disappears. Evaporation of water that oozes through the canvas also tends to cool the contents. When empty, the bag weighs comparatively little and takes up almost no space in transportation. /^ As the efficiency of the soldier depends so much upon his food, and as it is of importance for so many different reasons, it is not strange that it has been the subject of the most careful investigation. In fact, much of the Fig. 134. — Lyster bag supported by stacked filters. (Ford.) scientific knowledge now pertaining to dietetics is the result of the work of the various governments in their efforts to determine the most satisfactory and efficient military rations. Considering the men simply as machines, true economy requires that their food shall be ample in quantity and good in quality. Attention must also be given to its transportation and prepa- ration, and to its character as a source of heat and energy. A study of the standard daily rations of the various armies of the world at once shows a noticeable uniformity DRINKING-WATER AND FOOD 477 among them in the amounts and relative proportion of the food-principles and in the ratio of nitrogen and carbon. And as these have all had the test of long time and exten- sive experience, they serve to establish their own scientific accuracy, as well as that of the dietetic ratios which have been determined in other ways and to which they so closely correspond. Fig. 135. — Wheeled field kitchen, with acconipauyiuK supply wagon. In addition to the ovens, the kitchen has a large kettle for soup and a smaller one for coffee let in at the top. No part of a military administration is of more im- portance than the commissary department, for an army without food is soon worse than useless. But it is not easy to feed properly large numbers of men in an active cam- paign when the whole body is moving rapidly from place to place and when the exigencies of the day may seem to require all available means of transportation for other purposes. Consequently, much effort has been made to supply rations that are condensed in bulk and that require as little immediate preparation as possible. Considerable advance in this line has been made in recent years, and various soups, meats, and vegetables, 478 MILITARY HYGIENE condensed and ready-cooked, are now often supplied when the same cannot be had in a fresh state. That such may be entirely satisfactory cannot be denied, but those in authority must be especially careful as to certain points, viz., that the food is not lacking in quality and that the processes employed have not impaired its dietetic value or digestibility nor permitted harmful changes to take place in it. The temptations of the army contractor are often hard to withstand; moreover, tests have shown that if concentration be carried too far, not only the digestibility, but the nutritive value as well of the food may be seriously impaired. Thus the valuable salts and vitamines may be lost with the water in the compression of vegetables. Again, the processes may make the foods too uniform in taste, or there may be the omission of such accessories as vinegar, spices, etc., or there may be ignorance as to how to cook them properly; and it must always be remembered that palatability has much to do with digestibility. For these reasons it will be wise to have at least part of the food issued in as nearly the fresh or ordinary state as possible. Space does not permit the consideration of the various articles of food composing the prescribed ration, but it is evident that the laws of dietetics govern here as elsewhere. It may be well to say, however, that experience seems to show that alcohol should not be included in the regular ration, but should only be issued, if at all, in certain exigencies and in small quantities. At present it is even omitted from the outfit and stock of field hospitals and ambulance companies. /Regular and thorough inspection must be made not only of the food supplied to the troops, but of kitchens, mess-halls, store-rooms, warehouses, canteens, etc., in order that these may be kept in a sanitary and safe condition at all times. Particular care must be taken to exclude flies as well as other vermin, as these may be, as they have been in the past, the carriers of typhoid and other infections to the food of the men. Likewise, all cooks. THE CLOTHING OF THE SOLDIER 479 handlers of food and attendants at canteens should be examined in order to excKide typhoid and other " carriers," and prevent the consequent risk to those whom they serve. The same principles hold good in regard to soldiers' clothing as for that of other people, but " in selecting the material the chief points to be considered are its permea- bility, durability, and the property it has of conducting and absorbing heat." It would be well if the undergar- FiG. 136. — Wheeled field kitchen in service. ments were always, in part at least, of wool. The material of the uniforms and its weight should depend upon the exigencies of the service, considering both the locality and the season of the year. In cold weather wool should, of course, have first place; in hot climates the stout cotton fabric called khaki seems to meet the conditions most satis- factorily. "The color of the material has an important bearing on the hygienic value of the clothing, and in regard to the absorption of heat exerts more influence 480 MILITARY HYGIENE than the material itself. . . . White possesses very slight absorptive power compared to other colors, and, next to this in the scale, gray or pale yellow gives the best results. Gray is the best color for soldiers' dress on service,* for white is least suited to the field, as it soils so quickly. The khaki drill corresponds very closely with gray as regards absorption power. "^ Fig, 137. — Portable camp stove on brick foundation. Mess-hall and kitchen in rear vestibuled and screened to exclude flies. . The clothing should nowhere be so tight as to interfere with respiration or circulation or with free movement of the body. There should be a sufficiency of socks in each man's kit, for "a good sock kept clean, is a protective against sore feet." Boots or shoes should be comfortable as well as durable and water-proof. Leggings may often be used to advantage ; they may be of stout canvas, khaki, or leather. Helmets or other head-dress should be light and well ventilated, and of a non-absorbent color. Ab- 1 Notter and Firth, p. 955. DISPOSAL OF CAMP WASTES 481 dominal bands of flannel are excellent protectives against digestive disturbances, if the men can be induced to wear them. Each kit should contain a rubber or water-proof blanket or "poncho" to protect the soldier from the dampness of the ground at night; it can also be used as a cape in rainy weather. The weight of the kit, arms, accoutrement, etc., is often excessive, and should be kept as light as possible. In some armies as much as seventy pounds is to be carried by each soldier. It should be so divided that, when on the march, as much of this as possible can, and should, be carried in wagons for the men, they retaining only their arms and water bottles. " Weights are most easily borne when the following points are attended to: (1) They must be as near the centre of gravity as possible. (2) The weights must in no case compress the lungs, or interfere with the respiratory movements or the elimination of carbon dioxide, or hinder the transmission of blood through the lungs, or render difficult the action of the heart. (3) No important muscles, vessels, or nerves should be pressed upon. (4) The weights should be distributed as much as possible over several parts of the body."^ The last statement means that the pressure will be most advantageously put upon the tops of the shoulder-blades and upon the hip-bones and sacrum. The possibility of the transmission of typhus and trench fevers and probably other infections by means of lice and other vermin render imperative the provision, when possible, of well-equipped stations for freeing both the man and his clothing of such infestation. Such delousing stations become an esential feature of quaran- tine in preventing the introduction of the diseases in question and their "carriers" into the country-. The disposal of the wastes of a camp constitutes one of its gravest problems. If it is a permanent post and the men are quartered in barracks with a sufficient water- » Notter and Firth, pp. 961 anrl 962. 31 482 MILITARY HYGIENE supply, it may be best to construct a complete sewage and sewage-disposal system; but where the encampment is temporary the difficulties are greatly increased. Even though the camp is strictly policed, as it always should be, and the garbage and similar wastes destroyed by fire or burial, there remains the disposal of the excreta of large numbers of men, which, if neglected, is almost certain to become a source of infection. Fig. 138. — Garbage incinerator, with central pyramid to increase draught. The customary sinks are not only likely to pollute the ground-water and perhaps the water-supply of the camp, but they are also a constant offense to the senses, and we now know that infection may be carried by flies directly from them to the food in the kitchens and mess- tents. Where used, their contents should be cov- ered twice or thrice daily with a layer of fresh earth, lime or oil, and when the contents reach within two feet of the surface they should be filled with earth and new ones opened. At times, instead of using earth or lime for a covering, dry grass or straw may be spread over DISPOSAL OF CAMP WASTES 483 the contents and burned two or three times a day- This not only serves to disinfect the surface and sides of the trench by fire, but the ashes of the straw form a loose covering of several inches' thickness which completely conceals the subsequent additions and at the same time effectually protects all the contents from the access of flies. Colonel WoodhuU suggests the burning twice a day of small quantities of petroleum poured on the surface of the contents of the sink. If the sinks are primarily dug to the depth of several feet, this burning of straw and oil may be done without risk of igniting the seats, moreover; if the seats are made like inverted boxes completely covering the sinks, and if the interior of these boxes and the sides and ends of the sinks are well sprayed with a mixture of lamp black and crude oil, the interior is made so dark as to be almost completely shunned by flies, and one burning a day will be sufficient. However, it will often be wiser to do away with sinks altogether and to provide measures whereby the excreta can be at once chemically disinfected and then removed beyond the limits of the camp. Theoretically, the tub or pail system would seem to be available if proper dis- cipline and supervision could be had; but practical experience in certain camps rather proves it to be unsatis- factory. Unless the contents are disinfected immediately, the soil about the camp will be almost certainly polluted and infected when the receptacles are removed for empty- ing, and the flies will also be as numerous as at the sinks. If the tubs should be partially filled with a disinfectant before use, and if they should have close-fitting covers which would only be removed at the time of use, the objections to them would be diminished, but would still remain in part. At the time of the Spanish-American War the board of medical officers already referred to recommended, and the Surgeon-General and Adjutant-General adopted the recommendation, that the excreta be received into a large galvanized iron trough partially filled with an 484 MILITARY HYGIENE active disinfectant solution, preferably milk of lime on account of its combined efficiency and cheapness. The trough was to be located in a suitable building, and when full or at regular intervals was to be emptied by means BACK SAME -HEIGHT HANDLE BLOCKS 2"X 4" 2"x 4"acting as LEGS WHEN BOX TURNED OVER BRACES 2 INSIDE BOX LEATHER STRAP HINGES X 4 STRIP INSIDE ON WHICH BOX SETS MAKING IT FLY PROOF Fig. 139. — ^Latrine box used in the camps at Columbus and elsewhere. (Lewis and Miller.) GROUND AVAILABLE FOR TURNING BOX BACKWARD IN BURNING PIT 1 a URINAL 1 i i LATRINE BOX SCREEN rm L_l 1—1 V7X nnoR V7A Fig. 140. — Ground plan of latrine box, latrine, screen and urinal can used at Columbus and elsewhere. (Lewis and Miller.) of a pumping cylinder into a large water-tight tank on a wagon, similar to those of the ordinary odorless excavat- ing apparatus. It is probable that such apparatus under proper supervision would prove as efficient and practic- DISPOSAL OF CAMP WASTES 485 able as any that can be devised short of a well-constructed system of sewers involving water-carriage, the installa- tion of which is obviously not feasible in a temporary camp or in one not having an abundant water-supply, but the author has no information that any such methods or apparatus were in use in the service abroad or even in any of the concentration or training camps in this country. Provision should also be made for the disposal of garbage from the kitchens and other refuse of the camp. This can be readily done where fuel is abundant, by building a rough fireplace of stones in which a fire is kept burning. Garbage thrown inside against the hot stones quickly dries and bums without nuisance. The portable incinerators that have been devised for disposing of camp wastes are heavy and difficult of transportation, and so more suitable for permanent camps. Because of its content of grease and small particles of organic matter and its excessive volume, the used dish- or "sullage" water is often difficult to dispose of and capable of causing much offense to the senses, especially in a large camp in warm weather and where there is no sewerage. Evaporation is slow and wasteful of fuel, but may be the most satisfactory method of disposal. If time and conditions of soil are favorable for digging some form of septic tank or filtration might be tried, but the greasy residue does not yield readily to bacterial action, either aerobic or anaerobic, and the unpleasant odor is apt to attract flies and lead to their multiplication in the solid residue, unless this be burned over or worked under the surface of the ground. Garbage must be kept well covered and screened from flies until finally disposed of; the area about kitchens, mess-halls and barracks or encampments must be thor- oughly policed at all times. On account of its value as a food for domestic animals, the garbage may often be disposed of to persons living ia the vicinity of permanent camps but only the strictest of regulations and alert vigilance will prevent camp nuisance and pollution. 486 MILITARY HYGIENE In any but a temporary camp, the feces of the horses should be removed to a considerable distance from the camp or else treated with lime to prevent the breeding of flies. Space does not permit of a full discussion of military hospitals. At permanent posts they may have almost all the equipment and conveniences of the best city hospitals, but in the field in actual service much must be foregone. This often leads to censure from the uninformed and where censure is not deserved. But commanding officers, especially of the medical service, should foresee every emergency and provide for it as far as possible, overrating rather than underrating the probable needs and demands upon the hospital staff, and providing for the comfort as well as the necessities of the sick and wounded. The knowledge that typhoid fever, for instance, is almost certain to occur and become epidemic in any camp of considerable extent or duration in which the men have not been protected by antityphoid inoculation should compel preparation for the proper treatment of this disease in so far as this is possible in a field hospital. So also, epidemics of such diseases as measles, cerebrospinal meningitis, influenza or pneumonia may occur at any time and should be anticipated by like preparation and foresight. The trained nurse has proved her value in army hospital work, and now has a place in the regular army medical service. The enlistment and training of a sufficient number of hospital stewards is also of great importance, as is also the instruction of the soldiers themselves as to the care of themselves in emergencies. Undoubtedly this latter instruction, meagre as it was, and the "first-aid, packets" with which each man was supplied, greatly contributed to the excellence of results among the regular troops in the Spanish-American war, and even more so in the late war. A thorough course in the fundamental principles of hygiene should be a part of the education of every soldier in the regular army and navy, and especially should this subject be established as one of the most important in INSTRUCTION IN HYGIENE 487 Fig. 141. — Hospital tent, with wall furled for free ventilation. Fi^^^^^H k ' .