DISEASE PREVENTION DISEASE PREVENTION BY HERBERT H. WAITE, M.D. Professor of Bacteriology and Pathology, University of Nebraska mr”) )) LI IWOHD Jf eA MOHT v8 i baovse NEW YORK THOMAS Y. CROWELL COMPANY PUBLISHERS «111 1 a ’ - a : ; . - 5 A " . © : \ - iy i? ALF \ Fry A BR seg Vy \ b i i fad ht i: : 4 7 shecvs 597761 “.s LC i te / / v v A at ©) Tr on / 3 WwW / PUBLIC HEALTH CopyricHuT, 1926, By THOMAS Y. CROWELL COMPANY Second Printing Printed in the United States of America by J. J. LITTLE AND IVES COMPANY, NEW YORK PREFACE In the realm of medicine there is no division of greater importance than that of disease prevention. It is likewise true that there is mo division in which there are so many false conceptions concerning the causes, sources, modes of transmission, and methods of preventing disease or of controlling it after it has arisen. To solve any problem successfully it is necessary to know the various factors which are con- cerned in its solution. This book has been written with the intention of presenting some of the more important features of the transmissible diseases, together with logical procedures for their prevention and control. The prevention of disease as it is practiced today is based upon discoveries and experiences which have had their evolution in the past. It therefore seemed logical to trace the development of pre- ventive measures from the earliest times, in order to show that present- day practices have been determined by eliminating the visionary and mystic and substituting for them rational methods based upon facts which have been scientifically established. Historical material has been obtained from many sources; much of it from Garrison’s excellent work on the ‘History of Medicine.”’ The attempt has been made to emphasize those things which are generally regarded as established facts. Due consideration has been given, however, to procedures which, though still in the experimental stage, promise to be of value in the future. To include in a book of this size all that is known concerning the prevention of disease would obviously be impossible. Material has been gathered from many sources, which are cited in many instances in the text. The Bibliog- raphy at the end of the volume will be found to contain a list of the principal authorities. A discussion of some of the more characteristic clinical symptoms of individual diseases has been included, in order that the reader may gain some insight of their varied manifestations. Considerable space has been given to the diseases caused by animal parasites—more than is usually devoted to them in a work of this character—since they are more common than is generally believed, and might be avoided by preventive measures. It is not intended to make this book an exhaustive monograph, but it is a digest written especially for all those who have neither a medical nor an engineering background, and who would, therefore, have some difficulty in securing information from original sources. The prevention of the diseases of tomorrow is dependent upon the v COG 5 vi Preface information which is acquired today. It is quite generally admitted that too little attention is paid to the prevention of disease in the curricula of our educational institutions. If this book shall have some influence in creating a greater interest in health problems and disease prevention, particularly in students in our educational institutions and in laymen, the considerable work involved in its preparation will have been worth while. The book is primarily intended for social workers, state and muniei- pal officials, hospital workers, and all those who are engaged in the highly laudable work of combating disease. To add to the sum of human knowledge or experience in this regard is one of our greatest privileges. I wish to acknowledge my indebtedness to all those from whom I have obtained information, particularly those where the sources of citations are not specifically mentioned. In the preparation of the manuscript and in the reading of the proof I have received valuable assistance from Mr. Lawrence F. Lindgren for which I wish to express my warm appreciation. I likewise desire to express my appreciation to the publishers, for their uniform courtesy and forbearance towards me while this book was in the process of preparation. H. H. WaIre THE UNIVERSITY OF NEBRASKA. January 20, 1926 CONTENTS CHAPTER I PAGER INTRODUCTORY AND HISTORICAL . . . Fa 1 Early Contributions in Hysioneimalipos Tnoculetion-Per. sonal Hygiene—Greco-Roman Period—Middle Ages—Origin of Quarantine—Theory of Contagion—The Microscope—Spon- taneous Generation—Eighteenth Century Development— Edward Jenner—Prevention of Puerperal Infection—Louis Pasteur—Sir Joseph Jackson Lister—Period of the Dis- covery of Disease-Producing Bacteria—Public Demonstra- tion of Protective Inoculation Against Anthrax—Rabies Vaccine—Malaria—Robert Koch—Diphtheria Antitoxin— Production of Diphtheria Antitoxin—Lumbar Puncture— Theobald Smith-—Bubonic Plague—Vaccination Against Ty- phoid Fever—Method of Preparation of Antityphoid Vaccine —Method of Administration—Dosage—Filterable Virus— Hookworm Disease—Yellow Fever—African Sleeping Sick- ness—Syphilis—Relapsing Fever—Rocky Mountain Spotted Fever—Typhus Fever—Summary. CHAPTER II THE SCOPE OF SANITARY SCIENCE . . y B37 Sanitary Science—Air—Food Supple Conavimiatie sensi: ‘Water-Borne Diseases—Slow Sand Filtration—Rapid Mechan- ical Filtration—Milk and Other Foods in the Spread of Disease —Milk Inspection—Pasteurization—Graded Milk—Pasteuriza- tion in the Home—Bacterial Food Poisonings—Sewage Re- moval and Disposal—Disposal by Dilution—Sewage Treat- ment—Screening—Sedimentation—Purification ~~ Processes— Broad Irrigation—Intermittent Sand Filtration—Contact Beds—Trickling or Sprinkling Filters—The Activated Sludge Process—Disposal of Sewage in Rural Districts—The Chem- ical Closet—Solid Refuse Disposal—Collection of Solid Refuse — Incineration or Destructor Plants—Reduction Plants. CHAPTER III EPIDEMIOLOGY Pa . 1180 Reasons for Making Roidinloplod TntantaiionsTYisonto Distribution—General Epidemiological Data—Fundamental Data on the Propagation and Transmission of Disease—Sum- mary. vii viii Contents CHAPTER IV GENERAL METHODS OF DISEASE PREVENTION . , Heredity — Air — Temperature — Cleanliness — Constipation— Posture—Foods—Vitamins—Body Weight—Regulation of Diet — Children — Narcotics — Tobacco — Opium and Other Habit-Forming Narcoties—Care of the Mouth and the Struec- tures Within It—Tonsils and Adenoids—Care of the Eyes— Communicable Diseases—Isolation—Preventive Inoculation— Disinfection. CHAPTER V PREVENTION OF DISEASES SPREAD LARGELY THROUGH THE Dis- CHARGES FROM THE INTESTINAL TRACT . . Typhoid Fever—Asiatic Cholera—Hookworm Divkhsenhinelic Dysentery. CHAPTER VI DisEAsES TRANSMITTED THROUGH THE RESPIRATORY TRACT . Tuberculosis—The Common Cold—Influenza—The Pneumonias —Cerebrospinal Meningitis—Poliomyelitis—Diphtheria—Scar- let Fever—Measles—German Measles—Whooping-Cough— Smallpox—Chickenpox—Mumps—Glanders—Leprosy. CHAPTER VII PREVENTION OF DisEASES oF MAN CONTRACTED THROUGH ASSOCIA- TION WITH THE HIGHER ANIMALS . . : Anthrax—Bovine Tuberculosis—Bubonic Platontilnlolsn Paratyphoid Diseases—Foot-and-Mouth Disease—Malta Fever — Hydrophobia — Rat-Bite Fever — Infectious Jaundice — Dermatomycoses—Mycetomas—Tapeworms—Intestinal Flukes —Blood-Flukes—Lung Flukes—Trichiniasis—Larval Tape- worms in Man—Guinea Worm—Giardiasis. CHAPTER VIII Diseases CAUSED BY ANIMAL PARASITES . Hookworm Disease—Intestinal Worms of Evonavat Oochirence Which Give Rise to Mild Disturbances. CHAPTER IX PREVENTION OF INSECT-BORNE DISEASES . . . Malaria—Blackwater Fever—Yellow PovorDenguomTilaviasis —PF'lea-Borne Diseases—Louse-Borne Diseases—The Relapsing Fevers—Tick-Borne Diseases—'T'rypanosomiasis— Encephalitis Lethargica. PAGH 21 123 138 256 354 382 Contents CHAPTER X PREVENTION OF VENEREAL DISEASES . Sephilintionortiaa-sChineralammtinmnlona Tngaiidle: CHAPTER XI PREVENTION OF DISEASES CoNVEYED THROUGH MILK AND OTHER Foobs . Milk-Borne TtortionsiPrivontion of Milk. Bure Tnfortdons: CHAPTER XII PREVENTION OF Foop INFECTIONS AND INTOXICATIONS . Food Infection—Food Intoxication—Ptomain Poisoning. CHAPTER XIII PREVENTION OF WATER-BORNE DISEASES . . . . . . . Methods of Prevention. CHAPTER XIV PREVENTION OF SoIL-BORNE DISEASES . . . . ee Tetanus—Anaérobic Organisms Found in Wonde, CHAPTER XV MiscELLANEOUS COMMUNICABLE DISEASES OF UNCERTAIN CAUSE OR MopE oF TRANSMISSION . Pappataci Peover Tioihmetiotin-Braniate Tepid Oroa Fever—Verruga Peruviana. CHAPTER XVI PREVENTION OF DISEASES DUE TO INDUSTRIAL OR OCCUPATIONAL HAazARDS LowsTutpection-Madicil Banana iinet] Ventilation — Mechanical Ventilation — Heating—Lighting— Personal Cleanliness—Water Supply, Lockers and Towels— Toilets, Spittoons and Cuspidors—Sweeping and Cleaning of Premises—Lunch Rooms and Rest Rooms—Physical and Mental Strain—Protection Against Hazards—Safety Devices —Hoisting Machinery, Elevators, Grinding Devices, Chem- icals, Ladders, Nails, First Aid Kits, and Fire Protection— Occupational Diseases. CHAPTER XVII TuE PuBLic HEALTH NURSE AS A MEANS OF PREVENTING DISEASE ix PAGE 493 532 543 557 570 578 608 Xx Contents CHAPTER XVIII MEASURES FOR THE PREVENTION OF INFANT MORTALITY . CHAPTER XIX VALUE or ScHooL INSPECTION AS A MEANS OF CONTROLLING AND PREVENTING DISEASE CHAPTER XX PREVENTION OF DISEASES TRANSMITTED BY PARENTS To THEIR OFF- SPRING . REFERENCES INDEX oF NAMES . INDEX OF SUBJECTS PAGE 613 617 621 625 631 639 ACKNOWLEDGMENTS Permissions to use copyright material have been granted by the fol- lowing publishers: D. ArpLETON & Co., New York, publishers of: ) Louis Pasteur: His Life and Labors, by M. Radot, translated by Lady Hamilton Preventive Medicine and Hygiene, by M. J. Rosenau A Text-Book of Bacteriology, by H. Zinsser and F. F. Russell P. Brakiston’s Sox & Co., Philadelphia, publishers of : Practical Bacteriology, Blood-Work and Animal Parasitology, by E. R. Stitt Pathogenic Micro-organisms, by W. J. MacNeal Lea & FeBiger, Philadelphia, publishers of : Public Health and Hygiene, by W. H. Park McGraw-Hin Book Co., New York, publishers of : Mosquito Eradication, by W. BE. Hardenburg C. V. Mossy Co., St. Louis, publishers of: Epidemiology and Public Health, by V. C. Vaughan, H. F. Vaughan, and G. T. Palmer Tromas NeLson & Sons, New York, publishers of: Nelson’s Loose-Leaf Living Medicine, Vols. I, II, III, V, VII and Medical Service Volume G. P. Purnam’s Sons, New York, publishers of: Mosquito Control in Panama, by J. A. LePrince and A. J. Orstein ‘W. B. Saunpers Co., Philadelphia, publishers of: Histoire d’un Esprit, by E. Duclaux, translated by Smith and Hedges History of Medicine, by F. H. Garrison A Text-Book of Pathology, by W. G. MacCallum JouN Winey & Sons, New York, publishers of : Animal Parasites and Human Disease, by A. C. Chandler Detailed acknowledgments of the above will be found in the foot-notes PRES I ; Bah DISEASE PREVENTION CHAPTER I INTRODUCTORY AND HISTORICAL FroM the inscriptions of primitive man it is clearly indicated that diseases were thought to arise through supernatural agencies. The views of the ancient peoples of Babylonia, of the Slavs, the Greeks, the Romans, the Celts, the Scandinavians, the Polynesians, and of other races, in regard to disease, must have been very much alike. As a result of this mystical conception, the methods devised for the cure and prevention of diseases in prehistoric times were closely identified with religious beliefs. Relics of the beliefs and of the methods adopted to counteract the evil influences of these agencies have not yet wholly disappeared even among people who are otherwise considered to be intelligent. Natural phenomena, such as winds and storms, earth- quakes and voleanic eruptions, were commonly believed to be due to demons, spirits, gods and other mythical beings. Even as late as 1799 Noah Webster declared that epidemics or pestilences were caused by convulsions of the earth, particularly by earthquakes. From such a conception concerning disturbances in nature transition to the assump- tion that diseases were due to the same or similar causes was not difficult. It is not surprising, therefore, that in early times many objects were worshipped, such as the sun, the moon, stars, rivers, forests, winds, clouds, animals and numerous other objects. Diseases were conceived to be caused by an evil spirit, or they were even regarded as evil spirits in themselves. To appease this spirit primitive man indulged in burnt offerings or similar sacrificial rites. As he became further advanced, a malignant human agency with supernatural powers was considered to be the source of his' trouble, to counteract the effects of which, he resorted to incantations, charms and sorcery. Through dreams he was further led to believe that spirits existed which were released from dead men, animals and plants which exerted their evil influences upon him. To avoid these evil influences he resorted to various charms, incantations and other devices to ward them off or render them innocuous. Early Contributions in Hygiene.—The early Egyptians made some admirable contributions in personal hygiene; the early Persians and Babylonians directed their attention to the casting out of the demons 1 . 2... . .....:t Disease Prevention of disease. , Remains: ‘of the massive Babylonian drains show that the art vf. the proper.’ disposal of sewage had been mastered at this early ‘date. The ancient Hebrews were the founders of public hygiene and consequently the first people to devote their attention to disease pre- vention. This task was allotted to the high priests. The book of Leviticus contains specific and clear directions concerning the methods to be followed in accomplishing this object. Regulations were enacted for the personal hygiene of individuals, the selection of proper food, the avoidance of unclean objects and the prevention of contagious dis- eases. A few quotations from Leviticus and Numbers will clearly show that Moses was as great in hygiene and disease prevention as he was in founding a legal system. ‘‘And the flesh that toucheth any unclean thing shall not be eaten ; it shall be burnt with fire.’ (Leviticus VII, 19.) ‘“All the days wherein the plague shall be in him he shall be defiled ; he is unclean; he shall dwell alone; without the camp shall his habitation be.”” (Leviticus XIII, 46.) ‘‘He shall therefore burn that garment, whether warp or woof, in woolen or in linen, or anything of skin, wherein the plague is: for it is a fretting leprosy ; it shall be burnt in the fire.”’ (Leviticus XIII, 52.) ‘‘Then the priest shall come and look, and, behold, if the plague be spread in the house, it is a fretting leprosy in the house; it is unclean.”” ‘‘And he shall break down the house, the stones of it, and the timber thereof, and all the mortar of the house; and he shall carry them forth out of the city into an unclean place.’ (Leviticus XIV, 44, 45.) Segregation, isolation and disinfection are clearly detailed; garments and other objects are burned to secure complete destruction of the cause of disease. ‘This is the law, when a man dieth in a tent: all that come into the tent, and all that is in the tent, shall be unclean seven days.”” ‘And every open vessel, which hath no cover- ing bound upon it, is unclean.”” (Numbers XIX, 14, 15.) ‘Every thing that may abide the fire, ye shall make it go through the fire, and it shall be clean.’”” (Numbers XXXI, 23.) Smallpox Inoculation.—From very ancient times the Hindus and Persians inoculated normal persons with material taken from the pus- tules of those suffering from smallpox, cared for them during their illness, with a lessening of mortality. As early as the sixth century the Chinese knew of and practiced preventive inoculation against small- pox. Inoculation was performed by placing crusts from convalescing patients in the nostrils of the well, in whom they hoped to produce a mild attack, which would protect them against subsequent infection. It is, however, probable that this practice was not original with them but obtained from India. Personal Hygiene.—Though the Greeks contributed little to public hygiene, their attention to individual hygiene places them in the front ranks of both ancient and modern peoples in this particular field. Their conception of the causes of disease was such that it precluded measures directed towards public disease prevention. According to their view disease arose when any derangement occurred in the proportions or Introductory and Historical 3 combinations of the four elements, fire, water, air, earth, and the four qualities, moist, dry, hot, cold, and the four humors, blood, phlegm, yellow bile, black bile. This conception logically assumes that disease comes from within and hence is not due to something which enters from the outside world. Prevention, therefore, was a matter of individual and not public concern. That this conception of disease was not ac- cepted by all the Greeks is clearly shown in the Odyssey. Ulysses after having slain his wife’s suitors gave these directions: ‘‘Bring blast- averting sulphur, nurse, bring fire! That I may fumigate my walls.”’ Hippocrates, about 400 B. C., held that disease was caused by morbid secretions of the atmosphere, and denied that it arose through demons, spirits or other supernatural agencies. Galen, moreover, recognized the contagiousness of several diseases, such as itch, ophthalmia, rabies, plague and consumption. Greco-Roman Period.—During this period only three important con- tributions to preventive medicine were made. About 70 B. C. Varo is said to have suggested that fevers in swampy places were due to invisible organisms. Vitruvius, an architect (about 50 B. C.), left behind him a record of marvellous achievements in sanitary engineering. Ovid, writing at the beginning of the Christian era, states that the shepherds of his time used sulphur to prevent disease. Middle Ages.—The Middle Ages was a period, in which progress in nearly all activities was in a state of retrogression or at a standstill. According to the early teachings of this period a wound was considered unhealthy if pus did not appear in it, a doctrine which did not disappear until a very recent time. Since it was thought to be a necessary ac- companiment of the healing process, it was called ‘ ‘laudable pus.”” The- odoric, Bishop of Cervia, in a treatise completed in 1266, makes this observation: ‘‘For it is not necessary, as Roger and Roland have writ- ten, as many of their disciples teach, and as all modern surgeons profess, that pus should be generated in wounds. No error can be greater than this. Such a practice is indeed to hinder nature, to prolong disease, and to prevent the conglutination and consolidation of the wound.”” It is indeed interesting to note that only two other men, Mondeville and Paracelsus, upheld this doctrine until Lister in 1867 demonstrated its correctness after an interval of 600 years. Henri de Mondeville (1260- 1320) in his treatise on surgery, gave explicit directions for the aseptic treatment of wounds, following the advice which was credited to Hippoc- rates, of simple cleanliness. He was opposed to the practice followed by Galen and his disciples of putting salve and other preparations in wounds. He advises that the wound should be washed and nothing put into it. He says, ‘‘wounds dry much better before suppuration than after it.”’ ‘‘Many more surgeons know how to cause suppuration than to heal a wound.” Origin of Quarantine.—The Black Plague or Black Death, which is now known as Buboniec Plague, appeared in Europe about 1348 after having almost devastated Asia and Africa. This epidemic is said to have 4 Disease Prevention reached a mortality of more than sixty million people, one-fourth of the entire population. Bocecaccio’s ‘Decameron’ gives a most graphie description of this epidemic. To prevent the spread of this disease the Venetian Republic appointed three guardians of public health who were instructed to quarantine infected areas. The term quarantine is derived from quaranta giorni, which means forty days, the length of time estab- lished for this particular epidemic. As now practiced the length of time that individuals, families, or communities are kept in quarantine varies according to the disease against which quarantine is established. Theory of Contagion.—Girolamo Fracastoro (1483-1553) published a work in 1546, De Sympathia et Antipathia Rerum, De Contagionibus et Contagiosis Morbis, et eorum Curatione (On the harmony and antag- onism of things, on contagions and contagious disease, and their cure), which contains the first definite theory concerning contagion, infection, and the modes of transmission of infectious diseases. He believed that organisms of a colloidal-like nature, 4. e., viscous or gelatinous, and which he called Seminaria contagionum (Breeding places of contagions), though too minute to be seen, were, nevertheless, capable of reproduction in the proper medium, and that they caused disease through the influ- ence of the heat of the body. At about the same time or a little later Paré probably first observed the fly as a carrier of disease. Luigi Cor- naro in his Trattato della vita sobria (Treatise on proper living), brought out in Padua in 1558, is regarded by many as the best treatise on personal hygiene in existence. Sir John Harrington in his ‘‘The Metamorphosis of Ajax,’’ written in 1596, contributes an important improvement in sanitary engineering. In the latter half of this cen- tury special laws were passed governing the sale of foods and the adul- teration of alcoholic beverages. Such phases of municipal hygiene as street cleaning, occupations and the plague were regulated by ordinances in Germany and other parts of Europe. The Microscope.— The invention of the microscope, or rather great improvements on this instrument, furnished the means for more inten- sive investigations concerning the causes of disease. In 1658 Athanasius Kircher, in his Scrutinium pestis (Investigation of plague), gives the details of seven experiments upon the nature of putrefaction, which dem- onstrated how maggots and other living organisms are developed in decomposing matter. He also described ‘‘worms’’ which he saw in the blood of plague patients. Loeffler says they were not plague bacilli but probably red blood cells in rouleaux formation and pus cells. It is, however, quite possible that he did see some of the larger microérgan- isms. He certainly holds priority in ascribing a living contagion, ‘‘con- tagium amimatum,’”’ as the cause of infectious diseases. Antony van Leeuwenhoek, usually called ‘‘ The Father of the Microscope’ (although it was invented by Hans Zansz or his son Zacharias), a linen draper by trade, became interested in lens grinding, first devoting his time to spec- tacle lenses. He became very proficient in the art, and finally turned his attention to the microscope. He succeeded in making a lens which Introductory and Historical 5 was so powerful tnat he was able to see objects which were so minute they had never been seen before. He describes with great accuracy moving bodies, in water, in tartar scraped from the teeth, in feces and various infusions, which he saw through the aid of his microscope. In a paper submitted to the ‘‘Royal Society of Great Britain’ on September 12, 1683, he clearly shows that he actually saw bacteria. The drawings which he made of the objects he observed leave absolutely no doubt concerning their nature. His observations were purely objee- tive. He describes what he saw as follows: ‘With the greatest aston- ishment I observed that everywhere throughout the material which I was examining were distributed amimalcule of the most microscopic dimensions which moved themselves about in a remarkably energetic way.’ He believed them to be minute animals, and this view was held for nearly two hundred years. He has been called the ‘‘Father of Baec- teriology,”’ a designation fully merited. His discovery was that of an observer of facts in no way influenced by subjective assumptions. Spontaneous Generation.—Others were not slow in making similar investigations and formulating theories concerning the origin of these minute organisms. The discovery of van Leeuwenhoek led immediately to a controversy concerning the source from which they emanated. Speculation ran riot, many affirming that they arose spontaneously from the matter in which they were found. Opponents of this theory main- tained that life could not arise from inanimate substances but must arise from preéxisting life. In brief, their view was that of ‘‘biogenesis’’— “omme vivum ex vivo,” all life from life, in contrast with the view of ‘‘abiogenesis’ or spontaneous generation, Francesco Redi in 1668 seems to have been the first to attempt to overthrow the theory of spontaneous generation. He exposed meat in jars, some uncovered, others covered with parchment and finely meshed wire gauze. In the uncovered jars flies swarmed in large numbers and maggots were found on the meat. In a like manner the flies settled upon the covered jars and deposited their eggs upon the parchment and wire gauze. Since the eggs could not pass through the parchment, and were too large even to enter through the fine mesh of the gauze, mag- gots were not found in the meat but were hatched out in large numbers on the coverings of the jars. This experiment settled the matter of spontaneous generation, as far as visible organisms were concerned, in the minds of all thinking men. However, the real controversy over spontaneous generation, which began following van Leeuwenhoek’s discovery, did not reach its eulmina- tion until the middle of the eighteenth century, and was not completely subjugated until the latter half of the nineteenth. Eighteenth Century Development.—Although quinine was intro- duced in the treatment of malaria by the Jesuits as early as 1632, and Sydenham had popularized its use by 1658, it was not extensively used until the beginning of the eighteenth century. In 1712, Francesco Torti, professor of pharmacology at Modena, wrote an important trea- 6 Disease Prevention tise on pernicious malaria which led to the introduction of Cinchona bark in the treatment of this disease. The use of Cinchona, though empirical, was the beginning of a most important advance in the develop- ment of preventive medicine. In 1718 Lancisci ascribed to animalcules the role of being the cause of malaria. Boerhaave is said to have proved a little later that smallpox was exclusively transmitted by contagion. Albrecht von Haller, the master physiologist of his time, spent the latter years of his life as health officer of Berne, Switzerland, after his return to his old home in 1753. Bernardino Ramazzini (1638-1714), in his De morbis artificum diatribe (Modena, 1700) (A dissertation on the diseases of artisans) opened up an entirely new department of med- icine, in which he discusses tuberculosis of miners and stone-masons, describes the diseases and gives directions for the hygiene of these oc- cupations. Siissmilch, in his work published in Berlin in 1742, Die gottliche Ordnung im den Verdnderungen des wmenschlichen Ge- schlechts (The divine order in the changes of the human race), made a valuable contribution to the field of vital statistics which were of great importance in public hygiene. John Peter Frank, born at Rothalben, Bavaria, in 1745, has often been called the founder of public hygiene and sanitation. His work on public hygiene, System einer wvollstin- digen medicinischen Polizei (Complete System of Medical Polity), published by Schwann, at Mannheim (1777-1788), covers the entire period of life ‘‘ from the cradle to the grave.”” Sewerage, water-supply, school-hygiene, sexual-hygiene, suitable benches and meals for children, and medical inspectors or police are all included in his treatise, which may be properly regarded as a masterpiece. Much of the sanitary legis- lation of modern times is based upon his work. Plenciz in 1762 held that every infectious disease had its specific cause. Spontaneous Generation.—In 1745, Needham, an English Catholic priest, began some experiments on sprouting barley. He found that if he placed barley grains in a covered vessel containing water, and al- lowed them to remain in it for a few days, it was teeming with life. In 1758, while in residence on the continent, he continued his work using boiled meat infusions in his experiments. These infusions were placed in vials and sealed with mastic. Again he found the infusions contained, after standing, numerous living microorganisms, and con- cluded that they must have had a spontaneous origin. In 1777, Abbe Lazaro Spallanzani of Scandiano, Italy, a man of rare investigative ge- nius, believing Needham’s results were due to defective experimental methods, placed infusions of meat in flasks, sealed and then boiled them. There was no generation of life in the flasks treated in this manner. Needham held that the heating of the flasks had so changed the contents that life could no longer be generated in them. Spallanzani very easily demonstrated that this was not so by tapping some of the flasks gently and thus producing in them minute cracks. The minute eracks permitted the air to enter from the outside and the infusions soon became turbid from the development of microorganisms. Objeetions were made to these Introductory and Historical 7 experiments and the theory was not completely overthrown until Pasteur in 1860, through his epoch-making experiments on fermentation, showed conclusively that spontaneous generation was a myth. It is not difficult to understand that the full significance of Spallanzani’s experiments was not appreciated, when we take into consideration the stage of scientific development of his time. The full significance of its bearing on disease prevention awaited a later date. Charles White, a Manchester surgeon, in a work on obstetrics, published in London in 1773, reveals himself as a pioneer in aseptic mid-wifery. Johann Ernst Wichmann in 1786, in his ““ Aetiologie der Kritze’’ (Etiology of Scabies), described the itch mite, Sarcoptes scabies, and established its parasitic nature. At the close of the eighteenth century, Edward Jenner (1748-1823) introduced vaccination in England. Within five years after his an- nouncement of the success which he had attained, through the inocula- tion of material taken from cows suffering from cow-pox, its use had spread over the greater part of Europe and the Eastern coast of the United States. Many years before Jenner’s time the practice of pre- ventive inoculation had been carried on in the Orient. At what time it was introduced is not known. The Chinese certainly inoculated those who were in a good physical condition with material taken from the pustules of those suffering with a mild attack of smallpox. Many lives were undoubtedly saved by this procedure, but it was not without its dangers. Those who recovered from the effects of the inoculation were subsequently protected from smallpox. Of those inoculated, one in fifty to one in three hundred died. Since the mortality in smallpox, at the time when inoculation was introduced, was often as high as one out of every three infected, inoculation prevented many deaths. Inocu- lation, however, was a source of danger to those who had not been inocu- lated, since infection was transmitted as readily from an inoculated person as it was from one suffering from smallpox acquired in the usual manner. Moreover, inoculation not infrequently started epidemics of smallpox in communities where the disease was not prevailing. In the epidemics started in this way the mortality was often as great as in smallpox naturally acquired. It has been stated that preventive inocula- tion is mentioned in the Arthava-veda (about 1500 B. C.) and it cer- tainly appears in the ‘‘Regimen (the Flos) Samnitatis’’ (Regulation of Health), which was written about 1100 A. D., and it was at that time known to many of the Oriental Peoples. Inoculation in Turkey.—About the year 1674 preventive inoculation was introduced in Turkey. Dr. Timoni in 1714, Dr. Kennedy in 1715, Dr. Pylarini in 1716, wrote treatises on inoculation, and introduced it in England. The medical profession in England, without investiga- tion, as so often happens, refused to give any consideration to these communications. Sir Hans Sloane, founder of the Royal Society, later its Secretary and President, in 1717, advocated the practice of inocula- tion. Sloane seems to have been the only professional man in England who seriously considered its efficacy. He was not, however, able to 8 Disease Prevention win adherents to the practice of inoculation. To Lady Mary Wortley Montague, wife of the British Ambassador at Constantinople, is due the honor of the introduction of inoculation in England. The following extract from one of her letters is of especial interest: “The smallpox, so fatal and so general amongst us, is here entirely harmless by the invention of engrafting, which is the term they give it. There is a set of old women who make it their business to perform the operation, every autumn in the month of September, when the great heat is abated. People send to each other to know if any of their family has a mind to have the smallpox; they make parties for this purpose, and when they are met (commonly fifteen or sixteen to- gether) the old woman comes in with a nutshell and asks what vein you please to have opened. She immediately rips open that you offer to her with a large needle (which gives no more pain than a common seratch) and puts into the vein as much matter as can lie upon the head of her needle, and after that binds up the little wound with a hollow bit of shell, "and in this manner opens four or five veins. The children or young patients play together all the rest of the day and are in perfect health to the eighth. Then the fever begins to seize them and they keep their beds two days, very seldom three. They have very rarely above twenty or thirty on their faces (sic) which never mark, and in eight days’ time are as well as before their illness. Where they are wounded there remain running sores during the dis- temper, which I do not doubt is a great relief to it. Every year thousands undergo the operation, and the French ambassador says, pleasantly, that they take the smallpox here by way of diversion, as they take the waters in other countries. There is no example of anyone that has died from it, and you may well believe that I am satisfied of the safety of this experiment, since I intend to try it on my dear litlleson.. . .» On March 18, 1718, the three-year-old son above alluded to was inoculated while they were still in Turkey. After returning to England she introduced inoculation there, her five year old daughter being inoculated during April, 1721. For ten years following its introduc- tion in England it met with great opposition. It became more popular later and was practiced extensively until about 1800. On the Continent it never became popular. The London Smallpox Hospital discontinued inoculation of out-door patients in 1808 and of in-door patients in 1822. Prussia prohibited the practice of inoculation for smallpox in 1835. Gregory in 1843 wrote as follows: ‘In 1840 the practice of inoculation, the introduction of which has conferred immortality on the name of Lady Montague, which has been sanctioned by the College of Physicians, which had saved the lives of many kings, queens and princes, and of thousands of their subjects during the greater part of the preceding century, was declared illegal by the English Parliament and all offenders were sent to prison with a good chance of the treadmill. . . . Such are the reverses of fortune to which all sublunary things are doomed.’’ Dr, Introductory amd Historical 9 Zabdiel Boylston (1679-1766) in 1721, following the suggestion of Cotton Mather, introduced inoculation in America. During the sixth epidemic of smallpox in Boston, Mass., Boylston inoculated his son and two negro slaves on June 26, 1721. Before the epidemic ended he had inoculated 244 persons under great opposition and with threats of hanging. Of great interest are the tracts of the Colonial pamphleteers, very rare and most highly prized by those who are so fortunate as to possess them. The following Americans made contributions on inoculation: Benjamin Coleman (1721-22), Isaac Greenwood (1721), William Doug- las (1722-30), Cotton Mather (1722), Zabdiel Boylston (1726), Adam Thompson (1750), Nathaniel Williams (1752), Lauchlin MacLean (1756), Benjamin Franklin (1759), John Morgan (1776), and Benjamin Rush (1781). In the epidemic of 1752 Boston had a population of 15,684. Of this number 5,998 had previously had smallpox. During the epidemic 5,545 persons contracted the disease in the usual manner, and 2,124 took it by inoculation. 1,843 persons escaped the city to avoid the infection. There were, therefore, left in the city only 174 persons who had never had smallpox. In an epidemic in England which occurred in 1764-65, Dutton and Fewster inoculated nearly 20,000 persons. During the War of the Revolution inoculation was practiced to some extent on the Colonial troops. At the beginning of the nineteenth century inoculation had fallen into disrepute since the death rate in smallpox had not been reduced, and Jenner had developed vaccination with cow-pox virus which was almost absolutely without danger to the individual, furnished protection, and was never the origin of an epidemic of smallpox. As Rosenau has tritely said, ‘‘ Inoculation, therefore, protects the individual but endangers the community.”” According to the statement of Plehn inoculation is still practiced in certain parts of Central Africa. It is also said to be in use in certain parts of China and Algiers. Edward Jenner.—In 1798 Edward Jenner announced to the world in his ‘“An Inquiry into the Causes and Effects of the Variole Vaccine, a Disease Discovered in some of the Western Counties of England, Particularly Gloucestershire, and known by the Name of Cow-Pox,”’* the results of one of the most important investigations which has ever been made by man. Edward Jenner, son of a Gloucester- shire clergyman, was born on May 17, 1749. After receiving a general education, he was apprenticed, at the age of 19, to a country physician at Sudbury near Bristol. In 1768, while still engaged in his apprentice- ship, he was consulted by a young country woman. On asking her if she had ever had smallpox, she replied, ‘‘I cannot take that disease for I have had the cow-pox.”” This theory, though not credited by physicians, was commonly accepted by the people not only of the rural districts in England, but also in similar communities on the Continent. Peasants in different parts of Europe, especially in Holstein, Mecklen- & London, S. Low, 1798. 10 Disease Prevention burg, Hanover and Saxony, were firmly convinced of its efficacy. Im- mermann quotes von Humboldt as stating, in his accounts of his travels in the tropics in 1803, that the native shepherds of the Mexican Cor- dilleras believed in the protection afforded by vaccine against smallpox. He further quotes him as making a similar statement concerning the clan of Elihots in Baluchistan. In 1763 Dr. Heim, of Saxe-Meiningen, was told by his father, a clergyman, that milkmaids of the region believed that accidental infection from cow-pox subsequently protected them from smallpox. Benjamin Jesty, a Dorsetshire farmer, success- fully vaccinated his wife and two sons with material taken from a case of cow-pox in 1774. Plett, a schoolmaster near Kiel in Holstein, in 1791 vaccinated two children with bovine virus to protect them against the danger of infection during an epidemic of smallpox. In 1770 Jenner went to London and became a pupil of John Hunter, one of the foremost anatomists of his day, the founder of surgical pathology, a pioneer in comparative physiology and experimental pathology. He confided in Hunter, and asked his advice concerning the wisdom of mak- ing investigations to ascertain whether inoculation of man with cow-pox would furnish protection against smallpox. Hunter in his character- istic way said, ‘‘Don’t think, try; be patient, be accurate.”” In 1778, on returning to Berkeley, he began to make his observations. In the beginning he was himself sceptical, but, as he continued his investiga- tions, he became more and more convinced of its value. In 1780, in a confidential letter to his friend Edward Gardener, he says, ‘‘I have entrusted a most important matter to you, which I firmly believe will prove of essential benefit to the human race. I know you, and should not wish what I have stated brought into conversation; for should anything untoward turn up in my experiments, I should be made, par- ticularly by my medical brethren, the subject of ridicule—for I am the mark they all shoot at.”” During the next sixteen years he carefully studied the appearance of the vesicles and pustules appearing on the hands of those who had accidentally become infected with cow-pox. He kept records of those attacked by and those immune to smallpox, both in the case of those whom he had seen with infected hands and in those who gave a history of having been similarly affected. With the evi- dence he had collected he was now ready to actually test out artificial inoculation. Accordingly on May 14, 1796, he performed his first vac- cination. Jenner’s account of this is as follows:* ‘‘Case XVI.—Sarah Nelmes, a dairymaid at a farmer’s near this place, was infected with the cow-pox from her master’s cows in May, 1796. She received the in- fection on a part of her hand which had been previously in a slight degree injured by a scratch from a thorn. A large pustulous sore and the usual symptoms accompanying the disease were produced in conse- quence. ‘‘Case XVII.—The more accurately to observe the progress of the infection I selected a healthy boy, about eight years old, for the purpose 1 Jenner: Loc. cit. Introductory and Historical 11 of inoculation for the cow-pox. The matter was taken from a sore on the hand of a dairymaid,* who was infected by her master’s cows, and it was inserted, on the 14th of May, 1796, into the arm of the boy by means of two superficial incisions, barely penetrating the cutis, each about a half an inch long. “On the seventh day he complained of uneasiness in the axilla, and on the ninth he became a little chilly, lost his appetite, and had a slight headache. During the whole of this day he was perceptibly indis- posed, and spent the night with some degree of restlessness, but on the day following he was perfectly well. . . . ‘‘In order to ascertain whether the boy, after feeling so slight an af- fection of the system from the cow-pox virus, was secure from the con- tagion of the smallpox, he was inoculated the 1st of July following with variolous matter, immediately taken from a pustule. Several slight punctures and incisions were made on both his arms, and the matter was carefully inserted but no disease followed. The same appearances were observable upon the arms as we commonly see when a patient has had variolous matter applied, after having either the cow-pox or smallpox. Several months afterwards he was again inoculated with va- riolous matter, but no sensible effect was produced upon the consti- tution.” He was not able to continue his observations until the middle of March, 1798, when another epidemic of cow-pox broke out in several of the dairies of the neighborhood. On the 16th of March, 1798, he inoculated William Summers, a five-year-old child, with matter taken from the nipple of one of the infected cows. The vaccination was fol- lowed by symptoms almost identical with those recorded in the first case. The disease was transmitted to William Pead, eight years old, on March 28th, from the matter taken from William Summers. On April 5th several adults and children were inoculated. From the arm of one of these, Hannah Excell, a healthy girl seven years old, matter was taken and inserted in the arms of several children. From the arm of one of these, Mary Pead, five years of age, matter was taken and transferred to the arm of J. Barge, a seven-year-old boy. This investigation, in which he had transmitted bovine virus from one indi- vidual to another through five generations, established the fact that it could be transferred indefinitely and without deterioration. The following quotation from Jenner’s original publications shows how carefully this effectiveness was established: ‘After many fruitless at- tempts to give the smallpox to those who had had the cow-pox, it did not appear necessary, nor was it convenient to me, to inoculate the whole of those who had been the subjects of these late trials; yet I thought it right to see the effects of variolous matter on some of them, particularly William Summers, the first of these patients who had been infected with matter taken from the cow. He was, therefore, inoculated with variolous matter from a fresh pustule; but, as in the preceding * ‘From the sore on the hand of Sarah Nelmes. See the preceding case.’’ 12 Disease Prevention cases, the system did not feel the effects of it in the smallest degree. I had an opportunity also of having this boy and William Pead inoculated by my nephew, Mr. Henry Jenner, whose report to me is as follows: ‘I have inoculated Pead and Barge, two of the boys whom you lately infected with the cow-pox. On the second day the incisions were inflamed and there was a pale inflammatory stain around them. On the third day these appearances were still increasing and their arms itched considerably. On the fourth day the inflammation was evidently sub- siding, and on the sixth day it was scarcely perceptible. No symptoms of indisposition followed.’ “To convince myself that the variolous matter made use of was in a perfect state I at the same time inoculated a patient with some of it who had never gone through the cow-pox, and it produced the smallpox in the usual regular manner.” Jenner’s work was almost immediately taken up in Germany and the practice based upon it soon spread over nearly all Europe. It was introduced into Asia by de Carro. Luigi Sacco, a physician of Milan, spent his lifetime in behalf of preventive vaccination and to him credit is due second only to that of Jenner. Sacco established the use of bovine virus in place of human virus for which the world owes him a debt of gratitude. Vaccination was introduced into the United States by Ben- jamin Waterhouse, professor of medicine at Harvard, who, in 1800, vaccinated his four children. Soon after, Crawford and Smith in Balti- more, James Jackson in Boston, David Hosack in New York, and James Redmond Coxe in Philadelphia, followed in the footsteps of Wa- terhouse. James Smith organized the first vaccine institute in Bal- timore in 1802, and in 1813 Congress established a National Vaccine Agency under his direction. In 1803 Jenner founded the Royal In- stitute for the Extermination of Smallpox, of which he remained the director for many years. The fear of smallpox in New England during the prevaccination period is said by Waterhouse to have been so great that ‘‘the most democratical people on the face of the earth’ were will- ing to submit to ‘‘restrictions of liberty such as no absolute monarch could have enforced.”” Thomas Jefferson, in a letter to Jenner in 1806, wrote as follows: ‘‘Future nations will know by history only that the loathsome smallpox has existed and by you has been extirpated.’”’” The disease has not yet been fully suppressed. If universal vaccination were practiced the world over there is reason to believe this prophecy might be fulfilled. From 1796 to 1798, while carrying on the investigation to corroborate the first successful vaccination, Jenner neglected his prac- tice in order to obtain as much time as possible for work on this problem, which almost completely absorbed his attention. He has de- seribed his attitude at this time as follows: ‘“ While the vaccine discovery was progressive, the joy I felt at the prospect before me of being the instrument destined to take away from the world one of its greatest calamities, blended with the fond hope of independence and do- mestic peace and happiness, was often so excessive that, in pursuing my Introductory and Historical 13 favorite subject among the meadows, I have sometimes found myself in a kind of reverie. It is pleasant for me to recollect that these reflections always ended in devout acknowledgments to that Being from whom this and all other mercies flow.” The attitude of some of the leaders in science towards Jenner’s dis- covery is well expressed in the reply of the Royal Society of London to his request to be allowed to present his conclusions before the mem- bers of that organization. They advised that he ‘‘should be cautious and prudent, that he had already gained some credit by his communi- cations to the Royal Society, and ought not to risk his reputation by presenting to the learned body anything which appeared so much at variance with established knowledge, and withal so incredible.” In June, 1798, his first monograph appeared. It was not, however, presented before the Royal Society. In April, 1798, he had gone to London where he remained until July. Although he spent much time in trying to persuade his professional friends to allow him to demon- strate his discovery, he was not able to arouse their interest. Their antagonism to his findings, however, was vigorous and outspoken. On departing from London he left a supply of vaccine with Mr. Cline of St. Thomas’ Hospital. By Cline it was used as a counter-irritant in a case of hip disease. The usual course of vaccination followed and later Mr. Cline inoculated the child with smallpox matter. The child had been protected by the vaccine and smallpox did not develop. Mr. Cline was so impressed with the results that he became an enthusiastic supporter of Jenner. He tried to persuade him to settle in London and asserted that he would be able to secure an income of £10,000 a year from practice in that city. At this time he was nearly fifty years old, and his reply to Mr. Cline is especially interesting: ‘Shall I, who even in the morning of my days sought the lowly and sequestered paths of life, the valley, and not the mountains; shall I, now my evening is fast approaching, hold myself up as an object for fortune and for fame? Admitting it as a certainty that I obtain both, what stock should I add to my little fund of happiness? My fortune, with what flows in from my profession, is sufficient to gratify my wishes; indeed, so limited is my ambition, and that of my nearest connexions, that were I precluded from future practice, I should be enabled to obtain all I want. And as for fame, what is it? A gilded butt, forever pierced with arrows of malignancy. . . .”’ Nevertheless the years devoted to unremunerative investigation, with travel and other expenses, drew heavily on his resources. On the 17th of March, 1802, a petition was presented to Parliament. A Committee was appointed and following their report he was voted an allowance of £10,000. An amendment which carried an appropriation of £20,000 was lost by two votes. (However, in 1806, Parliament granted him the additional award of £20,000.) At this time a public subscription was suggested, but it was never solicited. For twenty-five years he had spent much time in his investigations before he published his first monograph. 14 Disease Prevention The adverse criticism of his work, which was brought out through the examination of many persons and documents, the open denial of his claim, and the bitter opposition of medical men caused him bitter dis- appointment. The opposition was, however, in a degree silenced by the public recognition given him through this act of Parliament. His feel- ings concerning the whole affair were expressed in a letter written in 1802, in which he says, ‘‘I sometimes wish this business had never been brought forward. It makes me indignant to reflect that one who has, through a most painful and laborious investigation, brought to light a subject that will add to the happiness of every human being in the world, should appear before his countrymen as a supplicant for the means of obtaining a few comforts for himself and family.”’ Jenner died on January 26, 1823, at the age of seventy-three. Among his papers was found a letter with the post mark January 14, 1823. The following quotation is taken from that letter: ‘‘ My opinion of vaccina- tion is precisely as it was when I first promulgated the discovery. It is not the least strengthened by any event that has happened, for it could gain no strength; it is not the least weakened, for if the failure you speak of had not happened, the truth of my assertions respecting those coincidences which occasioned them, would not have been made out.”’ Jenner’s transforming of a country tradition into a valuable method of preventing disease has conferred upon humanity untold blessings. Were it possible to introduce compulsory vaccination throughout the world, the same results might be obtained as have been secured in Prus- sia and Holland. Since the establishment of compulsory vaccination in these countries smallpox has practically ceased to exist. Further facts which have been established in the years since Jenner’s time will be related in a later chapter. Little advance was made in the discovery of disease producing micro- organisms until the latter half of the nineteenth century and as a re- sult little advance was made in the prevention of disease. Isolated obser- vations and minor discoveries, however, made it more and more evident that infectious diseases were due to something living, which could be transmitted from individual to individual. Gaspard, in 1822, took material from infected wounds and introduced it into animals with death as a result. Renuecci, in 1834, confirmed the work of Wichmann on the etiology of itch. Pasteur and Chevreuil, in 1836, showed that meat properly protected from contact with the air and outside objects, did not putrefy, and suggested that infection probably arose from some- thing which got in from the outside. Schulze, in 1836, prepared flasks by boiling as Spallanzani had done, and then introduced air which had first been passed through strong solutions of acids or alkalies. No decomposition took place. The same results were obtained by Schwann, in 1837, by passing the air through heated tubes, and by Schroeder and Dusch, in 1853, by filtering the air through cotton. In 1836 Cagnaird- Latour discovered that the yeast plant was the cause of certain fermenta- Introductory and Historical 15 tions, and had especially studied the organisms from fermenting beer. He observed that it was composed of cells which ‘‘were susceptible of reproduction by a sort of budding, and probably acting on sugar through some effect of their vegetation.”” Schwann, in 1837, showed that its action could be prevented by boiling the solution in which it was present. In 1837 Bassi’s discovery was amplified by Adouin, who showed that muscardine, a disease of silkworms, was caused by a mold (Botrytis bassiana) which was communicated from animal to animal by contact or through the air. Boehm, in 1836, saw organisms in the stools of those ill with Asiatic cholera. The organisms he saw were probably yeast cells which are not the cause of the disease. In the same year Donné described bacteria in syphilitic uleers. Schoenlein discovered the cause of favus in 1839, a vegetable parasite, a higher form than bacteria, which was subsequently named ‘“Achorion schoenleimi.’’ In 1840 Henle considered all the evidence which had been collected concerning infectious diseases, and came to the conclusion that they were due to minute living forms of life. No human disease had as yet been shown to be due to a microscopic orgariism. Assuming that such organisms were the cause of disease, he affirmed that to prove this as- sumption certain conditions must be fulfilled : 1. The microdrganism must be constantly present in the disease. 2. It must be completely isolated from the material in which it was present. 3. When completely isolated from all other material its introduec- tion into the body must produce disease. So complete were the demands which he made for the identification of the cause of disease that they were not essentially altered by Koch in his postulates for confirming the etiology of specific infectious diseases. During the period from 1840-1860, with one exception, no disease had shown a bacterial cause. In 1850 Pollender, Brauel, Davaine and Rayer saw minute rods in the blood of animals suffering from anthrax. The causes of infection in a few relatively unimportant diseases were discovered during this period. Gruby had shown that Herpes tonsur- ans (barber’s itch) was due to a fungus which was named Trichophyton tonsurans, in 1841-1843. Eichstedt had shown in 1846 that Pityriasis versicolor, another skin disease, was caused by the fungus Microsporon furfur. Robin, in 1847, had demonstrated that thrush was due to a yeast-like organism, Qidium albicans. One of the greatest advances in the conception of the mode of trans- mission of infection, together with advice concerning its prevention, was made by Oliver Wendell Holmes in his essay on ‘The Contagiousness of Puerperal Fever,” which first appeared in 1843, in The New England Quarterly Journal of Medicine, a publication of ephemeral existence. In 1855 it was reprinted in ‘‘Medical Essays.”” The impetus which led to this investigation came from a meeting of The Boston Society for Med- ical Improvement. At this meeting he heard a report on a fatal case of child-bed fever, followed by an animated discussion. The physician 16 Disease Prevention who made the postmortem examination had himself died in less than a week. During that week he had attended several women in confine- ment, all of whom were stricken with puerperal fever. Instead of gain- ing the support of the obstetricians, this report was received with ridi- cule and invective. Hodge and Meigs, who held, respectively, the Chairs of Obstetrics in the University of Pennsylvania, and in the Jefferson Medical College, led the assault. These two men were so prominent in obstetrics at that time, that they were at first able to autocratieally control the opinions of their brother practitioners. Since the accept- ance of the conclusions of Holmes was diametrically opposed to their teachings they attacked them with violent abuse and denunciation. In spite of the prestige of Hodge and Meigs, the acceptance of the doctrine of the contagiousness of puerperal fever began to gain a steadily increas- ing number of adherents in the United States and England. In 1852 and 1854 his conclusions were especially attacked, and when his essay was republished in 1855 he replied to these attacks in an intro- duction. In this introduction he says, ‘‘I am too much in earnest for either humility or vanity, but I do entreat those who hold the keys of life and death to listen to me also for this once. I ask no personal favor, but I beg to be heard in behalf of the women whose lives are at stake, until some stronger voice shall plead for them.”” In further com- menting on the vitriolic attacks—which were made by Hodge, Meigs, and others, he says, “When by the permission of Providence, I held up to the professional public the damnable facts connected with the convey- ance of poison from one young mother’s chamber to another’s— for doing which humble office I desire to be thankful that I have lived, though nothing else should ever come to my life—I had to bear the sneers of those whose position I had assailed, and, as I believe, have at last demolished, so that nothing but the ghosts of dead women stir among the ruins.” To obtain the convincing evidence, concerning the eontagiousness of puerperal fever, it was necessary for him to secure information from medical men of large experience in obstetrical practice. His appeal to physicians to furnish him with the necessary data was obtained even though it might mean personal loss and the ruin of their reputations. In the beginning of his essay he lays down the following dictum: “The disease known as puerperal fever is so far contagious as to be frequently carried from patient to patient by physicians and nurses.”’ After the collection of a mass of convincing evidence, he goes on to say, ‘‘The recurrence of long series of cases like those I have cited, re- ported by those most interested to believe in contagion, scattered along through an interval of half a century, might have been thought sufficient to satisfy the minds of all inquirers that here was something more than a singular coincidence. But if, on a more extended observation, it should be found that the same ominous group of cases clustering about indi- vidual practitioners were observed in a remote country, at different times, and in widely separated regions, it would seem incredible that Introductory and Historical 17 any should be found too prejudiced or indolent to accept the solemn truth knelled into their ears by the funeral bells from both sides of the ocean—the plain conclusion that the physician and the disease entered, hand in hand, into the chamber of the unsuspecting patient.’ He next cites a large series of cases of puerperal fever in the United States, the details of which were received in letters, in response to his questions concerning puerperal fever which had occurred in the prae: tice of the writers or had come under their observation. In one of these letters, the writer’s name not being given for obvious reasons, there are recorded two cases of puerperal fever occurring in 1817; in 1830 another much more extensive series. Concerning this series the following statement occurs: ‘‘Until the year 1830 I had no suspicion that the disease could be communicated from one patient to another by a nurse or midwife; but I now think the foregoing facts strongly favor that idea.”’ In 1835 another disastrous period occurred in this same man’s practice with a large series again of puerperal fever. In dis- cussing the cases of those attacked he details several precautions which he took without much avail until he used chloride of lime. While in at- tendance on the last two, who both died, he writes, ‘ While I attended these women in their fevers I changed my clothes, and washed my hands in a solution of chloride of lime after each visit. I attended seven women in labor during this period, all of whom recovered without sickness.”” This last quotation is of especial interest, since the practice of washing the hands in chlorinated lime water was not introduced by Semmelweiss as a routine practice until 1847. After he had given a detailed account of a series of cases sufficiently numerous to convince all fair-minded men, he closes his main conclusion as follows: ‘‘I have no wish to express any harsh feelings with regard to the painful subject which has come before us. If there are any so far excited by the story of these dreadful events that they ask for some word of indignant remonstrance to show that science does not turn the hearts of its followers into ice or stone, let me remind them that such words have been uttered by those who speak with an authority I could not claim.! It is as a lesson rather than as a reproach that I call up the memory of these irreparable errors and wrongs. No tongue can tell the heart-breaking calamity they have caused; they have closed the eyes just opened upon a new world of love and happiness; they have bowed the strength of manhood into the dust; they have cast the hap- piness of infancy into the stranger’s arms, or bequeathed it, with less cruelty, the death of its dying parent. There is no tone deep enough for regret, and no voice loud enough for warning. The woman about to become a mother, or with her new-born infant upon her bosom, should be the object of trembling care and sympathy wherever she bears her tender burden or stretches her aching limbs. The very outcast of the streets has a pity upon her sister in degradation when the seal of promised maternity is impressed upon her. The remorseless vengeance 1 Dr. Blundell and Dr. Rigby in the works already cited. 18 Disease Prevention of the law, brought down upon its victim by a machinery as sure as destiny, is arrested in its fall at a word which reveals her transient claim for mercy. The solemn prayer of the liturgy singles out her sorrows from the multiplied trials of life, to plead for her in the hour of peril. God forbid that any member of the profession to which she trusts her life, doubly precious at that eventful period, should hazard it negli- gently, unadvisedly, or selfishly !*’ To the world Dr. Holmes is best known for his literary productions. It should also not be forgotten that this contribution to medical advance- ment will preserve his name to all the generations yet unborn. The rapid advances in bacteriology during the next twenty-five years fol- lowing this contribution established the wisdom and accuracy of his conclusions. With the meager knowledge which existed at that time concerning the causes of infections, his conclusions as to what should be done to prevent them are intensely interesting. The rules which he formulated are as follows: “1. A physician holding himself in readiness to attend cases of mid-wifery should never take any active part in the post-mortem exami- nation of cases of puerperal fever. “2. If a physician is present at such autopsies, he should use thor- ough ablution, change every article of dress, and allow twenty-four hours or more to elapse before attending to any case of mid-wifery. It may be well to extend the same caution to cases of simple peritonitis. ‘3. Similar precautions should be taken after the autopsy or sur- gical treatment of cases of erysipelas, if the physician is obliged to unite such offices with his obstetrical duties, which is in the highest degree inexpedient. ‘“4, On the occurrence of a single case of puerperal fever in his practice, the physician is bound to consider the next female he attends in labor, unless some weeks at least have elapsed, as being in danger of being infected by him, and it is his duty to take every precaution to diminish her risk of disease and death. “5. If within a short period two cases of puerperal fever happen close to each other, in the practice of the same physician, the disease not existing or prevailing in the neighborhood, he would do wisely to relinquish his obstetrical practice for at least one month, and endeavor to free himself by any available means from any noxious influence he may carry about with him. “6. The occurrence of three or more closely connected cases, in the practice of one individual, no others existing in the neighbor- hood, and no other sufficient cause being alleged for the coincidence, is prima facie evidence that he is the vehicle of contagion. “7. Tt is the duty of the physician to take every precaution that the disease shall not be introduced by nurses or other assistants, by making proper inquiries eoncerning them, and giving timely warning of every suspected source of danger. “8. Whatever indulgence: may be granted to those who have here- Introductory and Historical 19 tofore been the ignorant causes of so much misery, the time has come when the existence of a private pestilence in the sphere of a single physi- cian should be looked upon, not as a misfortune, but a erime; and in the knowledge of such occurrences the duties of the practitioner to his profession should give way to his paramount obligations to society.’ One may gain some idea of how far in advance of the times Dr. Holmes was from quotations from Mumford, describing conditions as they existed in 1873, thirty years after his memorable essay. Mumford says, ‘‘In the hospitals sepsis ran rampant. Secondary hemorrhages, erysipelas, pyemia and ‘hospital gangrene’ were endemic. Some wards, or wings, or whole institutions were closed in vain attempts to stamp out these disorders.’’ ‘‘Sometimes a surgeon would wear the same old operating coat for years, and would pick waxed ligatures from the button-hole of his as- sistant who carried them there for the convenience of his chief.’’ Prevention of Puerperal Infection.—To Semmelweiss, however, is due the honor of having put into practice methods for preventing puerperal infection. In 1846 he was appointed an assistant in the first obstetric ward of the Allgemeines Kramkenhaus in Vienna. He soon noticed that the death rate in ward one, to which he was as- signed, was nearly ten times as great as that occurring in ward two. He discovered that in ward one the women were attended and examined by students who came directly from the dissecting room or morgue, sometimes not even observing the formality of washing their hands. In ward two the women were attended solely by midwives who observed the ordinary rules of cleanliness. From the beginning of his assistance- ship he paid especial attention to autopsies of fatal cases of puerperal fever. In 1847, Kolletschka, Rokitansky’s assistant, died as the result of a dissection wound, and Semmelweiss was present at the autopsy. He observed that the pathological appearances were the same as those he had observed in fatal puerperal septicemia. To him the evidence was convincing that something had been transmitted from the dead bodies to the parturient women. He, therefore, ordered that no student should examine a woman until he had thoroughly washed his hands and sub- sequently allowed them to remain for some time in a solution of chloride of lime containing free chlorine. This rule went into effect in the mid- dle of the year 1847. The results are shown in the table below. Confinements. Deaths. Per Cent. BS46 ec linties sv nnisins 4,010 459 11.4 Sd recs onineic sa iss aise 3,490 176 5, A ee ee vie eine re es 3,656 45 127 Semmelweiss demonstrated that puerperal fever could be almost completely prevented by simple cleanliness and the use of chloride of lime (calcium hypochlorite). He was the real pioneer in the introduc- tion of antisepsis in obstetrics. Like Holmes he was scathingly attacked by the orthodox obstetricians Scanzoni, Siebold, Carl Braun and others. 20 Disease Prevention In Vienna, however, he was warmly supported by Rokitansky, Hebra, Michaelis, and Skoda. Not gaining general support from the profes- sion he became disgusted and sought sympathy from all whom he chanced to meet. Disappointed over his failure to win support he left Vienna and became professor of obstetrics at Budapest in 1854. All his at- tempts to impress upon his colleagues and the medical profession at large the importance of his discovery were in vain. At every opportu- nity he preached his new doctrine, and tried to get it as widely dissemi- nated as possible, in the medical literature of that period. Disappointment over his inability to obtain recognition so affected his sensitive nature that he became insane. He died in an asylum in Vienna in 1865, the immediate cause of his death arising from a septic infec- tion of a finger received during an operation which he performed just before his commitment to the asylum. His first publication on his observations was in 1849, but the most important one, Die Aetiologie, der Begriff, und die Prophylaxis des Kinderbettfiebers (The Etiology, the Comprehension, and the Prophylaxis of Puerperal Fever), did not appear until 1861. The real importance of his work was not appreciated until Pasteur’s discoveries in bacteriology revolutionized medical knowl- edge concerning the origin of disease. In 1906 a monument was erected in his memory at Budapest in recognition of his contribution to pre- ventive medicine. Hermann Klencke in 1843 inoculated rabbits with tuberculous material and a little later had shown that tuberculosis might be trans- mitted by cow’s milk. In 1850 Griesinger became physician in ordinary to Abbas Pasha at Cairo, Egypt. During this service he discovered (1851) the Anchylostoma duodenale (hookworm) the cause of Egyptian Chlorosis. In the same year Bilharz announced the discovery of the Schistosomum hematobium, the cause of Bilharzia, and in the following year the Taenia solium (hog tapeworm) was demonstrated by Kucken- meister. Louis Pasteur.—In the history of science, in respect to the num- ber and importance of his discoveries, Louis Pasteur may be said to be almost without a rival. He was born at Dole, Jura, France, on December 27, 1822, and died near Saint Cloud, September 28, 1895. ‘While in school at Bensancon, he early became interested in chemistry. He continued his studies in chemistry at the Ecole Normale, from which he was graduated in 1847. In 1848, at the age of 26, he became professor of the physical sciences at Dijon and the following year professor of chemistry at the University of Strassburg. From 1854-1857 he was dean of the Faculty of Sciences and professor of chemistry at Lille; from 1857- 1863 director of scientific studies at the Ecole Normale Supérieure at Paris; from 1863-1867 professor of geology, physics, and chemistry at the Xeole des Beaux Arts; from 1867-1889 professor of chemistry at the Sorbonne; from 1889-1895 director of the Pasteur Institute. On the arches over his tomb are inscribed the following list of his most important discoveries: Molecular dyssymmetry (1848), fermenta- Introductory and Historical 21 tion (1857), spontaneous generation (1862), diseases of wine (1863), diseases oi silk-worms (1865), microorganisms in beer (1871), virulent diseases (anthrax, chicken cholera, 1877), preventive vaccinations (chicken cholera, 1880, anthrax, 1881, hydrophobia, 1885). While Pasteur was at Lille he began the study of alcoholic fermenta- tion. He was able to demonstrate that the yeast plant was the cause, confirming the views of Cagnaird-Latour, Schwann and Kiitzing. Dur- ing the next six or seven years he had discovered that the souring of milk, through the formation of lactic acid, was due to a microdrganism smaller in size and of a different form than the yeast cell. In a similar manner he demonstrated that the Mycoderma aceti (mother of vinegar) contained several different forms of microiérganisms and that these were essential for the formation of acetic acid in vinegar. Butyric acid was also found to be due to the presence of a still different form. He further found that the microorganism producing butyric acid, to which he gave the name Vibrione butyrique, did not develop where free oxygen was present. Previous to this discovery, which was made in 1867, it had not even been surmised that any form of life could exist without free oxygen. The importance of this work on fermentation was not fully appreciated at this time. Without doubt Pasteur saw the possibility of applying the same methods of study to the etiology of the infectious diseases, but he did not apply them until a later period. After he had completely demonstrated that alcoholie, lactic acid, butyric acid and acetic acid fermentations were due to the presence of minute organisms, he said, ‘‘The chemical act of fermentation is es- sentially a correlative problem of a vital act beginning and ending with it.”” In 1859, in recognition of his work on fermentation, the Academy of Sciences conferred upon him the prize for Experimental Physiology. The results of the investigations on fermentation led naturally to a re- newed debate among the academicians concerning spontaneous genera- tion, in which Pasteur took an important part. The experimentation which led to its overthrow and Pasteur’s active participation in these investigations has already been reviewed. Pasteur at this time foresaw the possibilities of discovering the causes of infectious diseases through investigations such as he had carried on in his work on fermentation. It is more than probable that he saw the analogy which marks the beginning, progress and ending of fermenta- tions and the similar sequences of events in infectious diseases. Both are marked by a period of inactivity followed by an activity which gradually increases until it reaches a definite limit; then begins to decline until it reaches quiescence. That such definite ideas were in his mind is clearly indicated in a letter which he wrote in 1863, after an inter- view with Napoleon III. In this letter he says, ‘‘I assured the Em- peror that all my ambition was to arrive at the knowledge of the causes of putrid and contagious diseases.” Two years after he had written the aforementioned letter the oppor- tunity came to him for making investigations to demonstrate the cause 22 Disease Prevention of an infectious disease. For several years a mysterious disease of silk- worms had appeared in epidemic form which threatened the destruction of the silkworm and consequently of the silk industry in France. At the request of his former teacher, Dumas, at this time a senator, he undertook the task, though previous to this time, as he wrote in a letter to Dumas, he ‘“had never touched a silkworm.’”’ The work was of an entirely new character since he had previously been chiefly inter- ested in crystallography and chemistry. His work in fermentation which had required the use of the microscope had been excellent preparation for the work which he now had in hand. During the first month of his investigation he discovered that moths, worms, and eggs were all in- fected. He also ascertained that the moth was the responsible agent in the transmission of the disease. By selecting moths which were shown by the microscope to be free from the infection, he was able to secure a new breed by using the eggs of non-infected moths. In this way the disease was arrested and finally suppressed. In this investigation he fed silkworms with infected mulberry leaves and reproduced the disease in them, which demonstrated another way in which it might be transmitted. His work on this investigation continued for five years, in which time he not only discovered the cause of the disease which he was investigating, pébrine, due to a protozoon, Nosema bomby- sis, but also the cause of another disease, flacherie, in which the infecting agent was a bacterium of intestinal origin. ‘While engaged in the investigation of pébrine he was still continuing his work on fermentation. At this time France was suffering heavy losses from the spoiling of wine in storage and in transportation. It be- came sour, bitter and muddy, and was often discarded on account of these so-called diseases. He ascertained that if the wine were heated and allowed to stand for some time at a relatively low temperature it retained its flavor and did not later deteriorate. To this process was given the name ‘‘pasteurization.”” The term pasteurization is now most frequently heard in connection with milk, but its use in the preserva- tion of milk was preceded by its application in the preservation of wine. As a result of his work on fermentation we apply today the principle of pasteurization in the preservation of other foods, and methods of canning where a much higher temperature is used, is based upon this principle. After the process of pasteurization had been shown to be of practical value, Pasteur said, ‘‘ Nothing is more agreeable to a man who has made science his career than to increase the number of discoveries, but his cup of joy is full when the result of his observations is put to immediate practical test.”’ In 1868 Pasteur was afflicted with a cerebral hemorrhage which left him partially paralyzed. Two years later the Franco-Prussian War broke out and all scientific work in Paris was arrested. During the decade from 1870-1880, although workers were busily engaged with prob- lems suggested to them by Pasteur’s discoveries, the actual realization of the goal which was being sought did not arrive until the following Introductory and Historical do decade. During the ninth decade the causes of several important infec- tious diseases were discovered, the principle of specific vaccine treatment was made clear, and Lister’s practice of antiseptic treatment was begin- ning to gather more and more adherents. Sir Joseph Jackson Lister.— Before Pasteur had announced his dis- covery that fermentations and putrefactions were caused by living organisms, Lister had believed in and practiced scrupulous cleanliness in his surgical operations. In addition he had used deodorants in the operating room with the hope of lessening death through infections of wounds which were then of exceedingly frequent occurrence. Accord- ing to his own statistics on amputations from 1864-1866 his death rate was 45%. He had noticed that wounds which healed by first intention were never accompanied by putrefaction. By chance he ran across some of Pasteur’s publications on fermentation and putrefac- tion. He was very much impressed and the suggestion was borne in upon him that the same or similar forms of life might be responsible for the suppuration which occurred so frequently in wounds. Pasteur had been able to sterilize the material in which fermentation was taking place through heat, but it was obvious that such a procedure could not be used on living tissue. It occurred to him that some chemical substance might bring about the same results in wounds that Pasteur had been able to secure in fermentation and putrefaction through heat. He accordingly tried zinc chloride and the sulphites, but did not get the results he had hoped to obtain. In the Lancet for March 16, 1867, Lister published an article ‘‘On a New Method of Treating Compound Fracture, Abscesses, etc., with Observations on the Condition of Sup- puration.”” In this article he says, ‘‘Turning now to the question how the atmosphere produces decomposition of organic substances, we find that a flood of light has been thrown upon this most important subject by the philosophic researches of M. Pasteur, who has demonstrated by thoroughly convincing evidence that it is not to oxygen or any of its gaseous constituents that the air owes this property, but to minute par- ticles suspended in it, which are the germs of various low forms of life, long since revealed by the microscope, and regarded as merely accidental concomitants of putresecence, but now shown by Pasteur to be its essential cause, resolving the complex organic compounds into sub- stances of simpler chemical constitution, just as the yeast plant converts sugar into alcohol and carbonic acid. “ Applying these principles to the treatment of compound fracture, bearing in mind that it is from the vitality of the atmospheric particles that all the mischief arises, it appears that all that is requisite is to dress the wound with some material capable of killing these septic germs, pro- vided that any substance can be found reliable for this purpose, yet not too potent as a caustie. ““In the course of the year 1864 I was much struck with an account of the remarkable effects produced by carbolic acid upon the sewage of the town of Carlisle, the admixture of a very small proportion not 24 Disease Prevention only preventing all odor from the lands irrigated with the refuse mate- rial, but, as it was stated, destroying the entozoa which usually infest cattle fed upon such pastures. ““My attention having for several years been directed to the subject of suppuration, more especially in its relation to decomposition, I saw that such a powerful antiseptic was peculiarly adapted for experiments with a view to elucidating that subject, and while I was engaged in the investigation the applicability of carbolic acid for the treatment of com- pound fracture naturally occurred to me. “My first attempt of this kind was made in Glasgow Royal Infirmary in March, 1865, in a case of compound fracture of the leg. It proved unsuccessful, in consequence, as I now believe, of improper management; but subsequent trials have more than realized my most sanguine anticipations. . . .”’ Lister’s method of treating wounds with carbolic acid is today still practiced in principle, though some of the details have been discarded. He cleansed wounds by wiping them out with carbolic acid and after- wards applied a dressing of lint saturated with it. The field of opera- tion, instruments, hands of the operator, assistants, and all others who came in contact with the patient, sponges, dressings, and in fact every- thing which was used in the operation, was cleansed in the same way. In addition the room in which the operation was performed was sprayed with vaporized carbolic acid. Today spraying of the well-kept operat- ing room with carbolic acid or other solutions has been discarded since danger of infection from the air is exceedingly slight. Although Lister’s method met with prompt and marvellous results in his own hands, its adoption by others was very slow. In 1870 he suggested that it be tried out in the Franco-Prussian War, but this advice was not followed until near the close of the war. In 1875 several of the more noted surgeons of Germany accepted Listerism, as the method was called, with most sat- isfactory results. Listerism, however, was not generally accepted until about 1883. When we consider the frightful ravages which were due to infections of wounds prior to Lister’s introduction of antisepsis, it seems strange that all surgeons did not adopt the method which he had so clearly demonstrated was the most potent means of saving life in surgical practice that had ever been introduced. It was the means by which ‘‘hospital gangrene,’’ the nightmare of all surgeons, was wholly abolished ; surgical fevers were reduced to a minimum; child-bearing was freed from its greatest peril; it permitted operations to be per- formed successfully on parts of the body which were previously avoided, such as the cranium, the abdomen and the thorax, since operations on these regions usually had resulted disastrously. Lister logically rea- soned that if fermentation and putrefaction were due to living organisms, suppuration had a similar cause. To avoid infection of wounds it was, therefore, necessary to employ some means of destroying or rendering ineffective these assumed living organisms. Tt is not possible to esti- mate the extent of relief from suffering and the number of lives which Introductory and Historical 25 have been saved as a result of the conclusions which Lister formed as a direct result of Pasteur’s experiments on fermentation and putre- faction. In an address delivered in 1892 at Pasteur’s jubilee, Lister pays the following tribute to this justly renowned investigator: ‘‘Truly there does not exist in the entire world any individual to whom the medical sciences owe more than they do to you. Your researches on fermenta- tion have thrown a powerful beam, which has lightened the baleful dark- ness of surgery, and has transformed the treatment of wounds from a matter of uncertain and too often disastrous empiricism into a scientific art of pure beneficence. Thanks to you, surgery has undergone a com- plete revolution, which has deprived it of its terrors and has extended almost without limit its efficacious power.”’ Period of the Discovery of Disease-Producing Bacteria.— Previous to 1880 in only three diseases had a bacterial cause been demonstrated. About 1850 Davaine, Pollender, Rayer and Brauell saw anthrax bacilli in the blood of cattle suffering from anthrax. In 1863 Davaine trans- mitted anthrax to healthy cattle by inoculating them with blood from animals suffering from this disease. In 1876 Koch demonstrated that the rods present in anthrax blood were the cause of the disease. In two diseases, where it was possible to recognize bacteria by direct examina- tion because of their number, Neisser, in 1879, discovered the gonococcus, the cause of gonorrhoea ; in the same year Hansen discovered the leprosy bacillus. During the decade 1880-1890 the causes of a number of im- portant diseases were discovered. Previous to this time the methods em- ployed for demonstrating and isolating bacteria were not sufficiently de- veloped, and as a result advance was slow. Direct examination of the discharges, secretions, blood, organs and tissue juices, the inoculation of animals with these and with cultures grown in fluid culture media, such as beef tea, milk, ete., were the methods then employed. If only one type of organism were present it was not difficult to obtain satisfactory results, but if, as frequently happened, several organisms were present in the material, it was almost impossible to separate them. This latter difficulty was overcome by Koch in 1881 through the use of a solid, transparent medium obtained by adding gelatin to beef broth. This medium enabled investigators to make rapid strides in isolating individual bacteria and thus separating them from one another and from all other material. This was accomplished in the following way: The material containing the bacteria was introduced into heated and, therefore, liquid gelatine in small amounts. It was then distributed as evenly as possible throughout the gelatine, allowed to cool and become solid. By this means individual bacteria were held in definite places in the gelatine. In a short time the individual germ began to multiply and numerous individual and iso- lated colonies were formed. This made it possible to obtain material from a single and specific original organism. Since some microdrgan- isms could not be grown at temperatures much below that of the body, gelatine was not suitable as a culture medium for separating such or- 26 Disease Prevention ganisms, since it became liquid several degrees below the temperature of the body. Frau Hesse introduced agar-agar a little after the intro- duction of gelatine, and this medium, since it was transparent and re- mained solid at body temperature, furnished a means of isolating bac- teria which would not grow at the ordinary or room temperature. An- other important aid in the study of microérganisms was the introduction of the aniline dyes, by Weigert, in 1876. In 1871 he had succeeded in staining bacteria with picro-carmine, but later found the aniline dyes vastly superior for this purpose. The introduction of the Abbé con- denser (about 1880) marked a still further advance, since it permitted of much more intense illumination of the microscopic field and hence made it possible for the microscope to reveal objects and details of objects which had not hitherto been visible. During the decade 1880-1890 the following discoveries were made: The causal relationship of bacteria to typhoid fever by Eberth in 1880, to lobar pneumonia by Pasteur and Sternberg in 1880 and by Fraenkel in 1884, to pus infections by Rosenbach in 1881, Pasteur, Koch, Ogston ~ and Fehleisen at a little later date, to tuberculosis by Koch in 1882, to glanders by Loeffler and Schiitz in 1882, to diphtheria by Klebs and Loeffler in 1883, to tetanus by Nicolaier in 1884, to B. coli infections by Escherich in 1886, to Malta fever by Bruce in 1887, to epidemic cerebro- spinal meningitis by Weichselbaum in 1887. Before continuing the account of the discoveries following the year 1890, let us return again to Pasteur and some of his important discoveries during the decade we have been discussing. In 1880, while Pasteur was investigating an epidemic of chicken cholera, he isolated the cause and was carrying on experimental work in connection with the causal microorganism. It was his usual practice to use, for inoculation of experimental animals, cultures which had been growing in culture media for only twenty-four hours. While away from home on a vacation, some cultures of the chicken cholera bacillus, which he had made just before his departure, had entirely escaped his memory. On his return he inoculated a fowl with one of these cultures. Much to his surprise the animal did not die. Since this was contrary to all his previous experience, he looked about to see if he could discover a reason for this result. He soon discovered that he had, quite by chance, used one of the old cultures instead of one which had been grown for only twenty-four hours. He next proceeded to inoculate a fowl with one of these cultures, waited several days, then inoculated it again with a fresh twenty-four-hour-old culture. At the same time he inoculated an- other fowl, which had not been subjected to the old culture, with the same twenty-four-hour-old culture. The fowl which had received the two in- oculations did not die, the one receiving only the fresh culture promptly succumbed. Subsequent experiments were followed by similar results. Pasteur’s active mind quickly grasped the significance of his dis- covery. A hundred years before Jenner had established empirically that vaccination with material from cow-pox protected against small- Introductory and Historical 27 pox, but he did not have the time or scientific foundation to determine why or how such protection was effected. Pasteur immediately grasped the meaning not only of his own discovery, but at the same time also saw that the fundamental principle was the same in smallpox vac- cination. Though in method and the nature of the diseases there were great differences, he was convinced that the reason in each instance was a weakened virus. In vaccination against smallpox the virus was weakened by passage through the cow; in chicken cholera by allowing the germ to grow in the presence of an abundant supply of oxygen and in the presence of its own waste products for a considerable period of time. In both instances, though the weakened virus did not cause death or severe disease, it did cause a mild form of the respective diseases, with subsequent protection against disease from the introdue- tion of virulent (unmodified) virus. The practical results from vaccina- tion in chicken cholera did not prove of as much value as was at first anticipated. Nevertheless, the principle established has led to results of immense value in other diseases. Anthrax Vaccination.—Following the work on chicken cholera, Pasteur next turned his attention to anthrax. In chicken cholera the virus had been weakened by prolonged artificial cultivation. About this time Toussaint had shown that cultures of the anthrax bacillus could be so attenuated (weakened) by heating to a temperature of 55° C., that animals inoculated with some of this attenuated material did not die, as a rule, when subsequently inoculated with a young and virulent culture. Since the virus attenuated by heating to 55°C. did not always protect, Pasteur began an investigation to find a method by means of which constant results might be obtained. Through experiments he found that if he grew cultures for some time at a temperature of from 42°-43°C. they became so attenuated that they were no longer capable of producing disease. The introduction of these cultures in animals protected them from subsequent infection with the virulent anthrax bacillus. To protect animals from infection with anthrax he proceeded as follows: Cultures of the anthrax bacillus were grown for four weeks at a temperature of from 42°-43°C., the ‘‘first vaccine.”” Animals were inoculated with cultures made in this way and after waiting twelve to fifteen days they were again inoculated with cultures grown at the above temperature for two weeks, the ‘‘second vaccine.” Public Demonstration of Protective Inoculation Against Anthrax.— In a translation from the French, by Lady Claud Hamilton of ‘‘Louis Pasteur: His Life and Labors,”’ by his son-in-law, M. Radot, the follow- ing account of Pasteur’s Public Demonstration is given. “It was on February 28, 1881, that Pasteur communicated to the Academy of Sciences, in his own name and in those of his two fellow- workers, the exposition of his great discovery. Loud applause burst forth with patriotic joy and pride. And yet so marvellous were the results that some colleagues could not help saying, ‘There is a little ro- 1D. Appleton & Co., 1885. 28 Disease Prevention mance in all this.” All this reminds one, in fact, of what the alchemist of Lesage did to the demons which annoyed him. He shut them up in little bottles, well corked, and so kept them imprisoned and inoffen- sive. Pasteur shut up in glass bulbs a whole world of microbes, with all sorts of varieties which he cultivated at will. Virulence, attenuated or terrible; diseases, benign, or deadly, he could offer all. ‘‘Hardly had the journals published the compte rendu of his com- munication, when the President of the Society of Agriculture in Melun, M. le Baron de la Rochette, came, in the name of the society, to invite Pasteur to make a public experiment of splenic fever vaccination. ‘‘Pasteur accepted. On April 28 a sort of convention was entered into between him and the society. The society agreed to place at the disposal of Pasteur and his two young assistants, Chamberland and Roux, sixty sheep. Ten of these sheep were not to receive any treat- ment, twenty-five were to be subjected to two vaceinal inoculations at in- tervals of from twelve to fifteen days, by two vaccines of unequal - strength. Some days later these twenty-five sheep, as well as the twenty- five remaining ones, were to be inoculated with the virus of virulent splenic fever. A similar experiment was to be made upon ten cows. Six were to be vaccinated, four not vaccinated ; and the ten cows were afterwards, on the same day as th: fifty sheep, to receive inoculation from a very virulent virus. ‘‘Pasteur affirmed that the twenty-five sheep which had not been vae- cinated would perish, while the twenty-five vaccinated ones would re- sist the very virulent virus; that the six vaccinated cows would not take the disease, while the four which had not been vaccinated, even if they did not die, would at least be extremely ill. . . . “The experiments began on May 5, 1881, at four kilometers’ dis- tance from Melun, in a farm of the commune of Pouilly-le-Fort, belong- ing to a veterinary doctor, M. Rossignol, Secretary-general of the Society of Melun. At the desire of the Society of Agriculture, a goat had been substituted for one of the twenty-five sheep of the first lot. On the fifth of May they inoculated, by means of the little syringe of Pravaz— that which is used in all hypodermic injections—twenty-four sheep, the goat, and six cows with five drops of an attenuated virus. . . . “On May 31 very virulent inoculation was effected. Veterinary doe- tors, inquisitive people and agriculturists formed a crowd around this little flock. The thirty-one vaccinated subjects awaiting the terrible trial stood side by side with the twenty-five sheep and the four cows, which awaited also their first turn of virulent inoculation. Upon the proposal of a veterinary doctor, who disguised his scepticism under the expressed desire to render the trials more comparative, they inocenlatea alternately a vaccinated and a non-vaccinated animal. A meeting was then arranged by Pasteur and all other persons present for Thursday, June 2, thus allowing an interval of forty-eight hours after the virulent inoculation. ‘‘More than two hundred persons met that day at Melun. The Pre- Introductory and Historical 29 fect of Seine-et-Marne, M. Patinot, senators, general counsellors, journal- ists, a great number of doctors, of veterinary surgeons and farmers; those who believed, and those who doubted, came, impatient for the result. On their arrival at the farm of Pouilly-le-Fort, they could not repress a shout of admiration. Out of the twenty-five sheep which had not been vaccinated, twenty-one were dead; the goat also was dead; two other sheep were dying, and the last, already smitten, was certain tc die that very evening. The non-vaccinated cows had all voluminous swellings at the point of inoculation, behind the shoulder. The fever was intense, and they had no longer strength to eat. The vaccinated sheep were in full health and gayety. The vaccinated cows showed no tumor, no elevation of temperature, and they continued to eat. “There was a burst of enthusiasm at these truly marvellous results. The veterinary surgeons especially, who had received with entire incre- dulity the anticipations recorded in the programme of the experiments, who in their conversations and in their journals had declared very loudly that it was difficult to believe in the possibility of preparing a vaccine capable of triumphing over such deadly diseases as fowl cholera and splenic fever, could not recover from their surprise. They examined the dead, they felt the living. . . .”’ As a final result, as Pasteur had predicted, all the vaccinated animals remained alive and well; all the non-vaccinated animals, which were inoculated with the virulent germs, died. This demonstration was the beginning of a new era in preventive medicine. In 1880 Huxley esti- mated that the economic value of the results secured by Pasteur were more than sufficient to pay the indemnity (about $1,000,000,000) which Germany received from France following the Franco-Prussian War. Rabies Vaccine.—In 1885 Pasteur and his co-workers announced the discovery of a method of treatment for the prevention of rabies. In solving the problem Pasteur was confronted by greater difficulties than he had experienced in his work on chicken cholera and anthrax vae- cines. The cause of rabies had never been isolated, and, in fact, is still unknown. That it was a virus disease could be reasonably assumed since it was possible to transmit it from one individual to another, under both natural and artificial conditions. Moreover, the chief manifesta- tions of the disease were observed to occur in the central nervous sys- tem. Dr. Deboué, of Pau, had made this observation and had concluded that the nerve substance, as well as the saliva, must be virulent. Nerve substance was accordingly emulsified in normal salt solution and in- jected underneath the skin. Transmission of the disease frequently failed following this method of administration. One of Pasteur’s co- workers suggested introducing the virus directly into the nerve centers, since it was there that it grew and reproduced itself. ‘‘Ordinarily an experiment once conceived and talked over was put under way without delay,” says Dr. Roux.! ‘‘This one, on which we were counting so much, 1 Duclaux, E.: Pasteur: Histoire d’un Esprit. Translated by Smith and Hedges, W. B. Saunders Co., 1920, p. 296. 30 Disease Prevention was not begun immediately. Pasteur, who had been obliged to sacrifice so many animals in the course of his beneficent studies, felt a veritable repugnance toward vivisection. He was present without too much squeamishness at simple operations, such as a subcutaneous inoculation, and yet, if the animal cried a little, Pasteur immediately felt pity and lavished on the victim consolation and encouragement which would have been comical if it had not been touching.” Roux then relates that in Pasteur’s absence he introduced some of the virus into the cranial cavity of a dog. On the day following this operation Roux brought the inoculated dog into the laboratory in order that Pasteur might see that the operation had not had any appreciable effect on its activity. In fourteen days the dog developed rabies. Similar experiments on other dogs led to the same results. Pasteur next tried out the effects on rabbits and, by passing the virus from rabbit to rabbit in a series, he was able to so increase its virulence that it killed the last of the series in six days instead of requiring fourteen as was the case in the first animal. The next question to be answered was that of decreasing the virulence of the pure virus contained in the spinal cord of the rabbit. The fact that the virus of anthrax was weakened by exposure to pure air led him to subject the spinal cord of a rabbit, which had died of rabies, to the same influence. This was accomplished by suspending portions of the spinal cord of rabid animals in sterile jars. In the bot- tom of the jars was placed caustic potash which removed much of the moisture and lessened the time required for drying the cord. It was discovered that the cord, treated in this way, lost its power of causing rabies even when introduced in enormous doses. As the period of drying decreased there was a corresponding increase in the virulence of the dried portions of cord. In other words, there was a progressive weak- ening from the fresh cord until the fourteenth day when all virulence was destroyed. Roux describes the experimental results in dogs as follows, ‘‘A dog that receives this rabic spinal cord 14 days old, then the following day the 13 days old, then that 12 days old, and so on until the fresh cord is used, does not contract rabies and has become im- mune to it. Inoculated in the eye or in the brain with the strongest virus, it remains healthy. It is, therefore, possible in 15 days to give an animal immunity against rabies. Now men, bitten by mad dogs, or- dinarily do not contract the disease until a month or even more after the bite, and this period of incubation can be utilized for rendering the bitten person immune. “‘Experiments made on dogs bitten and inoculated were successful beyond all hope. One recalls how, with the aid of MM. Vulpian and Grancher, the experiments were extended to man. Today almost 20,000 persons have undergone this antirabic treatment and the mortality occurring among these treated persons has been less than 5 per thousand. “The discovery of the prophylaxis for rabies aroused everywhere great enthusiasm. It increased the popularity of Pasteur more than all his former works, In return for such a benefaction, the great public Introductory and Historical 31 desired to manifest its gratitude in a manner worthy of itself and of the man it wished to honor. It was then that the subscription was started which has made possible the founding of the Pasteur Institute.’ ! After having shown that rabies could be prevented in dogs through the introduction of weakened virus, he was ready to complete the demonstration in man. The opportunity was afforded him in the person of Joseph Meister, a lad of nine years. Meister had been bitten by a rabid dog, receiving many lacerations on different parts of his body. Rabies did not develop, though it probably would have done so had not the treatment been given, since the wounds were numerous and extensive. Since world statistics on rabies are manifestly very incomplete, it is impossible to give in exact mathematical terms the results which have been attained through the treatment of rabies by the Pasteur method. Conservative estimates place the number of infections from the bite of rabid animals previous to the Pasteur method of treatment at from 15-20%. Since, without preventive treatment, the 15-20% who contract the disease from the bite of a rabid animal all die, the death rate in the infected animals is 100%. From the time of its introduction deaths from rabies have continuously decreased year by year. At the present time the number of those who die as the result of the bite of a rabid animal is less than 0.5%. If we contrast the present death rate (less than 0.5%) with that before the period of its introduction (more than 15%), its beneficence may be readily perceived. Malaria.—Malaria is derived from the Italian mal’aria which means bad air. In early times it was thought that the disease arose from effluvia emanating from stagnant pools, swamps, and areas where there was much plant decay. It was thought that the noxious agent escaped into the air and was carried by this medium to man. The history of malaria is clouded in obscurity; when and where it began is a matter of conjecture. Its distribution has varied somewhat at different periods. At the present time it is present in many areas throughout the world. It has been encountered in North America from the Arctic Circle to the Equator. In tropical countries it is especially widespread, and the number of its victims is enormous. As one passes from the tropics northward its prevalence progressively decreases. History does not clearly record whether it was present in North America before the arrival of Columbus, but it has certainly been pres- ent in America ever since colonization first began. It has prevailed in certain areas throughout the United States and is still responsible for very much illness, especially along the Atlantic seaboard and in the Gulf States. There are probably more than a million cases of ma- larial fever every year in the Southern States alone. In addition to these there is also a very large number of people who, though they are not themselves ill, harbor the parasite and are in consequence a source of danger to other people. Such people are called ‘‘carriers,’’ and it is through them that the disease maintains its constant presence ' Ibid, p. 298. 32 Disease Prevention in the population. We perhaps know more about malaria, and of methods of preventing it, than we do of any other communicable disease, and yet hundreds of thousands are incapacitated by it every year in the United States, many dying directly or indirectly as a result of its prevalence. Even though malaria was almost universally believed to be trans- mitted through the air, Varo, nearly 2,000 years ago, suggested that this and similar affections were in some way associated with the mosquito. Some of the savage tribes in Africa call malaria the ‘‘mosquito disease.’’ Nott as early as 1848 was firmly convinced that malaria was carried by the mosquito, and King in 1882 had collected sufficient evidence in its favor to convince a considerable following that such was the case. La- veran in 1880 discovered in the blood of malarial patients an animal parasite belonging to a class of protozoa called hemocytozoa or hemo- sporidia. In 1884 Laveran became convinced that King’s theory in regard to the mosquito was correct. In 1884 Manson affirmed that malaria, as it occurred in nature, was transmitted only by the mosquito. Bignami in 1896 called attention to the analogy of malarial fever in man to Texas fever in cattle which had been shown by Theobald Smith in 1893 to be carried from animal to animal by the tick. On August 20, 1897, Ross discovered the malarial parasite of one of the forms of ma- larial fever (@stivo-autumnale) in the stomach wall of a mosquito. On July 8, 1898, he discovered numerous parasites in the salivary glands of the mosquito, having been able to follow their passage from the stomach to the thorax and from thence to the salivary glands. The common duct of this gland enters the base of the median stylet or stab- bing process of the mosquito’s proboscis. Malarial parasites were shown to be injected into the wound produced by biting together with the ir- ritating fluid produced by this insect. Bignami, Grassi, Celli, Bastinelli, MacCallum and others worked out the life history of the parasite in the bodies of mosquitoes and man, and in the malaria of birds. In 1900 Manson and Warren completed the evidence of malaria transmission to man. They subjected themselves to the bites of infected mosquitoes, imported from Italy in cages, and as a result contracted malarial fever. An historical discussion of malaria should take into account the benefits which followed the introduction of cinchona, or, as it was first known, Jesuit’s bark. In 1632 reference is first made to the use of this substance. Its use was not popularized until it was introduced into England by Sydenham in 1658. In 1810 quinine, one of the alkaloids of cinchona, was introduced. The introduction of quinine, the active principle of cinchona, lessened the difficulty of administering the drug, since it did away with other constituents which were without specific action. To what extent the incidence of malaria was reduced by the introduction of quinine cannot be even conjectured. Nevertheless it must have reduced its prevalence, where it was used, and it certainly brought much relief to those who were suffering from the disease. Although yellow fever is in many respects similar to malaria, espe- Introductory and Historical 33 cially in its mode of transmission, and for that reason might be consid- ered with it, its discussion, if we are to follow development in a chronological order, should be reserved for a later time. Robert Koch.—Robert Koch was born at Klausthal, Hanover, in 1843. After receiving his preliminary training in the gymnasium of his native town, he repaired to Gottingen to study medicine. In 1868 he received his medical degree from the University of Gottingen. While a medical student he became greatly impressed with the views of Henle concerning communicable diseases. After serving in the Franco-Prussian War he settled down as district physician at Wollstein, a country vil- lage. Here he began his microscopic studies. In 1876 Koch wrote to Ferdinand Cohn that he had worked out the complete life history of the anthrax bacillus. In November, 1877, the methods which he had devised for the preparation of material and for staining with Weigert’s stains were published. His ‘‘Untersuchungen iiber die Aetiologie der Wundinfectionskrankheiten’’ (Investigations concerning the etiology of wound infections) was published in Berlin in 1878. The importance of these publications won for him recognition as one of the foremost inves- tigators in medical science. Through the influence of Cohnheim he received an appointment to a vacancy in the Imperial Health Depart- ment. Here he was ably assisted by Loffler and Gaffky. In 1882 he published the results of his work on the etiology of tuberculosis. Al- though he made numerous and important discoveries following his an- nouncements of his success in isolating the cause of tuberculosis, the Bacillus tuberculosis, this contribution will always be looked upon as his greatest triumph. Although there were some who believed human tuberculosis was a communicable disease, the majority believed it was inherited and consequently there was very little hope of being able to avoid it by sanitary procedures then in vogue. The discovery of the tubercle bacillus required the invention of new methods of study, since it could not be demonstrated by any of the procedures which had been devised for such investigations. The demonstration that tuberculosis was a communicable disease furnished a basis for constructive work in combating its spread. The cause was known, the channels through which it entered and left the body revealed, and, as a consequence, more intelligert measures could be instituted to control it. In 1890 it was announced that Koch had found in tuberculin a specific cure for tuber- culosis. The results following its administration did not, however, turn out to be as successful as had been anticipated. It has, however, found a great field of usefulness in the diagnosis of tuberculosis, since through its administration evidence of the disease may be ascertained when other methods are not positive. Following Koch’s announcement of the dis- covery of the Bacillus tuberculos’s men from all over the world tried to duplicate his work. Many were not able to confirm it since they were not men of scientific training and consequently lacked technical ability. As time wore on it became more and more evident that his conclusions were sound. All the claims which he made in his first con- 34 Disease Prevention tribution on tuberculosis have been confirmed the world over, even to the most minute details. The discoveries of Robert Koch were, like those of Pasteur, epoch-making, and will always remain conspicuous examples in the development of rational procedures in the prevention of disease. Diphtheria Antitoxin.—In 1884 Loffler demonstrated that the Bacil- lus diphtherice was the specific cause of diphtheria. After much study and reflection he came to the conclusion that the characteristic symptoms on the part of the heart and central nervous system must be due to some soluble substance, which was produced by the diphtheria bacil- lus at the point where the pseudomembrane was formed. From this area in the throat he assumed that this soluble substance gained admission to the circulation and was carried by the blood to all parts of the body. Roux and Yersin in 1888-89 were able to isolate this soluble substance and to demonstrate that it was the cause of the symptoms and tissue changes which occur in diphtheria. The name foxin was given to this poisonous substance. Ferran, Fraenkel and Brieger soon began exper- iments on animals seeking to produce an active immunity. At about the same time, 1890, Behring and Kitasato were successful in producing immunity in animals, 4. e., animals which were treated with the weak- ened germ, in gradually increasing doses, became less and less susceptible and finally did not succumb to injections of the fully virulent diph- theria bacillus in doses many times greater than would have been re- quired to cause their death before treatment was begun. At the same time they discovered that the blood serum from these animals if in- jected into normal animals protected them from a subsequent infection although they were inoculated with virulent diphtheria bacilli. They furthermore discovered that animals which had been inoculated with virulent diphtheria bacilli could be cured by the injection of the serum from an immunized animal provided they did not wait too long before giving the injection. They had, therefore, demonstrated that the blood serum from an immunized animal not only protected against infection but also was able to cure animals already suffering from the actual disease. It was first tried out in the treatment of a man suffering from diphtheria in von Bergmann’s clinic in 1891. At first the treatment, though promising, was not wholly satisfactory. The reason that better results were not obtained was later shown to be due to the fact that the antitoxin was weak and the dosage too small. Methods were soon devel- oped through which a stronger antitoxin was produced and larger doses were given. As a consequence of these procedures better results were obtained. The benefits which have been derived from the discovery of diph- theria antitoxin cannot be accurately determined. It can be conserva- tively affirmed that it has caused a lessening in the death rate from diphtheria of more than 50%. This result has been obtained notwith- standing the fact that there are many individuals suffering from diph- theria who do not receive the antitoxin treatment, and there are many Introductory and Historical 39 others in whom the treatment is not begun until the disease has existed several days. The earlier the antitoxin is given the better the results. In addition to the use of antitoxin as a curative measure it has shown itself to be very valuable in preventing disease in those who are susecepti- ble and have at the same time been exposed to infection. Production of Diphtheria Antitoxin.—In the early days of anti- toxin production the smaller animals, such as rabbits and sheep, were used. At first the weakened diphtheria bacillus was injected, but it was later discovered that the toxins of the germ could be used as effectively in the production of antitoxin. It was also ascertained that the horse could be immunized. This was a decided improvement, since the amount of serum which could be obtained from the horse was so much greater than that which was furnished by the smaller animals. For the production of antitoxin on a large scale the horse is used for the reasons already given. A healthy, vigorous animal, four to six years old, is selected. It is obvious that the animal should be free from disease of every kind whatsoever. Hspecially should it be shown that the animal is not suffering from glanders or tetanus. The usual method of immunizing the horse which is employed today is that in which the diphtheria toxin alone, or toxin together with antitoxin, is injected. In beginning the treatment with toxin a smaller amount is given as an inifial dose than is given when antitoxin is also introduced. The advan- tage claimed for the toxin-antitoxin mixture is that immunity can be brought about in a shorter time. The procedure in either case is essen- tially the same. A small initial dose is injected. The horse responds by a rise in temperature, appears ill and refuses to eat some of the food which is given him. At the end of from five to seven days, after all symptoms have disappeared in the horse, a second dose is given. Usually the dose is increased at each subsequent injection when toxin alone is given and the reaction in the horse has not been too severe. Park uses 5,000 toxin units combined with 100 units of antitoxin. This amount is given each time for the first three doses. From this time on the dose of toxin is increased. At the end of three months the horse is receiving more than ten times as much as was given in the initial dose. Some of the blood is now withdrawn from the horse, the serum is allowed to separate out, and if it is found to have suffi- cient strength, the horse is bled, under sterile conditions, the blood being received in high sterile glass cylinders. As much as six liters or more may be taken at intervals of a month. The cylinders are allowed to stand for two or three days at a temperature of 10° C. or lower. At the end of this time the serum is siphoned or pipetted off and stored in the refrigerator. In order to prevent chance contamination 0.5% phenol, or 0.3% to 0.4% tricresol, is usually added. It is ready to be used as soon as its potency or strength has been determined or it may be further purified chemically. In either case it should be placed in colored glass retainers and stored in a cool dark place to prevent deterioration. 36 Disease Prevention Lumbar Puncture.—In 1891 Quincke introduced lumbar puncture in the diagnosis of diseases of the central nervous system. Previous to this time there was no certain means of making a diagnosis of diseases of the central nervous system with the determination of the specific cause. The operation itself is relatively simple. A strong, hollow needle is inserted in the muscles in the lower part of the back, a little to one side of the median line, in the third or fourth lumbar space. When the needle enters the space surrounding the cord, the spinal fluid, which is almost invariably under increased pressure, will begin to flow from the needle. The fluid is collected in some sterile retainer from which portions are taken for various examinations. By means of these examinations the specific cause of the trouble can usually be determined. Theobald Smith.—Of much historical interest were the experiments of Salmon and Smith first reported in 1884. They were the first to propose immunization with bacterial products. Their experiments were carried out in hog cholera and although they were not working with the specific cause of hog cholera they were able to produce in pigeons an immunity to a bacillus isolated from hogs suffering from hog cholera (the so-called hog cholera bacillus) by using the products and dead bacteria. In 1889 Smith saw in the red blood cells of animals suffering from Texas fever a pear-shaped organism which was usually present in pairs. In 1893, with F. L. Kilborne, he succeeded in demonstrating that this germ was the cause of the disease and that it was trans- mitted from sick to well animals through a cattle tick. The name under which the protozoon which causes Texas fever is now known is Babesia bigemina; of the tick which carries it, Margaropus annulatus. Infection is caused by the larve and nymphe of the tick. The tick lives on the skin of the infected cattle obtaining its nourishment from the blood. At the last moulting the female drops to the ground where she lays about 2,000 eggs which contain the parasite. The development of the larve takes about 30 days and the parasite must live in cattle from 10 to 30 days before evidence of the disease is present. After having discovered the cause and mode of transmission of Texas fever methods of prevention were sought. It was soon found that animals could be freed from ticks by placing them in dips con- taining arsenic. After this treatment they should be removed to pastures known to be free from ticks. Resort to these measures have been highly successful in eradicating Texas fever. In 1898, Smith was able to show that the human tubercle bacillus was morphologically unlike the bovine bacillus. He further showed that its growth requirements and effect on lower animals were also dissimilar. This discovery, confirmed by many other investigators, was of much importance particularly in children who are frequently in- fected by the bovine tubercle bacillus. The use of properly pasteurized milk would entirely remove this danger, since the bovine bacillus is probably always conveyed to children through milk. Zl Introductory and Historical 37 Bubonic Plague.—In 1894, Yersin and Kitasato, working independ- ently, discovered the cause of bubonic or black plague, the Bacillus pestis. In ancient times it was observed that epidemics of plague were preceded by epidemics in rats, which were so fatal that many dead rats were found in the streets, in buildings and in many other places. This coincidence led many to believe that in some way these rats were connected with the spread of this disease. Yersin, in 1894, established the identity of the disease in man and rats. In 1898 Simond succeeded in transmitting plague to animals by using infected fleas. Verjbitski, in 1903, and Liston, in 1904, confirmed Simond’s rat-flea transmission experiments. The British Plague Commission in India proved conclu- sively that bubonic plague is conveyed from the rat to man through the rat flea in 1914. McCoy and Mitzmain were able to show in San Fran- cisco, that, under certain conditions, the rat flea bites man. This is especially the case if the food supply which naturally comes from the rat, its host, is shut off or limited. In Europe it has been shown that the common rat flea rarely bites man, and then only under very unusual conditions, which threw some doubt upon plague transmission through the flea. However, the evidence presented by the British Plague Com- mission was conclusive. It is also probable that transmission may occur through the flea in a mechanical way perhaps more frequently than through its bite. The cause having been ascertained, and the vehicle of *zansmission demonstrated, the way was cpened for devising effective methods of prevention. It has been shown that eight species of fleas are carriers of the plague bacillus. The rat flea, Xenopsylla cheopis, is the chief carrier in the great epidemics. The rat, however, is not the only rodent which has plague. In recent years it has been shown that the marmot (Arctomys bobac) has probably been the responsible agent in keeping the disease endemic in Thibet. In 1910-1911 some trappers and traders in Manchuria were bitten by the tarbagan (Arctomys bobac) a fur- bearing rodent, and as a result became infected with plague. From these infected men the Manchurian epidemic of pneumonic plague had its origin. In California the ground squirrel (Citellus beecheyi) has become infected and the disease has become so widely disseminated in these rodents as to make it probable that many years may be re- quired to stamp it out. All the rodents mentioned must be eradicated to eliminate the disease and it is very probable that there may be others which carry the infection. The rat is the chief offender and principal carrier. At least three species are concerned in the spreading of the disease, Mus norvegicus, the common brown sewer rat; Mus rattus, the black house rat and ship rat; and Mus alexandrinus, the Egyptian rat. Much has been written on the history of plague. Since there are many sources from which much interesting material may be obtained only some of the more noteworthy accounts are here recorded. Accord- ing to Osler the first description of bubonic plague was given by Rufus 38 Disease Prevention of Ephesus who lived from 96-117 A. D. In his writings he states that it made its appearance in Libya, Egypt and Syria during the third century B. C. Where it first appeared is a matter of conjecture but it probably had existed many centuries before the Christian era. Fragmentary accounts record numerous epidemics prior to the four- teenth century which, it may be inferred, caused great devastation. In 1348 Europe was invaded by an epidemic which had its origin in China. Just when it began in China is not known but it was probably some time after 1330. As a result of this epidemic 13,000,000 are said to have died in China and in the rest of the East about 24,000,000. Hecker estimates that 25,000,000, one-fourth the population of Europe, perished in this epidemic. From the fourteenth century to the present time numerous epidemics with frightful mortality have prevailed. While it has not been as widespread in its invasion of the whole world as it was in the fourteenth century, it has claimed a large toll and this is par- ticularly true in certain places. De Foe’s ‘‘Journal of the Plague Year’ describes the devastation which occurred in London in 1665, in which 70,000 persons perished. Grasshoppers, peddlers, corn factors, cornets and numerous other things were regarded as the cause of the pestilence. To stay its devastation many ordinances were passed and various measures were taken in the hope that it might be overcome. So great was the devastation during the fourteenth century that it was feared all animal life would be destroyed. None dared to perform burial rites. Thousands of corpses were cast into rivers and deep pits which had been dug for this purpose. Destruction was present on land and sea. Often entire crews perished, leaving none to man the drifting hulks. With the putrefying dead, lying about the decks, vessels were often cast upon the shores of the Black, Mediterranean and North Seas, spreading the pestilence to those on shore. Many of the ill were abandoned, even mothers forsook their plague-stricken children. The worldly-minded with the religious attempted expiation by be- stowing their gold and other earthly goods upon the Church. The ecclesiastics, in fear that the gold was tainted with the pestilence, refused to receive it. As in all great panies from pestilence, superstition banded together multitudes which hoped to accomplish much by asso- ciation. In Hungary and Germany there arose the brotherhood of the Flagellants. Made up at first of the lower classes, they gathered to their standard men and women of the highest rank. They marched from city to city, spreading the pestilence as they marched, clad in sombre gar- ments, with red crosses on their caps, breasts and backs, their heads covered to the eyes. Chanting they marched in solemn processions. With faces turned towards the ground and triple scourges with points of iron, they marched along waving banners. From time to time they lacerated their bodies with the scourges. After they had spread ever nearly the whole of Europe, Pope Clement VI, at the request of several of the erowned heads, prohibited their pilgrimages under the threat of excommunication. Introductory and Historical 39 During the pilgrimages of the Flagellants a widespread rumor aec- cused the Jews of causing the pestilence through poisoning the wells. Wherever they could be found they were seized, tortured and killed. To escape the terrors of the plague and of the pestilence many of them committed suicide. In Mainz alone 12,000 were murdered. In many places not a soul escaped the superstitious mob. The fear of the people aggravated the havoc of the pestilence, since it caused them to close their wells and to resort to other deprivations. Great as had been the devastation the Black Death was not wholly without beneficial results. The laboring classes, as in all epidemics, were most severely affected. So many had died that there were not enough left to do the necessary work, and consequently those who were left, were able to demand and secure better conditions of living than had hitherto fallen to their lot. In the great plague of Milan in 1630, in which there were 80,000 deaths, it was thought that virus was spread about on objects by evil persons. Garrison describes a particular episode of this character as follows: ‘On the morning of June 1, 1630, Guglielmo Piazza, a com- missioner of health of Milan, was seen going down the street, writing from an inkhorn at his belt, and wiping his probably ink-stained fingers against the walls of houses. Being accused by the ignorant women of the neighborhood of smearing the houses with deadly oint- ments, he was, upon motion of the council, haled to torture. The latter barbarity, a survival of the ordeal of feudal times, had an elaborate ceremonial, prescribed by legal code, in which the accused was stripped, shaved to the scalp; and purged before going through his misery; and, if he survived the atrocities inflicted upon his body three times, God was supposed to have intervened in a miracle. The unhappy Piazza stood for two applications of this hideous rite, but yielding to the third degree suggestions of his tormentors, finally stated that he had obtained a poisonous ointment from a barber named Mora. The latter, upon being apprehended, yielded to the first applica- tion of torture, and though both unfortunates recanted more than once, the clamors of the superstitious populace against them were such that, upon sentence, they were torn with red-hot pincers, had their right hands cut off, their bones broken, were stretched on the wheel, and, after six hours, burned. Their ashes were then thrown into the river, their possessions sold, the house of crime razed to the ground, and its site converted into a sort of Aceldama by the erection of a ‘column of infamy’ (colonna d’infamia).”’* Western Europe has been almost free from plague since the middle of the eighteenth century. In India, China and other parts of Asia it has been endemic for centuries. Since 1815 we have had relatively ac- curate and complete records of this disease. In modern times its first great extension began in China. It was first brought to the attention of the world through reports of bubonie plague in Hong Kong in 1893. 1 Garrison, F. H.: History of Medicine, W. B. Saunders Co., 1922, p. 309. 40 Disease Prevention In 1896 it broke out in Bombay and has since then become widely dis- seminated over the world. Official statistics show that from 1896-1917 it was the cause of about 10,000,000 deaths. The first known occurrence of black plague in the Western Hemisphere was reported from Santos, Brazil, in October, 1899. Since that time it has appeared in Hawaii, California, Mexico, Central America, in the states of Louisiana, Texas, Florida and Washington in North America; in Brazil, Argentina, Paraguay, Uruguay, Peru and Chile in South America; and in Panama, Cuba and Porto Rico. San Francisco, New Orleans and Seattle have all been invaded. There are at least five endemic foci of plague in the world today which are known and there are probably others which have not been located. Of the known foci two are in China, one on the eastern slope of the Himalayas, in the province of Yunnan; the other on the western slope; a third focus extends from the center of Arabia almost to Mesopo- tamia; a fourth in Uganda near the source of the White Nile discovered by Koch in 1898; a fifth in San Francisco. Plague has become endemic in California not only in rats but also in the ground squirrel, Citellus beecheyi. These rodents live in burrows and are infested with the squirrel flea Ceratophyllus acutus. These fleas are known to bite man and it is in this way that the disease is probably most frequently transmitted to man. The disease may be transmitted by the bite of the squirrel, such an infection having taken place in the case of a little girl in Los Angeles. In 1899 plague invaded Honolulu. From here it was carried to San Francisco in 1900 with at least 22 fatal cases. Since then the number of cases in California has varied, but there were in 1907, 156 cases with 76 deaths. It is reasonably certain that the plague which began in Hong Kong in 1893 would have spread over the entire world, with devastation on a very extensive scale, as in the Middle Ages, had it not been for modern "sanitation. Politics came very near wrecking the efforts of those who were striving to control the situation in the United States in 1907-1908. If the experts of the Marine Hospital Service had not worked with energy and determination a widespread and disastrous epidemic would probably have invaded the United States. By them the disease was promptly diagnosed, the rodents exterminated, and, for the first time in history, a large city was made rat-proof. Vaccination Against Typhoid Fever.—The results obtained by Pas- teur in protective vaccinations against anthrax, swine erysipelas, black leg and rinderpest in animals suggested the application of similar methods of protection in human diseases. Investigators, however, were loath to use attenuated cultures of the specific bacteria, isolated from human diseases, although the weakened viruses of smallpox and rabies had been used with success. Ferran, a Spaniard, seems to have been the first to make such an attempt in a bacterial disease. In 1884 he inoculated a number of individuals with weakened cultures of the spirillum of Asiatic Cholera obtained from the feces of cholera pa- Introductory and Historical 41 tients. His results were not very satisfactory and one reason for this is the fact that he probably did not use pure cultures. As early as 1893 Haffkine had begun prophylactic vaccination against cholera in India. His results were promising and subsequent experience has shown that cholera vaccination is of value. In 1896 Pfeiffer and Kolle in Germany and Wright in England pub- lished the results which they had obtained in inoculating men with dead typhoid bacilli. Two volunteers were inoculated by Pfeiffer and Kolle with cultures killed by heat and it was found that the immunity produced was similar to or identical with that which resulted from an attack of typhoid fever. During the same year Wright also inocu- lated two men with killed cultures and in 1897 published the results of the successful vaccination of 17 individuals. The first inoculations of any considerable number of men were made by Wright in 1898 in India. Four thousand men were inoculated with encouraging results. Wright and Leishman, in 1900, prepared a vaccine with which nearly 100,000 British troops were treated during the Boer War in South Africa. The results, though encouraging, were not as good as had been anticipated. Leishman later ascertained that the reason better success had not been achieved was due to the fact that in preparing the vaccine too high a temperature had been used. In 1904, through the advice of Koch, prophylactic inoculations were made in the Herero campaign in southern West Africa. The results, though good, did not come up to expectations. Since 1904 vaccination has been consistently practiced in the British Army in India. An improved vaccine has been given, the dose being increased from year to year, with uniformly good results. In the United States the first protective inoculations were advised and practiced by Richardson. When Leishman, in 1907, published the marked results which had been secured in India, through using an improved vaccine in ever-increasing quantities, studies on typhoid vaccination were already being made in the United States Army by Major Frederick F. Russell and his associates. Leishman’s work was of material advantage to Major Russell, enabling him to prepare a vaccine and use it as a protective measure on United States Army troops, at an earlier date than would have otherwise been possible. To obtain a clear conception of the marvellous results which have followed the introduction of antityphoid vaccination, a brief review of typhoid incidence and mortality in the prevaccination period should be contrasted with present day results. In the Franco-Prussian War there were 73,396 cases of typhoid fever, with 8,789 deaths in the Ger- man Army alone. Of all deaths 609, were caused by typhoid fever. In the British Army during the Boer War there were approximately 30,000 cases of typhoid fever with 5,877 deaths. In the Spanish-American War, of the 107,973 men of the United States Army, 20,738 contracted typhoid fever and of this number 1,580 died; 19.29% or nearly one of every five men being infected, and of those ill the death rate was 42 Disease Prevention 7.8%, of the entire army nearly 1.5%. The annual admission rate in typhoid fever during the first year of the Civil War was 70.69, with a death rate of 19.61. Without doubt these numbers are too low, as it is probable that many cases were not diagnosed as typhoid fever but as malaria, gastric fever, and other diseases. During the years 1898-1899 in the Spanish-American War and the Philippine Insurree- tion the annual admission rate was 91.22, the death rate 9.67. During the World War vaccination was compulsory in the United States Army. The admission rate for approximately 3,000,00C men who passed through the camps in 1918 was 0.17. Although army conditions were such that it is probable fhat the chances were as great or greater of con- tracting typhoid fever among the troops than among the general civilian population, the incidence of typhoid fever in the army was only one forty-fifth of that occurring in the same age group in the civilian population. In Europe sanitary conditions were exceedingly bad, particularly during the summer. In battle areas the opportunities for transmission not only of typhoid fever but of other infections were probably never greater during the history of the world, since sanitary measures were entirely out of the question and in many instances bad water supplies could not be made safe. Notwithstanding this condition there were only 488 cases of typhoid fever with 88 deaths in approxi- mately 2,000,000 troops in France. No more conclusive evidence could be given of the efficacy of antityphoid vaccination. In a like manner the value of this procedure was shown in all the armies engaged in the conflict. In the Massachusetts General Hospital, where 80% of the nurses and others exposed to typhoid had been inoculated during the previous three years, not a case of typhoid occurred in nurses or attendants in 1912. Never before had such a result been obtained. The morbidity rate in Massachusetts training schools for nurses during three years was nine times greater in the uninoculated than in the inoculated. The year 1909 was the first time any considerable number of men were inoculated in the United States Army. At first only volunteers were inoculated but by 1911 it had become sufficiently popularized so that, in March, 1911, when about 13,000 troops were mobilized at San Antonio, Texas, for duty along the Mexican border, it was made com- pulsory for all men under the age of forty-five years. In June of the same year it was made compulsory for the entire United States Army and has continued so until the present time. ‘While the army division already cited was in camp in San Antonio for about four months in 1911, of approximately 13,000 all were vac- cinated. Only one case of typhoid fever developed and this occurred in a man who had not completed his inoculations. During this period there were 49 cases with 19 deaths from typhoid fever in the civilian population of San Antonio, which at this time was estimated to be 96,614. During the period 1900-1910 inclusive, a period of eleven years, the average yearly ratio of deaths per thousand in the Army was Introductory and Historical 43 0.36. In the civil population for the same period, in the corresponding age group (20 to 29 years), both sexes being included, the average annual rate was 0.33. Since in the latter group there were included both males and females, the number is lower than that for the Army. In the males alone the rate among the civilian population is greater than is that in females, hence if males alone were included the rate would be as high, or higher, in the civilian group than it would be in the army. The same rule would also apply in the same groups after vaccination was made compulsory in the Army. During the period 1911-1918 inclusive, a period of eight years, the average annual death rate per thousand in the army was 0.03, in the civilian group (20 to 29 years) 0.11, the number of deaths being reduced at least 75%. During the years 1913 and 1915 not a single death from typhoid fever occurred in the United States Army. A striking example of the value of antityphoid vaccination may be seen in comparing the typhoid rate in the United States Army, in a division of 10,759 men in the Spanish- American War, with 12,801 vaccinated men living under very similar conditions in San Antonio in 1911. In the former there were 4,422 cases of typhoid fever with 248 deaths; in the latter there was only one case and no deaths. Method of Preparation of Antityphoid Vaccine. The vaccine is prepared by growing typhoid bacilli on agar in Kolle flasks. The growth is removed from the surface of the agar at the end of 18 hours by washing it with sterile normal salt solution. The number of bacteria per unit of volume is counted and after this has been ascertained the suspension is heated to 53° C. for one hour. Usually 0.25% tricresol is added as a precaution against the possibility of the presence of any living typhoid bacilli and to prevent contamination. Methods of prep- aration vary slightly but the main principles are universally fol- lowed. It has been found that certain strains of typhoid bacilli furnish greater protection than others. The early belief that the more virulent the strain the greater the protection has been considerably modified since it has been ascertained that strains of very little virulence often furnish greater protection than virulent ones. In the United States the ‘‘Rawlings’’ strain, which was isolated by Wright, and found by him to possess strong protective value in his work in the British Empire, is used. Method of Administration—The usual method of administration is to inject three doses of the vaccine subcutaneously at intervals of a week or ten days. The injection should be given in the arm at the point of insertion of the deltoid muscle. The dose should be injected beneath the skin (subcutaneously) and not into the skin or muscle. The spot chosen should be thoroughly cleansed with sterile soap and water and after cleansing painted with iodin. The injection is now made and the area gently massaged for a few minutes. The most suitable time for 1 Connecticut, Indiana, Maine, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Rhode Island, Vermont and the District of Columbia. 44 Disease Prevention vaccination is late in the afternoon. The person vaccinated should be directed to remain quiet and at rest until the following morning. No hard work should be engaged in during the succeeding day. The prac- tice followed in the Army is an excellent one, the first dose being given on Saturday evening, with twenty-four hour period off duty, followed by the same procedure on the next succeeding Saturdays, until three doses have been injected. If more than three doses are given the pro- tection afforded is greater than when only three are administered. Somtimes four or even more injections are given. Dosage.—Adults are given 500 million in the first dose, 1,000 mil- lion in the two succeeding doses. Children are given doses in the pro- portion their weight bears to the weight of the average adult. For example, a child weighing 30 pounds would receive an initial dose of 100 million followed by two doses of 200 million each, estimating the weight of the average adult at 150 pounds. The vaccine should be well shaken before injection. No dressing at all is necessary. Under normal conditions some reaction occurs, but this is usually not severe, and rarely lasts for more than twenty-four hours. Even when the reaction is severe and more discomforting, it rarely lasts more than two days and is followed by complete recovery. The local symptoms are redness and swelling over an area from two to four inches in diam- eter; occasionally the area is more extensive. It is tender to the touch but does not require special treatment, and usually subsides within forty-eight hours. The general symptoms are not unlike those of ton- sillitis, but are of much shorter duration, usually disappearing within twenty-four hours. The symptoms commonly complained of are chill- iness, bachache, headache, pains in the muscles and joints, and fever. In the more severe reactions there may be nausea, vomiting, diarrhea, constipation, and even slight albuminuria. When severe reactions occur, an event which is relatively rare, no especial treatment is necessary. Complete rest with treatment for the symptoms which may appear is all that is required. The symptoms without any treatment whatever disappear in one or two days. Army experience shows that severe symptoms occur in three of every thousand following the first dose, two in a thousand after the second, and one in a thousand after the third. In children reactions are rare, severe reac- tions occurring very infrequently. How long antityphoid vaccination lasts has never been definitely determined. Where exposure is more or less constant, vaccination should be practiced every year or even oftener. Physicians, nurses, hospital attendants and all others who are subjected to the danger of infection from contact with typhoid patients or from a suspicious water or milk supply, should be included in this class. In the Army it is the practice to reinoculate every four years, more frequently if it is thought the exposure is great enough to render it advisable. Under field conditions in the Army vaccination should be repeated every six months; at least one dose should be given. In civilian life repetition Introductory and Historical 45 every two years should be sufficient under ordinary conditions. In case of known exposure, or of probable exposure during an epidemic, if more than six months have elapsed since the last previous vaccination, reinoc- ulation of at least a single dose should be practiced. When there is reason to believe that those who are ill with some other disease have been exposed to typhoid fever, they should be vaccinated, since the dan- ger from vaccination is less than an attack of typhoid fever would be. Unless such danger exists only those who are in a healthy state should be vaccinated. Pregnant women beyond the fifth month in pregnancy should not be vaccinated. If the temperature is above normal, vae- cination should not be resorted to until it has become normal again. Those suffering from endocarditis or nephritis, particularly the latter, should not be vaccinated. Antityphoid vaccination seems to have very little if any influence on either active or inactive tuberculosis, hence tuberculous individuals should be protected by this measure if they have been exposed to typhoid fever. Since antityphoid vaccination in- volves no risks, those exposed to repeated or massive infections should avail themselves of the protection which is given them through this procedure. The members of the family where the disease exists or in which there is a carrier, soldiers in camps or in campaigns, nurses, attendants of typhoid patients, individuals in epidemic localities, auto- mobile tourists, and all others whose movements or associations ren- der infection probable should be vaccinated. The inmates of all in- stitutions in which there is intimate and continuous association, such as asylums, prisons, reform schools, ete., should be subjected to this protective measure. Where sanitary conditions in civiilan communities are such as to render the probability of infection remote, the necessity for vaccination is not great while such conditions exist. Within comparatively recent years it has been found that certain infections occur in which there are symptoms very similar to those encountered in typhoid fever. These infections are caused by several organisms similar to the typhoid bacillus. Of this group two have been especially studied, the paratyphoid bacillus A and the paratyphoid bacillus B. The diseases caused by this group are much milder than those caused by the typhoid bacillus and are rarely fatal. Nevertheless, though little dangerous to life, paratyphoid fever creates an economic loss, and, like other infections, reduces resistance so that other diseases are more easily acquired after an attack of this disease. For this reason paratyphoid vaccination was made compulsory in the United States Army during the World War. The vaccine which was finally adopted and which is used at the present time was incorporated with the anti- typhoid vaccine. It is called the ‘‘Triple Typhoid Vaccine.”” Each cubic centimeter of this vaccine contains 1,000,000,000 typhoid bacilli and 750,000,000 each of the paratyphoid bacilli A and B. The dose is given in the same way and under the same conditions as was the sim- ple antityphoid vaccine. The reactions are slightly more severe when the triple vaccine is given. The results were so good in the Army 46 Disease Prevention experience that the method is now used in the civilian population with corresponding results. Filterable Virus.