^^H^H^^s^^ ,^^^^^^^x y^fflB^'' --1k9^ 1^^ Fig. 148. — Munson hospital tent with fly. (Harrington.) DUTIES OF THE MEDICAL OFFICER 491 when compared with the effects of conditions obtaining in the ordinary transport ships, are incalculable. The work of the soldier, while excessive at times, ordinarily permits much leisure to the men, which, in turn, is conducive not only to attacks of hor^esickness and ennui, but to the development of injudicious and injurious habits. Consequently, anything that will profitably employ the attention and activities of the men Fig. 149. — Tents for winter quarters: furled at midday to admit sunshine. when off duty is beneficial. For this purpose reading- rooms, athletic sports, and the work of various trades may be mentioned. This need furnishes one of the strong arguments for the restoration and continuation of the army canteen, or soldiers' club. This question involves the treating "with human nature as it exists in the army, rather than attempting the attainment of impossible ideals," and it certainly seems that the favorable reports and commendation of the very great majority of army 492 MILITARY HYGIENE officers who have expressed their opinions concerning it, should warrant the continuance of the canteen-. At any rate, the abiUty to keep his men pleasantly and advantage- ously occupied is one of the qualities of a good com- mander, and medical officers should assist the latter in this respect whenever possible. The medical officer will also be watchful to guard against the causes of the diseases which are most preva- lent in the army, viz., phthisis, heart disease, pulmonary diseases, typhoid, malaria and continued fevers, and, not least in importance, venereal diseases. The latter do much harm in most standing armies, and it is as a pro- phylactic to these that the occupation of time and energy , referred to above is especially advantageous. That the incidence of venereal diseases among soldiers, and presum- ably among others, may be markedly controlled by the combined influence of well-ordered physical exercise, per- sonal education, agreeable recreation, wholesome enter- tainment, prophylaxis and effective disciplinary measures is demonstrated by the remarkable record of the American Army throughout the recent war, and much of 'he good results achieved is undoubtedly to be attributed to the extraordinary efforts that were made to eliminate oppor- tunity of temptation by keeping the men agreeably and properly occupied when not on duty. So, also, must the chief surgeon and his assistants keep oversight of the rations, water-supplies, etc. They must in- spect the men at regular intervals, weighing and measuring them, and examining for heart-strain or other circulatory disturbance; they must select suitable places of encamp- ment when on the march, caring for those who are over- come by the heat or exhausted; they must see that the troops do not injudiciously expose themselves when over- heated; in fact, they must be fully as zealous and active as the commanding officer to maintain the entire com- mand in its highest physical efficiency. The chief features of naval as distinguished from military hygiene are such as pertain to overcrowding. NAVAL HYGIENE 493 bad ventilation and excessive dampness in sleeping quarters, excessive heat in engine-rooms and stoke-holds, exposure to inclement weather, increased liability to tuber- culosis, rheumatism and diseases epidemic in foreign ports, such as cholera, yellow fever, and plague, and lack of fresh water, meats, and vegetables, with consequent increase in liability to scurvy. The general principles of hygiene, however, apply on ship-board as elsewhere and are to be observed to the fullest extent possible. For obvious reasons, cleanli- ness in every detail should be required by medical and other officers both as to the vessel and the men them- selves, and disinfection should also be resorted to whenever there is occasion or suspicion of its need. Crowding and intimacy of contact make the outbreak and spread of any infection a serious danger to all. Lastly, the necessity for constant preparedness, proper esprit de corps and full strength against an enemy on board battleships or other naval vessels render the duty of maintaining proper hygienic conditions among the men a most serious one to all who are responsible for it, and gives naval hygiene a dignity and importance equal to that of the army. For further information on this important subject the reader is referred to the article on Military Hygiene in the Reference Hand-book of the Medical Sciences, by Colonel A. A. Woodhull, M.D., and to the text- books on the same subject by General Edward L. Munson and Havard, Ashburn and Keefer, each of these being in its way excellent and having the authority of practical experience. Likewise, Gatewood's and Pryor's text-books on Naval Hygiene will supply much authoritative data and information relative to features or problems peculiar to sanitary admin- istration in the naval service of the government. CHAPTER XV. VITAL STATISTICS. Science is classified knowledge. By arranging known facts and units into groups, and considering them from different points of view, we discover the scope of a par- ticular science, and are also led to the discovery of new facts. In hygiene it is necessary to have this classification of facts to know what progress we are making, for the true test of any sanitary procedure is its efficacy in preserving health and preventing disease, and we cannot know whether it is efficient or not unless we tabulate and study the results and at the same time eliminate disturbing factors. In this connection it is to be noted that our facts must be accurate and derived from sufficient experi- ence, and that the disturbing factors are especially likely to be numerous. It is evident that we may study disease by direct observation at the bedside and at the postmortem table, or by experiment; and while our knowledge in the past has been gained principally by the former method, we now, since the advent of modern bacteriology and parasitology, may further investigate many diseases by reproducing them in susceptible animals. In this way we soon learn that some diseases are much more preventable than others, and we endeavor to discover the respective causes and predisposing conditions of each that we may the more readily estimate their effects and take measures to restrict and prevent their action. Our observations may be of two kinds: (1) By noting and comparing individual cases, or by following the track of a particular outbreak or epidemic. (2) By observing (494) STATISTICAL PRINCIPLES 495 large classes and groups of men, which necessitates a record of births, marriages, diseases, and deaths. The consideration of such records constitutes the study of vital statistics, ^h- i> Obt imp »rt mt object of which is, a.^'' • ' r vO givn vs-ar iiig of the undue increase of Q^ 1- death presumed to be due to preventable cause, a ) to indicate the localities in which sanitary effort is J it desirable and most likely to be of use." The reader w^ill also notice how the study of vital statistics broadens out into the science of demography — the study of the life of peoples and communities. The importance of the science of vital statistics, which has been well termed the "bookkeeping of humanity," is appreciated when we realize that "it points out where and to what extent disease and death are on the increase, and suggests therefor the inauguration ,of combative sanitary effort, the efficiency of which it enables us to measure. It furnishes the basis for the study of all the various social problems which affect increase and diminu- tion in numbers."^ The national census reports now give statistical returns not only for the wards and other political divisions of some of our large cities, but also for so-called "sanitary districts," in which the population is chiefly made up of those of marked racial or other characteristics that influence the vital problem. The study of such returns supplies much information and the explanation of many otherwise obscure phenomena in the vital statistics of a municipality. At this point it will be well to note certain elementary principles which must be observed in any statistical inquiry, in order that the results of that inquiry may have any value whatever. These are: 1. Our facts, or numerical units , must have precise, definite, and constant characteristics. For example, in determining the death-rate or sick-rate from typhoid fever, ' Harrington and Richardson, Practical Hygiene, p. 879. 496 VITAL STATISTICS every case used in the calculation must be accurately diagnosed and must be undoubtedly one of that disease. If there is any doubt as to preciseness, it is necessary to omit that unit. 2. The units are to be arranged into groups. These groups must have dividing characteristics so definite that there can be no doubt into which group each unit will come. No unit must be in more than one group at one time. It is difficult to group complex facts so as to analyze them properly and to discover all possible phases. 3. Having decided and arranged the groups, we must have a constant numerical standard by which the relation of the various groups to the total units may be expressed. It is generally 100 or some multiple of 100. 4. We must determine the variation in the proportion or relation of the component groups to the whole in similar series of cases. While only an approximation to an inva- riable proportion may be had in any one series, it may be shown mathematically that as the number of units in the series increases there is lessened variation and a greater probability that the proportions will approach uniformity, and that we may calculate the limits of variation by Poisson's formula, as follows: If m be the number of units in one group in the formula m-\-n = q, and n the number in the other, the proportion of m to g' will be — ' g.nd of n to q, -, and these proportions will vary in /2 77) 7? succeeding series within the limits indicated by 2 ^/ — ^ . Consequently, the greater the value of q, the less com- paratively will be that of 2 ^ , or the limit of \ q^ variation trom - and -• Example: Suppose that in a series of 1000 cases of diphtheria 700 recover; then, according to the above NUMERICAL UNITS 497 formula, the limit of possible variation in another series of 1000 similar cases would be 40, and the recoveries would be between 680 and 720; whereas, in a like series of only 100 cases the limit of variation would be 13 and the probable recoveries would vary between 63 and 77. The arithmetical mean is usually employed in medical inquiries, though the increase in population is often estimated by geometrical progression. The probable error or variation from the arithmetical mean is about two-thirds (0.6745) of the mean error, which latter is the mean of the mean error in excess and the mean error in deficiency. The mean error in excess is the difference between the mean of the series and the mean of all the units of the series above the mean. The mean error in deficiency is the difference between the mean of the series and the mean of all the units below the mean. The relative value of two series is as the reciprocals of the squares of their probable errors. Thus if the probable error of series A is 10 per cent, and that of B is 2 per cent., the value of A to B will be as liiy to f , or B will be twenty-five times as valuable as A. The relative value of two or more series is also as the square roots of the numbers of units in the respective series. From the above it is evident that the results from an average cannot be absolutely applied to any par- ticular case, for there is always the chance of such varia- tion as may be determined by Poisson's formula or by the estimation of the probable error. We apply averages to the aggregates of facts, and they will approach exactitude if they are founded on a sufficient number of facts. We must be careful in estimating the value of means and averages and in giving credit or blame accordingly. Guy says: "Averages are numerical expressions of probabili- ties; extreme values are expressions of possibilities." Statistical results are frequently expressed by graphic representations (see Figs. 150 and 151), and these are very valuable, especially for class or visual demonstration. The numerical units employed in the study and the cal- 32 498 VITAL STATISTICS culations of vital statistics are persons living and persons dead, and the groups into which these units are classified are characterized by such distinctions as age, sex, race, occupation, locality, etc. The sources from which we derive our information regarding these units are two, viz., the census or count, which every civilized country makes periodically, and the returns of births, marriages, deaths, and cases of contagious disease made to local governing sanitary bodies, such as boards of health, etc. These I.O ' 1 ^ T'^ 7.0 \ \ > i \ i a 4.0 , 1 \ 4 ft ^ \ 1 1 \ / \ / x^ 3.5 \ 1 \ L ^ t^:' J / ^^ "^ ^ X I \ / 4 s '" ^ \ \ / k > \ / — \ ^^ '■^ \ \ 9 ft 1.5 1.0 0.5 \ ^ V ,^ r N \ ,y ^, ,- ^, --* \ / \ _^, ^, ^- — ^- \ / ^. v.^ - — "~" ~~" ^• 0.5 \ \ \ \ \ ^ ; 3 \ \\ ■5 <. 1 1 \ I \ \ \\ 1 I i i \ I -1 r I i ^ f I \ 11 I I 1 I 1 1 ; 1 \ 1 1 s Fig. 150. — Graphic chart, showing percentages of typhoid fever deaths in total mortality in four cities. Unbroken line, Chicago ; lower line, New York; short dashes, Philadelphia; long dashes, Boston. latter returns localize the units and help especially in the classifications in which locality is a factor. The census returns give not only the population, but also particulars as to sex, age, race, occupation, etc. Of these the age-record is most important, as the death-rate varies most according to age. The natural increment of a population is the excess of births over deaths, but the actual increment differs from this, however, according to the difference between emigra- tion and immigration. And as the rate of increase does ESTIMATION OF POPULATION 499 not always remain the same, estimates of population at times other than of the census cannot be exactly accurate. Thus, we may have a lowered death-rate and yet a decrease in both the natural and actual increment, owing to a greatly lowered birth-rate and to increased emigra- tion, both of which may be primarily due to a long period of oppression or financial distress. However, to estimate FROM UNITED STATES MORTALITY STATISTICS 1913 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 19111912 1913 210 190 210 200 190 ^180 p 170 i 160 I 150 iliO s% <^* ^ N % \ \ S>^ r \ >*,^ % \ h < .f \ \ _ N _ QT \ / \ "^ \ j^' -Pi^E pT y\ V <> ,'*> -^ cl^^ U' / \ ^ \ 2130 cr UJ120 UJ 110 .— - ^110 0=100 1 90 UJ ° 80 70 y s. ^^ \^ / — fA p!> \ '-' — / p— j POP! EX^- .-^ =r= ir-- 5^ f^- ^ ::»- y 60 fiO ^r.M 'cTr' "'" 170 160 150 110 130 120 110 100 90 80 70 ao 50 Fig. 151.