— Although it had been suggested that there existed, in those communicable diseases in which no microorganism could be found, a virus which was so small or of such a nature it could not be seen, an actual demonstration was not made until 1898 when Frosch and Loffler reported that they had been able to produce infection in cattle, with material from foot and mouth disease, which had been passed through a filter with pores so small that the most minute bac- teria did not pass through. Since this discovery, many other so-called filterable viruses have been discovered in the diseases of man and the lower animals. Of the diseases in man in which the cause is a filterable virus, yellow fever is a conspicuous example. Reed, Carroll and Agra- monte demonstrated the filterability of the virus of yellow fever in 1901. Rembringer, in 1903, demonstrated that the virus of rabies could be passed through porcelain filters. The following have been shown to be due to a filterable virus: Dengue, by Ashburn and Craig, in 1907; three days or Pappataci fever, by Doerr and Russ, in 1908; infantile pa- ralysis, by Landsteiner and Levaditi, in 1909 ; typhus fever, by Nicolle, in 1910; tabardillo, by Howard Ricketts, in 1911 ; measles, by Goldberger and Anderson, in 1911. The virus of smallpox and vaccinia passes through the Chamberland filter. In all there are today about 40 viruses which are filterable. Eventually it will probably be possible, by other modes of investigation than those which have yet been devised, to isolate in vis- ible form the organisms which are today classed as ultramicroscopie. Hookworm Disease.—The symptoms of hookworm disease were so clearly described in the Egyptian papyri as to leave no doubt con- cerning its recognition by the Egyptians. For centuries the disease was named after its most marked symptoms of anemia. It was called Egyptian chlorosis, tropical chlorosis, miner’s anemia, and bricklayer’s anemia. Its prevalence in the St. Gothard tunnel was so extensive that it was called St. Gothard tunnel disease. It especially prevails in tropical and sub-tropical countries and is widely distributed over the entire world, diminishing in frequency with increase of distance from these areas. In cold climates it is not endemic except in mines. In Europe it is found in the mines in Germany, France, Spain, Belgium, The Netherlands, and Wales. In the United States it exists to an alarm- ing extent in the Southern States. More than 2,000,000 people, accord- ing to the estimate of Stiles, are infested with hookworm disease in the area extending from the Potomac River in the North to the Mississippi River in the West and the Gulf of Mexico in the South. In the mines in the United States the disease has been shown by Gunn to be especially prevalent in California where from 50-80% are affected. Where foreign labor is employed in the mines it is probable the disease will be found, especially in those which have been worked for some time. Looss discovered that hookworm disease is usually contracted through the skin while he was investigating the disease in Cairo, Egypt. In Introductory and Historical 47 1895 he accidentally spilled on his hand a few drops of water containing the encysted larvae of the hookworm. He noticed that they disappeared, nothing remaining behind except their sheaths. In 71 days he developed the disease. His experiment on a volunteer showed hookworm eggs in the stool in 74 days. Claude Smith was able to demonstrate eggs in the feces of two persons whom he infected through the skin, in 45 and 49 days respectively. Looss traced the route of the larvae from the skin to the intestine. The larvee penetrate the skin usually through hair follicles, though they may enter through parts of the skin devoid of hair. After pass- ing through the skin they enter the lymph spaces, pass through the lymph vessels and glands and finally reach the large vein, the vena cava, through which they enter the right heart. From the right heart they pass through the lesser circulation into the lungs and penetrating the capillary walls enter the air spaces. They are now free in the air spaces and are carried by way of the bronchi, trachea and larynx to the mouth. They are next swallowed, and in the adult form attach themselves to the wall of the intestine. The female worms soon begin to lay enormous numbers of eggs which pass out in the stools and, in the moist soil, under favorable conditions, become larve again in about 24 hours. In about ten days the larva becomes encysted and is now ready to enter the skin. It may remain in the soil in this stage, capable of causing infection, for as long as 12 months. There are two species of hookworm in the Eastern Hemisphere, the Ancylostoma dwodenale and the Amncylostoma ceylanicum, which cause the disease. In the United States the common cause is a different species, the Necator americanus. The prevention of hookworm disease is based upon the work of Looss. Yellow Fever.—As in other diseases in which the cause was not known, yellow fever was thought to be carried from person to person through direct or indirect contact or by fomites. Fomites are any objects upon which infectious material may be deposited, such as clothing, eating utensils and various other objects. Bacteria were isolated from yellow fever patients and from the bodies of those who had died from the dis- ease. None of the bacteria isolated stood the tests of time, and the cause was not discovered until the autumn of 1918. Dr. George M. Sternberg, later Surgeon General of the United States Army, while stationed at Governor’s Island in 1870, had his first experience in yellow fever. At that time he was an Assistant Surgeon, and the interest which was then aroused in him continued throughout his entire lifetime. He was able to show by his investigations that the organisms isolated by him or by others could not reasonably be assumed to be the cause of yellow fever. As early as 1848 the theory that yellow fever was transmitted by mosquitoes was advanced by Josiah Clark Knott of South Carolina. In 1881, Carlos Juan Finlay, of Cuba, expressed the same belief, and in addition picked out the common mosquito in Cuba. then known as the 48 Disease Prevention Culex fasciata, as the carrier of this infection. Not only was it later shown that the mosquito was the carrier, but the particular mosquito selected by Finlay, now known as the 4édes ~alopus or Aédes argenteus, was shown to be the specific host. Surgeon General Sternberg was inter- ested in Finlay’s theory, but it is probable that he did not regard it with much seriousness. Finlay based his theory on two major premises, the correspondence of yellow fever zones with the distribution of this mos- quito, and the prevalence of these mosquitoes in epidemic areas. In 1900 Surgeon General Sternberg appointed a commission to study sanitary conditions in Cuba. The Spanish-American War had just ended and sanitary conditions in Cuba were very bad. Malaria was very prevalent, and the dangers of yellow fever in the troops was very great. The commission was placed under the command of Major Walter Reed, Surgeon, U. S. Army. Associated with him were Drs. James Carroll, Aristides Agramonte and Jesse W. Lazear. In August, 1900, the commission began its work. Reed had been impressed with the belief of Finlay and eagerly set out to determine its value. The Aédes calopus was the species to which attention was especially directed, though others were also included in the experiments. The mosquitoes were allowed to suck the blood from yellow fever patients end were later placed on sus- ceptible individuals. They were allowed to remain until they had bit- ten them several times. Of the first ten experiments only one was sue- cessful. The reason why the first nine were negative was later deter- mined, and was found to be due to the fact that nothing was known of the life cycle of the parasite in the mosquito at this time. Later it was shown that the mosquito must obtain the blood from the patient during the first four or five days of the disease and that at least twelve must elapse after the blood has been taken into the body of the mos- quito before it is capable of producing infection in man. A member of the commission, Carroll, was the first of the® volunteers to succumb to the infection. He became ill four days after having allowed an infected mosquito to bite him. He recovered from the infection, but died on March 9, 1907, of myocarditis, which had undoubtedly been brought on through the previous attack of yellow fever. On the 13th of Septem- ber, Lazear, while working in the wards occupied by yellow fever pa- tients, noticed a mosquito on his hand. He did not remove it, and as a re- sult became infected, the symptoms of the disease appearing five days later. After a very serious illness he died on September 25, 1900. A systematic campaign was now started. ‘‘Camp Lazear’’ was established in the country a short distance from Havana, about a mile from Quemados. Three immunes and nine non-immunes, volunteers from the army of occupation, were selected as subjects of investigation. A strict quarantine was maintained, only the immunes and the mem bers of the commission being allowed to leave or enter the camp. Non- immune volunteers who left the camp were not allowed to come back again, their places being taken by other non-immune volunteers. Dur- Introductory and Historical 49 ing December, January and I'ebruary ten non-immune volunteers be- came infected with yellow fever through mosquitoes. Too much honor cannot be accorded to these enlisted men of the United States Army, who, after calm deliberation, and in the absence of the excitement and stress of battle, subjected themselves to an infec- tious disease which is so disastrous and fatal. Experiments were now devised to show that yellow fever was trans- mitted by the mosquito alone, all other reasonable opportunities for infection being excluded. A small building was erected, all windows and doors and every other possible opening being absolutely mosquito- proof. A wire mosquito screen divided the room into two spaces. In one of the spaces 15 mosquitoes, which had fed on yellow fever patients, were liberated. One of these 24 hours, 7 four days, 4 eight days, and 3 twelve days after the feeding. A mnon-immune volunteer entered the room with the mosquitoes and remained there for nearly half an hour, during which time he was bitten by 7 mosquitoes. Twice after this he entered the room, remaining in it 64 minutes, receiving 15 mosquito bites. Four days later he suffered an attack of yellow fever. Two other non-immune men slept for 13 nights in the mosquito-free room without disturbance of any sort. To show that the disease was transmitted by the mosquito and not through the excreta of yellow fever patients, or anything which had come in contact with them, another house was constructed and made mosquito-proof. For 20 days this house was occupied by three non- immunes after the clothing, bedding, eating utensils, and vessels, soiled with the discharges, blood and vomitus of yellow fever patients had been placed in it. The bed clothing which they used had been brought from the beds of patients who had died of yellow fever, without being subjected to washing or any other treatment to remove anything with which it might have been soiled. Every evening before retiring they shook out all the bedding and clothing. The experiment was twice repeated by other non-immune volunteers. During the entire period all of the men who occupied the house were strictly quarantined and pro- tected from mosquitoes. None of those exposed to these experiments contracted yellow fever. That they were not immune was subsequently shown, since four of them became infected either by mosquito bites or the injection of blood from yellow fever patients. During these investigations they succeeded in producing experi- mentally fourteen cases of yellow fever through infected mosquito bites, six by blood injection, two by the injection of filtered blood-serum. The use of the filtered blood-serum in 1901 demonstrated that the disease was due to a filterable virus. The facts demonstrated by the commission may be summarized as follows: Yellow fever is only acquired through the bite of the Aédes calopus. The mosquito to become infectious must bite the yellow fever patient during the first five days of his illness; some have since main- tained that this interval must be within the first three days. An interval 50 Disease Prevention of at least 12 days must elapse, after the mosquito has obtained the infected blood, before it can infect man. The importance of the results which have already accrued from these discoveries cannot be overestimated. Yellow fever has been elim- inated from the United States and practically so from the West Indies, and it is only a question of time when it will be eliminated from all parts of the world where it now exists. In February, 1901, Major William C. Gorgas began his work as chief sanitary officer in Havana, and, by carrying into effect the meas- ures suggested by this investigation, was able in three months to eradi- cate the disease which had been constantly present in this city for 150 years. The facts ascertained by the yellow fever commission made the building of the Panama Canal possible. Gorgas freed the Canal Zone not only of yellow fever, but also of other communicable diseases, changing it from one of the most dangerous spots on earth, ‘‘ White Man’s Grave,’’ to one of the healthiest of communities. African Sleeping Sickness.—In 1741, John Atkins, a naval surgeon, published the first account of sleeping sickness which has been discovered in a book (‘‘Physical Observations on the Coast of Guiney.’’) A more accurate description of the disease is given by Winterbottom in ‘‘ An Ae- count of the Native Africans,’”’ published in London in 1803. In 1841 Valentine discovered a protozotn, a flagellate, now known as Trypano- plasma valentini, in the blood of a trout. In 1842, Gruby found a flagel- late in frog’s blood which he named {rypanosome. The rat trypanosome, Trypanosoma lewisi, was discovered by Lewis in 1878. None of these trypanosomes were regarded as pathogenic since they appeared to exist in the blood of these animals as harmless parasites. An organism similar to those described above was found in the blood of an Indian horse, suffering from surra, by Evans in 1889. This parasite, the first patho- genic species discovered, was named Trypanosoma evans. In another horse disease of Zululand, nagana, Bruce, in 1894, not only discovered the cause, Trypanosoma brucer, but also demonstrated that it was trans- mitted by the tsetse fly, Glossina palpalis. Discoveries of other diseases caused by trypanosomes, occurring in various animals, have since been made. It has been found that some of these diseases may be communi- cated directly by contact ; some are also carried by other insects than the fly. In sleeping sickness there are two stages, one characterized by irregu- lar fever, enlarged glands, edema and a rash; the other by a protracted and progressive lethargy with nervous symptoms. Early investigators considered each stage as a separate disease which led to much confusion. The disease prevails in tropical Africa, especially about the head waters of the Nile, in the lake region, and in the Congo. It is gradually spreading with an ever-increasing morbidity and mortality. Recovery from infection rarely occurs. In 1901 Dutton discovered the cause of this disease, Trypanosoma gambiense, in the blood of an Englishman in Gambia. It was found during the febrile stage of the disease and Introductory and Historical 51 was not suspected, even after further work by Dutton and Todd, to be the cause of sleeping sickness. Castellani, in 1903, was able to demonstrate the trypanosome in the blood, spinal fluid and lymph glands of five cases of African sleeping sickness. Dutton and Todd only ree- ognized the trypanosome in the first stage of the disease, which they called Gambia fever. Bruce and Navarro, in 1903, showed that the tsetse fly, Glossina palpalis, is the carrier of the disease, and that Gam- bia fever and sleeping sickness are two stages of one and the same infection. Dutton and Todd, Koch and others have observed that tsetse flies are always abundant wherever sleeping sickness occurs; that it does not spread where this fly is absent; that if a case is brought into a place where there are tsetse flies it soon begins to spread. It has been abun- dantly demonstrated that the tsetse fly transmits sleeping sickness through its bite. It is probable that the flies usually transmit the infec- tion after the parasite has undergone development in the body of the insect. It has been shown that the parasites multiply in the intestines in from 5-10% of the flies and that they are found in the salivary glands and proboscis. The infection may occur in a purely mechanical way im- mediately after the fly has received infected blood. Other blood-suck- ing insects may also be carriers. In endemic areas only a small propor- tion of the flies (0.2-1%) are able to transmit the infection. Novy has shown (confirmed by Minchin) that tsetse flies may be the hosts of both pathogenic and non-pathogenic trypanosomes. The finding of trypano- somes in microscopic preparations is not enough in itself alone to deter- mine to which of these classes the given trypanosome belongs. In May, 1902, Novy and MacNeal succeeded in growing pure cul- tures of the Trypanosoma lewisi. This is the first instance of growth in pure culture, on an artificial medium, of a pathogenic animal parasite. Not only were they able to obtain a pure culture, but were also suc- cessful in producing infection in rats by inoculating them with these pure cultures. They were thus able to demonstrate the causal relation- ship of this parasite to the disease in rats. Later investigations in other animal diseases, caused by trypanosomes, demonstrated that the same results could be obtained. Chagas, in 1907, discovered in the blood in Barbiero fever, a disease which occurs in Brazil, the Trypanosoma cruzi or Schizotrypanum cruzi. This parasite has been grown artificially and cultures injected in animals produce infection. It has been shown that this disease is spread chiefly through a bug, Triatoma megista. The bedbug, Cimex lectularius, also transmits the disease. Stephens and Fantham, in 1910, discovered in a case of sleeping sickness in Rhodesia, the Trypanosoma rhodesiense. In 1912 Kinghorn and York showed that this disease was carried by the fly, Glossina mor- sitans. The disease is similar to sleeping sickness in Gambia, but is more acute and does not respond to treatment. The Gambian and Rhodesian trypanosomes have never been grown artificially, 52 Disease Prevention In 1906, Koch introduced Atoxyl, an arsenic preparation, in the treat- ment of sleeping sickness. It has a beneficial effect for a time in some cases if given early in the disease, and perhaps occasionally brings about a cure, but neither this remedy nor any other which has been tried gives much promise of ultimate recovery. Since it is probable that wild and domestic animals act as the chief sources from which the parasites are transmitted to man through the insect carriers, it will be necessary to also consider them in any campaign directed towards the control and prevention of sleeping sickness. Syphilis.—From the standpoint of public health the venereal diseases are a greater menace than all other diseases combined. Until 1912 no serious attempt had been made to control or prevent their spread. New York City was the pioneer in this work, and attacked it not on religious, social, or moral grounds, but as a sanitary problem. It is probable that there are in New York nearly 1,000,000 persons who have, or have had, one or more attacks of the venereal diseases. In the majority of those afflicted the disease is in an active stage. Biggs esti- mated that there were 800,000 or more cases of these diseases in New York City in 1912. The number of new infections occurring each year is thought to exceed all other reportable diseases combined. Syphilis is one of the most widespread and destructive of all diseases. It is, with gonorrhea, the other important venereal disease, the best illustration of a contagious disease. Very rarely does infection occur except through close personal contact. It is not transmitted through an intermediate host, and there is almost no danger in one’s environ- ment unless this environment means personal human contact. In rare instances the disease is contracted through clothing and other articles soiled with syphilitic discharges. Surgeons sometimes become infected in operations on syphilitic patients. It is much more difficult to control man than it is to control his environment, and as a consequence the prevention of venereal diseases is a difficult problem. It is estimated that there are from 8-10% of syphilitics constantly present in the general population. Its danger to the public needs no further argument. Sudhoff has made a most comprehensive and exhaustive study of syphilis, and as a result of his investigations concludes that it existed in very early times. Scholars of Chinese history state that Hoang Ti, who lived about 2600 B. C., writes concerning it, and it is said to be found in Indian records (Ajwe-Veda of Susrutas) about 400 A. D. General knowledge of its existence in Europe dates from the time of the discovery of America by Columbus. Since it was not known until Columbus returned from his first voyage to America, many believe that it was brought to Spain by sailors of this expedition, from whence it spread into Italy and over Europe with frightful rapidity. Its virulence was so great that it soon became a veritable plague. ‘‘It is believed that syphilis is a greater menace to the public health than any other single infectious disease, not even excepting tuberculosis,”’ is the con- clusion of Vedder. Introductory and Historical 53 The earliest account of the transmission of syphilis by inoculation is found in the records of Julius Bettinger. These records were written under an assumed name and signed Palatinus. The inoculations were made in human subjects, and were kept secret all his life. They were presented to the Society of the Physicians of the Palatinate in 1855. In 1903, Metchnikoff and Roux succeeded in transmitting the disease to the higher apes. In May, 1905, Schaudinn and Hoffmann discovered the cause of syphilis, now known as the Treponema pallidum. This was an exceptionally difficult accomplishment because of the technical skill required to demonstrate this almost invisible organism. Numerous inves- tigators have confirmed Schaudinn’s work and have made some improve- ments on his original technical methods. In 1906 Wassermann demon- strated that the disease could be diagnosed by the so-called Wassermann blood test. Noguchi and others have since improved on the original methods of diagnosis devised by Wassermann. In 1910 Ehrlich intro- duced salvarsan in the treatment of the disease and Noguchi in 1911 first grew the parasite on artificial media. Noguchi also introduced another diagnostic test at this time, the luetin test. These discoveries paved the way for more efficient methods of diagnosis, treatment and prevention. Relapsing Fever.—Dutton and Todd, in 1904, discovered that ‘‘ African tick fever,”’ relapsing fever, was transmitted to man through a tick, Ornithodorus moubata. Lice, fleas and perhaps other insects, as, for example, the bedbug, may convey the disease. Obermeier, in 1868, discovered in the blood of patients suffering from European relapsing fever a spiral-shaped organism which was named the Spirillum obermeiert. Recurrent fever occurs in certain parts of all the continents. In 1869 it was epidemic in New York and Philadelphia. At the present time it is practically non-existent in the United States though cases occa- sionally break out. The organism causing the disease is not the same in the different countries, but they are all very similar to one another. Novy and Knapp discovered the spirochaete causing the relapsing fever in South America, the Spirocheta novyi, in 1906. They were also able to immunize animals and to show that the blood-serum of immunized animals produced a passive immunity like that which is secured through diphtheria antitoxin. Noguchi, in 1912, succeeded in cultivating the organism of African tick fever, and later also the varieties from East Africa and South America. Rocky Mountain Spotted Fever.—For the past 48 years, a disease which has been called Rocky Mountain spotted fever, has existed in Idaho and Montana. A few cases have also been found in Colorado, Wyoming, Utah, Nevada, Washington, Oregon and California. The symptoms of the disease very much resemble those of typhus fever. It is ushered in with chills and fever, and a characteristic skin eruption is present. In Montana the death rate is high, nearly 90% ; in Idaho it is about 4%. The highest mortality occurs in the Bitter Root Valley of 54 Disease Prevention Montana. It occurs especially in the spring, about 500 cases per year occurring in the states mentioned, nearly all in Montana and Idaho. As early as 1902 Wilson and Chowning had suggested that Rocky Mountain spotted fever was transmitted by the tick. In 1905 McCalla and Brereton were able in two instances to transmit the disease through the tick. In 1906 Ricketts first showed that the disease could be pro- duced in the monkey and guinea-pig by injecting them with blood from patients suffering from the disease. He was able in his first exper- iment to infect a guinea-pig by allowing a tick to feed on an infected guinea-pig and then transferring it to a healthy guinea-pig. In his four years’ work on Rocky Mountain spotted fever he tried to isolate the cause, after having found the mode of transmission, and though he thought he had discovered it, he died of typhus fever before he had completed his work. Typhus Fever.—This disease was first clearly described by Fra- castoro in 1546. Contemporary Spanish and Mexican investigators also describe the same disease under the name of ‘‘tabardillo.”’ Some believe that the great pestilence of Athens, which occurred about 430 B. C., and of which Thucydides has left so vivid an account, was typhus fever. In 1606 Cober associated the louse with the dissemination of typhus fever. From the sixteenth century on there are records of many epidemics which were of great severity, leaving in their tracks enormous death rates. Since the disease prevails where people are closely crowded, where filth, squalor and poverty are associated, it was only natural that the disease should be named from places in which these conditions exist. It was, therefore, known as ‘‘camp fever,”’ ‘‘jail fever,” ‘‘hospital fever,”” and ‘‘ship fever.”” From the eruptions which are present it has also been called spotted fever and typhus exanthematicus. Previous to 1850 typhus fever was frequently the scourge of armies. Since 1850 it has not prevailed, at least in epidemics, except in squalid and vermin-infested districts. That the virus of the disease is present in the blood was shown by Moczutkowski in 1900. He acquired the dis- ease by inoculating himself with blood from a typhus fever patient. In 1909 Nicolle infected a chimpanzee by subjecting it to a louse which had fed upon a typhus patient. While working upon Rocky Mountain spot- ted fever Ricketts was struck by its similarity to tabardillo, the name by which typhus fever is known in Mexico. In December, 1909, he went to Mexico, and in 1910 he published the results of the investigations he was making there. He did not know of Nicolle’s work until after he had begun his investigation, and, although his demonstration did not precede that of Nicolle, it was none the less original, since it was planned without previous knowledge of Nicolle’s discovery. Ricketts showed that tabardillo was carried by the louse, and that it is probably not carried by other insects or arthropods. He also showed that fleas and bedbugs do not transmit the disease. Ricketts saw in typhus blood small bacillus-like forms similar to the bodies which he had seen in guinea-pigs infected with Rocky Mountain spotted fever. Prowazek, in Introductory and Historical ~~ 55 1910, working in Serbia, saw similar bodies, and others have published similar findings. Plotz succeeded in cultivating a bacillus from Brill’s disease, probably a mild form of typhus fever, which occurs in New York City. None of these have been shown with certainty to be the causal agent. The important finding, however, is that the louse conveys the disease—the body louse, Pediculus vestimentsi, and the head louse, Pediculus capitis. Knowing how the disease is conveyed, intelligent methods of control may be put into effect. Destruction of lice and their nits eradicates the disease. Typhus fever broke out in the Serbian Army in 1914. By Jan- uary, 1915, the epidemic had begun to spread, reaching its height in March and April. At this time as many as 9,000 cases were reported daily. The mortality was estimated to be from 30-60%, and within six months’ time, 150,000 people perished from this disease. The American Red Cross Commission under Strong, assisted by smaller units from Eng- land, France and Russia, were able in six months, by using delousing methods, to stamp out the disease. Summary.—The development of disease prevention has followed the same course as hav: all other historical events. From the earliest dawn of history, when the mind of man was just beginning to develop, we find mankind groping, largely in the dark, to find an explanation for what is gradually perceived to be transpiring in the environment. In the beginning progress appears very slow, and things which seem to us self-evident were totally unexplainable to primitive man. In seek- ing for light it was only natural that the unseen and the unknown should be conceived as evidences of supernatural agencies. Gradually natural phenomena were found to be due to natural causes, and though discoveries came through devious ways, ways often difficult to trace, they nevertheless manifest an ever-increasing progress. The invention of the microscope was an enormous advance, since it revealed objects too minute to be seen by the unaided eye, and it furnished an explana- tion for things which had hitherto been clothed in mystery. Methods were gradually developed by means of which many of these minute forms could be separated from all other material and grown in a pure state. When sc grown, if introduced in the body, they gave rise to the same disease as that which had occurred in the person from whom they had been obtained. Then followed diseases, such as malaria, in which the cause was demonstrated in the blood, and subsequently it was shown that this cause was transmitted by mosquitoes. In malaria, too, it was shown that the parasite present in the blood of a person suffering from malaria passed a part of its life eycle in man and a part in the mosquito. Later a number of diseases were investigated in which the mode of transmission was shown to be due to some insect or other small animal form. In some of these the cause itself has not been discovered because of its minuteness or simce it exists in a form which is not visible with our present-day methods of examination. Some of the forms pass through an unglazed porcelain filter with pores so small that the smallest 56 : Disease Prevention visible bacteria cannot pass through. At present these are designated as ultramicroscopic or filterable viruses. After methods had been devised for the growth of pure cultures, it was shown that these pure cultures could be weakened in various ways so that they were no longer able to produce disease. In some instances, as in typhoid fever, the introduction of these weakened cultures prevents a subsequent infection with the virulent typhoid bacillus. Finally there are still a considerable number of communicable diseases in which neither the cause nor the actual mode of infection is definitely known. In these diseases pre- vention is difficult and the best results will only be possible of attain- ment when the cause and the mode of their transmission are uncovered. CHAPTER II THE SCOPE OF SANITARY SCIENCE Sanitary Science.—Sanitary science is especially concerned with all those things which affect our environment, such as air, soil, water, climate and anything in our surroundings which may contribute to or be the actual means of inciting disease. Air.—In order that existence may continue it is necessary that the atmosphere contain a sufficient amount of oxygen. It is only under very unusual conditions that the amount is deficient. This may be the case in old wells, in the manholes of sewers, in deep mines, and, temporarily, at high altitudes. At one time it was thought that harmful effects from air in closed and crowded rooms came from carbon dioxide. This has been shown not to be the case. Under usual conditions the air which we breathe contains about 0.03% of carbon dioxide. Rarely does the con- tent of carbon dioxide in a closely erowded room rise above 0.5%. An increase of the normal amount up to 2% or more stimulates the respira- tion which may be increased to the extent of 50% or more. An increase to 5% never occurs unless some outside source of supply is added, and it is only when this degree of concentration is reached or surpassed that it becomes harmful. If we consider carbon dioxide from the standpoint of a poison, pro- duced from something else than respiration, there are conditions in which it is dangerous. In industrial plants such poisonings sometimes occur. In the usual experiences, however, it is carbon monoxide, not carbon dioxide, that is present in dangerous amounts from leaking gas, from running automobile engines in closed spaces, in which deaths have occurred, and from imperfect combustion. Poisonings occur from fumes or from dusts of various kinds in industrial establishments. Mercury, lead, brass, carbon monoxide, naph- tha, benzine, wood alcohol and other substances may be present. As a rule the danger is not known or if known is not appreciated. Such dangers might be mitigated or removed by using tightly enclosed machinery and blowers, hoods and exhaust fans to remove dust and gases. Mechanical irritation from the dust which is inhaled in many indus- tries leads to changes in the lungs which are in themselves harmful and in addition predispose to respiratory diseases, particularly tuberculosis. The presence of these foreign bodies, which are constantly inhaled dur- ing working hours, causes an inflammation, and this, in turn, is followed by an increased chronic secretion of mucus and a thickening of the walls 57 58 Disease Prevention of the air sacs in the lungs. As a result of these changes in the lung a chronic bronchitis arises varying in severity according to the extent of the injury. In those trades in which the dust does not have sharp and hard angles, the injury is slightest, as in flour mills. Coal dust and the dust from cement occupy an intermediate ground. In granite cut ting, metal grinding, and similar occupations, the dust hazard is greater, tuberculosis being much more prevalent in these trades, the rate being increased 100% or more. The hazard to workers in these trades may be greatly decreased by installing mechanical devices for the removal of dust, such as ducts and fans, by the use of masks, and by using mois- ture to prevent the dust from floating in the air. In most industrial establishments the temperature is maintained at too high a level. In addition to this, in some of them, there is an ex- cessive humidity. When both conditions exist at the same time the effect is correspondingly greater than where one of them alone is operative. This not only decreases the amount of work which may be done, but at the same time exhausts the body to a greater extent than where more work is accomplished under the proper heat and moisture conditions. Excessive heat and moisture lessen the resistance of the body and pre- dispose it to disease. The ideal condition is a temperature below 70° F. with moderate humidity and air movement. The best results are ob- tained when the temperature is about 65° F. and the mean humidity about 80%. Slight variations in humidity are better than a constant level. In dwellings proper ventilation may usually be secured by intel- ligent manipulation of windows. In schools, and buildings which are occupied by larger numbers, it is usually necessary to install some special contrivance to secure proper air movement. Various systems are in use, such as the gravity exhaust ducts, to carry away the heated air and bring in fresh cool air from the outside; centrifugal and propeller types of fans, In private dwellings the air is constantly too dry during the cold weather when artificial heat is employed. The evaporation of water from pans of water in furnaces, or placed on radiators, does not supply sufficient moisture, since the amount secured in this way is so slight. Much better results may be secured by using some fabric, preferably of coarse texture, of considerable area, so arranged as to be kept con- stantly moist. Food Supply.—The first requisite in a food supply for a community, state or nation is that it shall be sufficient in amount, of good quality and well balanced. In general, the chief food requirements are classified under the proteins, carbohydrates, fats and inorganic salts. Not only should there be an abundant supply of all of these, but they should be consumed in the proper proportions. In recent times it has been shown that we may have the proper proportions of protein, carbohydrate, fat, and inorganic salts and still the diet may be faulty and fail to keep the body in a state of good nutrition. Tt has been shown that this de- ficiency comes from a lack of substances which must necessarily be pres- ent in the diet to maintain a state of normal nutrition. These substances, The Scope of Sanitary Science 59 concerning whose chemical nature we know very little as yet, have been called vitamins. They may not be present in certain articles of food or may be present in too small an amount to supply the needs of the body.- During the World War, in addition to an insufficient food supply, there was a lack of the proper kind and amount of these so-called dietary factors. This was especially the case with the peoples of the Central Powers where it was impossible to secure sufficient amounts of the proper kinds of food, especially the fats. Much has recently been written on the proper diet, and though much has been learned of a practical nature, much still remains to be unravelled. Communicable Diseases.—In order that disease may be transferred from one individual to another, it is necessary that there should be some means of transporting the cause from the person who is ill to some one who is susceptible to the given infection. Sanitary science is con- cerned with the isolation of the cause, the part of the body it affects, the avenues through which it enters and leaves the body, its length of life in the outside world, and the effect of this outside environment upon its powers of resistance. Most of the parasites which cause disease do not live very long outside the body, and consequently it is necessary that they be transferred at short intervals from host to host. Multiplica- tion rarely occurs outside the body. Under especial conditions, how- ever, a rapid increase may occur. This happens when the germ gains admission to certain foods, especially milk. In milk there is an enormous increase of many species, notably of typhoid and diphtheria bacilli. In the air, in dust, and even in water, most forms soon die. In the early days of bacteriology much emphasis was laid upon the danger of acquir- ing disease through the air, water, dust and from so-called fomites. Fomites is the term applied to any article which may be soiled with discharges containing disease germs, such as clothing, bed clothes, cur- tains, rugs, eating utensils, toys, pencils or any object whatever outside the body. In recent years it has been quite clearly shown that although infection may occasionally occur in this way, it is so infrequent as to be of minor importance. Kxperience has taught us more and more that transference is short both in time and space. The chief danger, then, is in contact of individuals with one another, and this contact must be relatively close personal contact. In those diseases in which the germ leaves the body through the nose and mouth, it is not the exhaled air, as was formerly thought, which is dangerous, but rather the small droplets which are given off in speaking, coughing and sneezing, or which leave the nose and mouth through some other physical stim- ulus. Tt is the duty of sanitary science to break the chain of trans- mission, the chief effort being directed to the earliest links in the chain. Rarely is it possible to break the chain before the germ leaves the body, but especial efforts should be directed towards the destruction of the cause as soon as it reaches the outside world. This is possible in diseases in which the cause leaves the body in the intestinal discharges, as in typhoid fever. This may be done by destroying the germ in the 60 Disease Prevention discharges. In diseases which are transmitted by insects, the best method is the destruction of the insect which acts as the carrier. To accomplish this result in a most satisfactory manner requires a knowledge of the life history of the insect carrying the germ. Sanitary science requires the intelligent cooperation of men trained in many fields of science: bacteriologists, protozodlogists, entomologists, engineers, chemists, zoologists, and others who are skilled in related fields of investigation. If we measure progress by the lessening of the number of persons infected, it must be admitted that little advance has been made in those diseases in which the causal organism leaves the body through the nose and mouth. With the exception of tuberculosis, respiratory diseases have not been decreased appreciably since the discovery of their causes and modes of transmission. In other readily communicable diseases in which the cause has not been found, but which are logically assumed to be chiefly spread through the secretions of the respiratory tract, such as measles, very little has been accomplished. The remarkable results secured through sanitary methods evolved in the investigation of intes- tinal and insect-borne diseases should stimulate workers to so increase their endeavors that they may accomplish comparable results in respiratory infections. Water-Borne Diseases.—In the past water has been responsible for the most widespread epidemics of intestinal diseases, particularly typhoid fever and Asiatic cholera. To what extent polluted water has influenced the incidence of other diseases than those of the intestinal tract has not been ascertained, since we have no direct means of deter- mining the question. However, it is a matter of common observation that whenever a water supply is improved there is also a decrease in diseases other than those of the digestive tract. Our water supply comes from the moisture which has escaped from the earth, the sea and other bodies of water. It is condensed in the air and falls to the earth as rain. ‘While in the air it takes up soluble impurities and insoluble dust par- ticles, molds, bacteria, and some other microscopic forms. Until it reaches the earth it is essentially pure, since the living organisms which it carries down are,.almost without exception, harmless. It soon con- tains many organic and inorganic impurities which it accumulates as it descends from the mountains and hills. The discharges from many animals and ofttimes from man are constantly present so long as it remains at the surface. All the water which does not pass into the soil is called surface water. It is always potentially dangerous, and this is particularly true when it is of recent accumulation, and from well- populated districts. Water which is secured from wells and springs is called ground water, since it has passed through the soil for a greater or less distance. Such water is sanitary provided no pollution has entered it. Pollution, however, often occurs in poorly constructed wells and in springs which are not protected from surface washings. In the rural districts many wells are polluted, since they are so constructed The Scope of Sanitary Science 61 that they are subjected to the entrance of surface washings, are not located at the proper distance from privies and barnyards, or the direc- tion of drainage is towards rather than away from the wells. In the larger communities the water supply is usually obtained from a common source. It is often not possible to obtain water free from pollution, hence it must be subjected to treatment before it is safe to use for domestic purposes. Several methods are in use to remove the dangers from pol- luted water. The usual methods employed are storage, slow sand filtra- tion, rapid mechanical filtration, and disinfection. Slow Sand Filtration—The principle of slow sand filtration is modelled after the natural filtration which takes place through the soil. Large, shallow reservoirs are constructed and filled to the depth of about six feet with material of varying degrees of fineness. At the bottom is placed a layer of small stone. Other layers are placed on top of this, each layer being made up of smaller component elements, the last layer at the top being sand. Very soon there is a development at the surface of bacteria and other lower plant forms, which help to fill the interstices between the particles, which still further increases the efficiency of the filter. A layer of scum is formed on the surface of the sand, which has to be removed at intervals, since in time it becomes so impervious that filtration becomes too slow. When it is operating at its best, from 95-99% of the bacteria present in the water before filtration are removed. This removes mechanically most disease-producing germs and some are also destroyed by the more vigorous non-disease producers which are always present in large numbers. The nature and size of the under- drains should be such that filtration may proceed with the same rapidity in every part. A good filter, operating satisfactorily, should remove 99% of the bacteria originally present in the water. In any case there should not be present more than 100 bacteria per cubic centimeter and colon bacilli should be absent or present only in relatively large amounts of water. To secure good results it is necessary to have some one in charge of the filtration plant who is so well trained that he understands all the principles of its operation. The results which have been secured from filtration alone have been very satisfactory where the process has been intelligently supervised. It has greatly reduced the prevalence of typhoid fever and other water-borne infections. Although filtration alone has resulted in a decrease of disease, still better results are obtained where disinfection is also employed in conjunction with it. Rapid Mechanical Filtration.—This method is often called the American Method to distinguish it from the slow process known as the English Method. In turbid waters containing fine clay slow sand filtra- tion is not effective, since the clay passes through the sand, carrying with it sewage bacteria. It is in waters of this kind that the rapid mechanical filter is most useful. In connection with this filter a coagulant is used. Aluminium sulphate, alum, and iron sulphate are employed as coagu- lants. Of these sulphate of alumina is used most extensively. If calcium bicarbonate is not normally present in the water, lime or soda must be 62 Disease Prevention added to help break up the alum. When the coagulant is added to the water it forms a jelly-like mass or coagulum which mechanically carries down all matter which is in suspension, including bacteria. The coagu- lum, after it has settled, forms a layer on the sand which acts in a manner similar to the biological layer of the slow sand filter. Mechanical filters act much more rapidly than the slow sand filter. Water passes through at a rate of from 125,000,000 to 175,000,000 gallons per acre in 24 hours, an average of 150,000,000 gallons. By the slow process not more than 3,000,000 gallons per acre pass through per day, when it is running under the best of conditions. The mechanical filters require cleansing several times daily, and this is accomplished by reversing the flow of water. The cleansing of the sand may be aided by mixing air with the wash water or by employing high pressure. With this method of filtration the best results are obtained if the water is held in a special basin for a time to allow chemical changes and sedimentation to take place. This will lessen the frequency of washing the filters, since a con- siderable amount of material will be eliminated which would otherwise cause a more rapid clogging. Rapid filtration when intelligently carried out will usually remove 95% or more of the bacteria which are present. They are not as efficient as slow sand filters but are especially useful where there is much turbidity, since the latter does not hold back the finer particles of clay. Mechanical filters require even more expert super- vision than does the slow sand filter. In both cases daily examinations of the water should be made by a competent bacteriologist before and after filtration. In recent years disinfection of water has made rapid advances. Calcium hypochlorite was at first almost exclusively used for this purpose. At the present time liquid chlorine is rapidly replacing it. Sometimes it is used without previous treatment or filtration. If water contains only slight amounts of materials in suspension filtra- tion may be omitted. Even in well filtered waters there is always the danger of typhoid or other disease-producing germs passing through the filter through the lack of proper supervision or carelessness. To pre- vent any danger from this source chlorination of the effluent, controlled by bacteriological examinations, should always terminate the purifica- tion process. Other chemical substances are sometimes used instead of chlorine. Ozone is the most valuable of these substances, being more effective in killing bacteria than any process of treatment except boiling. At the present time it is not practical since the cost of production is too great where large amounts of water are to be treated. In swimming pools it is practical and on account of its effectiveness, reliability, cheap- ness, and ease of operation it surpasses all other methods of treatment which have yet been devised. Ultraviolet rays have also been used with good results in the disinfection of water. To be effective, the water should be relatively free of turbidity, since it does not act well unless the water is clear. It has not been used on an extensive scale chiefly because of the cost of production and the skill required in the operation of ultraviolet equipment. Such equipment has been installed in several The Scope of Sanitary Science 63 swimming pools, and the results on the whole have been good. For dis- infecting small amounts of water in hotels and similar establishments its installation has apparently secured the results desired. Other dis- infectants have been used, but none of them have proved to be of suf- ficient value to warrant their recommendation. Milk and Other Foods in the Spread of Disease.—Of all foods milk is the most important from the sanitary standpoint. Milk is the only food derived from animals which is regularly consumed in the raw state. No other article of food contains to so complete an extent all the ele- ments of a well-balanced diet. It is the only suitable food for infants and should be consumed in liberal amounts by older children and adults. Adults should include in their diet as least a pint of milk per day, and children twice this amount. No single article of food is subject to so many sources of contamination, and it is probable that milk causes more disease than all other articles of food combined. Milk is an especially good food for the growth of bacteria. Under favorable conditions a few bacteria in milk increase to enormous numbers. In the production of milk there is a continuous chance of its becoming contaminated through the handling to which it is exposed. Fresh milk products are quite as dangerous as milk itself if they are not produced and handled properly. Infected milk has caused numerous and, at times, extensive epidemics. No other food, except water, has been responsible for so much food-borne disease. There are three principal ways in which milk may convey infec- tion: (1) The animal from which the milk is obtained, usually the cow, may be diseased and the germs causing the disease may get in the milk; (2) the germs from diseased milkers or other diseased persons who han- dle it may get into it; (3) bacteria which produce putrefaction multiply rapidly if the milk receives a massive contamination during milking or subsequently, if it is not kept cool, if it is kept too long, or when any | combination of these conditions is operative. The principal diseases which are caused by an infected milk are the following: Tuberculosis, typhoid fever, diphtheria, septic sore throat, scarlet fever, foot and mouth disease, Malta fever, milk sickness, dysentery, infantile diarrhcea, and the food poisonings caused by the Bacillus enteritidis group. The diseases of importance in this connection are tuberculosis, typhoid fever, diphtheria, septic sore throat, scarlet fever, and the diarrheal and dys- enteric disturbances which are of especial importance in infants and young children. The sanitary measures which have been adopted in many places, but unfortunately have not been put into operation everywhere, have been of great value. It is obvious that milk should be produced and kept as clean as possible, and protected from contact with infected men and animals. That milk may be produced in a sanitary way certain measures have been adopted by health departments, and although the methods differ to some extent, and the requirements vary, they are similar in principle. One of the first attempts to better conditions was the intro- duction of a system of inspection, 64 Disease Prevention Milk Inspection.— Farms and dairies are visited and all the condi- tions about these places are carefully observed. This includes the farm and its surroundings, the water supply, the condition of the cows, the method of milking, the milk utensils, the care of the milk, provisions for cooling, the milk house, and in fact everything is closely scrutinized. A score card is filled out which shows both the good and the bad things which have been observed. Many animals suffer from tuberculosis, and these animals should be eliminated from the herd. At present it is not possible to discard all the milk from tuberculous cows, since it would decrease the amount and increase the cost to such an extent that those children, who need milk the most, would be deprived of an article of diet which they must have if they are to maintain a normal nutrition. The elimination of all tuberculous cows would, therefore, lead to greater disaster than would be caused by the consumption of tuberculous milk. A gradual weeding out of all tuberculous animals would be a wise pro- cedure not only from the disease standpoint, but also as an economic measure, since tuberculous cows are not profitable milk producers. Milk from tuberculous cows may be made perfectly safc for consumption through pasteurization. Not only does it make it safe, so far as bovine tuberculosis is concerned, but it also protects from milk-borne human tuberculosis and all other diseases which are likely to be conveyed through milk. Pasteurization.—There are two principal methods of pasteurization, the flash method and the holding method. The flash method consists in raising the milk to a high temperature (180°F.) and keeping it at this temperature for a minute or so and then rapidly cooling it. This method is not reliable. It is often called the commercial method. Sanitarians do not endorse it, but have almost unanimously adopted the holding method. The holding method consists in heating the milk to a temperature of 145° F. and holding it at this temperature for 30-45 minutes. If all the milk is heated to this temperature and held for 30-45 minutes, it will kill all disease-producing bacteria which are apt to be present in milk. Pasteurization does not in any way injure the nutritive value of milk. It does not affect the fat soluble vitamin, but it does lessen the amount of antiscorbutic vitamin. The loss, however, is no greater than results from keeping milk for too long a time. Babies should be breast- fed. This is nearly always possible, but is all-too-frequently neglected since it interferes with social or other engagements. Older children con- sume other foods with milk and in this way any deficiency in vitamins from pasteurization is supplemented. Any deficiency in vitamins, which may arise from feeding infants with pasteurized ecow’s milk, may be pro- vided for by giving orange juice or tomato pulp, which ought always to form a part of the diet of bottle-fed babies. It is possible for milk to become infected after pasteurization in the process of bottling, but this rarely happens. When it does it is due to gross carelessness. The ideal method of pasteurization consists first in filling the bottles, capping them The Scope of Sanitary Science 65 with the metal instead of the small paper caps, and then heating and holding according to the directions already given. This would remove all danger of infection from milk, since nothing comes in contact with it after pasteurization. The cost of pasteurizing in bottles is at the present time so high that it cannot be put into general practice. Graded Milk.—In some cities milk is graded and classified. Grade A is considered suitable for babies; grade B for adults; grade C can only be used in cooking. The goal which should be sought is that which will permit the sale alone of milk which meets the requirements of group A. It should come from properly inspected herds; it should be pas- teurized under the supervision of an up-to-date health department; the efficiency of pasteurization should be controlled by bacteriological exam- inations; milk from cows suffering from tuberculosis or any other dis- ease should not be permitted to be sold ; milk should be retailed only in bottles or some similar sanitary container and under no conditions should it be distributed in bulk. Pasteurization in the Home.—Pasteurization in the home, if properly done, is the best procedure of all. There are on the market several effi- cient home pasteurizers which will give excellent results if all the details of manipulation are carefully followed. In many instances failure would result from lack of appreciation of the necessity of paying exact atten- tion to details; hence, except in individual cases, pasteurization at a central station is the safer procedure. Rarely have epidemics of communicable diseases of considerable pro- portions arisen from articles of food other than milk and water. The reason that they are not of frequent occurrence is because they are not so subject to human pollution, since they are not usually consumed in the raw state. Within recent years attention has been called to several epidemics of typhoid fever due to the consumption of raw shellfish. This danger has been largely removed through legislation which does not permit oyster beds, or places for the growing of other shellfish, to be located in brackish water or in spots where there might be pollution through sewage. Celery, water cress, lettuce and other vegetables, con- sumed in the raw state, and fresh fruit have occasionally been impli- cated. Any article of food might be infected after cooking through a disease carrier or through gross carelessness. Sometimes the heat em- ployed does not destroy all typhoid bacilli, since it does not rise to a high enough temperature in the center of the mass. The celebrated “Typhoid Mary,’”” who was a typhoid carrier, is an illustration of a contamination of food after it has been cooked. Another illustration of what may result from the presence of living typhoid bacilli, which have escaped destruction in the process of cooking, was reported from Cali- fornia a few years ago. In 1914 there was an epidemic of typhoid fever in Hanford, California, in which 93 people were infected through eating spaghetti which had been prepared by a typhoid carrier. Bacterial Food Poisonings.—Another group of diseases arises from sources usually not human. The usual article of infected food is meat, 66 Disease Prevention though other articles, especially milk and its products, may occasionally be implicated. Members of the colon-typhoid group, or closely allied organisms, are the usual cause. Gaertner, in 1888, isolated from a cow, which had caused an epidemic of food poisoning or food infection, and from a man who had died as a result of such poisoning, a bacillus which he named the Bacillus enteritidis. Other poisonings have occurred since then in which the same or similar organisms have been found. The infection may come from consuming the meat of an animal infected before it was slaughtered, or it may arise from meat which has become infected subsequent to slaughter. To prevent such infections or poison- ings there should be competent inspection of all slaughtered animals. Cattle suffering from septic or pyemic diseases should be condemned, and the carcasses destroyed, especially if the Bacillus enteritidis is isolated from the diseased animal. Great care should also be taken to prevent the transmission of any infection from the diseased animal to other car- casses. Attention has been called quite frequently, during the past few years, to fatal poisonings through eating ripe olives and canned goods, particularly asparagus, spinach, cottage cheese, and some other foods. These poisonings have most frequently occurred in those who have eaten home canned foods, prepared by the cold pack method. In some instances commercial products have been the source of trouble, particu- larly in the case of olives. The cause of tunis specific form of poisoning 2s discovered by Van Ermengem in 1895. In an outbreak which oe- carred at Ellezelles, in Belgium, from eating pickled ham, 23 persons were made ill and three died. From the nam, and from the spleen and intestinal contents of one of the fatal cases, Van Ermengem isolated a bacillus which was shown by animal experimentation to be the cause of the poisoning. This germ belongs to the group of anaérobic organisms (those which only grow when air or oxygen is excluded), which he named Bacillus botulinus. This name was given to the cause, since most of the cases reported previous to 1895, had arisen from eating sausage (botulus) which is frequently eaten in the raw condition in Europe. In Europe this type of poisoning, which is called botulism, is more common than in the United States. It is generally due to the consumption of con- taminated meat. In the United States it has been caused most frequently by the consumption of canned foods such as asparagus, spinach, ete., which have previously been mentioned. The prevention of poisoning from eating canned foods is a simple matter, the only requirement for removing danger being that of boiling the contents of the ean for 10 min- utes before eating. This temperature destroys the poison (toxin) even when applied for this short period. If it is allowed to stand for some time it should again be boiled. Sometimes evidence of spoiling may be present, at other times there is no apparent change in the food. Any- thing unusual in the odor. taste, or appearance of canned foods should cause them to be discarded and destroyed. Since boiling removes all danger from canned foods, so far as botulism is concerned, it should be practiced even though they appear normal. The Scope of Sanitary Science 67 Sewage Removal and Disposal.—In early times, when people were not closely aggregated, the question of the removal and disposal of the bodily wastes was a relatively simple one. When people began to live in larger groups the problem became more difficult in proportion to the size of the groups and the restriction of the areas in which they dwelt. The introduction of more liberal supplies of water for cleaning and washing purposes demanded some means of disposal. At first the used water was thrown on the ground outside the habitation and, as the community became larger, it was allowed to flow in the streets, particu- larly in the gutters. Later water-closets were installed, and for some time the discharges from these were allowed to flow in the gutters with tha other waste waters. This method of disposal was always offensive, and in time became intolerable. For the betterment of conditions sub- terranean pipes were laid and sewage was conveyed away from the dwellings, which, to a large extent, removed the nuisance. It is only during the last fifty years that proper attention has been paid to this problem in the United States. During this period of ap- proximately fifty years the methods of the collection and disposal of sewage, which are practiced today, have had their development. In order to achieve the most satisfactory results two important fac- tors must be considered ; first, the design, construction, and maintenance of the system must be worked out in such a way as to remove nuisance and promote health; secondly, that plan should be selected which will best meet the requirements, at the lowest annual cost, and should include both fixed and operating charges. Collection and Disposal.—Two plans are still in operation, private and municipal. The general tendency today is in favor of municipal ownership and operation. If the city administration is efficient it can be done better, and at a less cost by the city than it can under private ownership. If for any reason it may seem best to collect or dispose of sewage through private contract efficient supervision is imperative. Combined and Separate Sewerage Systems.—A combined sewerage system receives domestic sewage, trade wastes and all rain water which must be carried away or removed. When the trade wastes and domestic sewage are carried away by one set of underground sewers, and the rain water by another, the system is called the separate system. Some- times the former is called the single, the latter the double system. Both may be satisfactory, local conditions determining which is best adapted to any given place. In general it has been found that the separate system is more expensive in large cities and in densely populated areas. However, local conditions may be in favor of the double system, espe- cially if sewage treatment is necessary. If a sewerage system is to be installed it should be done under the advice and supervision of an en- gineer whose past performances have shown that he is competent. Sewers should be built of the best and most durable material. No makeshifts should be installed with the anticipation that they will serve the purpose until a more permanent plant is established. 68 Disease Prevention Disposal by Dilution.—After a sewerage system has been designed the question arises as to what disposition is to be made of the outflow or effluent. The simplest and most primitive method is to turn it into the nearest body of water. This may be permissible if the body of water is large enough to so dilute it that a nuisance is not created, and if it does not prevent the continuation with safety of the uses of the water which prevailed before sewage was emptied into it. If it is reasonably certain that it renders the water inimical to health, or that it destroys animal life, its use as a receptacle for raw sewage should be prohibited. Sewage Treatment.—Although sewage in the raw state, if emptied into a stream, may be dangerous to health or create a nuisance, it may be treated in such a manner as to render it inoffensive and at the same time not dangerous to health. Sometimes it is treated directly without any preparatory process. This may be satisfactorily done if the amount of sewage is small and does not contain too much solid matter. As a rule, preliminary removal of the larger bodies in suspension is neces- sary if the best results are to be secured. Screening.—To remove the larger bodies in suspension, screens with meshes of different sizes are used. If the mesh is greater than half an inch, they are designated coarse; if less, fine. Whether large or small they become clogged in a short time, and it is consequently necessary that special provisions should be made for cleaning them. Several types of screen are on the market. Of these the Inclined Disc Screen, better known as the Reinsch-Wurl Screen, is perhaps the best. The screenings must be disposed of and this is done after first pressing to remove water and diminish bulk. The resulting mass is then burned, used for filling purposes, or buried. Sedimentation.—Of more importance than screening is the process of sedimentation. There are five methods of accomplishing this object which are commonly employed : (1) Grit Chambers—These are small settling basins in which the sewage is allowed to remain for a short time, often for only a few min- utes. The velocity of flow is from 10 to 20 inches per minute. The sediment which collects is composed chiefly of sand, gravel and other heavy materials. Some organic matter is also incorporated, the amount usually being sufficient to render the sludge offensive. They need fre- quent cleaning. (2) Plain Sedimentation Tanks.—Only a small part of the bodies in suspension are removed by screens, rarely more than 5-15%. Grit cham- bers only remove the heavier bodies which constitute a small part of the solids, 15-25% being removed in one hour; a much longer time than sewage is ordinarily allowed to remain in the chamber. In 6 hours plain sedimentation removes from 25-607, the larger amount from stronger sewage. As would naturally be inferred the weaker the sew- age the smaller the percentage of sediment. In plain sedimentation tanks the flow is slow, usually from 0.1-0.5 inches per minute. Sewage The Scope of Sanitary Science 69 is retained from one to twelve hours. The sludge must be removed at frequent intervals to prevent its becoming offensive. (3) Septic Tanks—In this process the basin is made large enough so that it retains sewage from 8-24 hours or longer. The flow is usually from 0.1-0.3 or more inches per minute. Oxygen is excluded, the de- composition being brought about almost exclusively by anaérobic baec- teria. By bacterial activity some of the solid organic matter is liquefied or converted into gas. A scum forms on the top and there is a con- tinual movement of the sludge from 'the bottom to the top and in the reverse direction. From 10-40% of the solid organic matter is decomposed, the larger amount occurring in strong domestic sewage. Septic tanks may take care of the small amounts of sewage for a single household or for a small number of residences. It is not safe to empty the untreated effluent in streams, since disease-producing bacteria may be present in it to almost as great an extent as in raw sewage. In individual instances, as in the country, where there is a water carriage system in the house, sewage may be satisfactorily disposed of by means of the septic tank. The effluent should not be allowed to escape at the surface, but should be conducted away by underground pipes, placed at least 18 inches below the surface. The drain is usually made of 3-4 inch tile, laid in rows 2-3 feet apart. The best results are obtained in sandy soil. In soil composed of clay this method cannot be satisfactorily used. The joints between the separate pieces of tile should be sufficiently loose to allow some of the effluent to escape at each joint. In this way all the sewage will be taken up by the soil if the drain has been properly con- structed. In septic tanks from 30-75% of the suspended matter is re- moved in 24 hours, the larger percentage from the stronger sewage. Much sludge is formed which has to be disposed of at longer or shorter periods. (4) Digestion Tank.—The best known and probably the most efficient form of digestion tank in use today is that known as the Imhoff or Emscher tank, or one constructed on the same principles. The Imhoff tank consists of two intercommunicating tanks, an upper flow cham- ber in which sedimentation occurs, and a lower chamber in which the sediment and larger solid portions settle in the form of sludge. In the lower chamber the organic matter is decomposed by bacterial action. The advantage which this method has over others is that it confines the septic action to the lower compartment, does not allow the decomposition products to mix with the sewage in the upper compartment, it more com- pletely decomposes the organic matter and hence improves the character of the sludge. From 40-85% of the suspended matter is removed, the amount depending on the strength of the sewage and the time it is kept in the tank. (5) Chemical Precipitation.—To hasten sedimentation and remove substances in suspension, chemicals are often employed. Lime, copperas and alum are used for this purpose. When lime is used alone, from 500-1,000 pounds are required per million gallons; with copperas the 70 Disease Prevention same amounts of lime as when used alone, and in addition from 100-1,000 pounds of copperas. From 500-1,500 pounds of alum are required per million gallons of sewage. In all processes of sedimentation a large amount of sludge is formed. To take care of this is a troublesome problem. Sometimes it is spread out and the water removed by evaporation, at others it is pressed to remove the water. Both methods are costly, and each may create a nuisance. After drying or pressing, the solid remains must be disposed of by burying, in filling low places, or by burning. The Miles process, in which sulphurous acid is used primarily to remove grease, and the extracting of fertilizing substances from the activated sludge, gives promise of being so developed that sewage treatment may become eco- nomical, and, in individual instances, where conditions are favorable, may actually become a source of profit. Purification Processes.—In many instances, the sewage, which has been subjected to the processes above described, cannot be directly dis- charged into a stream or otherwise disposed of without further treat- ment. Where the amount of sewage is small and the conditions are favor- able subirrigation may suffice. Larger amounts require further treat- ment to prevent nuisance and danger from disease. Various methods are used, the aim being to employ the one best suited to local conditions. Five recognized methods of treatment are in use, broad irrigation, inter- mittent sand filtration, contact beds, trickling filters and activated sludge tanks. Broad Irrigation.—Broad irrigation is practically confined to Europe. Berlin and Paris have extensive sewage farms on which their sewage is deposited. This method is similar to an irrigation system, the sewage being distributed through ditches or similar devices. Crops are raised on these farms and a sufficient revenue is derived from them to help pay the cost of operation. There is relatively little value derived from the sewage as a fertilizer, the principal advantage coming from the water which serves as an irrigant. The purification achieved by this method is usually satisfactory. Sometimes an offensive odor is produced, which, though harmless, creates a nuisance. Intermittent Sand Filtration.—In intermittent sand filtration the sewage is allowed to flow at intervals over especially prepared beds of sand. The amount applied is so regulated in quantity as to quickly disappear in the sand. Air is taken in and this aids in the decomposition which is brought about by bacteria. The organic matter becomes com- pletely nitrified if the filter is properly constructed and operated. Be- neath the filter are under-drains which carry away the effluent, the lat- ter being clear and almost free from sewage bacteria. This method is the most efficient of all the methods in use where local conditions are favorable. It can only be used in regions where there are convenient areas of sandy soil. Contact Beds.—Contact beds consist of water-tight compartments filled with broken stone from } to 2 inches in diameter. These beds are The Scope of Sanitary Science 71 from 2 to 8 feet in depth and are usually built in series, the effluent of the first flowing into the second, the second into the third, and so on if there are more in the series. When this method was first introduced the sewage was admitted from below until the bed was filled, and then allowed to stand for about 8 hours. It was then drained and allowed to stand idle for from 4 to 16 hours to permit of oxidation. Contact . beds are sometimes filled with other materials than stone, such as slag, coke, broken bricks, and coarse gravel. The usual procedure at the present time is to allow the effluent, which has passed through a septic tank, to slowly fill the contact bed. It is then held in the bed for about two hours to permit the suspended matters to settle in the interstices of the bed. During this period oxidizing bacteria act upon the organic matter which settles to form a film on the surfaces of the stones or other substances in the bed. An hour is the usual time allowed for emptying the bed. It now stands empty for about four hours, when it is again filled. ‘While standing still further oxidation of the organic matter, which is incorporated in the film, occurs. When sewage is passed from septic tanks, which have been properly constructed and operated, through a series of contact beds, as much as 70% of the organic matter, 85% of the bacteria, and 90% of the sediment may be removed. After several years’ operation, usually not more than five, contact beds must be cleaned. The stones and other materials are taken out and the substances adhering to them, which have caused the clogging, are removed. At best contact beds are not very satisfactory on account of the cost of operation and the character of the effluent, hence they are seldom used. Trickling or Sprinkling Filters.—The trickling filter, also known as ‘‘sprinkling filter’” and ‘‘percolating filter,’’ has a contact bed sim- ilar to that just described. The materials employed are usually coarser; broken stone, clinkers, coke, coal, and other hard, sharp substances are used. In the deeper beds coarser material is used; in the United States broken stone is the principal substance. The sewage is delivered to the beds through fixed or travelling, rectangular or rotary sprinklers. Some- times they are operated through the pressure of the sewage, at others through some other power. The object of using the trickling filter is to furnish a large surface for the incorporation of oxygen. The oxygen obtained in this way is used by aérobic bacteria which so decompose the organic matter that the effluent is not putrescible. If the filter receives the effluent from a sedimentation or septic tank, as much as 90% of the sediment and 95% of the bacteria may be removed, provided it is intel- ligently operated. The effluent is usually not clear and should, therefore, be passed into settling basins before it is discharged. This method is especially useful in places where there are no sandy areas which would make intermittent filtration too expensive. Each acre of a properly constructed and operated trinkling filter will take care of from 1,000,000 to 2,000,000 gallons of sewage per day, the plain contact bed of about half as much per acre. 72 Disease Prevention The Activated Sludge Process.—This process is based on the fact that sludge, which contains a large amount of oxygen, furnishes a favor- able environment for the growth of aérobic bacteria. In order to obtain the necessary amount of oxygen for this purpose it is introduced artifi- cially. In operation compressed air is forced through the sewage con- fined in a tank. After a few weeks the particles in suspension form a colloidal mass. The bubbles of air keep these little masses in a con- tinuous state of agitation, and the colloidal material becomes attached to these masses. Decomposition takes place in a manner similar to that going on in the films formed in the interstices of contact beds. After the preliminary activating process has reached the proper stage, sewage is admitted. Sometimes the continuous flow, at others the fill and draw method, is used. Some nitrification occurs, but it is not complete. The sludge which is formed has more manurial value than that obtained through other methods. As yet it may be said to be in the experimental stage. If this method proves successful, it will replace other methods, now in use, because of the simplicity of plant construction and opera- tion. Other factors, which will have to be considered, are the cost of aération and the removal of sludge. Whatever method is used for purification, the final step in the proe- ess should be disinfection of the effluent. It is now practicable to eco- nomically disinfect effluents. Calcium hypochlorite (chloride of lime) or liquid chlorine are both effective and economical. Septic sewage requires 300-400 pounds, crude sewage 150-300 pounds, effluents from contact beds or sprinkling filters 100-150 pounds of hypochlorite per million gallons of effluent. When calcium hypochlorite is employed it is used in a 1-2% solution. Calcium hypochlorite should contain 25-30% available free chlorine. When liquid chlorine is employed, an amount equivalent to the available free chlorine in calcium hypochlorite, should be used. Disposal of Sewage in Rural Districts.—In many rural distriets no provision whatever is made for the disposal of discharges from the body. They are deposited on the surface of the soil, freely exposed to insects and domestic animals. As a result of such practices, much un- necessary disease is produced, especially in the South where the warm season is prolonged. In this area hookworm disease is very prevalent, since the opportunities of infection are always operative, through the combined practice of going barefooted, and the careless deposit on the ground of exposed fecal matter. Other diseases, such as typhoid fever, and the diseases in which the cause is present in the intestinal discharges, are greatly augmented because of these conditions. In the disposal of the discharges of the body in rural communities, and in places where there is no provision for the collective disposal of sewage, the question becomes an individual one for every householder, and for buildings which are occupied by man, such as schools, lumber camps, or any other places which are permanently or temporarily oc- cupied by man. Several devices have been proven to be sanitary, pro- The Scope of Sanitary Science 73 vided they have been properly constructed, and the necessary attention is regularly paid to them after construction. In the adoption of any method for the disposal of discharges from the body, certain fundamental requirements should be observed. The principal requirements are those which will prevent any possibility of the discharges coming in contact with man himself, or any other animal which might carry infectious material, or with water, or any article of food, which may be consumed by man. It is, therefore, obvious that measures to prevent exposure should be provided for, whatever method is employed. In choosing a method of disposal due consideration must be paid to the cost of construction and maintenance. In general, it may be said, that the device which is simplest and at the same time efficient, will give the best results. The Chemical Closet.—The chemical closet, which consists of a water- tight metallic tank containing both a disinfectant and deodorant, is probably the most efficient receptacle; its cost, however, precludes gen- eral use. The privy, no matter what type of construction is used, should be screened in such a way that no insect may come in contact with the contents of the receptacle. - Every possible opening, not otherwise pro- tected, should be screened. The lid covering the seat should be provided with an automatic closing device. The receptacle should be water- tight. One of the best types of privy is that devised by Lumsden, Roberts and Stiles of the United States Public Health Service. In this type, the Li. R. S. privy, the solid excreta are deposited in a water chamber. Here the solid matter is decomposed by bacteria, chiefly by anaérobic forms. In the decomposition gases and soluble substances are formed. The liquefaction of the solid substances, and the decrease in volume through evaporation, lessen the amount of labor and the cost of disposing of the material. For the construction of the Li. R. S. privy the fcllowing are needed: * ‘“(1) A water-tight tank, barrel or other container, to receive and liquefy the excreta. ““(2) A covered water-tight can, pot, barrel or other vessel, to receive the effluent or outflow. ‘“(3) A connecting pipe about 214 inches in diameter, about 12 inches long, and provided with an open T at one end, both openings of the T being covered with wire screens. ‘“(4) A tight box, preferably zine lined, which fits tightly on the top of the liquefying barrel. It is provided with an opening on top for the seat which has an automatically closing lid. ““(5) An antisplashing device, consisting of a small board placed horizontally under the seat about an inch below the level of the trans- verse connecting pipe. It is held in place by a rod, which passes through a hole in the side of the seat and by which the board is raised and lowered. A layer of chips floated in the tank may be used instead of this antisplashing device. 8 Stimpson, W. G.: Prevention of Disease and Care of the Sick, U. S. Pub. Health Service, 1919, p. 43. 74 Disease Prevention ‘“(6) A ventilation pipe, such as a stove pipe or wooden flue, con- necting the space under the seat with the open air. “The liquefying tank is filled with water up to the point where it begins to trickle into the effluent tank. A pound or two of old manure should be added to the water to start fermentation. As an insect repel- lent some form of petroleum may be poured on the surface of the liquid in each container. ‘“When the privy is to be used the cord is pulled up so that the anti- splashing board rises to within about one inch of the surface of the water. The fecal material falls into the water, but this board prevents splashing. Before leaving the privy the person should sink the anti- splashing board by pushing down the rod so that the fecal matter and the toilet paper will float free into the water. ‘“ Although some of the fecal matter floats, it is protected both from fly breeding and fly feeding in the following ways: First, by the auto- matically closing lid; second, by the water; third, by the film of oil; and fourth, by having the apparatus located in a screened place, which should be done for additional safety. The film of oil prevents the breeding of mosquitoes in the tank. “The fecal matter ferments in the water and gradually liquefies. Disinfectants must not be used in the liquefying tank because they stop the fermentation. When the level of the liquid is raised the excess flows into the effluent tank, where it is protected from insects by the cover and a film of oil. The effluent may be allowed to collect in this tank until it reaches the level of the connecting pipe, when it may be dis- posed of in any one of the following ways: ““Burning.—In cities, towns, and villages privy contents may be disposed of most conveniently, most safely, and most economically by burning with other refuse in an incinerator. At country homes also disposal by burning is the safest method, but because of lack of facilities at such homes it is usually not feasible. ‘Discharge into a Sewer.—If a sewer is available, privy contents may be dumped through a manhole directly into it and the sewer flushed with water from a fire hose. In doing this precautions (grit chamber or gratings) should be used to prevent choking of the sewer with coarse insoluble matter. From a sanitary standpoint, the diluted privy contents are as safe for discharge through the sewer as is the sewage of the community. ““ Burial.—In small villages and country communities the disposal of privy contents by burial is usually the most available method that is practicable. The place selected for burial should be at least 100 yards away from any water supply and should not drain towards it. ““To take advantage of the natural agencies of purification in the soil and to protect underground sources of water supply as much ac possible, the burial should be in the upper two feet of the soil. Furrows (such as are made by an ordinary plow) or narrow trenches should be used rather than large pits, so that the purifying agents of the soil The Scope of Samitary Science 75 will not be overworked. As an additional safeguard, disinfection of the exereta by heat or chemicals may be employed before such burial. ““The effluent of the I.. R. S. privy is particularly adapted to dis- infection. If human excreta are disinfected by boiling, the matter is safe for use as a fertilizer, even near the dwelling. ““The field used for the burial of untreated excreta should be one which is not to be cultivated for at least 6 months; and in sections where hookworm disease prevails a minimum of 12 months should be allowed. In cold climates trenches should be dug before the ground freezes. They should be ample to take care of the contents during the winter and should be marked with stakes, so that they may be found even when covered with snow. The matter put into these trenches should be covered as soon as the ground thaws. Trenches for winter use should be about 2 feet deep. In open weather, the matter should always be covered immediately ; the furrows should be from 6-12 inches deep; and the excreta scattered along the furrow, in a layer not more than 2 inches in thickness, and covered with 6-12 inches of earth. ‘“The use of a field for the burial of human excreta in this manner increases the fertility of the soil. This is particularly the case if the matter is given as much as 12 months to undergo thorough rotting. “The effluent from the Li. R. S. privy is more readily purified by the natural agents of the soil than are crude excreta. It is liquid, and its volume is relatively small. It is therefore well adapted for direct disposal into the active subsurface soil. The place selected for such disposal should be well away from (at least 50 yards) and not draining towards any water supply. The effluent may be conveyed under ground through a water-tight pipe for the necessary distance and then dis- tributed into the soil by means of drain tile. The tile should be laid about 12 inches below the surface of the ground. If the soil is not porous, the distributing pipe may be laid in a trench filled with sand or gravel. The increased fertility of the soil along the track of the dis- tributing pipe may be used advantageously to cultivate an attractive hedge of rose bushes or other shrubs or to cultivate a row of corn or other plants, the edible parts of which are produced well above the surface of the ground.” The L. R. S. privy is perhaps the best type which has been devised for the disposal of excreta in rural communities. Its cost is not great, nevertheless so great, that it is not adopted by those living in poorer com- munities. For such communities the pail or pit privy may be installed. The pail privy should have an insect-proof box or vault in which is placed a pail, barrel, tub, or some similar receptacle for the excreta. The receptacle should not be allowed to become full, but should be emptied before this happens. This requires constant and regular at- tention. The contents may be burned or disposed of according to the directions already given under the L. R. S. privy. The pit privy, which is extensively used, is often not properly cared for and consequently becomes dangerous and at the same time a nuisance. Where the same 76 Disease Prevention pit is used year after year, it is necessary to clean it out at frequent intervals. Cleaning is often neglected, protection from access to flies, other insects, and animals is looked after inadequately or not at all Sometimes a pit is dug, and after it has become partially filled, another is constructed and the privy placed over it. The pit should not be allowed to become more than two-thirds filled before a new pit is dug. After the pit has become partially filled the excreta should be covered with earth, the upper third at least being filled with dirt. Sometimes pits are made of concrete. Such pits should have walls and bottoms 3-6 inches thick and should be water-tight. Screening, disposal of contents, and care, should be the same as for other types. The location of a privy depends upon several factors. In sandy soils they may be placed within 25 feet of a well, with probable safety. A distance of 50 feet or more is preferable even where there is a sandy soil. Due consideration should also be given to the elevation of the ground water and the direction of its flow. The greater the distance which separates the privy from the well the better. A privy should not be located at a higher elevation than the well. It should be so placed that the direction of the flow of the underground water is away from the well and towards the privy. In clay soils, which erack in dry seasons, and in limestone regions, privies should not be so constructed as to permit the leachings of fecal matter to percolate through the soil, since wells may be polluted at distances even as great as a mile or more. Cesspools.—Cesspools are constructed by digging deep holes in, the ground and lining them with walls which permit the escape of sewage into the surrounding soil. The walls are placed in the cesspool to prevent caving and are practically never of water-tight construction. In sandy soils they may be permissible under the same conditions as have been described for the leaching privy. Since they are covered the oxygen supply is very slight. Bacterial action is similar to that which takes place in a septic tank. Cesspools require periodic. cleaning, the dis- posal of the contents creating a problem in itself. Cesspools often overflow, especially when constructed in soils which are impervious, or when they are water-tight. It is not permissible to allow the contents to flow over the surface of the ground, hence it is necessary to take care of the overflow or effluent by subsurface irrigation as in the L. R. S. privy. The sludge removed in cleaning the cesspool should be buried or disinfected, preferably both. Solid Refuse Disposal.—Under the term refuse are included all of the solid wastes such as garbage, street cleanings, manure, dead animals, night-soil, rubbish, and ashes. Strictly speaking the disposal of solid refuse is not a sanitary problem since it is only in very rare instances capable of directly transmitting disease. It is rather an economic prob- lem; for esthetic reasons it should be removed as a matter of cleanliness. The odor from decomposing garbage, dead animals, or manure is offensive and creates a nuisance, but the odor has very little significance as far as disease is concerned. The Scope of Samitary Science Iu Since rubbish is often made up in part of old tin cans, bottles and other utensils in which water may collect, it should be removed at fre- quent intervals to prevent the breeding of mosquitoes. The removal of rubbish is a stimulus for cleanliness in other respects. Garbage should be removed at frequent intervals, especially in hot weather. If allowed to stand too long it decomposes, with the production of offensive odors, and may serve as a breeding place for flies. Manure usually does not become so offensive from its odor, only too frequently it is allowed to collect and stand for a sufficient time to permit of the breeding of enormous numbers of flies. Flies and mosquitoes are a nuisance and may serve as carriers of disease, hence, every effort should be made to destroy their breeding places. Collection of Solid Refuse.—The methods of collecting garbage and other solid refuse vary in different cities. In some the entire matter is cared for by the municipality through municipal labor; in others private contracts are made which may cover the collection and removal of all solid refuse. In still others, a part is cared for by the city, the rest by a private individual or company. Opinions differ in regard to the best method. For some communities it may be better cared for by private contract, in others by the municipality. In general it may be said, that it is possible for the municipality to look after all its refuse, in a better way and more economically, than it can be done by a private concern. Whichever method is used, the material should be col- lected in properly covered wagons, to prevent the blowing about of material from the surface of the load, and the scattering of offensive matter upon the streets. Covered wagons also minimize the offensive odor which is only too manifest when the load is exposed. For the removal of night-soil and dead animals, wagons especially designed for this purpose should be used with trained men to operate them. In many instances, garbage and other rubbish, ashes often being in- cluded, are all placed by the householder in the same can. This is called the mized system. When the garbage is put in one can, rubbish and ashes in another, it is called the separate system. In some places the separate system is the more economical if we consider the cost of disposal, in others the mixed system. Methods of Disposal.