— Chart from U. S. Mortality Statistics, 1913. the population for times other than the census year, we assume that the rate of increase, whether positive or negative, that prevailed between the last two census enumerations will continue until the next is taken. Now, as populations increase in regular geometrical progression when the rate of increase is constant, which we assume, the growth is after the manner of compound 500 VITAL STATISTICS interest. Thus, if a population of 10,000 increases by 2 per cent, annually, at the end of the first year it will number 10,200, at the end of the second year 10,404, etc. Hence, it can readily be shown that logarithm R = — (log. P' — log. P), where R is the annual ratio of increase, P the population of the census before the last, and P' the population of the last census. If we now multiply the logarithm of R, the annual ratio of increase, by the number of years since the last census, and add to it the logarithm of the last census (log. P') we will have the logarithm of the population at the middle of the given year — e. g., Q (log, of the pop. 1890 - log, pop. 1880) ^ , ^ ^^^ 8 — 1- log. pop. 1890 = logarithm of the population on June 30, 1898. For the reasons already given, such an estimate will not be absolutely accurate, and it would, consequently, be well to have a census taken every five years for certain data. The more accurate the estimate for any year hap- pens to be, the more reliable will be the statistical results. It is also to be noted that in this country the census is taken at the middle of the year, and that death-rates, etc., are based on the population estimated, as above, for the middle of the given year. Another method of approximately estimating the popu- lation in small and slowly increasing districts is to assume the growth to be by arithmetical progression, and, there- fore, to add to the population of the last census one-tenth of the difference between it and the population of the preceding census for every year since the last census. We may also estimate the population from the number of houses and use this as a check on either of the above estimates. The number of persons living in each house averages about the same for each city, but differs for different cities. So also the ratio of the school registra- tion to the total population, which is apt to remain rela- UNIFORM REGISTRATION METHODS 501 lively constant for any stable community, may be used to detennine the population for a given year. Local authorities always tend to overestimate the population, and a police census is invariably too high. As has been stated, we get the number of births, mar- riages, deaths, etc., from the registration records, the proper data being furnished to the registration bureau by duly authorized persons. For instance, the law should require a burial permit for each death in order to identify the person and to guard against criminal acts or neglect, and the death certificate on which the burial permit is issued should give the name, sex, color, age, occupation, and especially the cause of death of the deceased. The diagnosis concerning this last item should be as correct as possible, and the primary as well as the secondary cause of death should be given. And while it is difficult to determine the actual cause of death in many cases without, and sometimes even by a postmortem examination, there is fortunately not much uncertainty usually in diagnosing the diseases of which we most want statistical informa- tion, especially the so-called preventable or infectious diseases. As a consequence of the above, the certificate as to the cause of death will need to be signed by some one compe- tent to determine that cause, viz., by an educated physi- cian; and it is therefore necessary that the State should define who is and who is not an "educated physician.*' And as this information and the other required returns which the physician makes, as well as his professional services in general, are for the sake and benefit of the citizens of the State, it is evidently to the State's interest that it be very careful and explicit as to the qualifications of the physicians whom it allows to practise within its borders. Another reason for the enforced return of a certificate and the issuance of a burial permit for every death is that this is about the only way in which it is possible to secure a record of all the deaths. Any system for collating the 502 VITAL STATISTICS list of deaths only at the end of the year will fail to record from 25 to 40 per cent, of the number. The statements made in the introductory chapter and elsewhere show the importance of vital statistics in determining the sanitary conditions and improvement of communities. In order that comparisons and correct judgments may be readily made, it is evident that all classifications, returns, and registrations should be on a basis or system as uniform as possible, but almost the opposite has obtained, since almost every State, city, or local authority has used its own system and without any concert of action until comparatively recently. Accord- ingly, in order to amend this and to secure not only uniform, but also correct and thorough returns from the whole country, the Division of Vital Statistics of the U. S. Census Office is making extraordinary efforts to bring about uniform legislative requirements in the various States and to secure the adoption of the International Classification of Causes of Death, which is intended "to harmonize the features of the most generally used systems in order to afford a common basis of union," and which has been adopted by the U. S. Census Office for the com- pilation of mortality statistics. To this end a circular has been sent to the physicians of the country " describing the details required by the Standard Certificate of Death (see next page), and giving the titles of the International Classification of Causes of Death, with explanatory notes showing the significance of various terms to the titles under which they are compiled, and a list of indefinite and unsatisfactory terms very frequently used in reporting deaths, with a statement of why such statements are unsatisfactory." This circular is very instructive, and its recommendations should henceforth be observed by all physicians in making death returns.^ 1 This circular can doubtless be had on application to the Division of Vital Statistics of the Census Office at Washington, together with a cir- cular on Medical Education in Vital Statistics, relating to the instruc- tion of medical students in registration methods, uses of registration data, and the duties and obligations of physicians ; and one on Practical Registration Methods, for the information of local registrars, PACTORS AFFECTING MORTALITY-RATE^ 503 8-209. MARGIN RESERVED FOR BINDING. y. S. No. 98. Write Plainly, with Unfading Ink— this is a Permanent Record. N.B.— Every item of information should be carefully supplied. AGE should be stated EXACTLY. PHYSICIANS should state CAUSE OF DEATH in plain terms, that it may be properly classified. The "Special Information for persons dying away from home should be given in every instance. z < o b. Oq ffi < o z < o z _ ■o IT V < z z < u o Ik o hi 3^ c o ° O i^ s s . *s -o F K ♦J as O O) zS og <^ oS lijo 8il ^2 o * I. SI « 0) o C .2 ^ 8 •> 1-4 H P4 :«i ^ P4 ^ 1 i t-; o § ^ J s o o 1^ ^^ H OQ Jh H flB •«1 „«v flC ^ |W P 1 a ^ § Ul u 5 1 is as 1^ 11. li. UJ = u.» UJ o>. z ^ S < . 03 Or < 03 o So < ?> U. < ? Z ugj •o &rsc 0) ^lT ?^^ s Os ^s & ^1 ■5 &•& j{ S:S s fPB «C •^ «s t: S-2 S *'l •s t ^ 1^ 3 g 1 n o ><^ 8 • •♦- ?, 504 VITAL STATISTICS The gross death-rate varies with the size of the com- munity. Newly settled communities have a lower death- rate than older ones, because the proportion of adults is larger and of children smaller in the former. With large communities and short periods the probabilities of error are very great, and the longer the period the less likelihood of error. Birth-rates, marriage-rates, and death-rates are usually calculated as rates per thousand of the popula- tion living at the middle of the given year, and are determined by multiplying the number of births, mar- riages, or deaths by 1000, and dividing the product by the population. What were looked upon as fair maximum death-rates a decade or more ago are now considered to be too high, and the average rate of the present closely approximates the minimum of the comparatively recent past. However, if the death-rates of any community are continuously reported as much below the average for similar popula- tions, the chances are that the population has been over- estimated or that all deaths have not been recorded. If higher than this average, there is probably some special cause for the high mortality. In statistical computations we must exclude the popu- lations and deaths in hospitals, prisons, etc., except for such of the inmates as belong to the district in which such institution is located. To find the weekly or daily death-rate, the number of deaths for the week or day must be multiplied by 1000 and divided by the so-called weekly or daily population: ,1 11 1 ^. total population ^. , ., the weekly population = J^ tl ^ ; the daily popu- , . total population _^- , . . . , lation 94.00A ^^^ monthly population equals the daily population multiplied by the number of days in the particular month. The zymotic death-rate is the rate from the seven principal zymotic or infectious diseases, viz., smallpox, measles, scarlatina, diphtheria, whooping-cough, fever DEFINITION OF TECHNICAL TERMS 505 (typhoid, typhus, or other continued fever), and diarrhea.^ It is given per 1000 of population, and in the same way we can give the special rate for any particular disease, but this is now usually stated as the rate per 100,000 of popu- lation. ¥oT example, the average annual zymotic death- rate for England and Wales for the decade from 1861 to 1870 was 4.11, for 1871-80 it was 3.36, and for 1881-90, 2.35 — a striking proof of the decided benefits follo^^^ng proper attention to hygiene and sanitation. The mortality from certain diseases is affected by age, sex, race, occupation, density of population, seasons, cyclical changes, etc. Contrary to the general rule, the rate of infant mortality is not expressed per thousand of population, but measured by the proportion of deaths of infants under one year to the births registered in that year, and is determined by multiplying the number of deaths by 1000 and dividing the product by the number of births. The infant mortality-rate is always high, owing to various causes, viz., early marriages and weakly parents, hereditary tendencies or diatheses, insanitary surround- ings and unfavorable social conditions, improper feeding, insuflBcient clothing, infant life insurance, etc. Death-rates vary greatly for the different ages, being much higher for the first five years of life. For this reason it is well to express the death-rate of children under five as the rate per thousand of children under that age, rather than as a proportion of the total number of deaths. Otherwise, a town with a large number of chil- dren might apparently have an abnormally high death- rate. There might also be a difl^erence in the death-rates of two localities due to sex-distribution, for the sexes differ in their susceptibility and resistance to the various diseases. More boys are born everywhere than girls, but more males die than females, so that the tendency is to a preponderance of the latter, except in newly settled coun- » Wilson, Hand-book of Hygiene, 8th ed., p. 570. 506 VITAL STATISTICS tries or localities. Age-distribution and sex-distribution favor a low mortality in rapidly increasing towns, new localities, and manufacturing districts; in rural districts they tend to increase the death-rate. Consequently, when the death-rates of two or more towns or localities are to be compared, there must be cor- rections for age-distribution and sex-distribution. The mean annual death-rate of the country for each age and sex for the decade preceding the last census is applied to the town or district, with age-distribution and sex-distri- bution according to the last census. The total number of deaths thus calculated, multiplied by 1000, and divided by the population of the last census, gives the standard death-rate of that town. The mean annual death-rate of the country divided by the standard death-rate gives the factor for correction, which being multiplied by the re- corded death-rate of any year gives the corrected death- rate. The comparative mortality figure is determined by multiplying the corrected local death-rate by 1000 and dividing by the death-rate for the whole country, and only indicates that the same population which gave 1000 deaths in the whole country gave or would have given so many deaths in the town or district in question. The morbidity-rate or sick-rate of a community is diffi- cult to estimate, since there is usually no complete record and registration of cases of disease. Where returns are required to be made of the infectious diseases, the mor- bidity due to them may be determined in the same way as the mortality for the locality. It is estimated that there is a total of about two years' sickness in a com- munity for every death, and members of beneficial societies are said to average about one and one-half weeks' sickness annually. "Applying this estimate to the United States, in which about 1,500,000 persons die per annum, there are probably at all times about 3,000,000 persons seriously ill. This means an average of thirteen days for each inhabitant."^ ^ Report on National Vitality, Fisher, p. 34. AVERAGE DURATION Of LIFE 507 In this connection, the following definitions are given of terms that are employed in discussions of vital statis- tics, especially in relation to longevity: The mean age at death of a population is the average age at which death occurs in that population, and is indi- cated by the total of the ages at death divided by the number of deaths. Inasmuch as it depends largely on the age-distribution of the population, it is neither a good test of longevity nor of sanitary conditions, except when it is calculated or taken from life-tables for an entire gen- eration. The probable duration of life is the age at which any number of children born will be reduced one-half, the chances thus being even that each will survive to that age. For a million children the probable duration of life is for males less than forty-five years; for females, forty- seven years. The mean duration of life is the same as the mean age at death when the population is stationary as to age- distribution and sex-distribution. Otherwise, it is indi- cated by the mean after-lifetime. The expectation of life is the mean after-lifetime of a person at any age, as indicated by a life-table; or, in other words, it is the average number of years which persons of that age continue to live. At birth it is identical with the mean duration of life, and " as applied to communities, it is the mean lifetime of a generation of persons traced by the life-table method from birth to death, and is the only true test of the health of populations." According to Farr, "a life-table is a barometer which indicates the exact measure of the duration of life under given circum- stances, and is indispensable in gauging the influence of sanitary or insanitary conditions." The essential factors of a life-table are the number and ages of the living and the number and ages of those that die, and these factors are obtained from the mean population for each age and sex and from the total death-returns between two censuses. 508 VITAL STATISTICS "Contrary to common impression, there is no iron law of mortality. Recent statistics for India show that the average duration of life there is less than twenty-five years. In Sweden it is over fifty years; in Massachusetts, forty-five years. The length of life is increasing wherever sanitary science and preventive medicine are applied. In India it is stationary. In Europe it has doubled in three and a half centuries. The rate of increase during the seventeenth and eighteenth centuries was about four years per century; during the first half of the nineteenth century, about nine years per century; during the latter half of the nineteenth century, about seventeen years per century. And in Germany, where medical and sanitary science has reached the highest development, about twenty-seven years per century. The only comparative statistics available in this country are for Massachusetts, where life is lengthening at the rate of about fourteen years per century, or half the rate in Germany."