—In smaller communities the disposal of refuse is usually not a difficult problem. The ashes are hauled away and used for filling purposes. Rubbish is cared for in a similar way, much of it being burned at a dump. Dead animals are disposed of at rendering plants or are buried. Night-soil is buried or used for fertilizing pur- poses. When night-soil is used as a fertilizer it creates a hazard, especially if left exposed to flies. Vegetables eaten in the raw state, such as lettuce, should not be grown in a soil fertilized in this way. Garbage is sometimes burned and it is frequently fed to hogs. In larger communities the problem is more difficult. In large sea- board cities, like New York, the refuse is loaded on barges and carried out to sea where it is dumped. This is not an ideal method since some 8 Disease Prevention of the material is washed back to shore where it collects and creates a nuisance. In other cities, particularly those which are inland, other methods of disposal must be employed. The two methods which are most commonly used are the incineration or destructor and the reduction processes. Incineration or Destructor Plants.—Incinerators are constructed on two general principles, the combined and the single unit furnace. In the combined type there are several grates and divided ash pits. The heat from below aids in removing water from the material on the upper grates and the products of combustion are collected together in a single furnace. The heat generated varies from 1,200-2,000° F. In some incinerating plants all the solid refuse is burned including manure and street sweepings; in others, as, for example, Boston, the refuse is sorted, paper and other articles of commercial value are taken out, the re- mainder incinerated. Several other cities have adopted the same prac- tice. Since many of the articles, designated as garbage or rubbish, come from the homes where communicable diseases exist, the practice is ques- tionable even though revenue is derived from it. Sometimes plants are installed which operate at a lower temperature than incinerators. These so-called crematories have not proved satis- factory. When incinerators are properly constructed and intelligently operated, very little odor is observed and the smoke produced is not objectionable. Reduction Plants.—This method of disposal is used in several of the larger cities of the United States. New York, Boston, Buffalo, Los Angeles and other cities dispose of their garbage through contract with private owners of reduction plants. Los Angeles let a contract in 1913 under which 51 cents per ton was received for garbage delivered at a private reduction plant. In 1905 the city of Cleveland, Ohio, bought the private reduction plant which had been taking care of its garbage. In 1910 Columbus, Ohio, built the first municipal plant. The yearly reports of these cities on garbage disposal show that the returns received from grease, and the tankage which is used as a fertilizer filler, are in excess of the capital and operating charges on garbage after it is delivered at the plant. Other cities which operate municipal destructors record similar results. To obtain the best results and to prevent damage to the plant, only animal and vegetable household and market wastes should pass through the reduction plant. When other things such as bottles, glass, tin cans, and similar articles are present, they should be removed before the garbage is put in the plant. As a rule the construction of reduction plants requires a smaller initial outlay than does an incineration plant. Reduction plants save some of the material which is destroyed in the incineration plants, Grease and tankage recovered have a com- mercial value which in part pays for the disposal. The garbage is passed through a series of digesters and kept under a steam pressure of about 60 pounds from 6-12 hours or longer. It is then pressed The Scope of Samitary Science 79 to remove the water and grease, which are then conducted into settling tanks where the grease, which rises to the top, is skimmed off. The water is then allowed to flow into the sewer, or it is evaporated and the solid residue added to the tankage. Sometimes the tankage is treated with hot naphtha to remove the grease which is not removed with the water. The treated, or untreated tankage is next dried and ground, after which it is used directly as a fertilizer, or is mixed with phosphates and other fertilizing substances as a filler. As much as 3% of grease and 20% of tankage may be recovered. Sometimes the grease is par- tially purified at the plant but it is usually sold without much refining. The grease recovered is used in the production of soap. In the best plants all vapors are condensed and the gases purified, or conveyed to the boiler furnaces and burned. In poorly designed reduction plants, or in the better type carelessly operated, there may be offensive odors. If they are properly designed, and operated by skilled men, this may be almost or wholly prevented. The type of garbage disposal plant depends for economic reasons on local conditions. Where power is expensive, the steam generated may have enough value to render operation by incineration cheaper than by reduction. Where power is cheap the reverse will usually prevail. In smaller communities, particularly those where the cost of build- ing a disposal plant would be relatively high, the feeding of garbage to hogs has been proved to be profitable. Where the pens are kept in a sanitary eondition there can be no objection to this procedure. It was estimated that $6,000,000 worth of garbage-fed pork was produced in the United States in 1916. Hogs utilize the proteins and sugars which are removed by other disposal methods. Under the scope of sanitary science should be included the control of diseases caused by insects, contact diseases, and the diseases due to indus- trial hazards. Since they are to be treated later under separate head- ings they will not be further considered in this chapter. CHAPTER III EPIDEMIOLOGY IN the preceding chapters the history of the more salient discoveries, which have laid the foundation for present-day methods of preventing disease, has been traced for the most part in chronological order. In the earliest times, when disease was supposed to be caused by super- natural agencies, it was not possible to develop and establish systematic and purposeful methods of preventing and controlling communicable diseases. Little by little the conception arose among a few of the more advanced thinkers that disease, like many other things which came under their observation, was due to natural causes. As time went on, the view that this natural cause was not only living but that it also had the power to increase, gained more and more adherents. The development of the microscope and the discovery of living forms in the saliva and other secretions and excretions of the body, stimulated in- vestigators to examine various substances to determine whether similar bodies might not be found in them. It was soon discovered that in various fermenting substances similar bodies were present. The next step in advance was the discovery that these bodies were the actual causes of fermentation and putrefaction. The demonstration that alco- holic fermentation was caused by living cells, and that other fermenta- tions and putrefactions were due to similar living microscopic forms, paved the way for the conception that disease might have the same origin. From 1840-1860, Pasteur, busily engaged in the study of fermen- tation and putrefaction, was able to demonstrate the mierodrganismal cause of both of these processes. | Not until 1880 were the causes of any of the important communicable diseases discovered and isolated. During the decade 1880-1890 the causes of several important diseases of man were discovered, and since that time more have been added to the ever- growing list. With the actual demonstration that diseases originated from a ‘““contagium vivum’’ it was possible to devise more logical methods for preventing and controlling them. ‘When disease was believed to be due to supernatural forces, and charms, incantations, and sorcery were practiced to drive it away; the usual result was a wider dissemination than would have been the case had it been left entirely alone. As soon as it was thought to be the result of natural laws logical methods were adopted to avoid and sup- press it. This conception marks the beginning of epidemiology. Epidemiology has been defined by Vaughan as ‘‘the science of epidemic diseases, and these may appear in a given community at any 80 Epidemiology 81 time singly or by the hundreds.” In a restricted sense epidemiology would only be concerned with those diseases which are due to a living cause, capable of multiplication, and endowed with certain definite characteristics. As usually employed it also includes those diseases which from analogy are assumed to be due to a living cause such as measles, smallpox and scarlet fever. In the former two diseases a definite organ- ism has not as yet been discovered. Other diseases, which exist in large numbers in certain localities, though not due to a living cause, such as the so-called deficiency diseases, beriberi, war edema, scurvy, rickets, pellagra, and xerophthalmia, have been investigated and the sources of the troubles determined by using the methods employed in epidemiology. The albuminal diseases, best illustrated perhaps in hay fever, ergot poisoning, and poisonings due to the consumption of de- composed foods, have likewise been solved by similar methods. Other diseases, as yet of doubtful etiology, will probably in part, if not wholly, be explained through investigations of an epidemiological nature. Epidemiology is concerned with the mass phenomena of disease in its broadest sense. It calls to its aid medical and related sciences. The epidemiologist should have a good knowledge and understanding of all these fields. He should know the general signs and symptoms of disease, the clinical course, and the pathological changes which are brought about in the body. He should be conversant with vital statistics, and able to deduce from these statistics, what procedures would probably lead him to the solution of his problem in a systematic and logical way. Such knowledge, with many possible exceptions, should enable him to choose those characteristics of the epidemic which might be of aid to him, and to eliminate those which are of relatively little importance. To secure the best results he should call to his assistance all possible data, which should be classified, analyzed, and summarized. Previous to the days of bacteriology there were some who based their observations of disease qn the theory of a vital cause, and in con- sequence, when living organisms were discovered in disease, many were ready to accept the conclusion, that communicable diseases were due to these organisms. Through the labors of Pasteur, Koch and others, the specific causes of several communicable diseases were discovered, isolated and shown to be specific. These discoveries were of great im- portance in the development of epidemiology and disease prevention. During the last two decades of the nineteenth century attention was focused upon man suffering from infectious diseases as the essential source of communicable diseases. Transmission was assumed to be mechanical, the cause being transported from those who were ill to those who were well. Isolation of the sick was, therefore, logically practiced with the hope and expectation that by this means the spread of any given disease might be prevented. In some diseases this procedure alone was followed by good results, in others the results were disap- pointing. The discoveries which have been made during the present century 82 Disease Prevention have furnished an explanation for these failures. It has been found that there are other sources of infection than the individual actually incapacitated through illness. In many instances infectious organisms have been found in those who are apparently well, and in those who have completely recovered from illness. Those who are not ill, but nevertheless harbor disease organisms, are called ‘‘carriers.”” Carriers may be grouped in several classes. In an epidemic there are some who may receive into their bodies and carry the germ without in any way being affected. Such individuals are called ‘‘passive carriers.”” In other instances the disease may be so mild that the patient does not consult a physician, or if a physician is consulted, the symptoms may be so mild or indefinite that the correct diagnosis is not made. Such individuals might be classed as ‘‘missed cases’’ carriers. Another group of cases is made up of those who have recovered from the disease but may carry the causal organism for varying periods of time. These are called ‘‘convalescent carriers,’’ the period during which they may carry the organisms varying from a few weeks to many months. Carriers are further classified according to the vehicle in which they are found: (1) Intestinal and urinary carriers, as in typhoid, cholera, dysentery, ete.; (2) Oral carriers, as in diphtheria, pneumonia, ete.; (3) Naso- pharyngeal, as in cerebrospinal meningitis, anterior poliomyelitis, ete.; (4) Blood and tissue carriers, as in malaria and yellow fever. Besides the human carriers, certain insects not only carry micro- organisms, but their continued existence requires that a part of their life cycle must take place in the body of an intermediate host. Con- spicuous examples of such organisms are those which cause malaria in man, birds, and other species. Yellow fever is carried in the same way as malaria, the insect carriers in these instances being mosquitoes, the malaria parasite being carried by several species of the anopheles mos- quito, yellow fever by a single species, the Aédes calopus. Other animals, in fact almost any animal which comes in contact with infectious ma- terial, may act as a mechanical carrier. Since human carriers have been shown to exist, it is evident that isolation of the sick alone, in those diseases in which there are car- riers, will check the spread of such diseases only to a limited extent. The problem of carriers has not been settled as yet and it still con- stitutes the greatest problem in disease prevention. The discovery that insects serve as carriers, however, has led to exceedingly important re- sults. It has been shown beyond any reasonable doubt, that malaria and yellow fever are only transmitted by certain mosquitoes, hence, meas- ures which will destroy mosquitoes and their breeding places will prevent malaria and yellow fever. Had it not been for this knowledge the Panama Canal could probably not have been built, or had it been built without this knowledge, the death role would have been enormous. It has been found possible to eradicate yellow fever in areas where it has been prevalent for many centuries, and it is not improbable that the day will come when it will be eradicated from all places where Epidemiology 83 it now exists. Owing to the habits and distribution of the anopheles mosquitoes the problem of malaria is a much more difficult one. Much has been done, but there still remains much to be accomplished, and the final solution of the malaria problem still remains unsolved. Reasons for Making Epidemiological Investigations.—As soon as a communicable disease appears in a community the question at once arises, Where did it originate? The epidemiological investigation is con- cerned not only with the source, but also the mode of transmission, and all the various conditions which may have contributed in bringing about infection. There are certain conditions which furnish permanent sources; others in which the source is orly temporary. The permanent sources are those which are essential for the continued existence of the infecting microorganism. These sources may be the human body, the bodies of the lower animals, or the inanimate environment of man. Since most diseases are transmitted from man to man, the human sources are of the most importance, and inasmuch as the inanimate environment furnishes the smallest number, it is the least important. Diseases in which the human body is the essential source would, therefore, have a potential geographic distribution equal to that of man. Periodic epi- demics of certain diseases, such as influenza, and the world-wide distribu- tion of tuberculosis at all times, are examples of such diseases. Typhoid fever has its essential source in man but its distribution is limited to a greater extent by conditions which have little influence on influenza or tuberculosis. Diseases in which the primary source is some lower animal are less widely distributed geographically, and are, as a rule, irregularly distributed, since the animals themselves are not found in all parts of the world. Diseases in which the source is the environment rather than some living organism, are found only where conditions are favorable, and are limited to a still greater extent geographically. Since man associates more intimately with his fellow beings than he does with the lower animals, diseases with human sources spread more rapidly and widely than do those where the source is some lower animal. Conditions of Transn:ission.—In most diseases the route is from re- spiratory tract to respiratory tract; from digestive tract to digestive tract; from genito-urinary tract to genito-urinary tract; from con- junctiva to conjunctiva; from blood stream to blood stream. In certain diseases, as in malaria, the organism which is present in the blood, is taken into the body of the mosquito, undergoes a cycle of develop- ment in this insect, and is then transmitted to man again by this same mosquito. As a class the respiratory diseases have a wider distribution than do those of the digestive tract or those transmitted by insects. Specific genito-urinary diseases, the venereal diseases, are also very widely distributed. Respiratory diseases are transmitted usually by what might be termed direct contact, the interval in time being brief and the space short. More rarely the discharges from the respiratory tract are car- ried by a third person, or some inanimate object serves as the vehicle of 84 Disease Prevention conveyance. Venereal diseases are almost wholly transmitted by direct personal contact, very rarely in some other way. Respiratory diseases are the most difficult of all diseases to control, and the only reason why everyone is not infected, is because all do not have the same suscep- tibility. The conditions of exposure are almost universal, hence, almost universal transference must take place. In some diseases, as smallpox and measles, which by analogy are classed as respiratory diseases, ex- posure is nearly always followed by the respective diseases unless the individual has had smallpox, or has been protected through vaccination, or has had measles. Diseases of the digestive tract, in which the cause is mechanically carried through the excreta, are less widely and more irregularly distributed. Careless individuals and communities, which neglect proper sanitation, such as the proper disposal of excreta, the selection and protection of a sanitary water supply, and the protection of food supplies, offer abundant opportunities for the spread of these diseases, while the converse limits or prevents their occurrence. Diseases which are communicated either mechanically, or biologically by insects, are still more limited in their distribution because of the habits and distribution of these insects. Infection is due to other factors than that of exposure alone. In order that it may occur, it is necessary not only that the microérganism enter the body, find conditions favorable for its growth, but it must, in addition, produce recognizable abnormalities in the body. These changes may be assumed from the symptoms induced, such as elevation of tem- perature, pain, ete., or there may be observable tissue change, such as swollen tonsils, abscess formation and other abnormalities. In some dis- eases exposure alone is nearly always followed by infection. This is notably the case in smallpox and measles. In other diseases exposure is less frequently followed by infection, and it is very evident from observations which have been made in epidemic cerebrospinal meningitis and infantile paralysis, that exposure does not lead to infection in the majority of those exposed. In an epidemic of meningitis, the menin- gococeus, the organism which causes the disease, may be found in the posterior part of the nasal passages of persons who are at the time in good health and who do not subsequently develop the disease. The number of those harboring the germ without becoming ill is always greater than is the number of those who become infected. If on exposure to disease infection results, the individual so exposed is said to be susceptible. Susceptibility is a predisposition to infection; resistance is the lack of such predisposition. Susceptibility is subject to much variation. In some diseases nearly every one exposed becomes infected, as in smallpox. In other diseases a large number of those exposed escape infection, as in epidemic meningitis. Resistance to infection may be a natural attribute, or it may be acquired by an attack of the given disease. After recovery from an attack of many of the infectious diseases, the individual does not subsequently become infected though subjected to exposure. Rarely does one suffer from a second attack of smallpox, Epidemiology 85 typhoid fever, scarlet fever, measles, and a number of other infectious diseases. On the other hand, an attack of certain diseases renders the individual more susceptible to subsequent infection with the same organ- ism. Erysipelas and pneumonia are good examples of diseases in which one attack is not followed by an increased resistance, but rather by an increased susceptibility. Disease Distribution.—Some diseases are characterized by a wide or even a world-wide distribution. Tuberculosis and influenza are found in all parts of the world. From this it must be inferred, that conditions which permit of the transmission of these diseases are of world-wide distribution. Again it is found that malaria and yellow fever are con- fined to certain regions. The conclusion is, therefore, drawn that con- ditions exist in these areas or regions which are not present in other parts of the world. In the latter case, though the disease seems to be limited to certain areas, a change in the conditions in the areas where it did not previously occur, may lead to its introduction in these regions. From historical data much has been learned concerning the prevalence of the various communicable diseases, their geographic distribution, and the variations which occur according to seasons and in cycles of years. With the knowledge which has been gathered together and systematized, a foundation is established upon which epidemiological investigation is dependent for the establishment of the sources and means of trans- mission in epidemics. General Epidemiological Data.—From the available statistics a summary is made of the various groups in the area under investigation. This summary should be arranged in racial, sex and age groups of the population. For each individual affected a record should be obtained which should contain the following data: Age, color, sex, nationality, definite or probable date of onset, date of definite symptoms, location of residence and its character, number of occupants, general character of the immediate neighborhood, any conditions which might cause or con- tribute to the transmission of infection, the movements of the individual for some time previous to the onset of symptoms, his association with those outside or visitors to his residence, the source and character of the water and food supply, and in fact anything which might directly or remotely have some connection with the disease under investigation. Much of the required information may be obtained by any intelligent and observing person and does not require especial training. Often there is some question as to the diagnosis and this must be determined by those who have been especially trained to render this service. The determination should be based upon clinical evidences, laboratory find- ings, and all other factors which might have a bearing upon the question. Fundamental Data on the Propagation and Transmission of Disease. —For most of the important communicable diseases the method of propagation is known. Some are propagated through human sources, others require in addition some other source. In typhoid fever the only 86 Disease Prevention source, so far as is known, is man himself. In yellow fever and malaria an insect carrier, as well as man himself, is necessary for the propaga- tion of the’ parasites of these diseases. In typhoid fever the sources are varied, since the infection may be transmitted from a clinical case, from a missed case, from a temporary convalescent carrier, from a chronic carrier, or from a carrier who harbors the germ but has never had the disease. The mode of transmission may be even more varied than the source. It may result from direct contact through the hands becoming soiled with excreta from a typhoid patient and later carried by them to the mouth, or in numerous other possible ways; through being transported by some third person who has been in contact with a typhoid patient; through food contaminated by flies or other insects which have had access to typhoid excreta ; through water, milk and other foods which have been polluted through any of the sources already men- tioned, as well as in other ways. If real progress is to be made in an epidemiological investigation those factors should receive especial at- tention which the evidence shows are of primary importance. As an illustration let us consider an actual epidemic of typhoid fever. In this epidemic the following conditions prevailed: * The water supply of the city involved was derived from deep wells. In the early days, before much was known about typhoid transmission, three deep wells were constructed. In order to place the pumps in a favorable position for lifting the water excavations were made which practically con- verted the deep wells into shallow ones. Upon investigation of the epidemic it was soon discovered that the distribution of the cases was almost wholly confined to the area which was potentially supplied by one of these wells. In the distributing system numerous colon bacilli were found, but none were found in the well in question. The only factor common to all the individuals involved was the city water. From the evidence in hand the conclusion was drawn that the epidemic had its origin in this well. To prevent further trouble the installation of a calcium hypochlorite plant was advised. This advice was not heeded. About four months later, following a heavy rain, a severe epidemic of so-called ‘‘winter cholera’’ broke out in the same area. During the next month another typhoid epidemic appeared which was of much greater severity than the first. An investigation of the suspected well was made during the first few days of this epidemic diarrhoeal disturbance, ‘and it was discovered that water was being discharged into the well from a six-inch pipe situated a little north of west in the wall of the Rice well about 15 feet below the surface. Samples taken directly from this pipe showed gross pollution. No information could be obtained as to where this pipe came from and for what purpose it entered the well. On December 20, it was found that this pipe was the main source of contamination of the Rice well, and the latter was permanently aban- doned as a source of water supply. A large part of the wall of the well * Waite, Two Lincoln (Nebraska) Typhoid Fever Epidemics of 1911 and 1912, Jour, Infect. Dis., 1913. Epidemiology 87 was moist, the moisture being due to seepage; though at no place was there enough trickling to obtain a sample of the seepage water. “On December 21, excavation was begun for the purpose of ascer- taining the whereabouts of the pipe outside the well through which the polluted seepage was entering. It was found to end about 14 or 15 feet outside the well. The end outside the well was open. Earth had entered this open end for a few inches, otherwise the inside of the pipe was clear. Samples of water taken from the seepage which collected at the open end as well as along the pipe showed evidence of gross pollu- tion. Notwithstanding the fact that the water level towards the west was apparently lower than the open end of the pipe outside the well, suspicion was aroused that the seepage water which collected around the open end of the pipe outside the well might come from the sewer which ran from south to north on the west side of the well. This sewer pipe was at a distance of only 37 feet from the wall of the well and consequently only 22 or 23 feet from the open end of the pipe which entered the well. Besides this sewer there were other things in the immediate surroundings of this well of a very objectionable character. At a relatively short distance from this well to the south and east there is a low spot which the city has been filling with street sweepings for a considerable period of time. It has also served as a dumping ground for other refuse. In the immediate vicinity of this dumping ground there are still a number of open privies in use at the present time. Rain water or water from any other source not only might but probably would carry material from this dumping ground and from these privies into the well. “The combined rainfall of December 9 and 10 was 1.40 inches. It is highly probable that this precipitation was the chief cause which brought about the contamination of the Rice well. At no time when the investigation of the water was being made from August 29 to December 18 was anything of a suspicious character found in the Rice well. Why contamination did not occur after some of the heavy rain- falls during August, September, October, and November is difficult to explain. ‘“At the time the first sample of water was taken from the pipe which was contaminating the Rice well it was estimated that the amount of seepage which was entering the well through the pipe was one quart per hour. This estimated amount was determined from the amount which was actually collected and measured after an interval of ten minutes, on December 19. The amount was greater than it was at any subsequent date and it was probably much greater in amount on the days immediately following the rainfall of December 9 and 10.”’ Records of the city engineer’s office showed that a stoppage had occurred in a sewer in the alley between N and O streets, a short dis- tance from the Rice well, on December 12 and 13. On January 24 this sewer was blocked at the manhole and the sewage was allowed to rise to the point which it had previously reached on December 12 and 13. An 88 Disease Prevention excavation was made near the sewer and it was observed that sewage entered the excavation from the side next the sewer. Two joints of the sewer were now uncovered and it was found that both leaked. Just north of the excavation the sewer had been laid in a filling composed of ashes and cinders. One of the joints, laid in the filled area, showed an apparent slight settlement. Around this joint some of the earth was washed away, which indicated that at some time a considerable amount of sewage had leaked out at this point. The distance from the sewer pipe to the outer end of the 6-inch pipe leading into the well was only 22 or 23 feet. Sewage was percolating through the material used for filling, and entering the open end of this pipe. In addition, there were several other ways by which this sewage might have entered the well, but the open pipe was certainly the principal way by which it entered. In this investigation it was furthermore shown that at least nine cases of typhoid fever were reported on this sewer line. The closing of this well, and the administration of calcium hypochlorite to the water supply brought the epidemic to an abrupt end. In the same city, two years later, an epidemic of diphtheria occurred, which had its origin in a contaminated milk supply. The conditions sur- rounding this epidemic were such that it was more easily solved. “On April 21, nine cases’ of diphtheria ‘‘were reported in three families. In one family there were four, in another three, and in the third two cases. On the 22d seven more cases were added and at this time the observation was made that they were all reported from families which obtained their milk supply from the same dairy. On the 23d an investigation of this dairy was made by the City Health Officer. ‘This investigation disclosed the following facts: On Sunday, April 13, Mr. J. consulted a physician for a sore throat. The physician whom he consulted told him his throat looked suspicious and suggested that Mr. J. should be seen again on the following day. Mr. J. requested that the physician should not come unless called again. The physician was not called at any subsequent time. ““On Tuesday, April 15, Mr. J. began work at the dairy, which was shown later to be the source of infection in this epidemic. On April 23 cultures were taken from the throats of both Mr. and Mrs. J. and these showed diphtheria bacilli on April 24. At this time there was no membrane in the throat of Mr. J. In the throat of Mrs. J. there were well defined patches of membrane on the tonsils and adjacent parts of the pharynx. “Mr. J. confined his activities to the dairy, getting his meals at home. He did not enter the house of the dairyman, his duties not requiring such entrance. He assisted in milking and poured the contents of his pail into a common container where it was mixed with the rest of the output of the dairy. Mr. J. and his wife were at once quarantined and the dairy was ordered to stop selling milk on April 23. This order ! Waite, Report of a Milk-Borne Epidemic of Diphtheria, Amer. Jour. Pub. Health, 1914. Epidemiology 89 resulted in the permanent closing of the dairy. Inspection of this dairy showed that it was otherwise excellent from the sanitary stand- point. “Of the 110 cases which were included in this report 109 revealed diphtheria bacilli. No culture was made in one instance where death and diagnosis (clinical) were almost synchronous. ““The dairy which supplied the infected area furnished milk to about 15% of the families living in this section. In all 301 families were supplied, diphtheria developing in 79 of them, a percentage of 26.24. In these 79 families there were 110 cases. There were two cases (each) in 18 families, three (each) in five families, and four in one family. In this area there occurred during this period only four other cases. These four individuals were reasonably sure that they had not partaken of the milk. Two of the four gave a clear history of intimate contact with individuals who had diphtheria at about the same time. The other two did not give any history of known contact. ‘‘In all the rest of the city during this period six cases were reported. Of these, two gave a very definite history of contact with diphtheria patients. All of these six individuals were reasonably certain they had not partaken of this milk. “In the 79 families from which diphtheria was reported, there were 337 individuals. Nearly all of these had partaken of milk from the infected dairy. Of 337 individuals, 110 had diphtheria or 32.84%.’ As a rule it is not possible to secure so much confirmatory evidence in an epidemiological investigation as was possible in this particular in- stance. Nevertheless a thorough search will usually uncover sufficient evidence to make clear the epidemiology of the vast majority of epidemics. i In both of the epidemics just described, a common factor was found for groups of cases in each instance. No other factors common to all were found in either of the groups. Summary.—In making an epidemiological investigation one should not be hasty in jumping at a conclusion. Unless the evidence is ex- tremely convincing at the beginning of the investigation, no opinion should be given until a mass of evidence has been collected. Usually conditions exist which furnish a working hypothesis. To adequately study these conditions, the location of the cases should be determined, and graphically represented on a map covering the area involved and surrounding areas. In the investigation, if possible, all cases should be visited, all the facts such as age, sex, environment, ete., should be ascer- tained. If this be impossible, a large enough group should be can- vassed to make it reasonably sure that it is representative of the whole group. An epidemiological investigation should include not only those who have contracted the disease under investigation, but also the whole population. In many communities statistical data are very incomplete, nevertheless much valuable information may be obtained from various sources, and a confirmation of this information will furnish evidence 90 Disease Prevention which will be valuable for comparison with the data obtained in the investigation of the epidemic group. ‘When a disease exists continuously in a community, or in a large area, it is said to be endemic. For centuries yellow fever was endemic in Havana. Bubonie plague, as has already been recorded, still has several endemic foci. Cholera is endemic in certain parts of India and China. All of the great plagues or pestilences which have spread over large portions of the world have had their origin in endemic foci. When the number of cases of an endemic disease shows a considerable increase over the usual prevalence, or if a disease appears affecting a considerable number of people in a community where its presence has not been previously recognized, it is said to be epidemic. In epidemics the disease is limited to larger or smaller areas. If it spreads over a large part of the world it is said to be pandemic. Influenza was pandemic in 1918; a large percentage of the population of the world was infected and an enormous number of deaths resulted. When isolated cases of a disease appear in different parts of a community, without apparent connection with one another, the occurrence is characterized as sporadic. Since all epidemics and pandemics have their origin in endemic foci, the logical procedure in making an epidemiological investigation would be to discover these foci, and the conditions which are operative in the propagation and transmission of the disease under investigation. When these data have been ascertained, measures should be devised to eliminate the various links in the chain, which have been instrumental in keeping the disease active. What may be accomplished is well illustrated in the results obtained by Gorgas in Havana in 1901. Shortly after Walter Reed and his associates had shown how yellow fever was transmitted, Gorgas, as chief sanitary officer of Havana, Cuba, put into operation measures which, in three months, freed it from yellow fever, a condition which had not existed for 150 years. This was accomplished by sereen- ing yellow fever patients; by destroying the infected mosquitoes; and by eliminating or rendering unsuitable the breeding places of the Aédes calopus, the mosquito which carries the infection from man to man. Later, Gorgas was able to accomplish similar results in Panama. In typhoid fever much has been done following analogous sanitary procedures. In the past, much of the epidemiological work has been done after the epidemic has gotten well under way ; hence, little could be accom- plished in preventing infection, since the disease had become so widely disseminated. In the future, the goal towards which the epidemiologist should direct his major efforts, is that of discovering endemic foci and of introducing procedures which will destroy and render them ineffective. CHAPTER IV GENERAL METHODS OF DISEASE PREVENTION THE earliest efforts to prevent disease were wholly limited to com- municable diseases. In the beginning these efforts were carried out under great difficulties, since little was known concerning the mode of their transmission, and nothing concerning their cause. Little by little discoveries were made, which constantly furnished increased knowledge of the cause and means of transmission. With this increased knowledge more effective methods of control and prevention were developed. In some diseases so much is known concerning the cause, source of infection, and means of transmission, that it would seem an easy matter by applying this knowledge, to wholly eliminate certain diseases, such as yellow fever, typhus, and some of the other insect-borne diseases. Much has also been ascertained concerning diseases which have their origin in the intestinal tract, but as yet little has been accomplished in the control of diseases which are communicated through discharges from the respiratory tract. Within very recent times attention has been called to other abnormal conditions which affect the individual but are not, except in very rare instances, communicated to others. These abnormal conditions or dis- eases should receive the same attention as has been given to the com- municable diseases. First, since they are a greater or less menace in themselves ; and second, because they lower bodily resistance and render the affected individual more susceptible to communicable diseases. Often these diseases, since they cause no discomfort, are entirely unknown to the individual, or when they cause physical impairment the reason for this impairment is not discovered or is attributed to other causes. To discover these unsuspected physical defects, periodic physical examina- tions should be made of all persons, beginning in infancy and continuing throughout life. These periodic examinations should be made at inter- vals not too widely separated from one another. A yearly examination is not too frequent, and should there be any reason for suspecting any abnormality, an examination should be made without delay. A little more than ten years ago the first thorough physical ex- aminations on a large scale were made by one of the large life insurance companies. The results of these examinations were of an impressive character since they disclosed so large a percentage of supposedly normal persons with physical defects. The facts which were discovered through these investigations led to the foundation of the Life Extension Institute in New York in 1914. Through this Institute, and on their 91 92 Disease Prevention own initiative, several of the life insurance companies have established the practice of furnishing the opportunity to their policy holders, of obtaining periodic physical examinations. The practice is not only of economic importance to the companies, but it also discloses to the policy holders defects of which they were ignorant, and gives them instructions concerning the procedures which should be followed in order to correct the impairment. Industrial establishments have followed in the footsteps of the in- surance companies, many of them requiring physical examination of their prospective employees before they are hired, and if accepted, later periodic examinations. The number of industrial establishments which are adopting this plan is constantly increasing with mutual advantage to employer and employee. In some establishments, men with varying degrees of impairment are allotted to tasks which they are able to perform without danger of increasing their defect or of otherwise injuring them. The report of the results obtained by the Life Extension Institute, after 5,000 individuals had been examined by especially trained examin- ers, were looked upon by many with some doubt. In these examinations defects were discovered which would have escaped detection by the ordinary methods, since they were systematic and included every part of the body, even though, at first glance, it appeared normal. The actual value which this report disclosed was not appreciated until the re- sults of the examination of the first draft of United States troops were published shortly after war was declared with Germany in 1917. In this draft, which included the most favorable age group, those be- tween 21 and 31, 34% were rejected because they were physically unfit. Since it was necessary to examine a large number of men in a short time, and since many of the examiners were not accustomed to making sys- tematic physical examinations, they were hurried and incomplete and minor defects escaped detection; nevertheless 47% showed some form of defect. The high percentage of defect in the best age group of the male population emphatically called attention to the condition which must exist in the population at large. The condition being known, it is only the part of wisdom to institute measures to correct these defects, which are of quite as much importance as the prevention of com- municable diseases. Heredity.— Many of the physical defects which exist in the popula- tion are due to habits which could be more or less easily remedied. Many inherited defects, such as harelip, various foot deformities, ete., which only too frequently are wholly neglected, might be remedied by proper treatment, and the earlier such treatment is instituted the better the results. Air.—One of the most essential conditions for the development of the body, and the maintenance of good health, is an abundant supply of outside air. To secure the best results one should live out of doors. Civilization, with its ever-increasing complexity, is continuously in- General Methods of Disease Prevention 93 creasing the difficulty of securing even the minimum amount required for keeping the body in the proper physical condition. Out-of-door occupations furnish an abundant supply of air and are to be preferred to indoor confinement. It is especially necessary for those who are confined by their work in buildings, which limit air supply, to sleep in rooms where an abundance of air may be obtained. Those who sleep out of doors are in better physical condition than are those whose sleep- ing hours are spent within some dwelling. The sleeping porch, which has become so popular during the last 25 years, is an important advance in the development of measures to increase bodily vigor and resistance to disease. If one does not have a sleeping porch, very satisfactory results may be secured by using the window tent. The open-air school has demonstrated the value of utilizing air which has not been confined within a room or building. Such schools not only improve children physically, but they also learn more easily than do those shut up in the conventional schoolroom. Temperature.—Nearly all rooms are kept at too high a temperature. In addition there is never enough moisture present and the air is not kept in motion. The four requisites of good ventilation are motion, coolness, a proper humidity, and a continuous supply of fresh air. The temperature should not be above 70° F., and preferably 65° F. Hines states that he found the best work was done by school children at a temperature of 68° F. Dust should be prevented from getting into the air as far as possible. This is best accomplished by using a vacuum cleaner, and by using damp, or, better still, oiled cloths for dusting. A carpet sweeper is better than a broom, a vacuum cleaner than either. Articles of furniture which permit of the collection of large quantities of dust are not hygienic. Rugs are better than carpets, since they may be readily taken up and cleaned. Sunlight should be abundant, since bacteria are soon killed when exposed to the direct rays of the sun. The best results are secured when windows are left open, since some of the light rays are rendered ineffective when they come in contact with glass. Dark rooms favor uncleanliness and this condition is usually accompanied by lack of ventilation. While moderately dry air is to be preferred to that which is quite humid, humid air is better than inside air, notwithstanding the popular prejudice to the contrary. The practice of deep breathing should be developed by everyone. For those who are indoors a large part of the time, a dozen or more deep breaths of outside air should be taken systematically several times a day. Forced deep breathing is not as effective as slow, deep, rhythmic breathing, and sometimes it is harmful. Slow, deep breathing removes some of the residual air in the lungs and replaces it with fresh air. At the same time, the circulation, not only in the lungs, but in the abdomen and other parts of the body, is likewise stimulated and the blood more uniformly distributed. Cleanliness.