^ ^ Abstract of Report on National Vitality, Fisher. CHAPTER XVI. THE EXAMINATION OF AIR, WATER, AND FOOD. In this final chapter the author has endeavored to arrange a series of methods for the examination or analysis of the subjects respectively considered in such a manner that anyone who has had a little laboratory experience may be enabled to determine their hygienic conditions, sanitary influence or degree of purity, and this at the cost of a minimum of time and expense. The methods outlined have been selected from a variety of sources, and some have been especially modified for the purpose; so that while it is not claimed that they will give the absolutely accurate results desired by the professional bacteriologist or chemist, nor that they will suffice as a basis for expert testimony in court or to establish legal rights, it is believed that, if carefully carried out, they will not fail to yield the information sought for, viz., whether the sample of air, water, or food examined is sanitarily pure or safe for use within the accepted limits. Only such apparatus is to be used as can be readily obtained or improvised without much expense, and every effort has been made to render everything clear to the student and reader, so that he may not hesitate to un- dertake the necessary investigation whenever occasion requires or an opportunity offers. For further details regarding any of the methods, should these be found necessary, reference may be made to the text-books indicated, as they will render clear any points that may here seem uncertain or abstruse. AIR. The solid impurities in the atmosphere may be col- lected for microscopic examination as follows: Tightly (509; 510 EXAMINATION OF AIR, WATER, AND FOOD cork a large glass funnel and fill it with cracked ice. As the aqueous vapor of the air condenses on the exterior, the dust particles adhere to the moistened glass, and are carried down by the condensed water into a vessel placed below, in which they are allowed to settle. From this they are transferred by means of a pipette to clean slides and examined under the microscope. Other methods that may be used to collect the dust are oiled plates; paper, cloth or cotton wool filters; wash bottles, etc. To make a qualitative bacteriological examination the air may also be drawn through sterilized glass tubes coated interiorly with gelatin. Bacteria and their spores, moulds, etc., adhere to this coating, and from each individual or group of individuals colonies develop, from which pure cultures and subsequent bacteriological experiments may be made; or the sterilized gelatin may be exposed in flat (Petri) dishes to the air for a short time to allow the bac- teria, etc., to fall on the surface. The tubes or dishes are then covered and set aside to allow the colonies to develop. To make a quantitative bacteriological examination a known quantity of air may be drawn through a small tube filled with sterilized pulverized sugar. The sugar is then transferred to tubes or flasks of melted and sterilized gelatin, and dissolving leaves the bacteria, etc., free to develop in the gelatin, which may be poured upon sterilized Petri dishes before cooling. A temperature just sufficient to melt the gelatin will not be too warm to harm the bacteria. The number of colonies that develop may be assumed to represent the number of living microorganisms in the volume of air drawn through the tube. The relative humidity or percentage of moisture in the air is determined by some form of hygrometer, of which one of the most convenient is the psychrometer, which is simply a combination of a dry- and a wet-bulb thermometer. The latter has its bulb enclosed in a jacket of absorbent wicking^ muslin, or silk, which dips into a EXAMINATION OF AIR 511 Fig. 152. — Sling psychrometer. 512 EXAMINATION OF AIR, WATER, AND FOOD small reservoir of clean, soft water. The thermometer bulb is thus kept wet by capillary attraction, and, unless the air be "saturated" with aqueous vapor, evaporation takes place more or less rapidly, heat is abstracted or made "latent," and the temperature, as indicated by Fig. 153. — The Tyeos hygrodeik. this thermometer, is lowered. Hence, by the difference in reading of the two thermometers we may determine not only the relative humidity of the atmosphere, but also the "dew point," weight of vapor per cubic foot of air, and even the "tension" or influence upon barometric pressure due to the presence of this vapor. These results PSYCHROMETER AND HYGRODEIK 513 are usually and most conveniently determined by using tables that have been prepared for all variations of tem- perature and humidity within practical limits, and which are supplied with the instruments. The " hygrodeik/* however, has a chart fixed between the two thermome- ters which shows graphically by a series of curved lines and a movable indicator all the facts that would be derived by using the official tables. A sling psychrometer is one devised so that it may be whirled rapidly in the air, thus facilitating evaporation from the wet-bulb and lowering to a constant temperature. Test for Carbon Dioxide, CO2. — Boom's Modification of Wolpert's MetJiod. — Make a mark on any test-tube, say one inch from the bottom. Fix the bulb of an atomizer to a glass capillary-tube sufficiently long to reach to the bottom of the test-tube, and in such a manner that a definite quantity of air is forced from the bulb through the tube at each compression. To use: Fill the test- tube exactly to the mark with a saturated solution of lime-water, take the apparatus into the out-door air and driving the air slowly through the lime-water each time, find out how many compressions of the bulb are needed, to make the lime-water just turbid enough to obscure a pencil-mark on white paper placed beneath the test-tube and viewed from above. Then rinse out the test-tube, fill exactly to the mark again with lime-water, and repeat the process in the room the air of which is to be examined. We then assume that the out-door air con- tains the normal amount of carbon dioxide — 0.04 per cent, (unless we happen to know the actual amount in the atmosphere at the time), and estimate the percentage of carbon dioxide in the air of the room by the following proportion: Let .T = the percentage of CO2 in the air of the room. Then the number of compressions of the bulb required in the outer air is to the number of compressions required in the room as x is to 0.04. If the actual per- centage of CO2 in the outer air is known, substitute this for the 0.04 per cent, in the formula. Care must be 33 514 EXAMINATION OF AIR, WATER, AND FOOD taken in using this device not to draw any of the lime- water into the bulb. A Modification of Angus Smith's Method. — To a mod- erately large, wide-mouth bottle (one-quart) fit a per- forated rubber stopper, the perforation being just large enough to admit the tip of a 1 c.c. pipette; first fill the bottle with the air of the room by filling it with water and then emptying it in the room, taking care that the entering air does not bubble through the out-going water. Fit ia the stopper and introduce 1 c.c. at a time of a standardized alkaline solution, slightly colored with a few drops of a neutral alcoholic solution of phenolphtha- lein; close the perforation with a piece of glass rod and shake the bottle well after each addition of the alkali, continuing until the color ceases to be discharged by the carbonic acid of the contained air. Then, since the quantity used of the alkali solution indicates a certain definite amount of carbon dioxide. The number of c.c. of solution v^ed multiplied by the amount of CO2 each c.c. represents, multiplied by 100, and divided by the capacity of the bottle in c.c. less the number of c.c. of solution u^ed — x = the percentage of CO2 in the air examined. A suitable alkaline solution may be prepared as fol- lows: Dissolve exactly 2.409 grammes of pure sodium carbonate (free from the water of crystallization) in 1 liter of distilled water. Only a fraction, say one-fourth or one-tenth, of this quantity need be made up at a time. Each c.c. of this solution will neutralize to 1 c.c. of CO2. For use: To 10 c.c. of this solution add a few drops of neutral alcoholic solution of phenolphthalein and dilute to 100 c.c. Each c.c. of this dilute solution is then equiva- lent to 0.1 c.c. of CO2, and used as above will give close results. The phenolphthalein is used as an indicator, as the pink or rose color due to it disappears when sufficient carbon dioxide is absorbed to exactly neutralize the alkalinity of the soda solution. The stock solution should be kept in well-filled, tightly stoppered bottles. TEST FOR CARBON DIOXIDE IN AIR 515 Example: If 9 c.c. of the above dilute solution be used, and the capacity of the bottle is 1200 c.c, then 9 X0.1 X10Q_ 90 _ _..,.-.. 1200-9 -1191 -"^-^-^^^^^ the percentage of CO2 in the air of the room. Pettenkofers Method. — This test, like the preceding one, depends upon the fact that the acid carbon dioxide in a measured sample of air tends to neutralize the alkalinity of a stock solution of calcium or barium hydrate when the latter is agitated with the given volume of air, and that the amount of carbon dioxide can thus be measured by the loss of alkalinity in the solution. The absorption of the carbon dioxide is more rapid if a solution of barium hydrate instead of lime-water (calcium hydrate) is used, the former taking up the gas within an hour or so, whereas eight or ten hours are needed for its com- plete absorption by the lime-water. However, the latter, which is a well-known solution of the official pharmacopoeia, is more readily ob- tained and gives equally good re- sults, if proper time be given to the test. The barium hydrate solution is made by dissolving about 4.5 grammes of barium hydrate and 0.5 gramme of barium chloride in a liter of distilled water, which has been previously boiled to drive off any contained carbon dioxide. The solution, if made up in considerable quantity for repeated tests, is best kept in a bottle with a stopper having a U-tube for an inlet, as in Fig. 154. This U-tube contains small pieces of pumice soaked while hot in strong caustic potash solution, and prevents the ingress of CO2 from the air when the liquid is drawn from the bottle. In Fig. 154.— Bottle for barium hydrate. (Har- rington.) 516 EXAMINATION OF AIR, WATER, AND FOOD the description of the test the term lime-water will be used to indicate the alkaline solution, although it be prepared with either base. The Test. — The air to be tested is collected in one or more large, clean bottles, the exact capacity of each having previously been ascertained and noted. The bottles may be filled by pumping in the air with a bellows or by first filling with water and then removing the latter by siphoning or by carefully decanting it, care being taken that the air does not bubble through the water which readily absorbs carbon dioxide. Into each bottle containing an air sample an exact quantity of the lime-water, say 50 c.c, is introduced, the bottle quickly stoppered, and then well shaken, so that the air may be thoroughly washed with the solution. The shaking is to be repeated at intervals until the necessary time for complete absorption of the gas has elapsed. If the lime-water is measured into the bottles by means of a pipette, care must be had that the delivery is not hastened by blowing through the pipette, since the carbon dioxide of the expired air would thus vitiate the test. The strength of the lime-water, being as yet unknown, is now determined by means of a solution of oxalic acid of such a strength that 1 c.c. corresponds in alkalinity to 0.5 c.c. of CO2. (Such a solution is made by dissolving exactly 2.808 grammes of pure crystallized oxalic acid in 1 litre of distilled water.) Supposing that 50 c.c. of lime-water was introduced into each bottle containing air to be tested, exactly 25 c.c. of the stock lime-water is measured into a clean beaker, into which the oxalic acid solution is run from a graduated burette until the alkalinity of the lime-water is just destroyed, the neutral point being indicated by means of a phenolphthalein solution, which may have been pre- viously added to the stock solution, or a few drops may be placed with it in the beaker. The phenolphthalein retains its color as long as the solution is alkaline, but loses it the moment the neutral point is reached. When PETTENKOFEWS TEST FOR CARBON DIOXIDE 517 the lime-water is exactly neutralized, the exact amount of the acid solution used is noted. Then, after the time necessary to allow the complete absorption of the carbon dioxide in each testing bottle by the lime-water therein, 25 c.c. of that lime-water is measured into a beaker, and the alkalinity exactly determined by means of the oxalic acid solution in the same manner as was done with the stock solution. Now, inasmuch as part of the alkalinity of the lime- water which was in the bottle has already been neutralized by the carbon dioxide in the air of the bottle, it will require less of the acid solution to neutralize the lime- water from the bottle than was required for the same quantity of stock lime-water, and as 1 c.c. of the acid solution corresponds to 0.5 c.c. of carbon dioxide, the difference in the amounts of acid solution used expressed in c.c. will express the number of c.c. of carbon dioxide in the volume of air in the bottle. For, though each c.c. of acid solution is equivalent to only 0.5 c.c. of carbon dioxide, the loss of alkalinity of only one-half the lime- water primarily introduced into the bottle has been determined, and the total loss of alkalinity would have to be expressed by multiplying 0.5 c.c. CO2 by twice the difference in c.c. between the amount of acid used in testing 25 c.c. of the stock lime-water and that used in testing the 25 c.c. (one-half) of the lime-water from the bottle. But twice 0.5 = 1. Therefore the difference between the readings in the two tests gives the amount of carbon dioxide in the air in the bottle. The quantity -of carbon dioxide in the bottle having been thus determined and the quantity of air tested being known by deducting the amount of stock lime-water introduced into the bottle from its total capacity, which has been already found by measuring the quantity of water it will hold, the percentage of carbon dioxide in the air examined is readily determined. Example: Suppose that 25 c.c. of stock lime-water requires 30 c.c. acid solution and 25 c.c. of lime-water from the bottle requires 27 c.c. of acid solution. 518 EXAMINATION OF AIR, WATER, AND FOOD Therefore 30 c.c — 27 e.c.= 3 c.c.= amount of carbon dioxide that was in the air in the bottle, which latter con- tains (for example, say) 2550 c.c. when exactly filled. ^, 3X100 300 • ,„ ^ , ,. ., Ihen T^^ri^ ^ = ^^777; = 0.12 per cent, carbon dioxide zoou — 50 2500 in the tested air at current temperature and pressure. To be absolutely exact in the result, correction must be made by bringing the air volume to the standard temperature (0° C.) and barometric pressure (760 mm.), but this is unnecessary in most cases. The phenolphthalein "indicator" is made by dissolving 0.5 gramme of phenolphthalein in 100 c.c. of alcohol. WATER. To test for color, turbidity, etc., compare with distilled water, using tall glass jars and looking down through equal depths upon a white surface. The smell of a water may be detected by heating it to about 140° F. for a few minutes in a glass-stoppered bottle. This test may or may not indicate fecal contamination. Few polluting impurities, when only in moderate quantities, give any taste to water, and a dangerously polluted water may have a good taste. Iron in small quantities, one-fourth of a grain to a gallon, will give a taste to the water. Use caution in tasting suspicious waters. Aeration is indicated by the lustre of the water and by the presence of air-bubbles on the sides and bottom of the vessel. ^ Test for Chlorin. — Solutions required: (1) Standard nitrate of silver solution : to 1 liter of pure distilled water add 4.788 grammes of pure silver nitrate; 1 c.c. of this solution is equivalent to 1 mg. of chlorin. (2) Potas- sium chromate solution — a 5 or 10 per cent, solution of potassium chromate made up in distilled water free from chlorin. 1 See also pages 222 to 228. TEST FOR CHLORIN 519 Process, — To 100 c.c. of the water add from 0.5 to 1 c.c. of potassium chromate solution, and then run in from a burette or graduated pipette the standard silver solution, adding it drop by drop, and stirring the water with a glass rod. Continue until a faint but permanent orange- red tint has been produced, showing that all the chlorin has combined with the silver, the persistent reddish color being due to silver chromate. The number of c.c. of silver solution used indicates the number of milli- grammes of chlorin in 100 c.c, or parts per 100,000; this multiplied by 10 gives the number of milligrammes in 1 liter, or parts per 1,000,000. If the water contains but little chlorin, accuracy will be furthered by evapo- rating 250 c.c. of the water to 50 c.c. over a water-bath, and proceeding as above; the result multiplied by 4 wdll give the amount of chlorin in 1 liter. On the other hand, if the water contains much chlorin, the test will be facilitated by using 50 c.c. or even 25 c.c. of the sample, adding a corre- spondingly smaller quantity of the potassium chromate indicator. Water containing much organic col- oring matter or iron should be decolor- ized before making the above test by adding from 3 to 5 c.c. of milk of alu- mina, free from chlorides, to about half a liter of the water, heating to boiling and filtering. Test for Nitrates. — Solutions required: (1) Phenol- sulphonic acid: 6 grammes of pure carbolic acid; 37 c.c. of strong sulphuric acid, and 3 c.c. of distilled water. (2) Fig. 155.— Bottle for collecting samples of water at different levels. 520 EXAMINATION OF AIR, WATER, AND FOOD Standard potassium nitrate solution: add 0.722 gramme of fused potassium nitrate to 1 liter of distilled water. Each c.c. of this solution contains 0.1 mg. of nitrogen as nitrates. The water used in making the solution must be free from nitrates. Process. — Evaporate 10 c.c. of the water to be exam- ined (or 25 c.c. if it is presumably low in nitrates) just to dryness in a small and clean porcelain dish. Add 1 c.c. of phenolsulphonic acid, stir with a glass rod, and add 1 c.c. of distilled water and 3 drops of strong sulphuric acid; warm, and dilute well with distilled water; then add ammonia until the fluid is strongly alkaline, and dilute with water to 50 c.c. Be careful throughout the test, but especially when evaporating, not to dissociate and drive off any of the nitrates by too prolonged or intense heating. Treat 1 c.c. of the standard solution in an exactly similar manner and compare the tints produced, placing the resulting solutions in two Nessler or other tubes of equal caliber, and diluting the more intense until the tints match exactly; then calculate the amount of nitrogen present by the amount of dilution necessary — e. g., sup- pose that in testing a certain sample, the tint from 1 c.c. of standard potassium nitrate solution is darker and requires the addition of 50 c.c. more water — i. e., up to 100 c.c. to match the tint of the tested sample. Therefore 100 c.c. : 50 c.c. : : 0.1 mg. N : x =0.05 mg., the amount of nitrogen as nitrates in the 10 c.c. of water examined. The propor- tion would be reversed, of course, if the water tested had the stronger tint. The test is based on the facts that some of the phenolsulphonic acid is converted by the nitrates into picric acid, which forms ammonium picrate upon addition of the ammonia and gives a yellow tint to the water, and that the amount of picric acid and picrate formed and the consequent depth of color depend on the amount of nitrates present in the water. "The accuracy of this test is diminished by the presence of chlorides in notable amounts, say more than 2 parts TEST FOR NITRATES 521 in 100,000, but not by nitrites. On this account, Mason recommends the addition of corresponding amounts of sodium chloride in the preparation of the color scale."^ Test for Nitrites. — Solutions required: (1) Sulphanilic acid: dissolve 0.5 gramme of sulphanilic acid in 150 c.c. of dilute acetic acid, sp. gr. 104. (2) Naphthylamine acetate: boil 0.1 gramme of solid naphthylamine in 20 c.c. of distilled water, filter through a plug of washed absorbent cotton, and mix the filtrate with 180 c.c. of dilute acetic acid. (3) Standard sodium nitrite solution: dissolve 0.275 gramme of pure silver nitrite in pure water and add a dilute solution of pure sodium chloride until a precipitate ceases to form, and dilute to 250 c.c. with pure water. For use, dilute 10 c.c. of this stock solution to 100 c.c. Each c.c. of the dilute solution contains 0.01 mg. of nitrogen as sodium nitrite. Keep both solutions in the dark when not in use, preferably in amber bottles. All water in these solutions must be free from nitrites; like- wise all water used in the tests, except the sample under examination. Process. — Place 25 c.c. of the water to be examined in a cylindrical vessel, and in a similar vessel of the same caliber dilute 1 c.c. of the (diluted) standard sodium nitrite solution to 25 c.c. with nitrogen-free distilled water; add to each vessel 2 c.c. of first one and then the other reagent, using a separate pipette for each. "If nitrites are present (in the w^ater tested) a pink to a garnet color is developed within half an hour, the intensity of color depending upon the amount of nitrite present. Since the air of laboratories in which gas is burning is very likely to contain traces of nitrites, which are absorbed readily by water, it is well to keep the tubes corked or otherwise protected."^ Compare the colors at the end of half an hour, or sooner if the tints seem permanent, and estimate the amount of nitrites by diluting the darker tint until it matches the lighter, and comparing the respective volumes, as in the * Harrington, Practical Hygiene, 5th ed., p. 463. « Ibid., p. 462. 522 EXAMINATION OF AIR, WATER, AND FOOD test for nitrates; the result will give the quantity of nitrogen as nitrites in the water, and should not be more than a trace. The above test is a very delicate one. Schuyten's Method} — "When 5 c.c. of a 1 per cent, solution of antipyrin in acetic acid (1 to 10) is added to a solution containing nitrites, a green color is produced.'^ Measure 45 c.c. of the water to be examined into a Nessler tube, and in another of equal caliber mix 1 c.c. of the standard sodium nitrite solution (dilute) with 44 c.c. of distilled and nitrite-free water. To each tube add 5 c.c. of the antipyrin solution. Allow to stand for one-half hour and compare as above. "This method will show the presence of 1 part of nitrogen as nitrous oxide in 20,000 parts, and while not so delicate as the other method, is not hindered by the presence of any of the ordinary contaminations in water. "^ Test for Free and Albuminoid Ammonia. — Wanklyn^s Method. — Solutions required: (1) Standard ammonium chloride solution: dissolve 0.382 gramme of pure dry ammonium chloride in 100 c.c. of ammonia-free water. For immediate use dilute 10 c.c. of this standard stock solution up to 100 c.c. with ammonia-free water; each c.c. of the dilute solution contains 0.01 mg. of nitrogen as ammonia. (2) Alkaline potassium permanganate solu- tion: dissolve 200 grammes of potassium hydrate (in sticks) and 8 grammes of potassium permanganate in 1 liter of distilled water, evaporate to about 750 c.c. to drive off the ammonia present, and make up to 1 liter again with ammonia-free water. To make ammonia-free water, add about 1 gramme of sodium carbonate to 1 liter of distilled water and boil until about one-fourth is evapo- rated. (3) Nessler's reagent: dissolve 1.5 grammes of potassium iodide in 10 c.c. of distilled water and 1.7 grammes of mercuric chloride (HgCW in 30 c.c. of dis- tilled water; add the mercuric chloride solution to the potassium iodide until a permanent precipitate is formed, ^ Bergey's Hand-book of Practical Hygiene, p. 95. ^ ibid. TESTS FOR NITRITES AND AMMONIA 523 and then dilute to 100 c.e. witli a 20 per cent, solution of sodium hydrate, add the mercuric chloride solution until a permanent precipitate again forms, and allow to stand until clear; this reagent gives a brown or yellowish-brown coloration if ammonia be present in water, and improves on keeping. Process. — Place in a retort 500 c.c. of the water to be examined, connect with a condenser, and boil gently so that the water may distil over slowly. The retort Fig. 156. — Distilling apparatus used in determining the ammonias in water. (Harrington.) and condenser should have been thoroughly rinsed with ammonia-free water. Collect the distillate, 50 c.c. at a time, in Nessler tubes matched as to caliber, add 2 c.c. of Nessler's reagent to each 50 c.c, and determine the amount of ammonia or nitrogen in each as follows: Place in another Nessler tube of the same caliber a little less than 50 c.c. of ammonia-free water and 2 c.c. of Nessler's reagent, run in from a burette the dilute standard ammo- nium chloride solution until the color exactly matches that of the first 50 c.c. of the distillate, taking care to bring 524 EXAMINATION OF AIR, WATER, AND FOOD the fluid to the same level in the two tubes by the addition of ammonia-free water to one or the other. Repeat the process for each 50 c.c. of distillate until the test shows no more ammonia is coming over from the retort. The total amount of (dilute) ammonium chloride solution used indicates the total amount of nitrogen of the free ammonia. Usually all the free ammonia will come over in the first 150 or 200 c.c. of distillate. Compare the colors by looking down through the tubes on a white surface. Some waters yield so much ammonia in the first 50 c.c. of distillate that a precipitate is formed upon the addition of the Nessler reagent. In such case the process should be repeated with a new 500 c.c. of the water to be examined and one-half or even lesser fraction of the first 50 c.c. distilled should be taken and diluted to that volume with ammonia-free water before adding the reagent. Or all of the distillates may be mixed together, 50 c.c. of this mixture taken, treated with the reagent and its content of ammonia determined by matching its color against that produced in another tube by the standard ammonium chloride solution used as above. This result must, of course, be multiplied by the proper multiple to indicate the amount of free ammo- nia in the total distillate. The free ammonia being deter- mined, allow the retort to cool and add to the water remaining in it 50 c.c. of the alkaline permanganate solution. This, when heated, converts a certain propor- tion of the nitrogenous organic matter of the water into ammonia. Distil as before, estimating the amount of nitrogen in each 50 c.c. of the distillate until ammonia ceases to come over. The amount of ammonium chloride solution thus used will indicate the nitrogen of albuminoid ammonia, and the total amount of ammonium chloride solution used in the whole process gives the nitrogen of the total free and albuminoid ammonia in one-half liter of water. Test for Hardness. — Solutions required: (1) Soap solu- tion: dissolve 10 grammes of old, dry castile soap, free from sodium carbonate and hydrate, in 1 liter of weak (60 per cent.) alcohol. (2) Standard lime solution: dis- TEST FOR FREE AND ALBUMINOID AMMONIA 525 solve 1.11 grammes of chemically pure calcium chloride in 1 liter of distilled water: 1 c.c. of this solution is equiva- lent to 1 mg. of calcium carbonate. Process. — Ascertain how much soap solution is required to make a standard lather with 100 c.c. of distilled water, as follows: Place the water in a flask holding about 250 c.c, and run in the soap solution from a burette, a few drops at a time, corking and shaking the flask well after each addition; the lather should be made up of small bubbles, have a depth of at least one-fourth of an inch and be permanent for at least two minutes. Then standardize the soap solution by diluting 5 c.c. of the standard lime solution to 100 c.c. with distilled water, and determine how many c.c. of the soap solution are required to make a permanent lather as above with it; this quantity, less the number of c.c. needed to make a lather with 100 c.c. of distilled water, represents the amount of soap solution that will neutralize 5 mg. of calcium carbonate or its equivalent. Lastly, determine in the same way the number of c.c. of soap solution neces- sary to make a permanent lather with 100 c.c. of the water to be examined; again subtract the quantity of soap solution requisite to make a lather with 100 c.c. of dis- tilled water, and estimate the amount of calcium carbonate or its equivalent present, as follows — e. g., it takes 2 c.c. of soap solution to make a lather with the distilled water, and 12 c.c. with the diluted standard lime solution; then 12 c.c. — 2 c.c. = 10 c.c, which is equivalent to 5 c.c of the standard lime solution, and accordingly each c.c. of the soap solution is equivalent to 0.5 c.c. of the standard lime solution, or to 0.5 mg. of calcium car- bonate; consequently, if 100 c.c. of the water examined require 17 c.c of soap solution, it must contain (17 — 2) X 0.5= 7.5 mg. of calcium carbonate or its equivalent, or 75 mg. to the liter. This test is not exactly accurate, since there is a gradual lessening in the amount of soap solution needed as the amount of lime increases. A better method, if time permits, is to dilute from 1 to 10 cc of 526 EXAMINATION OF AIR, WATER, AND FOOD the standard calcium chloride solution successively to 100 c.c, testing each dilution with the soap solution as above and thus making a scale to which the amount of soap solution needed for the sample water may be referred. If the sample water shows a hardness greater than that indicated by 10 c.c. of the standard calcium chloride solution, a fractional part of 100 c.c. of the water may be diluted up to that amount with distilled water and the test repeated, making a proper calculation later for the amount used. Tests for Lead, Copper, and Iron. — To 50 or 100 c.c. of water in a white porcelain dish, or in a tall glass jar over white paper, add a few drops of ammonium sul- phide; a dark coloration or precipitate indicates the pres- ence of either lead, copper, or iron, due to formation of their respective sulphides. If only small quantities of one or more of the metals are present, it may be neces- sary to concentrate the water by boiling in order to secure the reaction. It should be remembered that the ammonium sulphide gives some color and that the later addition of acid may also cause some turbidity. Then add a few drops of hydrochloric acid: if the color disap- pears, iron only is present; if it persists, lead or copper is present. In the latter case add a few drops of acetic acid and about 1 c.c. of a strong solution of potassium cyanide: if the color disappears, it is due to copper; if it persists, it is due to lead. If lead only is present, the above test should detect one-tenth of a grain per gallon. The above tests may be corroborated as follows: Partly fill two test-tubes with the original water. To one add a little potassium chromate solution: a turbidity and the deepening of the color to canary-yellow indicate lead. Harvey claims that 0.3 milligramme of lead in 1 liter of water "will show a turbidity from chromate when 250 c.c. are treated with 0.1 gramme of potassium bichromate, and that in twelve hours the precipitate will settle and become still more distinct."^ To the second test-tube add a drop of hydrochloric acid and a few drops of potas- TESTS FOR LEAD, COPPER, AND IRON 527 Slum ferrocyanide solution: a blue color indicates iron, in either the ferrous or ferric form ; a bronze or mahogany- red color indicates copper. Quantitative tests for the above metals may be made by making standard solutions of the respective elements or some of their salts, treating a measured quantity of the original water with the proper reagent as indicated above, and comparing the color produced with that given by a definite quantity of the respective standard solution. Test for Phosphates. — Solutions required: Ammonium molybdate: dissolve 10 grammes of molybdic anhydride in 41.7 c.c. of ammonia (sp. gr., 0.96) and pour slowly into 125 c.c. of nitric acid (sp. gr., 1.20); allow to stand in a warm place for several days until clear. Process. — Slightly acidulate 500 c.c. of water with nitric acid, evaporate to 50 c.c, and add a few drops of ferric chloride and ammonia to slight excess; filter, dis- solve the precipitate in the smallest possible quantity of nitric acid and evaporate to 5 c.c. ; heat nearly to boiling, add 20 c.c. of ammonium molybdate solution; keep the solution warm for one-half hour. If there is an appreci- able quantity of precipitate, collect it on a small, weighed filter-paper, wash with distilled water, dry at 100° F., and weigh. The weight of the precipitate multiplied by 0.05 gives the amount of phosphorus tetroxide (PO4) in the 500 c.c. of water. The importance and relative value of the results of the foregoing tests in determining the purity or safety of a drinking-water, have been given in Chapter V on pages 225 to 228, inclusive. FOOD. Milk. — Good Milk. — Characteristics: ivory white, opaque, neutral or slightly alkaline reaction, no sediment, no unusual or offensive taste or odor, specific gravity, 1.029 1 Harrington, loc. cit., p. 469. 