—One of the most important requisites in the main- tenance of a healthy body is cleanliness. This applies both to the 94 Disease Prevention environment and the body itself. For ethical as well as for health rea- sons, a daily bath should be the routine of everyone. Much has been written concerning the daily cool or cold bath. Some say they cannot stand it, that it depresses rather than invigorates them. Usually the reason they are not invigorated is because they have only tried it once, or at most a few times, and consequently do not know whether it would be beneficial or the contrary. To establish the habit of cold bathing, it is well to begin the practice in the summer and continue it throughout the year. The best time for daily cold baths is the first thing in the morning. If it is difficult to get it at this time some other may be chosen. It should never be taken shortly after a meal. The face, hands and finger nails need especial and frequent attention, particularly the hands and nails. It is very probable, as recent experi- ments and investigations have shown, that the hands are the most fre- quent offenders in the transmission of infectious diseases. The hands should be given a thorough washing before partaking of meals and after the use of the toilet. Not only should one be physically clean, but in order to maintain the body in a state of health, he should likewise be morally clean. vDisregard of moral cleanliness leads to a host of diseases. Venereal diseases in the past, and even today, are a serious menace to health. The examination of large bodies of men during the World War opened the eyes of all to the seriousness of venereal diseases. The United States Public Health Service has started a vigorous educational program which has already accomplished a great deal, and will in the future undoubtedly achieve still greater results than have already been obtained. Many diseases which follow in the wake of venereal diseases, as a direct result of these infections, such as blindness, so-called rheumatism, diseases of the heart, of the central nervous system (paralysis and insanity), and numerous other impairments, add to the sum total of the destructive- ness of these diseases. The value of the cold bath is not alone its cleansing effect, but also its promotion of resistance to disease. In our artificial methods of living, due in part to convention, and to a still greater extent to the extremes of temperature in our environment, the skin of the greater part of the body is covered with clothing. This permits the air to come in direct contact with only those parts of the body which are constantly exposed, such as the hands and face. As a result of this artificial protection some of the functions of the skin have been lessened. This is especially true of the heat-regulating function of the skin. As a result, exposure to extremes, particularly cold temperatures, are often followed by dis- comfort, and, at times, actual disability. To increase our resistance to such hazards, the exposure of the naked skin to the air, for at least a short time each day, would aid very materially in securing the desired result. The benefits to be derived from a cold bath have been discussed. At least twice a week the ordinary person should take a warm bath. Soap General Methods of Disease Prevention 95 should be freely used, and it should be applied to the face as well as to the rest of the body. Emphasis should be placed on the term warm bath, since hot baths are or should be used only as therapeutic meas- ures. One exception should be made to the hot bath. After exposure to extreme cold, a hot bath followed by protection to keep the body in a warm condition is a valuable method for preventing colds. Russian, Turkish, and other hot baths may be useful in preventing colds but they are usually given to those who are too lazy to perform the function for themselves. Out-of-door bathing is more beneficial than any other form of bath- ing provided certain precautions are observed. At no time, and par- ticularly if the water is unpleasantly cold to the body, should one re- main for a long time in the water. One should never remain in the water if he feels chilly, if his lips or any other part become blue, or his teeth begin to chatter. Twenty minutes to half an hour should be the extreme limit of time to remain in the water; a still shorter time is preferable. The air, the sunshine, and the exercise involved in swimming make this form of bath especially desirable as a means of promoting health. Out-of-door bathing is dangerous for those with known heart disease, especially if complicated with fainting spells, palpitation or any other known disturbance. Out-of-door bathing is not advisable for the elderly unless they are accustomed to cold bathing. Constipation.—Proper attention to personal hygiene would in a large measure prevent constipation, and in case it exists, would do much to overcome it. Constipation is frequently the signal of a lack of health. ‘When it exists it indicates a lowered bodily resistance, and consequently, a more than average susceptibility to disease. Constipation is due chiefly to improper diet, the use of refined or concentrated foods, too little exercise, the failure to obey the physiological summons for bowel movement, the habit of using purgatives, salts and mineral waters. The measures to be followed to overcome these defects are largely self-evident. Bulky, coarse foods, which have not been over-refined, should constitute a very large part of the diet. Whole wheat or graham flour, bulky vegetables and fruits are especially to be recommended. An insufficient intake of water is often one of the chief faults which leads to constipation. The obvious thing to be done, therefore, is to increase the amount of water consumption. The amount of water which should be drunk daily is from six to eight glasses or more. Vigorous exercise increases the desire for water. Not only does exercise increase the water intake, but it also increases the activities of the organs and tissues of the body. Above all things, a daily habit should be estab- lished of evacuating the bowels at least once, preferably two or three times. Usually the failure to follow the defecation impulse is not because of some necessary obstacle, but is rather a matter of neglect. Even the established constipation habit could nearly always be cor- rected if one consistently took the required amount of exercise, ate a sufficient amount of coarse, bulky food, consumed a sufficient amount 96 Disease Prevention of water at the proper time, and immediately answered the call of nature when summoned. Posture.— Correct posture is one of the effective measures for keep- ing the body in a state of health. In standing or walking the entire body should be kept in the erect position; in sitting the trunk should be erect and not allowed to assume a slouching position. Correct posture aids in maintaining the organs in the proper positions and relations and hence promotes health through its influence on physiological activity. Proper direction and position of the feet in walking will prevent many foot difficulties. If such defects have already developed, much may be done to prevent further injury. Often corrective measures will in part or wholly remove the disability. In walking the feet should be parallel with one another, or the toes should incline inwards (toe in). They should not incline outwards (toe out), since such a position is apt to weaken the arches. Exercises to strengthen the muscles of the leg, especially the calf muscles, will often accomplish much in preventing flat foot, or in relieving it if it exists. Foods.—The food which is taken into the body to relieve hunger serves other purposes as well. A part of it is consumed as fuel and furnishes the energy which is expended in our bodily movements, and in keeping up the physiological activities of the tissues and organs of the body. The foods which especially serve this purpose are the starches, sugars and fats. A food, however, made up exclusively, or in too large a proportion, of the starches, sugars and fats would soon lead to disease. The food necessary for building up the body, and maintaining it in a state of equilibrium, is derived from the proteins which may be of either animal or vegetable origin. To obtain the best results proteins should be obtained from both of these sources. The animal sources of the proteins are the lean meats obtained from cattle, and other animals used for food, fish, shell-fish, fowls and other birds, and from the prod- ucts derived from them, such as milk, butter and eggs. From peas, beans and similar vegetables, large amounts of proteins are obtained. A considerable quantity is also obtained from the cereals. Minerals are likewise necessary for building and repair. They may be procured from milk, eggs (especially the yolk), fruit, green vegetables, and cereals which have not been refined, but which contain all of the constituents of the original seed. Much of the cereal food which is consumed today has lost a large part of its nutritive value through milling. Our diet should be so made up that it contains considerable bulk. In the foods which have been refined, there is a loss of so-called dietary factors, the vitamins, which are as necessary in keeping up a normal nutrition as is a sufficient quan- tity of proteins, carbohydrates and fats. If the food is deficient in bulk, the normal physiological activity of the digestive tract is dimin- ished, and this may lead to constipation and other disturbances. To provide against any deficiency, our diet should include whole wheat General Methods of Disease Prevention 97 bread, graham bread, fruits, the leaves and skins of plants, and the skin of the tubers of these plants, especially of the potato. In order that the teeth may be kept in good condition, it is necessary that they be given a sufficient amount of work to do. Soft and refined foods do not meet this requirement. Hard crackers, crusts, fibrous vegetables, meat which is not too tender, fruits and nuts furnish the proper resistance for keeping the teeth and gums in a healthy condition. They should, therefore, always be included in the diet. Vitamins.—Much has been written in recent years concerning cer- tain substances which are found in minute amounts in parts of the plants and animals used as food. The absence of these substances leads to such diseases as scurvy, beriberi, xerophthalmia, and other so-called deficiency diseases. To obtain these accessory dietary requirements our food should include liberal amounts of milk, eggs, all the constituents of the cereals, the green vegetables, especially the leafy parts, represented by such plants as spinach, lettuce, etec., potatoes, citrus fruits and tomatoes. Cooking destroys some vitamins, particularly the vitamin in milk which prevents scurvy. Pasteurization decreases the amount of this vitamin in milk, but not to a greater extent than it is decreased in milk which has stood for some time. In the customary diet of the adult a sufficient amount of this vitamin is ingested. All infants should be breast-fed. Unfortunately there are many who receive only artificial foods. The milk which is used in artificial feeding should be pasteurized. Any deficiency in vitamins, which may result from this process, may be readily supplied by giving the infant orange juice or the juice from the tomato. Even the juice of the canned tomato may be used, since it contains a sufficient amount of the antiscorbutic vitamin to prevent seurvy. Body Weight.—Our knowledge concerning the dangers from over- weight has been secured from the statistical data of 43 American life insurance companies. From these statistics, which have been accurately collected and assembled, it is shown that those who have passed the age of thirty-five are better risks when their weight is below the average weight for this age group. Underweight in early life shows a slightly increased mortality, due exclusively to tuberculosis. After thirty-five light weight is distinctly favorable to longevity. As the weight increases above the average for the group, the death rate progressively increases. Increase in weight after full maturity is a distinet disadvantage and measures should be taken to prevent it. If it has already taken place, measures should likewise be taken to restore the body to the proper weight. Unless overweight is due to some disease, in which case it will require careful medical supervision, it may be corrected by dietetic measures alone, or by such measures in combination with physical exercise. If physical measures are employed, the exercise should be moderate, espe- cially in the beginning. After some reduction has taken place, the amount of exercise may be increased, since the removal of weight also 98 Disease Prevention lessens the work of the heart. It is probable that the heart muscle of all those who are overweight, and who have passed middle life, is de- creased in its efficiency. Weight may be reduced by dietetic measures alone. One might go to bed and stay there and still reduce his weight. All that it is necessary to do is to decrease the amount of carbohydrates and fats. To avert hunger, which may result from’ the restriction of these articles of diet, one may select bulky foods which do not have high fuel value. Many have adopted the practice of cutting out some meal or meals during the day, usually luncheon. The practice is questionable and may even be harmful. The time spent in getting luncheon has its benefits, not the least of which is the break in the monotony of constant application to work. § Regulation of Diet.—When one weighs more than is normal for the average person at a given age he is an overweight. To intelligently deal with this condition, it is necessary to determine the cause. Increased weight may be due to increased consumption of food, to decreased oxida- tion, or it may be due to a retention of water in the body as a result of disease. In order to ascertain to which of these causes it is due, a physician should be consulted. If due to disease, as for instance some disturbance of the thyroid gland, disease of the heart or kidneys, the physician should give directions and advice concerning the best plans to follow to relieve the individual. If the person is found to be normal, ex- cept for his fat accumulation, it should be a relatively easy matter to overcome the abnormality by applying appropriate methods. To follow the widely advertised schemes of physical culture faddists, exploiters of ‘glandular extracts and other products, is unwise and may lead to serious results. Reduction in weight may be accomplished by lessening the amount of food consumed, or by increasing the amount of exercise. A combination of both is the better procedure. Too vigorous exercise in a fat individual is many times positively harmful. Too rapid or too ex- tensive diminution in diet is also dangerous. The starches, sugars and fats should not be withdrawn too rapidly. It is better to decrease weight slowly, by decreasing the amount of these foods to a reasonable degree, than to almost or wholly eliminate them from the diet. Starch, sugar, fats, butter and cream are fat-producing foods in a concentrated form. The cereals are also high in fuel values. To reduce weight, a reduction in the consumption of foods of high fuel value, with an increase of the bulky foods of low fuel value to appease hunger, such as cabbage, lettuce, spinach, celery, string beans, cucumbers, carrots, turnips, tomatoes, and the fruits, will usually bring about the desired result. : The average individual does not have time enough, or sufficient inclination, to remove surplus weight by exercise alone. For the most part the chief reliance for weight reduction must be placed on diet. The combination of increased exercise and decreased diet is the best method to be pursued. General Methods of Disease Prevention 99 Children.—The child requires more abundant diet than dees the adult. Boys 15 or 16 years of age require and consume considerably more food than does the sedentary adult. More food is required be- cause of the excessive activity in which the normal boy participates, and he also uses more for building purposes. If left entirely to their own inclinations children do not, as a rule, choose their food wisely. They require the same constant supervision in regard to food that they do for their many activities. They need an abundant supply of the cereals, butter, milk, with a moderate supply of eggs and meat. Care should be taken that there is plenty of bulky food in the diet and they should not be allowed to reduce the variety to narrow limits. Each child is an individual problem and deserves careful attention in the selection of food which will meet his growth requirements, with due regard to his individual choice in selection. Fruit, green vegetables and milk should be included in his daily diet. Of milk he should be given a liberal supply, a quart or more daily. Narcotics.—All are familiar with the narcotic effects which follow the consumption of alcohol. For many years it was affirmed by some that the moderate consumption of alcohol did not lead to permanent tissue changes in the body ; others with equal positiveness asserted that the consumption of alcohol, even in smail amounts, was regularly fol- lowed by impairment which shortened the span of life and predisposed to disease in general. Statistical data have shown that even moderate indulgence in alcohol shortens life; that as the amount consumed in- creases, the length of life decreases. Information, collected from many sources, has demonstrated that indulgence in alcohol is an important factor in the causation of disease. It is still asserted by some that aleohol as such is valuable as a medicinal agent. This may be true in individual instances. Even in these cases a substitute can nearly always be found which will answer the purpose quite as well or better than aleohol. If it should be found that alcohol is of more value than anything else in certain pathological conditions, its use should not be abandoned as a therapeutic agent. Statistical, laboratory and clinical evidence have all shown that the use of alcohol as a beverage is harmful even when used in moderation. Since the manufacture and sale of alcoholic beverages are now forbidden by law, it is only a question of time when its use as a beverage will only be known by reverting to past history. The House of Delegates of the American Medical Association, which is made up of representatives who voice the best medical opinion in the United States, have expressed their opinion on the use of aleohol in unmistakable language. The resolutions of this body are as follows: “WHEREAS, We believe that the use of alcohol is detrimental to the human economy ; and “WHEREAS, Its use in therapeutics as a tonic or stimulant or for food has no scientific value; therefore be if 100 Disease Prevention ‘“ Resolved, That the American Medical Association is opposed to the use of alcohol as a beverage; and be it further ‘Resolved, That the use of alcohol as a therapeutic agent should be further discouraged.” From these resolutions, ‘which were drawn up after mature con- sideration, it seems logical to assume that the use of alcohol as a thera- peutic agent is rarely, if ever, necessary. Tobacco.— Without going into detail concerning the use and abuse of tobacco, some of its more important effects, and the effects of some of the chemical bodies derived from it, will be considered. It has been conclusively shown that nicotin at first slows the heart and increases vthe blood pressure; later the blood pressure is lowered, the rapidity of the heart action increased. The effect on the brain is depressing, the ability to do mental work is decreased, the ability to do work which re- quires accurate physical coordination is lessened to a marked degree, it always diminishes the respiratory function, which is evidenced in the shortness of breath, and it often causes palpitation and pain in the region of the heart. From the excessive use of tobacco, digestive dis- turbances, insomnia, catarrhal conditions of the nose and throat, some- times with extension to the middle ear, and even blindness may result. Life insurance statistics show that those who use tobacco lessen their life expectancy about four years. It is needless to say that tobacco has a harmful effect on the average person addicted to its use, and especially does this apply to those who use it to excess. Opium and Other Habit-Forming Narcotics.—Legislation has to a great extent suppressed the traffic in habit-forming drugs notwith- standing statements to the contrary. It hardly seems necessary to point out the dangers of using any drug which may lead to a habit, since so much information has been given to the public during the decade just past, concerning the dangers of acquiring some narcotic drug habit or disease. Formerly the opium habit was in many instances acquired from first having received the drug as a therapeutic measure usually for the relief of pain. Often the drug was given for so long a time that it produced a habit. It was not a difficult matter for the person who had acquired the habit to obtain the drug and hence its use was continued with ever-increasing doses until it was almost impossible to overcome the practice. Today the habit is practically never acquired except through those who are still able to evade the law. The drug habit may also be acquired from other derivatives of opium and morphin, par- ticularly heroin. The cocain habit is even more difficult to break than the morphin habit. Frequently it was acquired from the practice of giving it in the treatment of inflammatory conditions of the mucous membrane of the nose. Here it was applied locally, often for simple colds. Its use for this purpose promptly gave relief followed by a depression which created a desire for more. The prolonged use of cocain leads to diges- - General Methods of Disease Pravviifion C01 tive disturbances, muscular twitchings, sleeplessiess;, various: nervous. manifestations, mental, moral and physical deterioration. Since it lowers * the resistance of the body it predisposes the addict to the many infections which inflict the human race. Habit-forming drugs should never be administered except when their use is positively indicated. Their continued use always leads to disas- trous results. The prolonged use of narcotics can only be justified in those who are suffering from some incurable disease to relieve pain and distress. After a drug has accomplished the purpose for which it was administered its use should be discontinued, and this applies to drugs in general as well as to the narcotics. Care of the Mouth and the Structures Within It.—Of the structures within the mouth and adjacent to it, the teeth and tonsils deserve especial attention. The vast majority of all people have one or more teeth in a diseased condition, usually several. Not only does this dis- eased condition frequently lead to discomfort, which interferes with the normal pursuits of life, but the daily absorption of purulent material also insidiously lowers the resistance of the body and predisposes it to disease. Frequently the diseased part does not remain confined to the local area in the tooth, but extends from this point, invades surround- ing tissues, and often the cause, which has produced the changes in the tooth, is transported by means of the lymph and blood vessels to other parts of the body. An inflamed knee joint may be the result of the transportation of infectious organisms from a decayed tooth. Since remote infections may arise from what appears to be a slight infection in a tooth, it would seem the part of wisdom to either prevent infection in teeth or remove the diseased portion if infection exists, or the whole tooth if necessary, to prevent possible extension. One of the most potent measures for preventing infections of the teeth and the structures surrounding them is to keep the mouth and teeth scrupulously clean. If the teeth are irregular in alignment, or individual teeth present irregularities, pits, and depressions, it is diffi- cult to keep them clean. If the surfaces are made smooth by removing any roughness which may result from deposits or from any other cause, “it will be a much easier task to keep them clean. Especial attention should be given to the first set of teeth in young children. If the align- ment is not good the dentist can more easily correct the fault at this time than at some later period. The teeth should be frequently examined by a dentist, and if any abnormality is found it should at once be cor- rected. If cavity formation has taken place the tooth should be filled and not allowed to undergo further destruction, even though it is only a temporary tooth. Many advise the cleaning of the teeth after each meal to remove any food which may be deposited between and in de- pressions in them. If care is taken not to use too much force in the cleaning process this practice will prevent much infection and destruec- tion of teeth and keep them in a sound condition. Even though teeth are kept scrupulously clean, decay sometimes occurs. Anything which . . 162-.: .% 1¥iN° Disease Prevention “towers “the re§istance. of the body renders each and every part more “susceptible to infection, and this applies to teeth as well as other parts of the body. Within recent years it has been observed that in acute infections, particularly of joints, it is difficult to determine where the primary in- fection began. In many of these infections careful examination has re- vealed a chronie infected area in some other portion of the body, often far removed from the acute process. At first attention was directed almost exclusively to the tonsils as the probable primary focus of these infections. Through the removal of these organs many acute infections of joints and other structures cleared up rapidly. Often the removal of the suspected tonsils was not followed by cessation of the acute process in other parts. In some of these cases diseased teeth have been discovered and their repair or removal has led to speedy recovery of the joint or other infected area. Since these chronically infected tonsils, teeth, and other structures, in which the same conditions may be found, occupy very limited areas, they have been called infectious foei. The infections themselves are designated focal infections. A focal infection of the teeth may lead to various diseases. The so-called rheumatisms, both acute and chronic, possibly arthritis deformans, gastric uleer, duodenal ulcer, appendicitis, organic heart diseases, acute and chronic kidney diseases, infections of the cavities or sinuses of the face and head, brain abscess, arteriosclerosis, and in fact almost any infectious process, which is caused by the pus organisms, may have had its primary focus in a diseased tooth. The preservation of the teeth, through preventive measures, is of great importance also in the prevention of other mouth infections. In the future many infections of this nature will not occur because of better care of the teeth. If one examines teeth which have not been brushed or cleaned he will observe that they are covered with a thin filmy deposit. In this film there are many bacteria which produce acids. The acids formed, espe- cially lactie, which is the principal one present, act upon the hard por- tions of the teeth, the enamel and dentine, causing their destruction. After this has been accomplished, other bacteria get into the root canal and destroy the pulp. In times gone by many infected pulps, or remnants of infected pulps, were enclosed by bad dentistry. As a result the bacteria which were left behind continued to develop, sometimes causing the condition known as subinfection; at others acute and more serious infections. From these focal areas, infection was often carried to other parts of the body. If teeth which have been infected can be saved without danger of causing disturbance locally or elsewhere, they should not be sacrificed. If there be any doubt, it is better to extract the tooth than to run the risk of later infection in some other part of the body. In the past much attention has been given to the construction of mechanical devices to take the place of lost teeth or parts of teeth, General Methods of Disease Prevention 103 in order to restore function and fill in defects. Even today no incon- siderable amount of work is being done. Much of this erown and bridge work is a menace, since it not only shields and shuts in infected areas, but it also increases the difficulty of keeping the teeth and mouth clean. Much has been written concerning pyorrhaa alveolaris, an infection of the gums around the tooth sockets. It is thought that a deposit of tartar or lime deposit is perhaps the most common predisposing cause of this condition. It begins at the border or edge of the gum and gradually extends along the root of the tooth. Pus pockets are formed and the tooth becomes loose. The pus escapes continuously and is con- stantly being swallowed. Gradually the tooth becomes loosened and pus and bacteria are forced out into the mouth and into the tissues through the pressure to which the teeth are exposed in the act of chewing. Just as in other infections of teeth, pyorrhea alveolaris is probably quite frequently the focus from which bacteria are transported to other parts of the body with resulting secondary infections. Many cases of pyorrhea alveolaris could be prevented if the teeth were frequently examined and properly cared for in the daily routine. After the condition has become established it is difficult tc cure. Care- ful, periodical inspection, by a competent dentist, with the correction of anything which is found abnormal, will give the best promise of pre- vention. If tartar has collected along the edge of the gum it should be removed, due care being taken to interfere as little as possible with the gum. Disregard of this precaution often leads to the production of pockets between the tooth and gum, which may furnish an opening for the development of pyorrheea alveolaris. Infections may occur in any portion of the root canal, the apex often being affected, and from here the infection may spread to the surrounding structures and involve an area of greater or less extent. Since inspection frequently shows nothing abnormal, and since there may be no pain or other symptoms, infection may continue in and around root canals without being discovered. Whenever systemic dis- ease occurs, even though a diseased tonsil or other diseased area may appear to be the place of origin, the teeth should be x-rayed, since they may reveal conditions which might cause the trouble. Tonsils and Adenoids.—If enlarged or diseased tonsils and adenoids have not been discovered by systematic inspection or examination of the mouth, attention is first called to them through a sore throat (ton- sillitis) or because of the habit of mouth breathing. If the tonsils are considerably enlarged the condition can be readily recognized by any one. The more experience one has had in looking into throats, the better will he be able to judge regarding their size. Usually, if the tonsils are enlarged, there is a corresponding increase in the adenoid tissue, espe- cially in children. The adenoids cannot be seen by direct inspection but may be detected by manual examination. The only efficient treatment for either trouble is complete surgical removal of these structures. En- 104 Disease Prevention larged tonsils and adenoids interfere with breathing, and are often the predisposing causes of colds and other respiratory infections. Adenoids exert pressure on the openings of the tubes which connect the mouth cavity with the middle ear, the eustachian tubes, and this may lead to earache (middle ear disease), sometimes with extension to the mastoid, and in still rarer instances to the brain. Other more direct and visible signs are observed in the child. The mouth is held open, the expression is stupid, he is dull in school, the upper jaw is narrow, the roof of the mouth is high and arched, the lips are thick, and the openings of the nostrils contracted. Often a change occurs in the shape of the chest. It becomes narrow and extends out in front, giving an appearance similar to that of the breast of a chicken or pigeon, hence called the chicken- or pigeon-breast. Usually the voice is nasal and often whining. Headaches and colds are frequent. There is loss of energy, which, with backwardness and stupidity in school, char- acterize the condition. ‘When enlarged or diseased tonsils and adenoids are removed, they not only relieve the condition for which they were directly responsible, but at the same time they bring about a marked improvement in the general health. Care of the Eyes.—Many persons suffer from eye defects. The most common abnormalities are due to variations in the curvature of the eye as a whole, of the cornea, or of the lens. If the globe is elongated from before backward, if the cornea or lens is too convex, the rays of light entering the eye come to a focus in front of the retina. This is the cause of myopia or shortsichtedness. If the globe is shortened from before backward, if the cornea or lens is diminished in convexity or flattened, the rays of light will focus behind instead of on the retina. The defect which arises from this abnormality is designated hyperopia or farsightedness. If there are variations in different axes of the eye, usually the cornea, sometimes the lens, the condition is known as astig- matism. This defect may be overcome for a time by accommodation if it is not of too high a degree. In time accommodation is lost, and the objects upon which the eyes are focussed become blurred and dis- torted. Accommodation may also correct for a time both short- and far-sightedness, but not without eye strain and other symptoms. Vv The eyes of all school children should be carefully examined, and any defects which are found should be corrected by a competent oculist to prevent an increase in the defect, and to give relief from the symp- toms which are caused by the abnormality. Many times the correction of eye defects, by the use of properly fitted glasses, changes the at- titude of the child towards his work, since it removes an almost insur- mountable handicap. Eye defects, of which the most common are the errors of refraction already described, likewise have their effect on the general health and comfort of those who are so unfortunate as to be afflicted by them. Defective vision may cause ill health or it may be the sign of some disease. Having once determined and cor- General Methods of Disease Prevention 105 rected an eye defect does not mean that the eyes will need no further attention. They should be examined frequently, in order that any changes which may occur may be corrected by the proper glasses. Many reflex disturbances are the result of eye strain due to defective vision. There may be headache, dizziness, nausea, blurring of printed letters and other objects, choreic movements and other nervous mani- festations. It is often surprising to see how quickly the symptoms dis- appear after the eye defects have been properly corrected. Eyes which have no optical defects may be used so continuously, or under such ad- verse conditions, too much or too little illumination, ete., as to elicit symp- toms similar to those caused by errors of refraction. These symptoms may be promptly relieved by rest. As one advances in years the crystalline lens becomes hardened and the power of accommodation is lost. This usually first makes itself manifest at 40-45 years, and increases until about the age of sixty. If the eyes have never caused any trouble before this time, some difficulty may now be experienced in seeing objects distinctly. Even if there is no discomfort, the eyes should be examined and any defect which is found should be corrected. Subsequent examinations should be made every year or two, since eye conditions change as the years advance. The eyes frequently furnish the avenue for the entrance of infections. The infections which enter through this channel are not always localized. How frequently infections in other parts of the body may have their portal of entry through the eye is not known, but such entrance prob- ably occurs more frequently than has been generally suspected. When masks are worn the eyes are nearly always left uncovered which leaves this avenue of infection unprotected. If the microorganisms which cause the respiratory diseases gain entrance to the conjunctival sae, it is an easy matter for them to pass down the lachrymal or tear duets into the nose and from thence into the throat. Diphtheria, influenza, pneumonia, the common colds, measles, and other respiratory diseases may have their primary focus in this region. It is probable that in- testinal diseases may also be contracted in this way. ‘Whenever infections of the eye are present, the persons so infected should have separate towels and individual wash bowls in order that others may not become infected with the discharges. This applies par- ticularly to gonorrheeal infections and trachoma since diminished vision and even blindness is not an infrequent occurrence in these infections. Communicable Diseases.— Whenever illness occurs it should be re- garded as potentially communicable. Until a diagnosis is made the patient should be placed in a room by himself and kept in isolation. In making a diagnosis both clinical and laboratory methods should be employed. Reliance should not be placed on either one of these methods to the exclusion of the other. If the disease is found to be communicable, the person afflicted should be kept in isolation and other methods of prevention which have been found to be of value, should be immediately put into operation. 106 Disease Prevention Isolation.—Those suffering from communicable diseases may be iso- lated in their homes, provided the facilities are such that it may be done without danger to them or to others. If these conditions do not maintain, the sick person should be removed to a hospital or similar institution which has been provided for this purpose. The isolation of the patient should be made as complete as possible. Only those should be allowed to come in contact with him whose presence is absolutely necessary to give him the required care and attention. He should have a room, or suite of rooms, entirely separated from other rooms in the house so far as possible contact is concerned. The best person to care for the patient is a trained nurse. Sometimes the nature or severity of the disease demands that the care of the patient should only be entrusted to a nurse. When the attendant is some member of the family, or a friend, he should be given very specific instructions concerning the routine to be followed for the protection of others against infection. No one should be allowed to enter the sick room except the attending physician or physicians and the health authorities. Under no conditions should the nurse or attendant prepare food for other mem- bers of the family except the patient, nor should she handle any article of food which may be consumed by them. The room in which the patient is isolated should be well ventilated, screened, and there should be an abundance of sunlight. All superfluous furnishings should be removed from the room previous to occupancy. A tub or other receptacle containing some good disinfecting solution should be present in the room at all times. A basin or some similar utensil con- taining a disinfectant should be kept on a table outside the door of the sick room. Isolation should be complete. This means that no one, not even friends or members of the family, should be allowed to enter the room. Only those whose presence is required to take proper care of the patient should be allowed to come in contact with him. The nurse or attendant should see that all articles which are needed in the sick room are provided for at the time the patient is isolated. A gown, large enough to cover the clothing, should be worn in the sick room to prevent any infectious matter from coming in contact with the clothes. This gown should be removed when leaving the room and on returning it should again be put on before touching anything or render- ing any service to the patient. Contact with the patient should be limited to the smallest possible extent, only those things being done which are necessary for his care and comfort. After the hands have come in contact with the patient, or with anything which may have been in contact with him, they should be immediately washed and placed in a disinfecting solution. Articles of every sort should be kept out of the mouth. This includes such things as pins, pencils, and, above all, the fingers. The hands should be frequently washed and always before eating. Nothing should .be eaten by the attendant which has been prepared for the patient or has come in contact with him. All remnants General Methods of Disease Prevention 107 of food should be disinfected before leaving the room and subsequently destroyed, preferably by burning. The attendant should have separate drinking glasses and eating utensils which should not be handled or used by any one else. This regulation would also apply still more forcibly to the patient. The hands should not be allowed to come in contact with the face, after coming in contact with the patient until they have been washed. When the attendant is some member of the family, par- ticularly if the patient is a little child, there is often an impulse to kiss or caress him. This impulse must not be gratified, since such indul- gence offers the most favorable opportunity for the transmission of infection. Theoretically isolation should be the most effective single method of preventing and controlling communicable diseases. It has been asserted, that if all cases of typhoid fever were isolated, and all discharges disin- fected, the time would be relatively short when this disease would disappear. If these measures were strictly carried out in all cases of typhoid fever which are recognized as such, it would not eliminate this disease but it would prevent the transmission of infection to many per- sons. The bacillus carriers and ‘‘missed’’ or unrecognized cases of the disease would still keep the germ alive and capable of producing infec- tion whenever the opportunity of transmission presented itself. It is not claimed that isolation will prevent all infection. If only one person is protected from infection for every individual isolated, it is well worth while, since it has not only protected him but others to whom he might in turn communicate the disease. When isolation is looked after by a trained attendant secondary infections are reduced to a minimum. Isolation with no one to enforce the necessary regulations increases secondary infection from 2-5 times; entire disregard of isolation increases the number 5-10 times or more. Isolation varies in degree and method according to the nature of the infection. In malaria and yellow fever all that is necessary is to protect the patient from mosquitoes. This may be done by placing the patient in a mosquito-free room so protected by screens that mosquitoes cannot get in. At the other extreme, as in the communicable diseases smallpox and measles, isolation requires the putting into practice of all measures which have been found to be of any value. The question is often asked, ‘“ What shall be done with disease car- riers?’’ In the case of diphtheria carriers, if treatment does not cause the germ to disappear, cultures should be made and the virulence of the germ be determined. If it is non-virulent the carrier should not be kept longer in isolation. If it is still virulent the release of the carrier would be a dangerous proceeding. If the typhoid carrier does not be- come free of typhoid bacilli, after a reasonable period of isolation, he should not be indefinitely restrained from resuming his activities, pro- vided they do not bring him in contact with food which is consumed by others. He should not be allowed to work in kitchens, dairies, bakeries, markets, or in any place where foodstuffs are prepared, transported or 108 Disease Prevention sold. In tuberculosis there is absolutely no reason for isolating the patient so long as the case is a closed one. When the case becomes an open one the patient is a source of danger to others if he is careless about distributing and disposing of his discharges. This carelessness may result from ignorance; from lack of facilities for taking precau- tions because of indigence; from inability to care for himself because of the severity of the disease; or to indifference. Under whichever of these classifications he is placed matters little; he is a public menace and as such should be isolated. Fortunately we now have public in- stitutions where such individuals may be placed. If this cannot be done with their consent, the laws of some states permit of their com- mitment upon the proper presentation of evidence against them. The question often arises as to whether the well children in a family where a communicable disease exists should be excluded from the schools. Should the bread winners be prevented from pursuing their usual voca- tion provided they do not come in contact with those who are ill even though they remain in the same house? The majority still believe that normal children from homes where a communicable disease exists should be excluded from school for periods varying in length according to the nature of the disease. The length of time for the individual diseases is determined by the local health ordinances or the rules and regula- tions of the board of health. The answer to the question concerning the bread winners might be answered as follows: If the community deprives the bread winner of the opportunity to provide for those dependent upon him, it should take care of the matter by granting him compensa- tion. Irom the humanitarian standpoint this should be done and it is not at all certain that this would not be an economic saving to the whole community. Preventive Inoculation.—In those diseases for which an effective vaccine or antitoxin has been prepared, it should be the invariable practice to inoculate all the members of the family, whenever a com- municable disease makes its appearance. The same practice should be followed when a communicable disease occurs in any member of an organization or institution. All who have been more or less closely associated with an infected individual in an asylum, prison, school, busi- ness establishment, factory, manufacturing plant, camp, or any similar institution, should be protected by this measure. What may be achieved by adopting this practice in individual diseases has been described in discussing smallpox, typhoid fever, and diphtheria. Although the results have not been so satisfactory in other diseases, for which a vaccine has been prepared, the success in some of them has been sufficient to warrant the application of this procedure to them. Disinfection.— When all infected discharges, and all articles which have come in contact with them, are immediately placed in a disinfectant or destroyed, the procedure is designated concurrent disinfection. Dis- infection of the premises, after the removal of the patient from the room or quarters where the illness has occurred, is called terminal dis- General Methods of Disease Prevention 109 infection. Of the two methods, concurrent disinfection is the better, since the infectious material is immediately disposed of and destroyed. By many terminal disinfection is considered of little value. If terminal disinfection prevents even a small number of infections, and it is very probable that it does, it should not be discarded. The wisest procedure is to employ both methods. Concurrent Disinfection—Many substances have been advised and employed ror concurrent disinfection. Some of them are very efficient; others of little or no value. It is better to use a few tried and efficient disinfecting agents than a large number of varying degrees of effective- ness. Experiment and experience have shown that the following disin- fectants may be expected to accomplish the desired result: Bichloride of mercury, carbolic acid, phenol, the ecresols, liquor eresolis ecompositus, lysol, chlorinated lime, milk of lime, and formalin for general applica- tion; for certain specific uses iodin and silver nitrate. For the destruc- tion of protozoa, and the eggs of the parasites which cause disease, other disinfectants should be used, since those employed for general purposes are not always effective. Stiles recommends 3% sodium hydroxide (caustic soda) or 0.49% sodium dichromate for this purpose. Bichloride of mercury ‘‘corrosive sublimate,’’ is a very efficient dis- infectant if used under certain conditions. For the disinfection of discharges from the body it is not reliable, since the discharges contain protein or albuminous material which combines with the mercury and destroys its effectiveness. It is useful for disinfecting the hands and other external parts of the body but should not be applied to mucous surfaces. Floors and woodwork may also be disinfected by washing with a solution of this substance. It should not be applied to metals on account of its corrosive action. For disinfecting purposes it is used in solution, 1 part of mercuric chloride to 1,000 parts of water. Mercurie chloride forms a colorless solution in water. It is very poisonous and hence some coloring matter should be added to the solution as a warn- ing that it is poisonous. A small amount of laundry bluing will answer the purpose very well. In this connection, it might be added that it is a wise precaution to add some bluing to all solutions. which are to be used for disinfecting purposes. Since mercuric chloride has a cor- rosive action on all metals, solutions of this chemical should be made in glass or earthenware vessels. It likewise follows that no metallic in- struments or other metallic articles should be placed in a solution of mercury. A solution of bichloride of mercury, which contains 15 grains in one quart of water, has a strength of approximately 1 to 1,000. Since mercuric chloride is very poisonous, since there are other effi- cient disinfectants which are much less poisonous, since its effectiveness is greatly diminished in the presence of albuminous material, which is present to a greater or lesser extent in nearly all the discharges of the body, it would seem advisable to limit its use to office and hospital practice where it may be more carefully controlled. In the private 110 Disease Prevention residence some of the other disinfectants, which are less dangerous since they are less poisonous, should be recommended. Carbolic Acid, Phenol and Other Coal Tar Derivatives—The term carbolic acid is indiscriminately applied to both the crude and the chemically pure phenol. Crude carbolic acid contains phenols, cresols and other compounds. The erude drug, carbolic acid, has a greater disinfecting power than has the pure substance, phenol. Crude carbolie acid is used in the strength of 1 part of acid to 20 parts of water, a 5% solution. The effectiveness of carbolic acid, of phenol and other coal tar deriva- tives which are used as disinfectants, is increased by the addition of com- mon salt in the proportion of 12 to 14 ounces to the gallon of solution. Crude carbolic acid is only used for disinfecting floors, barns, stables, outhouses, and the discharges from man and animals. It is not used on the body, in the disinfection of clothes or eating utensils. For the latter purposes phenol is used in 5% solution, 1 part of phenol to 20 parts of water. A 2-3% solution of eresol or lysol is as effective as a 3% solution of phenol and both may be used for the same purposes. An efficient solution containing cresol, liquor cresolis compositus, may usually be obtained at the drug store, which, when used in the strength of 1 part to 20 parts of water, is of equal or greater value than phenol as a disinfectant. Calcium Hypochlorite.