528 EXAMINATION OF AIR, WATER, AND FOOD or above; cream, 10 to 40 per cent, by volume; fats, 3 per cent, or more; total solids, 12.5 per cent, or more. Water is indicated by low specific gravity and by low percentage of cream. Skimming is indicated by a slightly raised specific gravity (2°), by a low percentage of cream, and by a poor color, though the deterioration in color may be dis- guised by the addition of annatto, etc. Watering and skimming are indicated by lowered specific gravity, by low percentage of cream, and by poor color. The specific gravity is determined by the lactometer, or lactodensimeter, in using which correction must be made for temperature, provided the latter varies much from 60° F., the standard. The percentage of cream is determined by the cream gauge or creamometer; the milk should be allowed to stand in the creamometer for at least eight to ten hours, and should be covered. A very high percentage of cream tends to lower the sp'ecific gravity theoretically; but when a milk is rich in fat it is also rich in solids not fat. An acid reaction, unless very slight, indicates souring of the milk or the addition of some preserving acid. A strongly alkaline reaction indicates the addition of some substance like chalk, sodium carbonate, etc., to increase the specific gravity. Such addition is verified by an excess of total solids, and by the effervescence of the latter — after drying — upon the addition of a drop or two of hydrochloric acid. To determine the percentage of total solids: Weigh a small evaporating dish, ' preferably platinum, add 5 to 10 c.c. of milk, and weigh dish and milk to get weight of milk; evaporate to dryness over a water-bath, completing the drying in a water-oven until there is no further loss of weight; weigh dish and contents (total solids); sub- tract weight of dish, multiply by 100, and divide by weight of milk. Result: the percentage of total solids. MILK 529 To determine the percentage of ash: Ignite the total solids over a naked flame until all black specks have Fio. 157. — Lactodensimcter. (Harrington.) Fio. 158. — Bottle for determin- ing percentage of fat by means of the centrifuge. disappeared; cool and weigh; multiply weight of ash by 100, and divide by weight of milk. Result: percentage of ash. 34 530 EXAMINATION OF AIR, WATER, AND FOOD To determine the percentage of fats: Proceed as above with 10 c.c. of milk, and evaporate until the residue is a tenacious pulp, extinguish the flame, fill the dish half- full of ether, stir and triturate the residue thoroughly with a glass rod, decant the ether and filter it through a small filter-paper, reserving the filtrate; add more ether to the residue, stir and triturate as before, and filter, repeating the process three times or until the residue is perfectly white; wash the filter-paper well with ether, collect the latter and add to the preceding filtrate; evaporate the ether filtrate until only the fat remains and its weight is constant; weigh the fat, multiply by 100, and divide by the weight of the milk. Result: percentage of fat. This method when carefully performed is said to be fully as accurate as the extraction (Soxhlet) method, and does not require the more expensive apparatus of the latter. If the residue from which the fat has been exhausted is carefully dried on a water-bath at 100° C. until there is no further loss by evaporation, its weight will be that of the "solids not fat" of the milk. Centrifugal method: Where a centrifuge is available for use, the following method for the fat-determination will be found to give results that are probably accurate to within 0.2 per cent, of fat: Two solutions are necessary: (1) Fusel oil, 37 c.c; wood or methyl alcohol, 13 c.c; hydrochloric acid, 50 c.c (2) Sulphuric acid, sp. gr., 1.83. Into the milk bottle (Fig. 158), which is made to fit the centrifuge and which has a long, graduated neck, 5 c.c of the milk to be examined are introduced by means of a pipette, and to this 1 c.c. of the alcohol solution (1) is added and the mixture well shaken by hand. The sulphuric acid is then added, little by little, with frequent shaking, until the bottle is filled to the topmost (zero) graduation. It is then rapidly whirled in the centrifuge until only the fat occupies the neck as a clear layer, when the actual percentage can be read from the graduations. When the milk is very rich — i. e., containing more than DETERMINATION OF FAT IN MILK 531 5 per cent, of fat — it will be necessary to dilute the milk with an equal volume of water, and then to multiply the Fig. 159. — Meeker tube for test- ing milk in centrifuge. Fio. 160. — Soxhlet extraction apparatus. (Harrington.) 532 EXAMINATION OF AIR, WATER, AND FOOD result by 2. Likewise, cream should be diluted with 4 parts of water and the result multiplied by 5. The same principle is employed in the Babcock and other cream- testers now largely used by dairymen, etc. A somewhat simpler method has been devised by Prof. Meeker, in which the only reagent is sulphuric acid, sp. gr. 1.83, and a tube of different form (Fig. 159) is used. Into this tube the milk is introduced from a pipette holding exactly 8.8 c.c, and having a long delivery end to carry the milk beyond the constricted and grad- uated portion. The sulphuric acid is then added in equal volume, filling the tube to the zero mark, after which the stopper is inserted and the milk and acid thoroughly mixed by inverting and reinverting the tube. This breaks up the casein of the milk and frees the fat, which will collect in the graduated part when the tube is whirled in the centrifuge. Owing to cooling, there may be a slight contraction of the liquid, and the top may be slightly below the zero mark, so it is well to again warm the milk by immersing the tube in hot water, and to give a second whirling for but a moment or two. The percentage of fat is indicated by the difference of the reading of its upper and lower limits. The extraction method:'^ "About 10 grammes of milk are carefully weighed in a glass or porcelain capsule and mixed with about 10 grammes of freshly ignited sand, pumice-stone, or asbestos, and evaporated to dryness on a water-bath. The dish with its contents is then finely pulverized and transferred to a Soxhlet extraction appa- ratus and the fat extracted with ether for at least five hours. The ether extract of the fat is then evaporated to dryness on a water-bath and the residue dried to constant weight (at 100° C.) and weighed. The increased weight of the flask (of the Soxhlet apparatus) will represent the fat in the 10 grammes of milk." A Soxhlet apparatus is so constructed that a quantity 1 Bergey's Hand-book of Practical Hygiene, p. 129. CENTRIFUGAL AND EXTRACTION METHODS 533 of ether is repeatedly evaporated and condensed in it without loss, the condensed ether being made to percolate through substances placed in the upper part of the appa- ratus and to extract therefrom soluble matters, such as fat, which are collected in a small flask below, and from which the ether can finally be evaporated. Test for annatto: A percentage of cream considerably lower than the color of the milk would indicate justifies the suspicion that some coloring-matter has been used. This is frequently annatto. "To about 100 c.c. of milk in a cylinder add a few cubic centimeters of sodium carbonate solution to insure a strongly alkaline reaction during the examination, and then introduce a strip of heavy white filter-paper about 0.5 by 5.5 inches, and set the whole away in a dark place over night. If any annatto color is present, it will, through selective affinity, pass from the milk to the fiber of the paper, which thereby acquires a salmon tint, the depth of which is dependent, naturally, upon the amount of substance present. The strip is withdrawn from the milk, washed gently in running water, and laid upon a piece of paper of the same kind as itself. If so much as 1 part of the annatto solution in 100,000 is present, the strip will show a distinct salmon tint. On dipping the strip into stannous chloride solution the color is changed to pink."^ Test for boric acid: Upon igniting the total solids, boric acid or boron gives a greenish tinge to flame. Place in a porcelain dish 5 c.c. of milk, 1 drop of strong hydro- chloric acid, and 2 drops of a saturated tincture of tur- meric. Dry on a water-bath, remove as soon as dry; cool, and add 1 drop of ammonia on a glass rod. A slaty- blue color, changing to green, is given if borax is present. This test will show tdVit grain of borax. Less will give the green color, but not the blue. Test for salicylic acid and salicylates (Bergey) : Dilute the milk (100 c.c.) with an equal bulk of distilled water ^ Harrington, Practical Hygiene. 5th ed., p. 168. 534 EXAMINATION OF AIR, WATER, AND FOOD at 60° C; precipitate with 8 drops of acetic acid and 8 drops of a solution of mercuric oxide in nitric acid; shake and filter. To the filtrate add 50 c.c. of ether, which takes up the salicylic acid; decant, and filter the super- natant ether. Evaporate this filtrate nearly to dryness, and add a few drops of highly diluted neutral ferric chloride. A violet color indicates the presence of salicylic acid, the depth of color increasing with the amount. To test for salicylic acid in butter, it is first treated with sodium carbonate and the homogeneous mixture acidulated with sulphuric acid, and then shaken with a mixture of equal parts of ether and petroleum ether, after which the supernatant ether is filtered off and treated as above. Ted for formaldehyde (Bergey) : Add an equal volume of water to the milk or butter to be tested, place in a flask on a steam-bath and distil over about one-fourth the total volume. Treat 10 c.c. of the distillate with 2 drops of ammoniacal silver solution (made by dissolving 1 gramme of silver nitrate in 30 c.c. of distilled water and adding ammonia until the precipitate that first appears is redissolved, then diluting to 50 c.c. with water). If formaldehyde is present, it causes a black cloud in the distillate after standing for several hours in the dark. Harrington gives the following test among others: ''Mix in a porcelain dish 10 c.c. each of milk and hydro- chloric acid (sp. gr., 1.2) and 1 drop of ferric chloride solution. Heat and stir vigorously. If formalin has been added, a violet color will appear before the boiling- point has been reached, varying in intensity according to the amount present. This process is exceedingly deli- cate and will detect 1 part in 500,000 in the fresh condi- tion."i According to Hehner, "no formaldehyde could be detected at the end of a week in a sample (of milk) to which had been added 1 part in 100,000; after two weeks none could be detected in a sample of 1 part in 50,000; and 1 For other tests for formaldehyde see Harrington, 5th ed., pp. 170 and 171; and Leffmann and Sevan's Food Analysis, pp. 220-222. TEST FOR FORMALDEHYDE 535 after three weeks only a faint trace could be detected in a sample of 1 part in 25,000."i Butter and Oleomargarine. — Pure butter should have good taste, odor, and color; it should not be rancid, and should not contain too much water or salt, nor should it have any added coloring-matter. The average composi- tion should be about as follows: fat, 82 per cent.; casein, 2 per cent, (riot over 3 per cent.); ash or salts, 2 per cent.; water, 13 per cent. Butter-fat is a compound of glycerin wuth certain fatty acids, some of them volatile and soluble in hot water, others non-volatile and insoluble in hot water. Oleomargarine consists of ordinary animal or vegetable- fats, melted, strained, cooled with ice, worked up with milk, colored, and salted. The fats are usually beef or mutton-fat, lard, or cotton-seed, palm, or cocoanut oil. If care and cleanliness are observed in the manufacture, oleomargarine is not harmful nor innutritions, but it should not be sold as butter. Fraud is to be detected by observing the difference in composition and properties of the fats. For instance: BUTTEB-FAT. BeEF-FAT, ETC. 1. The specific gravity is very 1, Beef-fat, etc., is never above rarely below 910, never below 909.8. 904.5. 2. The soluble, volatile fatty 2. Rarely more than 0.5 percent., acids average between 6 and 7 per never above 0.75 per cent. cent., never below 4.5 per cent. 3. The insoluble fatty acids form 3. Generally about 95 per cent, about 88 per cent, of the total weight of butter fat. 4. The melting-point of the fat 4. Rarely, if ever, above 82** F. varies from 86° to 94° F.; is usu- ally from 88° to 90° F. 5. Is readily and completely solu- 5. Less so, and leaves a residue, ble in ether. 6. Under the microscope pure 6. The contours of the small oil butter-fat consists of a collection of globules are less distinct, and the small oil globules, with an occasional larger ones are more numerous and large one. irregular in size. 7. No crystals, except when the 7. Crystals of the non-volatile fat has been melted. acids are often seen. ^ Lefifmann and Bevan, loc. cit. 536 EXAMINATION OF AIR, WATER, AND FOOD To determine the specific gravity of butter-fat: Melt a quantity of the butter in a beaker in a water-bath at about 150° F. When the fat is perfectly clear and trans- parent, carefully decant the fat from the lower stratum of water, curd, and salt into a fine filter; collect the filtrate and pour into a specific gravity bottle, which has been previously weighed, both when empty and when filled with distilled water at 100° F. See that the bottle is exactly full of the fat, wipe clean, and weigh when the temperature is as near 100° F. as possible, because solidi- fication soon begins below this temperature. Subtract the weight of the bottle, divide by the weight of the water which the bottle will hold, and multiply by 1000; the result is the specific gravity. To find the melting-point: Pour a little melted fat into a small test-tube (2" x i'O and cool. Partly fill two beakers of unequal size with cold water; place the test- tube in the smaller (taking care to allow no water to mix with the fat), and the smaller in the larger, and gently heat the outer beaker. Suspend a thermometer in the smaller, near the test-tube, and note the temperature when the f Sit begins to melt; this is the melting-point. To determine the percentage of insoluble (non-volatile) fatty acids: To 6 grammes of butter-fat add 50 c.c. of alcohol containing 2 grammes of caustic potash (KHO) and boil gently for fifteen or twenty minutes to saponify the fat. Dissolve the soaps thus formed in 150 to 200 c.c. of water, and decompose with about 25 c.c. of dilute hydrochloric acid. The separated fatty acids are poured upon a weighed filter-paper, washed with 2 liters of boiling water, dried at 95° to 98° C, and then weighed. The weight of these insoluble fatty acids should not be over 90 per cent, of the weight of the butter fat. Flour and Bread. — Wheat Flour. — Characteristics: almost perfectly white, smooth and free from grit; no mouldy or unpleasant odor; cohesive when lightly com- pressed; no signs of parasites under the microscope; water less than 18 per cent.; ash less than 2 per cent. BUTTER, FLOUR, AND BREAD 537 "The roller process yields a slightly rough flour, and the hard winter wheat may give a yellowish tinge. Good flour is slightly acid to test-paper, but not to the taste, and an acidity that may be recognized by the senses means a change. Acid flour means sour bread, and any disagree- able taste or odor indicates bad flour. When boiling water is poured on a little flour, there should arise no odor but that of freshly ground wheat."^ To determine the percentage of water and ash: In a weighed platinum (or porcelain) dish place about- 50 grammes of flour, w^eigh, and dry over a water-bath for an hour or so; then complete the evaporation in a water- oven until there is no further loss of weight; weigh, sub- tract this weight, less the weight of the dish, from the original weight of the flour. Multiply the remainder by 100 and divide by the original weight of the flour. The result is the percentage of water. Then ignite the dried flour in the dish and incinerate until there are no longer any black particles and only the ash remains; cool, weigh, subtract weight of dish, multiply the remainder by 100, and divide by the original weight of the flour. The result is the percentage of ash. To determine the percentage of gluten: By means of a glass rod mix a weighed quantity of flour with a little dis- tilled water into a stifle dough; then repeatedly wash away the starch and soluble constituents, kneading the dough with the rod or fingers, and continuing until the wash- water comes away clear; the gluten and a small amount of fat and salt remain. Spread on a weighed dish or crucible lid, dry in a water-oven, and weigh; multiply by 100 and divide by the original weight of the flour. The result is the approximate percentage of gluten. The gluten should pull out into long threads; otherwise, it is poor. "The relative strength and elasticity of the gluten, which are determined comparatively by manipulating a small quantity of flour intimately mixed with half its * Colonel A. A. Woodhull, M.D., article on "Military Hygiene," in The Reference Hand-book of the Medical Sciences. 538 EXAMINATION OF AIR, WATER, AND FOOD weight of water, make a standard for comparison. This is known as the dough-test, and its failure shows weak flour, from poor wheat or imperfect milHng and defective gluten."! An excess of water impairs the keeping quality and lessens the amount of nutriment in the flour. An excess of ash indicates the addition of mineral substances. A deficiency of gluten may also indicate that the flour is not pure wheat flour. Parasites and fungi are especially likely to be found in old, damp, or inferior flour. To test for mineral substances: Shake a little flour in a test-tube with some chloroform, and allow it to stand for a few minutes. The flour floats and any mineral matter sinks to the bottom, when it can be removed with a pipette and examined under a microscope. Wheat Bread. — Characteristics: fairly dry, light, and spongy; clean and nearly white; of pleasant taste; not sodden, acid, or musty; ash not over 3 per cent.; no para- sites or mouldiness; no flour other than wheat; but little, if any, alum; no copper sulphate. Test for alum: Add 5 c.c. of a 5 per cent, tincture of logwood and 5 c.c. of a 15 per cent, solution of ammonium carbonate to 25 c.c. of water; soak a crumb of the bread in this for a few minutes; drain and gently dry; alum is indicated by a violet or lavender color; its absence by a dirty brown color on drying. For further tests and details in work pertaining to a laboratory of hygiene the reader is referred to Fox's Examination of Food, Air, and Water; Kenwood's Hygienic Laboratory; Bergey's Hand-book of Practical Hygiene; Harrington's Practical Hygiene; Leffmann and Bevan's Food Analysis; Standard Methods of Water Analysis of the American Public Health Association; Thresh's Simple Method of Water Analysis. In the latter the author has devised a series of tests requiring the simplest possible apparatus and a group of solid reagents which can be prepared in tabloid form, each piece containing exactly the quantity required for the respective test. The entire outfit, which can be had of Burroughs, Wellcome & Co. or their agents, can be packed in com- paratively small space and is easily transported from place to place, thus enabling the investigator to make his tests at or near the source of supply. 1 Colonel A. A. Woodhull, M.D., loc. cit. INDEX Absorption of foods, 240 Accessory foods, 251 Acetylene gas, 86 Adulterants and preservatives, 274 Adulteration of foods, 274 Aerobic beds for sewage, 423 Air, 69 bacteria in, 75 collection of, 510 currents, determination of ve- locity of, 111 direction of, 115 diseases caused by impure, 91 distribution of, 112, 117 dust in, effect of, 92 examination of, 509 filtration of, 108 purification of, 74 by fire, 131 saturation of, 80 Air-propeller, 122 Air-supply, conduits for, 107 source of, 107 volume of, 106 Alcohol, 279 indications for use and absten- tion, 280 relation of, to food, 280 rules governing use of, 282 use of, in sickness, 281 Alexins, 57 Altitude, effect of change in, 70, 71 Alum in bread, test for, 538 use of, in purifying water, 187, 194, 205 Amboceptors, Ehrlich's, 62 Ammonia, in air, 74 "albuminoid," in water, 226 "free," in water, 226 Amvlopsin, action of, 239 Anderson's process for purifying water, 188 Anemometer, 112 Annatto, test for, in milk, 533 Antigens, 56 Antimicrobin, 67 Antiseptics, 339 Antitoxins, 58 methods of preparing, 63 statistics of use of, 66 theory of, 58 Apparatus for lighting, 83 for steam disinfecting, 343, 344 Aqueous vapor, 73, 79 Area drained by wells, 162, 167 Argon, 72 Army canteen, 491 medical officers, duties of, 457, 492 rations, 476 Arsenic f)oisoning, risk of, 452 Artesian-water, 151, 164 Artesian-wells, 164 Artificial ventilation, 108, 120 Ashes, 389 Ashley biological reduction tank, 433 Aspiration, 110 Atavism, 291 Atmosphere, 69 composition of, 69 impurities in, 74 of mines, 90 natural purification of, 74 of ships, 91 • (539) 540 INDEX Atmosphere of sick-rooms, 105 weight of, 69 Atmospheric contamination, ex- tent of, 103 index of, 103 Autogenetic diseases, causes of, 32 B Bacilli, 40 Bacillus, the colon, in water, 224 Backus heater, 130 Bacteria in air, 75 atypical forms of, 39 classification of, 40 collection of, in air, 510 definition of, 37 differentiation of, 45 discovery of, 37 as an index of purity of filtered water, 204 involution forms of, 39 isolation of different species of, 41 parasitic, 48 in sewer-gas, 87 pathogenic, 48 requirements of, 37 saprophytic, 47 Bacterial examination of air, 510 of water, 224 Bacteriology, 36, 37 Bacterioproteins, 56 Barracks, construction and ar- rangement of, 464 Bathing, 300 rules for, 302 sea, 301 time of, 302 Baths, cold, 301 pubhc, 303 Russian, 304 Turkish, 303 warm, 303 Beans, nutritive value of, 273 Bedding, disinfection of, 362 Beef, 264 Beef -fat, characteristics of, 535 Beef-tea as a stimulant, 278 whole, recipe for, 269 Berkefeld filter, 213, 219 Beverages, 283 carbon dioxide in, 284 ice-water as a, 221 sanitary precautions concern- ing, 284 Bichloride of mercury as a disin- fectant, 348 Bile, action of, 239, 240 Biological action in soil, 158 Blackboards, school, 322 BoiUng, disinfection by, 360 Boric acid, test for, in milk, 533 Bread, 271 test for alum in, 538 Broiling, 268 Broths, 268 Biichner, humoral theory of, 57 Burial permits, 501 Butter, 263 examination of, 535 Butter-fat, characteristics of, 535 Buttermilk, 257 Calcium hydrate, 351 Calcium hypochlorite for polluted water, 188, 476 Camp hospitals, 464, 486 Camps of detention, 384 diseases of, 471 disposal of excreta in, 481 of garbage in, 485 important points regarding, 463 infectious diseases in, 465 latrines, 482 location of, 460 pollution of, 467 of probation, 384 of refuge, 385 typhoid fever in, 466-469 water-supply of, 473 Canteen, army, advantages of, 491 Carbohydrates, functions of, 230, 232, 245 sources of, 245 Carbolic acid as a disinfectant, 349, 369 Carbon dioxide, 72 in atmosphere, 73 INDEX 541 Carl)on dioxide in beverages, 284 in dwellings, 78 effects of, 77 excretion of, 78, 297 normal proportion of, 73 Pettenkofer's test for, 515 poisoning by, 96 respiratory, 82 in soil-air, 89 tests for, 513 monoxide from stoves, 129 poisoning by, 97 proportion of, to nitrogen in diet, 243 Carbonic acid. See Carbon di- oxide. Care of school-houses, 327 Carpets, etc., disinfection of, 362 Census, the, 498 reports, U. S., statistics from, 22-26 Centralized heating, 130 Cereals, 269 Cesspools, dangers of, 392 disinfection of, 391 Cheese, 262 Chemical disinfectants, 347 treatment of sewage, 418 of water, 185 Child labor, 443 Chimneys, use of, for ventilation, 118 Chloride of zinc, 351 Chlorides in water, test for, 518 Chlorin, 188, 352 or chlorides in water, 226, 518 test for, 518 Chlorinated lime, 188, 347 Eoda, 347 Chromium poisoning, risk of, 452 Cistern filter, 153 Cisterns for rain-water, 150, 153 Clark's process for purifying water, 185 Cloak-rooms in school-houses, 325 Closets, earth-, 392 pail-, 392 water-, 405 Clothing, 304 advantages of woollen, 305 conveyance of infection by, 309 Clothing, disinfection of, 362 influence of, upon health, 308 materials usckI for, 305 purpose of, 304 relative absorption of heat by, 309 of soldiers, 480 sophistication of, 308 tests for materials for, 307 Coal, products of combustion of, 82 Coal-gas, composition of, 98 I poisoning by, 98 j products of combustion of, 83 ; Coffee, 278 Cold baths, effects of, 301 Colony, a bacterial, 41 Combustion products, 82 influence upon health, 96 specific gravity of, 84 Comparative mortality figure,506 Condensed rations, 478 Condiments, 251 Congenital diseases, 291 Consanguineous marriages, ob- jections to, 294 Construction and care of wells, 166 of school-hou&es, 322 Contact beds for sewage, 423 Contagion, nature of, 51 Contagious dise'ases, definition of, 32 in schools, 329-335 ophthalmia in schools, 334 Contamination of atmosphere, ex- tent of, 103 Convected heat, 125 Cooking, object of, 241, 267 thoroughness of, 267 of vegetables, 273 Copper sulphate in water, 526 Corn, 270 Corrosive sublimate at a disin- fectant, 348 Cotton in clothing, 306 Cowls, ventilating, 109 ** Cramps," cause of, when bath- ing, 302 Cream, digestibility of, 256 Creolin, 349 Cresols, 349 "Crowd-poison," 81 542 INDEX "Crowd-poison." effects of, 94 Cubic space in ventilation, 106 Culture-media, preparation of, 44 reaction of, 41 sterilization of, 43 temperature of, 41 Darnall filter, 474 Death-certificate, standard, 503 Death-rates,^ 504 d^ily or weekly, 504 showing sanitary gain, 22 standard, 506 zymotic, 504 Deep water, 151, 164 wells, 164 Deficiency diseases, faulty diet in, 252 vitamines in, 251 Delousing stations, importance of, 481 Deodorants, 339 Detention at ports of entry, 375 camps of, 384 period of, in quarantine, 375, 378 Devices for ventilation, 113 Dietetic rules, 241 Dietetic^, 233 esthetic factors in, 233 Differentiation of bacteria, 45 ' Diffusion, 108 law of, 70 rate of, 108 Digestion, gastric, 237 hydrolysis in, 235 intestinal, 239 physiology of, 234 sahvary, 236 Digestive ferments, 234 Diphtheria antitoxin, method of preparing, 63 Direct radiation, 140 Direct-indirect radiation, 141 ■ Diseases affecting animals used for food, 286 bacterial, immunotherapy in, 56 Diseases, classification of, 31 congenital, 288 deficiency, vitamines in, 251 definitions of, 31 and causes of autogenetic, 32 due to drinking-water, 173 to impure air, 91 to respiratory vitiation, 95 endemic, 50 epidemic, 50 important, of war, 471 incubation periods of. 331 infectious, in schools, 329 inherited, 291 methods of combating, 291 occupational, 439 pandemic, 50 specific, 50 study of, 494 transmissible by heredity, 288 zymotic, 50 Disinfectant, definition of, 338 Disinfectants, application of, in quarantine work, 381 chemical, 347, 369 comparative table of, 359 gaseous, 352, 364 mechanical, 342 physical, 363 physiological, 342 thermal, 342 Disinfecting apparatus, steam, 343, 344 Disinfection, 33, 338 of bedding, 362 of carpets, etc., 362 of cesspools, 391 of clothing, 361, 362 by dry heat, 346 efficacy of, 341 evidence as to, 341 of excreta, 348, 349, 360 final, of rooms, 361 by fire, 342 by formaldehyde, 354 by hot water, 345, 364 of infectious cases, 360 personal, 361 of rooms, 361 Schering's method of, 356 of school-houses, 325 of sewage, 437 INDEX 543 Disinfection of sick-room, 360 of spores, 342 by steam, 343, 364 thoroughness of, 341 Trillat's method of, 355 of vessels in quarantine, 381 Disinfector, duties of a, 338 Distillation of drinking-water, 208 Distribution of air, 112, 115 Domestic purification of water, 206 Dress, influence of improper, 308 Drinking-water, distillation of, 208 examination of, 222, 518 infection by, 173 necessity for boiling, 217 Drip-safes, 405 Dry heat, disinfection by, 346 Duration of life, mean, 507 provable, 507 of school work, 315 Dust, influence of, in air, 92 Duties of army medical officers, 457, 492 Duty of physicians, 27 Earth-closets, 392 peat in, use of, 393 Economy in heating, 126 Eggs, value of, as a food, 263 Ehrlich's lateral chain theory, 60 Ejector eewerage system, 391 Emscher tank, 420 Environment, influence of, 34 on predisposed constitutions, 291 Enzymes, action of, 234 characterifcticf of, 235 digestive, 234 of vegetable origin, 242 Epidemic, definition of, 50 Estimation of radiating surfaces, 144 Examination of air, 509 of butter, 535 of drinking-water, 222, 518 of flour, 536 of food, 527 Examination of milk, 527 Excreta, disinfection of, 348, 349, 360 disposal of, in camps, 481 Exercise, 295 amount necessary, 300 effect upon brain development, 299 upon digestive functions, 298 upon excretion, 298 upon heart and circulation, 298 upon heat production, 298 upon muscles, 296 upon respiratory organs and functions, 296 importance of, 295 Exhaust system, 121 Exhaustion theory of Pasteur, 57 Expectant attention, danger of, 286 Expectation of life, 507 External ventilation, 101 Eye-strain, 317 Factors of ventilation, 102 Factory sanitation, 445 Fans, ventilating, 121 Farr, Dr. Wm., 20 Fatigue, causes of, 300 Fats, constructive property of, 248 digestibUity of, 249 functions of, 230, 232, 247 I)roperties of butter- and beef-, 535 sources of, 247 to determine specific gravity of, 536 melting-point of butter-, 536 Fatty acids, to determine insol- uble or non-volatile, 536 Feeble-mindednesj , transmission of, 292, 293 Ferments, digestive, 234 Ferrous sulphate in mechanical filtration, 205 FUter-beds, plan of, 192 Filters, action of sand-, 193 544 INDEX Filters, cistern, 153 cleansing of sand-, 202 construction of sand-, 194 Darnall, 474 functions of sediment layer in, 193 hou&e, 212 material used in sand-, 196 mechanical, 203 percolating, 423 preliminary, 202 ~ rough, 202 sprinkling, 423 trickling, 423 Filtration, 190 of air, 108 of rain-water, 152 rate of, 201 regulation of, 195 of sewage, 424 Fire, disinfection by, 342 Fireplaces, 126 Fish, 265 Fixtures, location of house-, 398 traps of house-, 398 Flies as carriers of infection, 467, 478 Floor space of school-rooms, 324 in ventilation, 107 Flour, characteristics of wheat-, 536 . test for minerals in, 538 to determine the ash in, 537 gluten in, 537 water in, 537 Flues, hot-air, size of, 136 Flush tank. Field's siphon, 413 Food, 229 amount necessary for life and health, 243 cooking of, 241 definition of, 229 functions of, 229 inspection of, 478 of the soldier, 476 tests of, 527 Food-principles, classification of, 229 functions of, 232 properties of, 232 use of, 230 Food-relationship in diet, 243 Food-salts, function of, 232, 249 sources of, 250 Foods, absorption of, 240 accessory, 251 adulteration of, 274 relative value of, 276 use of preservatives in, 275 Forbes sterilizer, 208 advantages of, 211 Forces of ventilation, 108 Formaldehyde, 354, 365 as a deodorant, 359 disinfection by, 354 methods of using, 355 production from methyl alco- hol, 357 regenerators for vaporizing, 355 solutions of, 354 test for, in milk, 534 with permanganate of potash, 358 Formalin, 354, 369 Formic aldehyde, 354 Formula for problems in ventila- tion, 106 Free pratique, 383 Fruits, 274 Frying, 269 Fumigation, 352, 362 Furnaces, hot-air, 133 Furs, 307 Garbage, disposal of, 389 in camps, 485 Gaseous impurities, 76 Gases, poisonous, of occupations, 452 Gas-stoves and grates, 130 Gastric digestion, 237 Germ theory, 37, 49 arguments for, 50 Germicides, 338 Gluten, to determine percentage of, 537 Glycogen, 246 Graphic charts of statistics, 497 Grate fires, open, 126 Grates, ventilating, 127 ! Grease trap, 401 INDEX 545 Crirdirg grain, effect of, 270 Ground-water, 151, 167 current of, 160 purification of, 168 Growth-promoting substances, 252, 257 Haptopbores, 61 Hard water, 154 Hardness of water, 154, 227 permanent, 154 temporary, 154 tests for, 625 Headache in school-children, 317 Health, definition of, 30 of soldiers, 455, 473 Heat, air-movement due to, 110 convected, 125 distribution of, 134, 139 radiant, 125 relative absorption by clothing, 309 transmission of, 139 Heating by hot air, 133 by hot water, 139 by steam, 140 Heliotherapy, 311 Heredity, definition of, 288 importance of observing laws of, 289 Hippocrates, hygienic rules of, 19 Hospital ships, 488 tent, the Munson, 488, 490 tents, 487, 490 Hospitals, impurity of air in, 106 military^ 464, 486 ventilation of, 106 Hot-air flues, shape of, 136 size of, 136 furnaces, 133 air-supply of, 136 combustion of fuel in, 137 limitations of, 139 location of, 134 requirements of, 134 Hot water, disinfection by, 346, 364 heating, 133, 139 House-drainage, 394 35 House-drains, 396 i air inlets to, 397 I connection of, with sewer, ! 397 j with soil-pipes, 397 ' construction of, 397 House-filters, 212 cautions regarding, 212, 220 classification of, 213 dangers of, 212 materials for, 217 requisites of, 213 House-fixtures, connection of, to waste-pipes, 398 House-quarantine, 386 House-warmingj 124 Human exhalations, efifects of, 96 Humidifier, 138 Humidity, excessive, 80 relative, determination of, 510 of warmed air, 137 Humoral theory, 67 Hydrocarbon lamps, 86 Hydrocyanic acia as an insecti- cide, 353 Hydrogen dioxide as a disinfec- tant, 351 peroxide as a disinfectant, 351 sulphide, symptoms due to in- halation of, 98 Hygiene, ancient, 20 definition of, 17 development of, as a science, 20 industrial, 439 military, 456 naval, 492 I order of study of, 26 I personal, 285 ! progress in, 21-26 j reasons for study of, 27-29 I school, 314 scope of, 17-19 ' Hygrodeik, the, 512, 613 Hygrometer, use of, 610 Hypochlorites, use of, to purify water, 187 Ice-water, abuse of, 221 purity of, 221 546 INDEX Illuminating agents, influence of, 83 Illuminating-gas, composition of, 98 poisoning by, 98 Illumination, apparatus for, 85 influence of, on health, 84 Imhoff tank, 420 Immunity, theories of, 57 Immunotherapy, 62 in bacterial diseases, 58 Importance of dietetic habits, 242 Impure air, diseases due to, 91 water, diseases due to, 173 Impurities in air, 74 mortality due to, 93 due to combustion, 82 to respiration, etc., 76 gaseous, 76 Impurity of air in hospitals, 105 Incubation, period of, 53 of infectious diseases, 330 Index of atmospheric contamina- tion, 103 Indirect radiation, 141 Industrial hygiene, 439 fundamental conditions of, 441 Infant mortaUty, causes of, 505 rate of, 505 Infection, conditions requisite for, 53 conveyance of, by clothing, 309 by oysters and clams, 266 by drinking-water, 174 "droplet," 94 Infectious diseases, caufees of, 32 disinfection of cases of, 360 period of incubation of, 53, 330 Inherited diseases, 291 Inland quarantine, 384 Inlets, air, to house drains, 397 ventilation, location of, 116 size of, 117 Inoculation, 50 Inspection, quarantine, 376, 383 Intermittent filtration of sewage, 424 Internal ventilation, 102 Intestinal digestion, 239 Involution-forms, causation of, 39 Iron, effect of, in water, 173 sulphate, 205, 351 test for, in water, 526 Irrigation treatment of sewage, 426 Kefir, 257 Kitchens, camp, care of, 464 in&pection of, 478 rolUng field, 497 Koch's postulates, 52 Koumiss, 257 Kresols, 349 Kuhn formaldehyde generator, 358 Labarraque's solution, 347 Lake-water, 157 Lateral chain theory of immun- ity, 60 Lead, occupations utiUzing, 449 poisoning, risk of, 449 test for, in water, 520 in water, 174 Leather, 307 Leguminous plants, food value of, 273 Level of ground- water, 160 Life-table, factors of, 507 value of, 507 Light, 310 germicidal effect of, 311, 342 importance of an abundance of, 312 influence of, upon health, 310 upon metabolism, 312 penetration of sun-, 311 therapeutic effects of sun-, 311 Lighting agents, influence of, 83 increased by prismatic devices, 313 of school-rooms, 322, 325 Lime, chloride of, as a dibinfec- tant, 347 chlorinated, as a disinfectant, 347 milk of, as a disinfectant, 351 Linen in clothing, 306 INDEX 547 Location of school-houseE, 325 of ventilation inlets, 116 outlets. 115 of Avells, 162, 167 Loomis-Manning filters, 215 Lysins, 62 Lyster bag, the, 476 M Malaria and typhoid fever, 468 prevalence of, among troops, 471 Marriage, 289 proper age for, 289 Marriages, objections to consan- guineous, 294 Mastication, value of, 237, 241 Mean after-lifetime, 507 age at death, 507 duration of life, 507 Meat, characteristics of good, 264 composition of, 264 Meats, cooking of, 267 digestibility of various, 265 diseased, 266 relation of, to disease, 266 Mechanical filters, 203 Medical inspection in schools, 329 Mercury, bichloride of, as a dis- infectant, 348 poisoning, risk of, 452 Metchnikoff, theory of, 57 Meters, water, 148 Micrococci, varieties of, 40 Military hospitals, 464, 486 hygiene, 455 importance of, 456 rations, 476 Milk, 253 care and preparation of, 255 as a cause of disease, 255, 258 characteristics of good, 262, 527 diseases due to, 258 epidemics due to, 260 of lime, 351 pasteurization of, 255 as a protective food, 257 scarlet fever due to, 259 as a source of infection, 258, 261 test for annatto in, 533 ! Milk, test for boric acid in, 533 to determine the ash in, 529 fats in, 530 total soUds in, 528 for formaldehyde in, 534 for salicylic acid in, 533 tuberculosis and, 259 typhoid fever due to, 259 use of preservatives in, 262 Milk-borne epidemics, character- istics of, 260 Mines, atmosphere of, 90 I Moisture in warmed air, 137 I Morbidity of wage earners, 440 I rates, 506 i Mortahty, cause of infant, 505 I due to impurities in air, 93 rate of infant, 505 j Mortality-rate, typhoid, an index ! of water purity, 177, 180 Mortality-rates, 504 ; Movement of heated air, 1 10 Munson hospital tent, 488 Mutton. 265 N Natural ventilation, 108 Naval hygiene, 492 ! Nervous diseases in school-chil- i dren, 315, 318 Nessler's reagent, 522 New York, water supply of, 185 Nitrates test for, 519 in water, 227 Nitrification of organic matters, 47, 158 Nitrites tests for, 521 Schuyten's, 522 in water, 227 Nitrogen, 72 proportion of, to carbon in diet, 243 Nuts, 274 Oatmeal, 270 Objections to stoves, 129 Occupational diseases, 439 prophylaxis of, 453 548 INDEX Occupational morbidity, 440 Occupations, classification of, 446-448 harmful and dangerous, 446 poisonous gases of, 452 utilizing poisonous metals, 449 Oil-stoves, 131 Oleomargarine, 535 Open-air schools, 326 Ophthalmia, contagious, in schools, 334 Opsonic index, 59 Opsonins, 59 Organic excretion, 81 matters in water, 227 Outlets, location of ventilation, 115 Overwork, effects of, in school, 315 Oxygen, 71 absorption of, 78, 297 tension, effect of reduced, 71 Oysters, infection by, and clams, 266 Pail-closets, 392 Pancreatic digestion, 239 juice, 239 Paraform, 354 Paraformaldehyde, 354 Parasites, transmission of, by water, 177 Parasitic bacteria, 48 Parasitology, 36 Pasteur filter, 214 Pasteurization, 255 • Pathogenic bacteria, 48 Peat, use of, in earth-closets, 393 Pepsin, action of, 238 Percolating filters, 423 Percolation of ground-water, 158, 160 Perflation, 110 Period of incubation, 53, 330 Permissible impurity in air, 103 in soil, 159 Peroxide of hydrogen as a disin- fectant, 351 Personal disinfection, 361 hygiene, 285 Petri dish, 43 Pettenkofer's test for carbonic acid, 515 Phagocytosis, theory of, 57 Phosphates in water, 227 test for, 527 Phosphorous poisoning, risk of, 451 Physical examination of water, 222, 518 exercise, effects of, 293 training, aim of, 299 Physiology of digestion, 234 Playgrounds, 328 Plenum system, 121 Plumbing for sewage, 394 Pneumatic sewerage system, 390 Pneumonia, infectiousness of, 26 Poisonous gases of occupations, 452 metals, occupations utiHzing, 449 Pollution of well-water, 162, 167 Population, actual increment of, 498 daily, 504 estimation of, 499 natural increment of, 498 weekly, 504 Pork, 2d5 Portable steam radiator, 130 Post hospitals, 486 Postulates of Koch, 52 Precautions in sick-room, 360 Predisposing conditions, 34 Preparation of culture-media, 44 Preservatives, adulterants and, 274 in milk, 262 use of, in foods, 275 Prismatic devices, increased Ughting by, 313 Probable duration of life, 507 Probation, camps of, 384 Products of combustion, 82 Prophylactic infection, 67 intoxication, 67 Prophylaxis, 33 continuous, necessity for, 25 I of occupational diseases, 453 INDEX 549 Protection bv vaccination, 386 Proteid food, functions of, 230, 232, 244 sources of, 245 Protozoa as a cause of disease, 55 Psychronieter, the, 510, 511 Ptomains, 49 Ptyalin, action of, 236 Public baths, 303 Pumping, effect of excessive, on quality of water in wells, 162, 164 Pure food and drugs act, provi- sions of, 274 Purification of air by fire, 131 of atmosphere, 74 of ground- water, 158 of river-water, 155 of sewage, 416 of subsoil- or ground-water, 158 of water, 178 by chemical treatment, 185 domestic, 206 by filtration, 189 by subsidence, 182 Quarantine, 370 at Canadian and Mexican ports, 383 conditions requiring, 375 history of, 370 house, 386 inland, 384 laws, purpose of, 371 local, 386 origin of, 370 original meaning of, 370 railroad, 385 regulations at ports of depart- ure, 372 of entry, 374 during voyage, 374 school, 330-334 stations, location of, 376 requisites for, 377 treatment of passengers in, 378 of vessels in, 380, 381 Quarantines, inspection of, 376, 383 Radiant heat, 125 Radiating surface, estimation of, 144 Radiation, direct, 140 direct-indirect, 141 indirect, 141 Railroad quarantine, 385 Rainfall, amount of, per acre, 152 Rain-water, 151 cisterns, 150, 153 conductors, trapping of, 398 filtration of, 152 softness of, 154 storage of, 153 Rations, army, 476 Raw vegetables, typhoid fever and, 273 Receptors, Ehrlich's, 61 Recruits, age of, 457 examination of, 456 habits of, 460 qualifications of, 456 rejection of, causes for, 454 Refuge, camps of, 385 Registers, size and locations of, 136 Registration area, 24 records, importance of, 501 Rejection of unfit recruits, 26 Relation of water-supply to typhoid fever, 176 Relative size of school-rooms, 324 value of foods, 276 Removal of sewage, 390 Rennin, 238 Reservoirs, purification in, 182 Respiration impurities, effect of, 77 Respiratory vitiation, diseases due to, 95 Retention theory of Chauveau, 57 River-water, 154 self-purification of, 155 Roasting and broiling, 268 Rooms, final disinfection of, 361 Rubber, use of, as a protective, 307 550 INDEX Salicylates, test for, in milk, 533 Salicylic acid, test for, in milk, 533 Saliva, functions.of, 236 Salivary digestion, 237 Salts, food-, functions of, 232, 249 sources of, 250 Sand ejectors, 202 filters, 192-204 separators, 203 Sanitarians, need for, 29 Sanitary cordon, 384 Sanitation, 33 factory, 445 improved, results due to, 21-24 value of, 21 Saprophytes, functions of, 47 Schering's lamps, 355 method of disinfection, 356 Schizomycetes, 36 School children, eye-strain in 317 headache in, 317 nervous diseases in, 315, 318 physical defects of, 319, 335 prevention of infection of 329 spinal deformities in, 319 teeth of, 336 vaccination of, 334 furniture, arrangement of, 321 influence of, on health, 319 hygiene, 314 infirmaries, 332 pathology, 314 quarantine, 330-334 rooms, dimensions of, 324 Ughting of, 322, 325 relative size of, 324 work, duration of, 315 School-houses, care of, 327 cloak-rooms in, 325 construction of, 322 disinfection of, 325 lighting of, 322, 325 location of, 325 ventilation of, 322 warming of, 322 water-supply of, 326 Schools, contagious diseases in, 329-334 medical inspection of, 329, 335 open-air, 326 Sea-bathing, 301 Seats, arrangement of, in schools, 321 Sedimentation, 182 Self-study, importance of, 286 Septicemia, definition of, 54 ''Septic-tank" system of sewage treatment, 418 advantages of, 418, 421 Sewage, changes in, 416, 421 composition of, 390 disinfection of, 437 disposal of, 415 filtration of, 424 intermittent, 424 pail system of removal of, 392 purification of, 416 removal of, 390 methods of, 391 treatment of, by biological re- duction tank, 419, 433 by chemicals, 417 by electricity, 437 by irrigation, 426 by sedimentation, 417 by the "septic-tank" sys- tem, 418 by straining, 417 by sub-irrigation, 426 ultimate disposal of, 415 water-carriage of, 390, 411 Sewage-plumbing, 394 requirements of, 394 Sewage-pollution of water, 155 Sewage-traps, 399 (see Traps) Sewerage, ejector system of, 391 pneumatic system of, 390 Shone system of, 391 Sewer-gas, 87 bacteria in, 87 composition of, 87 influence of, on health, 99 Sewers, 411 advantages of "combined," 412 shape of, 411 of "separate," 413 construction of, 411 "separate," 413 INDEX 551 Sewers, "separate," specification for, 414 ventilation of, 412, 414 Shallo^v wells, 161 Shoes, influence of improper, 309 Shone sewerage system, 391 Sick-rates, 506 Sick-room, care of, 360 disinfection of, 361 impurity of air in, 105 precautions in, 360 screening of, 360 Silk in clothing, 306 Siphonage of sewer traps, 401 Size of ventilation inlets, 117 Skimmed milk, 257 Smead system of ventilation, 1 16, 323 Soda, chlorinated, 347 Soil, 88 limit of permissible impurity in, 159 purifying action of, 158 Soil-air, 87 bacteria in, 90 circulation of, 89 composition of, 89 influence of, on health, 99 Soil-pipe, 395 connection of, with house- drain, 397 location and construction of, 395 testing of, 403 ventilation of, 395, 397 Soldier, clothing of, 479 food of, 476 instruction of, in hygiene, 486 work of, 491 Soldiers, weights carried by, 481 SoUds, total, in water, 225 Soups and broths, 268 Source of air-supply, 107 Sources of water-supply, 149 Specific diseases, 50 Spinal deformities in school-chil- dren, 319 Spirilla, 40 Spores, characteristics of, 39 formation of, 38 Springs, 151, 160 Spring- water, 160, 165 ! Spring-water, purity of, 160 I Sprinkling filters, 423 I Statistical inquiry, principles of. I 495 I Statistics showing sanitary gain, 21-24 Steam, disinfection by, 3.43, 364 j Steam-heating, 140 Steapsin, action of, 240 Sterilization of apparatus, 43 fractional, 43 mechanical, 342 methods of, 43 of water by boiling, 206 Sterilized milk, 255 Sterilizer, Forbes's, 208 Sterilizers, 44, 207 Stills, 208 Stimulants, 277 cautions in use of, 281 classification of, 277 function of, 277 indications for use of, 277 Stoves, 128 gas-, 130 gases from, 129 objections to, 129 oil-, 131 ventilating, 128 Studies in school, order of, 316 Subirrigation, 426 Subsidence, water purification by , 182 \ Subsoil-water, 151, 157 Sullage water, disposal of, 485 Sulphate of iron, 351 Sulphur dioxide, 352, 364 fumigation with, 353 Sulphuretted hydrogen, 98 Sulphurous acid gas, 98, 352 Surface-water, 151, 154 Tea, 278 and coffee, abuse of, 278 Tents, crowding in, 461 hospital, 489, 490 Tests of well-water, 168 Theory of antitoxins, 58 of Biichner, 57 552 INDEX Theory of Chauveau, 57 of Ehrlich, 60 germ, 48 of Metchnikoff, 57 of opsonins, 59 of Pasteur, 57 of phagocytosis, 57 of Wright, 59 Total soHds in water, 225 Toxalbumins, 48 Toxemia, definition of, 54 Toxins, 48, 58 Training, physical, aim of, 299 Transmission of heat, 139 Trap, bell, 400 grease, 401 McClellan's antisiphoning, 402 S or siphon, 400 Traps, 399 seal of, 399 siphoning of, 401 vent-pipes for, 401 Trickling filters, 423 Tricresol, 350 Trillat's method of disinfection, 355 Trypsin, action of, 240 Tuberculin, use of, 258 Tuberculosis and milk, 259 constructive value of fat in, 248 due to school-life, 319 effect of dust in causing, 93 of pure air in, 79 influence of heredity on, 292 of sunlight on, 311 as an occupational disease, 452 recrudescence of, 319 reduction in mortality-rate of, 24 25 Turkish bath, 303 Typhoid fever as an index of water purity, 177 in camps, 466-469, 473 death-rates in cities, 171 dissemination of, 466-469 due to flies, 467 to milk, 259 to oysters and clams, 266 epidemics of, 176 incubation period of, 466, 469 inoculation against, 469, 473 Typhoid fever, malaria and, 468 raw vegetables and, 273 in rural populations, 169 Tyrotoxicon, 258 Vaccination of school-children, 334 protection by, 386 statistics, 386-388 Variety in food, necessity for, 233 Vegetables, 272 cooking of, 273 typhoid fever and raw, 273 Velocity of air-currents, deter- mination of. 111 Venereal diseases, control of, 492 Ventilating apparatus, 113 grates, 127 stoves, 128 Ventilation, artificial, 108 definition of, 102 devices for, 113 extent of, necessary, 104 external, 101 of factories, 453 factors in, 102 fans, 121 forces of, 108 heating and, 101 inlets, location of, 116 internal, 102 natural, 108 plenum system of, 121 practical points in, 123 problems, formula for, 106 of school-houses, 322 of sewers, 412, 414 Smead system of, 1 16, 323 of soil-pipes, 395, 399 of vent-pipes, 401 of water-closets, 410 Ventilators, 109, 113 Vessels, entry of, 375 treatment of infected, 370 Vigor, conditions for maintain- ing, 244 Vital resistance, value of, 33 INDEX 553 Vital statistics, 494 j grouping in, 496 | influence of, 24 ! methods of obtaining, 498 1 numerical standard in, 496 i units in, 495 of occupations, caution re- ; garding, 441 \ probable error in, 497 recent, 22-24 value of, 495 of series in, 497 variation in, 497 Vitamines, 230, 251 in deficiency diseases, 251 W Warmed air, humidity of, 137 Warming of school-houses, 322 Waste-pipes, 395 connection of, to house-fix- tures, 398 with soil-pipes, 402 Water, 146 ammonia in, 226, 522 bacterial examination of, 224 boiling of, 206, 217 bottle for collecting samples of, 519 chemical examination of, 225 treatment of, 185 chlorin in, 226, 518 classification of, 170, 228 collection of, for analysis, 224 cost of sickness due to polluted, 180 deep- or artesian-, 151, 164 diseases caused by impurities in, 173 double supply of, 148 effects of impure, 177 examination of, 22, 518 excretion of, 297 filtration of, 190 ground- or subsoil-, 151, 157 hardness of, 154, 227, 525 lake-, 157 lead in, 174, 526 level of subsoil-, 160 meters, 148 Water, nitrates in, 227, 519 nitrites in, 227, 521 organic matters in, 227 percolation of, 158, 160 phosphates in, 227, 527 physical examination of, 222, 518 purification of, 155, 158, 178 in household, 206 purity of subsoil-, 161 quantity of, necessary, 146 rain, 151 river-, 154 sewage-pollution of, 155, 162 sources of, 149 spring-, 160, 165 purity of, 161, 165 sterilizer for schools, 207 storage of, 182 subsoil, 157 supply of camps, 473 of New York City, 185 of schools, 326 typhoid fever and, 169 surface-, 151, 154 tests for physical properties of, 222, 518 total sohds in, 225 transmission of infection by, 174 of parasites by, 177 Water-carriage of sewage, 394 Water-closets, 405 connection of, to water-supply, 410 hopper, 408 location of, 410 pan, 406 plug or plunger, 407 requisites for, 405 siphon, 409 valve, 406 ventilation of, 410 washout, 408 Water-puritv, index of, 177, 180 Water-supply of camps, 474 of cities, 147, 171 infection of, 176 relation of, to typhoid fever, 169, 171, 179 of school-houses, 326 Weights carried by soldiers, 481 554 INDEX Well-water, pollution of, 161, 167 testing of, 168 Wells, area drained by, 162, 168 construction and care of, 166 deep or artesian, 164 location of, 162, 167 shallow, 161 Welsbach light, 85 Wheat, 270 bread, characteristics of, 538 flour, 270 characteristics of, 536 Winds as ventilating agents, 109 Women, labor of, 443 Woollen clothing, advantages of, 305 Wright, opsonic theory of, 59 Zinc chloride as a disinfectant, 351 Zooglea, 40 Zymotic diseases, 50 lO 35 67 U. 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