—Caleium hypochlorite, also known as chlorin- ated lime, chloride of lime, and ‘‘bleaching powder,” is a very reliable and powerful disinfecting agent. To be effective it should contain at least 25% of available free chlorine. It should be kept in an air-tight container until used. As soon as it is exposed to the air free chlorine gas is given off until it entirely disappears. In order to be assured of its effectiveness, it should be obtained from a container which has never been opened. It is used both for general and specific pur- poses. For the disinfection of discharges, floors, furniture, ete., it is used in a 3-5% solution. Since chlorine has a corrosive action and is a powerful bleaching agent, solutions of chlorinated lime should be kept in glass or earthenware vessels, and nothing which is injured by it, such as metals, clothes, etc., should be placed in it. It is sometimes used in the dry state, as when it is sprinkled over discharges from the bowel. Chlorine, either in the form of hypochlorite, or as liquid chlorine, is used extensively for the disinfection of water supplies and sewage. Taking everything into consideration it is the best disinfectant which we have today for the disinfection of water supplies on account of its effectiveness and relatively low cost. Chlorination of Water—For disinfecting water either calcium hypo- chlorite or liquid chlorine is usually employed. Sodium hypochlorite is superior to calcium hypochlorite since it does not increase the hardness of water, but rather softens it, and it does not produce a sludge. Its cost, however, is so much greater that it is rarely used. Calcium hypo- chlorite should contain from 25-85% available free chlorine. Ordinarily General Methods of Disease Prevention 111 from 5-15 pounds are used per million gallons of water. Rarely is more than 25 pounds per million gallons added, since larger amounts impart an unpleasant taste and a distinet odor. In water relatively free from organic matter smaller amounts are required. For disinfecting small amounts of water for military use, camps, tourists, and others who travel from place to place, a solution may be prepared by adding 1 teaspoonful of calcium hypochlorite to 1 quart of water. This solution will keep for a short time if it is well stoppered. It is used as a stock solution. For disinfection add 5 teaspoonfuls of this solution to 10 gallons of water; 30 drops to 1 gallon; 8 drops to 1 quart. It should stand for 15 minutes or more before it is used. Tablets containing hypochlorite may be obtained in the market. Since they are not stable, to be effective they must be fresh. Liquid Chlorine.—A few years after chlorinated lime was introduced, more effective methods were devised for the manufacture of chlorine gas. At the same time apparatus was developed for the introduction of the gas, compressed in cylinders, into the water. The amount of gas intro- duced is automatically controlled. This treatment is known as the liquid chlorine treatment. It has largely replaced calcium hypochlorite over which it has several advantages. The quantity intreduced can be more accurately controlled; its composition is constant; it does not produce any sludge; it does not increase the hardness of the water as does hypochlorite ; it imparts less taste and odor; it does not deteriorate on standing since it is enclosed in a gas-tight eylinder; and the required apparatus takes up less space. The cost of application is less than chlorination with calcium hypochlorite. The amount of chlorine added to the water is usually designated in parts per million. A gallon of water weighs 8.3 pounds, hence 8.3 pounds of chlorine in 1,000,000 gallons of water would be 1 part of chlorine to 1,000,000 parts of water. The amount to be added to any given water supply depends upon the amount of organic matter present. If the amount is small, 0.2 parts per 1,000,000 may be sufficient ; with a large amount of organic matter present as much as 1 part per 1,000,000 might be required. Wherever chlorination has been introduced and intelligently super- vised typhoid fever and other intestinal diseases have decreased markedly in number. It is also believed that chlorination has had something to do with the decrease of other diseases which invariably follows the better sanitation of water supplies. Chlorination plants should be installed in duplicate in order to keep up chlorination in case of any emergency which might arise. Milk of Lime.—A useful preparation for the disinfection of discharges from the bowel is made by adding freshly slaked lime to water, in the proportion of 1 part of lime to 4 parts of water. The lime should be fresh and not air-slaked. It should be broken up into small pieces before slaking. It should be slaked by adding 1 part of water to 2 parts of lime. Ome part of the slaked lime is now added to 4 parts of water. 12 Disease Prevention As only a small part of the lime dissolves, it should be thoroughly mixed just before using, in order to get the undissolved lime evenly distributed in the mixture. The volume to be used should be equal to, or, better still, twice as much as the amount of the material to be disinfected. Milk of lime is especially used for the disinfection of bowel discharges. In order that it may act most effectively, the hard masses should be broken up into small pieces, to allow the disinfectant to come in contact with all parts of the feces. The disinfectant should be allowed to act for at least two hours. A simple method for the disinfection of bowel discharges is to first pour into the receptacle a sufficient amount of boiling water to cover the entire mass, then add an amount of quicklime equal to } the entire bulk in the container. From 1-2 large cups of lime will be sufficient. By the use of this method the combined action of the lime, the heat generated in slaking it, and the heat from the boiling water is obtained. Milk of lime, in the form of whitewash, is often used in outhouses, stables, ete., both for cleansing and disinfecting purposes. It is not as efficient as are other disinfectants, since calcium hydrate is soon changed to calcium carbonate which has little if any disinfecting value. Formalin.—Formalin is a 40% solution of formaldehyde gas in water. It is useful for the disinfection of bowel discharges, sputum, urine, pus, and similar discharges. It is used in a 10% solution which would be equivalent to 4% formaldehyde. Since it is a powerful de- odorant, as well as a powerful disinfectant, it is especially useful. It removes the odor from feces, sputum, pus and other malodorous ma- terial. Two volumes of the solution should be used to one of the ma- terial to be disinfected. Hard masses of excreta should be broken up in order that the solution may come in contact with all parts of the solid matter. Iodin.—In recent years iodin has come into prominence for the dis- infection of superficial wounds on the external surface of the body, and in preparing superficial areas for surgical operations. The diluted tincture of iodin is employed for this purpose. Tincture of iodin should be diluted two or three times, preferably with 70% pure alcohol. If impure alcohol is used it may cause undue irritation. It is also useful as an application to accessible mucous membranes, particularly in simple ulcerations of the mouth. Silver Nitrate—This compound has a particular field of usefulness in the prevention of gonorrheeal infection of the eyes. It is most effective in preventing ophthalmia neonatorum, ophthalmia of the new- born, which is caused by the gonococcus in about 65% of all cases. The eyes should first be cleaned by applying a pledget of sterile absorbent cotton saturated with boric acid solution. Care should be taken that none of the discharge comes in contact with the hands or anything else before it is placed in a disinfecting solution or is destroyed. The lids are now separated and 1 or 2 drops of a 1-2% solution of silver nitrate is instilled (a medicine dropper is useful for this purpose) and then General Methods of Disease Prevention 113 washed out in a few minutes with normal salt solution. This treatment is called Credé’s method. Argyrol in a 25% solution, and protargol in a 3% solution, are also used. Silver nitrate is better than the other silver preparations and should therefore be the agent of choice. Standard Disinfectants—There are many patented and proprietary disinfectants on the market, for which great merit is claimed. Most of them cost much more than the standard disinfectants. Their value is often less than is claimed for them, and some of them have little disin- fecting power. In choosing a disinfectant it is, therefore, advisable to select a standard one which has been shown to be effective. The following formule are quoted from Rosenau’s ‘‘ Preventive Med- icine and Hygiene’’ as illustrations of simple solutions which are to be especially recommended for general disinfecting purposes:?* ‘“Bichloride of Mercury: Corrosive Sublimate. Bichloride of Mereury ...vceessssess 1 dram |1 gram er rs a ah en ea al 1 gallon | 1 liter ““Mix and dissolve. Label ‘Poison!’ This is approximately a 1 to 1,000 solution. One ounce of this solution contains nearly half a grain of corrosive sublimate. Useful for disinfecting clothing, the hands, the surfaces of walls, floors, furniture, ete. Not serviceable for feces or material containing much organic matter. ‘‘Formalin. Formalin =. ve... ice, st cn sete 13 ounces | 100 c.c. Water... ......... i de. 1 gallon 1 liter “‘Formalin is a watery solution containing 40 per cent. formaldehyde. The above solution contains approximately 10 per cent. of formalin and is useful for the disinfection of clothing and a. great variety of objects. As it has no corrosive action it does not bleach pigments or rot fabrics. ‘When used to disinfect feces a stronger solution may be used. “‘Milk of Lime.—Slake a quart of freshly burnt lime, in small pieces, with three-fourths of a quart of water, or, more exactly, 50 parts of water by weight with 100 parts of lime. A dry powder of slaked lime (calcium hydroxid) results. Prepare the milk of lime shortly before it is to be used by mixing 1 quart of this dry calcium hydroxid with 4 quarts of water. Air-slaked lime is worthless. Slaked lime may be preserved some time if inclosed in an air-tight container. Milk of lime is especially useful for the disinfection of feces; an equal quantity should be added to the mass and thoroughly mixed. ‘“Carbolic Acid. Crude carbolic acid (or phenol) .... 7 ounces [50 c.c. Water... he 1 gallon 1 liter ““The solution is facilitated by dissolving in hot water. This makes approximately a 5 per cent. solution. The addition of from 12 to 14 2D. Appleton & Co., 1922, p. 1425. 114 Disease Prevention ounces of common salt to each gallon increases its germicidal power, especially when used for the disinfection of excreta. The crude earbolie acid is more powerful than pure phenol, but ean only be used for rough work, such as floors, feces, sputum, ete. For the disinfection of clothing phenol should be used and the solution may be mixed half and half with water, making approximately a 2} per cent. solution. ‘“Chlorinated Lime (‘Chlorid of Lime’). Chlorinated Tie... nei. hiv iii vas 3 ounces | 30 grams AlCl hs delish dat a hr a 1 gallon | 1 liter “‘Mix. This is about a 3 per cent. solution. It is exceedingly powerful and is useful for the disinfection of excreta, privy vaults, cesspools, and many other purposes. It is an active bleaching agent and destroys fabrics in this concentration.” Of the general measures to be employed in preventing disease, two of the more important methods of disinfection have been left until the last in order that their importance may be duly emphasized. The first of these is the maintenance of cleanliness both of the body and the envi- ronment ; the second the destruction of disease germs by heat. vCleanliness.—The basis of all sanitary measures is cleanliness. If it were necessary to choose between cleanliness without disinfection, and disinfection without cleanliness, the former should be the choice. When the individual and his surroundings are made clean, disinfectants are important adjuvants in destroying disease germs. If organic matter, such as sputum, pus, nasal, and other discharges are deposited on the person, his clothes, articles of furniture, or any other objects, and are not removed, little should be expected from disinfection. Most disinfectants do not penetrate solid substances to any considerable extent. Sputum which has dried into a hardened mass is not penetrated easily by any disinfectant. If disinfection is to be of any value, the sputum should be removed mechanically before the disinfectant is applied to the spot where it was deposited. To successfully remove organic matter, and the germs contained within it, the cleaning should be done with soap and water. Dry cleaning is bad, since the dust raised in sweeping contains germs which will be again deposited with the dust on the sur- faces from which they were removed, through the settling of the dust. Cleanliness today means not only cleanliness of a visible nature, but cleanliness which also removes invisible dirt. To remove this invisible enemy, we must destroy or remove all organic matter which may contain it; all insects and other animals which may harbor and transmit it; all breeding places and food supplies which are necessary for its continued existence. Lynch and Cumming have recently pointed out the danger of conveying infection through soiled hands. To prevent such transmis- sion one should be scrupulously careful in washing his hands after visiting the toilet; before handling food which he is going to consume himself or which is to be consumed by others. The fingers should be General Methods of Disease Prevention 115 kept out of the mouth and nose. If, for any reason, it is necessary that they should enter the nose or mouth, they should be washed immediately before and immediately after such entrance. The value of a soap solution rests upon its cleansing and not upon its disinfecting properties. It removes germs mechanically; it does not kill them. To insure safe hands, disinfection with some good germ destroyer should follow washing with soap and water. If the water to which soap is to be added is not soft, it should be made so with some softener. The soap solution should contain at least 10 per cent. of soap. A greater amount will do no harm. To increase its efficiency an ounce of common soda should be added to 3 gallons of the soap solution. A stronger and more effective solution may be made by dissolving 4 pound of common soda in 3 gallons of hot water. This solution should be applied with a hard serubbing brush. Medicated and disinfecting soaps are of little or no value as disin- fectants. The soap prepared by McClintock, which contains from 0.5 to 2 per cent. of the double iodide of mercury is a possible exception to the general rule. Heat—Infected articles of little value are most effectively disin- fected by burning. Articles which are of too much value to be burned, and which are not injured by subjecting them to hot water, are best disinfected by boiling them in water or subjecting them to steam in an enclosed vessel. All of the common disease germs are destroyed by boiling or by steam in 10 minutes. Even the spores of the more resistant disease germs, such as tetanus and anthrax, will certainly be destroyed by boiling for one hour. Disinfection of the Hands and Person.—If the hands, or any other part of the body, become soiled through contact with the discharges from a communicable disease, they should be immediately placed in some disinfecting solution and allowed to remain in it until they are thor- oughly soaked. If any portion of the patient’s body should become soiled with infectious discharges, it should be treated in the same manner. Any of the solutions which have been recommended are suitable for this purpose. If carbolic acid is used on the hands or other parts of the body the solution should be only one-half as strong, as the solution used for general purposes, on account of its irritating properties. For the hands and other body surfaces a 2} per cent. solution should be used ; for other purposes a 5 per cent. solution. Bichloride of mercury may be used for the same purpose in a 1-1,000 solution. After immer- sion in the disinfectant they should be washed in soap and water and again immersed in the disinfectant. Before eating, or coming in contact with the mouth, they should be soaked in disinfectant and then thor- oughly washed in soap and water. Whenever it is necessary to leave the sick room this practice should always be followed. /The fingernails should be kept short and clean, since it is difficult to remove the dirt which collects underneath them when they are not cut. 116 Disease Prevention Soiled Clothing, Bed and Body Linen.—All articles which have come in contact with those suffering from communicable diseases should be disinfected. This should be done immediately, since they have very probably become infected. Towels, napkins, sheets, pillow cases, hand- kerchiefs, underwear, and similar articles, which have come in contact with the patient, should be subjected to steam or boiling for half an hour, or they may be immersed for an hour or more in carbolic acid; or in 10 per cent. formalin. Articles which cannot be washed, such as woolen clothing, mattresses, etc., should be so protected that infectious material does not come in contact with them. Before they are allowed to leave the sick room they should be exposed to formaldehyde gas. Books.—If books in the sick room have not been disturbed or exposed, except by their presence in the room, only the external surfaces require disinfection. Under such conditions exposure to formaldehyde gas in the terminal disinfection is all that is necessary. If they have been handled by the patient, or his attendants, they require other treatment. Chambers have been constructed for the purpose of disinfecting books with formaldehyde gas. For practical purposes, where the number of books is not large, a few drops of formalin, well distributed between all the pages, will serve the purpose, provided they are placed in a tight box or drawer which has been well sprinkled with the solution. The air in the box or drawer should be kept at a temperature of at least 70°F. and the books should not be removed for 24 hours or more. Food and Drink.—All remains of food or drink should be disin- fected before they have left the sick room. The dishes or other utensils which have been used in serving them should be treated in like manner. They should be immersed in a 5 per cent. carbolic acid solution, or a 10 per cent. formalin solution, and allowed to remain in it for at least an hour. The remnants of food and drink should be boiled for half an hour after they have been removed from the disinfectant before they are finally disposed of; the eating utensils should be treated in the same way before they are washed. Discharges.—Discharges of all sorts from the mouth, nose, bladder and bowels should be received in glass or earthen vessels which contain an abundant amount of the disinfecting solutions above mentioned. They should be allowed to remain in the solution for at least an hour before they are emptied. The difficulty of disinfecting bowel discharges has already been sufficiently emphasized, and directions have been given which, if followed, will prove effective. Although certain discharges may contain all, or nearly all the germs which are eliminated from the body, such as the feces and urine in typhoid fever; the secretions and excretions of the respiratory tract in diphtheria, measles, smallpox, and many other respiratory diseases; the safe procedure is to regard all dis- charges, from all parts of the body, as probable carriers of infection. Especial attention should, therefore, be given to all discharges. Sputum.—The discharges from the nose, mouth and respiratory tract might all be included under the term sputum, although it is usually General Methods of Disease Prevention 117 restricted to the discharges from the throat and lungs. Altogether too little care is taken in disposing of these discharges and its importance is underestimated. Of all diseases, those of the respiratory tract are the most difficult to control and prevent. How much of this difficulty is due to the promiscuous disposition of the discharges of the nose and mouth, in every conceivable place, and on all sorts of articles and surfaces, is hard to estimate. It must, however, be one of the most important means of transmitting respiratory diseases. It is, therefore, evident that all these discharges should be so cared for that the danger from them may be reduced to the smallest possible degree. In the home the best method of disposing of sputum, and other discharges from the nose and mouth, is to collect them in sputum cups, on pieces of cloth, or on paper napkins, which should not be left around, but disposed of immediately by burning. If this cannot be done, because of the severity of the disease or for any other reason, the discharges should be received in a covered cup, or similar receptacle, which contains an abundant supply of 5 per cent. carbolic acid or some equally efficient solution. They should stand for at least an hour after receiving the last installment of the discharges before they are emptied. Among the more important diseases in which the germ is present in the sputum are: tuberculosis, the common colds, influenza, the pneu- monias, measles, diphtheria, scarlet fever, whooping cough, tonsillitis, smallpox, mumps, chickenpox, sore throat, septic sore throat, the pul- monary form of plague, cerebrospinal meningitis, infantile paralysis, and at times other diseases not commonly conveyed through the nose and mouth. If the discharges are not large in amount they may be received on pieces of cloth, gauze, paper, or some similar article of little value. These articles should be immediately burned. If the quantity is great- er, a covered paper sputum cup or a sputum bottle may be used. The paper cups should be burned. If metal cups or sputum bottles are used they should contain some disinfectant solution. If no disinfectant has been placed in them, they should be immersed in one of the following solutions and allowed to remain in it for an hour or more: carbolic acid 5 per cent.; formalin 10 per cent.; calcium hypochlorite 5 per cent. Bichloride of mercury (corrosive sublimate) should not be used for disinfecting sputum, since it is not efficient in the presence of albumin which makes up the greater part of the sputum. Bath Rooms, Kitchen and Hallway Sinks, Privies, etc.—If the bath tub or some other vessel is used for bathing a person suffering from a communicable disease, a sufficient amount of carbolic acid should be added to the water after the bath is finished to make a 5 per cent. solution ; if formalin is used, a 10 per cent. solution; if calcium hypo- chlorite is used, a 5 per cent. solution. After adding the disinfectant the water should be allowed to stand for at least an hour before it is emptied. Nothing should be emptied in the closet bowl until after it has been disinfected. After the disinfected contents of the ped pan 118 Disease Prevention have been emptied, one of the disinfecting solutions should be poured into it and allowed to remain until it is used again. Sinks may be dis- infected by filling them with one of the above-mentioned solutions and allowing it to remain for the usual length of time. Eating Utensils.—Dishes, knives, forks, spoons, and all other articles used in eating, should not be removed from the room and should be kept for the exclusive use of the patient. After they have been used, they should first be placed in carbolic acid solution, removed from this to boiling water, which should contain at least 10 per cent. of soap, and finally rinsed in hot water. Sanitary Measures for Private Homes and Public Buildings.— When disease does not exist in the home there is always danger of its being unexpectedly brought in and communicated to the members of the household. In the day’s routine of activities one is constantly coming in contact with a multitude of objects. To provide for any contingencies which may arise, certain general measures should be practiced for safe- guarding the individual and the public at large. All water-closets, whether public or private, should be frequently flushed with an abun- dance of water. They should be thoroughly cleaned both inside and out, the woodwork, floors, and all other articles in the room should be frequently scrubbed with hot soapsuds and water. Crude carbolie acid, or calcium hypochlorite in strong solution, should be placed in the bowl at frequent intervals and allowed to stand for some time, the longer the better. At night water-closets are used much less than during the day, hence the best time to add the disinfectant is just before retiring. Cesspools, privy vaults, latrines, ete., should receive daily an abun- dance of chlorinated lime. The contents should be frequently removed to prevent the accumulation of large amounts. Floors, door knobs, woodwork, and other objects with which the hands or other parts of the body may come in contact, in schools and other institutions, where many are congregated, whether public or pri- vate, should be scrubbed daily, or as often as they are used, with hot soapsuds and water. Frequent application of a disinfectant after washing is a useful adjuvant to the washing. If the cleaning with hot soapsuds is thorough there is little danger even though no disinfectant is used. All public conveyances should receive like treatment. Among the public there is a widespread habit of spitting promiscu- ously in all sorts of places and on all sorts of objects. Ordinances and regulations, which aim to prevent this practice, have not to any great extent decreased the habit. How much infection is caused in this way cannot be estimated with any great degree of accuracy, but it must be an important factor in respiratory diseases. When cuspidors or spit- toons were introduced, it is probable that esthetic rather than sanitary reasons were responsible for their appearance. Today we encounter them wherever we go, in all states and conditions of filthiness. Very rarely do they contain any disinfectant, and all-too-infrequently are they cleaned. They should be emptied and scrubbed with hot soapsuds at General Methods of Disease Prevention 119 least once daily, and after they have been cleaned carbolie acid, or some other good disinfectant, should be placed in them. For these, as well as all other articles upon or in which material containing disease germs has been deposited, the most effective means for the removal and destruction of infectious agents, is based upon effective measures for the removal of dirt and the production of cleanliness. This may be best accomplished through thorough serubbing and removing of all extraneous material by hot soapsuds. Terminal Disinfection.—Many sanitarians place little confidence in terminal disinfection. The reason for this attitude is based upon the comparative results obtained with and without such disinfection. In New York, Providence, and other places, it has been found that the num- ber of cross infections is practically the same in both instances. They contend that if concurrent disinfection (disinfection of the discharges immediately after they leave the body) is rigidly practiced there is no need of terminal disinfection. One thing is certain, concurrent dis- infection destroys the organism as soon as it has left the body, and the probability of any organisms remaining alive, provided concurrent dis- infection is effectively practiced, is not great. However, if terminal disinfection destroys any vital germs which may by accident have escaped concurrent disinfection, it should not be discarded. Moreover, it often gives an added feeling of security. Under all circumstances concurrent disinfection should be our chief reliance, and terminal disin- fection regarded as a matter of secondary importance in preventing disease. For terminal disinfection, formaldehyde, or its 40 per cent. solution, formalin, and sulphur are most commonly used. Other disinfectants are employed for special purposes, but they are all inferior as disinfectants or dangerous in the hands of those who are not acquainted with their chemical nature and, therefore, might not take the necessary precau- tions which must be rigidly followed to prevent serious accidents. Sulphur.—Sulphur has been used for many centuries as a disin- fectant. Homer refers to it in the Odyssey, and Ovid states that the shepherds of his time were acquainted with its use in the prevention of disease. Sulphur is inferior to formalin in the destruction of bac- teria, but is superior to it for the extermination of insects and other animal carriers of bacteria, protozoa and other parasites. For the prac- tical disinfection of rooms from 4-6 pounds of sulphur should be used for every 1,000 cubic feet of space. The powdered form of sulphur, the flowers of sulphur, should by preference be used. If it is used in the form of sticks or rolls, they should be broken up into small pieces in order to facilitate ignition and burning. To be effective the room chould be made as air-tight as possible in order to prevent the escape of the gas which is generated. This may be accomplished by filling or covering all openings in the room, such as windows, ventilators, registers, the cracks around windows and window frames, doors and door frames, and any other openings which may communicate with other rooms or 120 Disease Prevention the outside. Cracks may be made air-tight by covering with gummed paper, electrician’s tape, or by plugging with any material which can be tightly packed, such as cotton, strips of cloth, ete. Every article in the room should be so exposed as to present its entire surface free from contact with other objects. All furniture, including beds, should be moved away from the walls. The doors of closets; drawers in dressers, bureaus and desks; and everything else which is closed should be opened to permit the gas to diffuse to the widest possible extent. The air in the room should be saturated with moisture. This may be accomplished by evaporating water in the room. Precau- tions should be taken against fire. Place in the center of the room, at some distance from other objects, some large water-tight receptacle. A wash tub of galvanized iron will answer the purpose very well. Place in the bottom of the tub two or three bricks. Pour in water until it covers the bricks to the depth of a quarter to half an inch. Place on the bricks some iron container of sufficient capacity to conveniently hold 4-6 pounds of sulphur. An old iron kettle will serve the purpose admirably. Sulphur does not ignite readily, hence something should be added to cause it to ignite. Burning charcoal, burning coals, alcohol, kerosene, old oil waste, ete., may be used. Before ignition the necessary articles for sealing the door of exit should be prepared and in readiness for im- mediate application. It should now be ignited and a hasty retreat should be made from the room to avoid irritation from the gas which is immediately generated. To get the best results a temperature of 70°F. or higher should be maintained. Moisture and heat are necessary for securing good results. A cold, dry atmosphere renders the gas ineffective. Sulphur bleaches clothing and tarnishes metals. It is not as effective as formaldehyde for the destruction of bacteria. Its chief usefulness is found in the destruction of insects, rats, and other animals classed as vermin, which formaldehyde does not appreciably affect. Formalin—Formalin is a solution of formaldehyde gas in water. It varies in composition, sometimes having a strength of not more than 25 per cent., at others it may be as high as 40 per cent. For practical purposes it is the best gaseous disinfectant which has yet been discovered. It does not accomplish all that might be desired, but is distinetly superior to sulphur for destroying bacteria. It has a high germicidal value, it does not injure the texture of fabrics, it does not remove or change colors (with the exception of some shades of lavender or purple), it does not tarnish metals, it does not injure oil paintings and other works of art, it is not destructive, and it is not poisonous. It has very little effect on animal life and hence is not useful in destroying the animal carriers of disease. Flies, bedbugs, roaches, mosquitoes and other insects are little if at all affected by it. The preparation of the room, or enclosed space in which formalde- hyde gas is to be generated, should be made in the same way and with the same care as that which is put into operation in sulphur fumigation. The temperature of the room should be above 65°F., since formaldehyde General Methods of Disease Prevention 121 gas decreases in effectiveness as the temperature decreases. At tempera- tures above 65°F. its effectiveness increases as the temperature increases on account of its greater penetration at higher temperatures. The rela- tive humidity should be 60 per cent. or more. This humidity may be secured by the evaporation of water in the room. At best formaldehyde gas does not penetrate to any appreciable extent, and consequently it only disinfects surfaces. All surfaces should, therefore, be freely exposed. The more rapidly the gas is generated the greater is its ger- micidal effect. After it has been generated the room should not be opened until 12 or more hours have elapsed. At the end of the exposure to the gas the doors and windows should be opened widely to allow the gas to escape. If this can be done from the outside, little if any irritation of the mucous membranes of the eyes and nose will be experienced. If the room must be entered, irritation may, to a large extent, be avoided by covering the nose and mouth with a moist towel. Of the many methods which have been devised for the liberation of formaldehyde gas, only those will be described which have been shown to be effective, practical and simple in operation. The earlier methods required considerable apparatus and were, therefore, somewhat com- plicated. In 1904 Johnson described a simple method of formalin fumi- gation. When formalin is brought in contact with potassium perman- ganate very active oxidation takes place, formic acid is produced, and the heat generated through the oxidation liberates formaldehyde gas. Since only 60 per cent. of the gas contained in the formalin is liberated, the method is a wasteful one from the chemical standpoint. As far as the other methods, which depend upon the use of some oxidizing agent to liberate the gas, are concerned, the waste from the chemical standpoint is still greater. The high cost of potassium permanganate has led to the use of other oxidation agents which are less expensive. Since more gas is liberated and in a shorter time by the permanganate method, it is the most effective of the chemical agents used. The Minnesota State Board of Health advises the following method of using potassium per- manganate and formalin, The formula for each 1,000 cubic feet of space is as follows: Potassium permanganate (erystals) ................ 11 ounces Solution formaldehyde (U. 8. P. 1000) .. ....da0ns 11 ounces DW OREr cv hi anh hs dives aiid a aia A a aes sa Te 0 9 ounces Since formaldehyde solution frequently does not contain as much formaldehyde gas as the U. S. P. requires, and since rooms are often so constructed or prepared as to allow gas to escape, it is advisable to increase the amount of formaldehyde solution (formalin) to 16 ounces for each 1,000 cubic feet of space. After the room has been prepared as described for sulphur fumiga- tion, bricks should be placed at the bottom of a galvanized iron tub or similar receptacle, and water poured in until it nearly covers the bricks. 122 Disease Prevention A metal pail with lapped (not soldered) seams, or an earthenware receptacle of a capacity of at least 4 gallons, in which the ingredients are to be mixed, is placed on the bricks. No part of the receptacle which is to contain the mixture should come in contact with the water. The potassium permanganate is now distributed evenly over the bot- tom of the container. The formaldehyde solution (preferably 16 ounces) is mixed with the water, and the mixture is then poured over the per- manganate crystals. A rapid exit should be made from the room to avoid the irritation from the formaldehyde gas which is rapidly given off. The door should at once be sealed from the outside as described for sulphur fumigation. If the room has a capacity of less than 1,000 cubic feet the same amount should be used as for 1,000 cubic feet. If the room has a capacity of more than 1,000 cubic feet use a separate container for each 1,000 cubic feet and for any fraction which is left over. In this case the containers should be placed in different parts of the room. A larger container, sufficient to hold enough for a room of more than 1,000 cubic feet capacity, should not be used. If several, or all the rooms in a house are to be disinfected, begin with the most distant one, and after having mixed the formalin and per- manganate, seal the door and proceed in the same manner with all of the rooms. Nothing inflammable should be left near the disinfecting outfit. This particularly applies to paper, cotton, cloth, ete. No flame should be permitted near the disinfecting outfit. For rooms of small size, as in the case of closets, the clothes, walls, floors and ceilings may be liberally sprinkled with formalin, after which the door should be closed, sealed, and left closed for 12 hours or more. Another simple method of disinfecting rooms of small size is to sus- pend a bed sheet, which has been completely saturated with formalin, from a cord stretched across the room. The room should be kept closed for 12 hours or more. This method is not as satisfactory as the perman- ganate method. Sometimes paraform or trioxymethylen is employed for disinfection. These compounds are solid and are usually put up in tablets of one gram. Special forms of apparatus are used for generating formaldehyde gas from these compounds. They are more expensive than the formalin- permanganate mixture. If used, double the amount recommended by the manufacturers should be employed. CHAPTER V PREVENTION OF DISEASES SPREAD LARGELY THROUGH THE DISCHARGES FROM THE INTESTINAL TRACT IN no group of diseases is our knowledge concerning the cause, mode of transmission, and measures of practical prevention, so complete as in the communicable diseases of the intestinal tract. As a consequence more advance has been made in the prevention of these diseases than has been made in any other group. In all of them hygiene takes on a particular significance, sanitation may be intelligently and, therefore, effectively applied, and in one of these diseases, typhoid fever, protective inoculation has shown itself to be of great value. In diseases in which the causal organism is present in the discharges of the intestinal tract, the patient should be isolated. Isolation should not, however, be limited to diseases of the intestinal tract; it should be the universal practice in all communicable diseases. Whenever disease appears it should be regarded as probably communicable until it is shown to be otherwise. The person who is ill should be isolated until this fact is determined. To ascertain whether the disease is com- municable or not requires an accurate diagnosis, which can only be determined by exact clinical, pathological, and other laboratory examina- tions. If the disease is found to be communicable, the patient should be kept in isolation until he has recovered, and until the organisms which have caused his illness are no longer present in his body. As soon as it is determined that the disease is communicable, it should be reported to the health authorities. The house should be placarded to warn people to keep out. Concurrent disinfection of all the discharges from the patient should be strictly carried out, especial attention being paid to the discharges from the intestines and kidneys. The room should be thoroughly cleaned after the patient has been removed, with an abundant application of soapsuds and water. If terminal disinfection is desired, formaldehyde gas should be the method of choice. For the prevention of diseases of intestinal origin the following meas- ures of protection should be especially emphasized : : 1. Isolation should be practiced in all cases of disease until it is determined whether or not they are communicable. If they are communicable, isolation should be continued. 2. Diagnosis should be made as early as possible. 3. A sanitary water supply should be secured and maintained. (a) This may be done by selecting a protected source of supply, by 123 124 Disease Prevention the proper disposal of sewage, of the contents of cesspools, privies, latrines, and of the discharges of the bowels and kidney wherever they may be deposited. (b) Filtration, chlorination, or some other effective method of disinfection of the water supply. 4, Inspection of dairies, and of the entire personnel which comes in contact with the milk from the time of its production until it reaches the consumer. Pasteurization of all market milk. 5. Supervision of all places where food is sold and prepared, to eliminate all mild cases of disease and carriers. 6. Regulation of the breeding grounds of shell-fish, with provisions which prohibit the use of brackish, or sewer-contaminated water. 7. Suppression of flies and their breeding places. 8. Vaccination in all cases where vaccine has been shown to be effec- tive or gives promise of having some value. Vaccination should not be relied upon to overcome the effects of bad sanitation. It should be used in connection with sanitary measures. Typhoid Fever.—Typhoid fever is a bacterial disease and is caused by the Bacillus typhosus. Eberth first saw the bacillus in the tissues in 1880, and Gaffky isolated and grew it in pure culture in 1884. For many years typhoid fever stood fourth in the list of the United States Mortality Tables. Tuberculosis came first, the pneumonias sec- ond, cancer third, and typhoid fever fourth. Within the past two decades, especially the last, the typhoid rate has markedly decreased. This decrease has been almost wholly due to improved sanitation in the cities. In the rural districts the rate has remained almost stationary. In 1900 the number of deaths due to typhoid fever was about 45,000. In 1910 it had decreased to 25,000. At the present time (1925) it prob- ably has fallen to about 15,000. From fourth in the mortality list it has dropped probably to the ninth or tenth place. Since every death from typhoid fever represents about ten actual cases of the disease, the death rate being approximately 10 per cent., the total number of cases per year, at the present time, would be at least 150,000. Typhoid fever is a communicable disease. It is, therefore, both infectious and contagious. It may occur at any time of the year, but occurs more frequently during the summer and autumn. It may be regarded as both endemic and pandemie, since it is constantly present all over the world. Epidemics due to a contaminated water supply occur most frequently in the fall and winter, but are not limited to these seasons. Milk outbreaks may occur at any time during the year. Vaca- tion typhoid prevails in the early autumn, and is the result of an infection acquired away from home, usually while on a vacation. Typhoid fever is more prevalent in the country than in the city. In rural districts, where excreta are often deposited promiscuously on the surface of the ground, the rate is highest. Symptoms of the disease are usually recognized by the patient on the 10th to the 14th day after exposure. They may appear in seven days or be delayed for as long Diseases Spread Through Intestinal Discharges 125 as a month. Typhoid fever attacks the strong and the weak, the old and the young, and is impartial as to sex. It especially attacks the age group which is of the greatest economic value to the community. The yearly economic loss from typhoid fever must be at least $100,000,000. It is an infection from which the individual cannot protect himself unless the community is so educated that every individual in it knows what should be done to prevent the transmission of the disease to others. Source of Infection—The principal source of infection in typhoid fever is through the discharges from the intestinal tract and the urine. In rare instances the typhoid bacillus may be present in other discharges, such as sputum and pus. This occurrence is so infrequent as to be of little significance in the spread of typhoid fever. The intestinal dis- charges are of the greatest importance in the spread of the disease, since the typhoid bacillus is probably always present in them, although it cannot be isolated at all times during the course of the disease. They may be found during incubation and often continue to be present until long after recovery has taken place. They are usually to be found in the greatest numbers during the second to the fourth weeks of the disease. An average of the combined findings of many investigators shows that they are present in the urine in about 30 per cent. of the cases. According to Raubitscheck they may be found in every case if the proper investigation is made. They are found in the greatest number after the appearance of rose spots. Typhoid Carriers—In all cases of typhoid fever the bacilli persist in the intestinal discharges, and frequently in the urine, for some time after recovery from the disease. Since the length of time during which they may remain varies, carriers are classed as temporary carriers if they disappear before the end of three months, chronic carriers if the period is longer than three months. Chronic carriers may harbor the germ for many years. In addition, there is another group which may carry the bacillus without giving any history of ever having had the disease. These are called healthy carriers. It is probable that some of the latter group may have actually had an attack of the disease of so mild a character that it was not recognized. It has been estimated that from 4-5 per cent. of those who have recovered from typhoid fever become chronic carriers. When this condition exists the germ is usually lodged in the gall bladder where it may not give rise to any symptoms or may cause inflammation which may terminate in the formation of gall stones. More rarely the bacilli are not found in the gall bladder but may be obtained directly from the intestinal tract. Conradi and Drigalski found that healthy individuals, who had come in contact with typhoid patients, might become temporary carriers. As a rule they did not develop typhoid fever, and the bacilli usually disappeared in a short time. Vaccination will probably become an important factor in the increase of carriers, since it will either prevent the disease even though the germ has entered the body, or will cause it to appear in so mild a form that 126 Disease Prevention it will not be recognized. This will permit larger numbers to trans- port the organism, and since they are not ill, it may not be suspected that they are carriers. Under such circumstances the disease will not be diagnosed and as a consequence these individuals will not be isolated and their discharges will not be disinfected. The primary source of infection in typhoid fever is the infected human body. In 1824 Nathan Smith asserted that infection was always the result of direct or indirect transmission of the cause from the body of a person ill with typhoid fever to healthy individuals. Budd, in 1856, declared that transmission was through the intestinal discharges directly, or sewage indirectly. It is mow positively known that every case of typhoid fever results from the transfer of the discharges, from a typhoid patient or carrier, to the mouths of other persons. Diagnosis—Clinical diagnosis alone should not be relied upon to determine that a given individual has typhoid fever, since there are not a few other diseases in which the symptoms are very similar. Through bacteriological examinations much information may be obtained which may either confirm or refute the clinical diagnosis. In 1896 Widal introduced the agglutination test in typhoid fever. He had demonstrated that if blood is taken from the patient during the last part of the first week or early part of the second week, and from then on until some time after convalescence is established, the blood itself, or the serum which separates out on standing, will, if added to a suspension of typhoid bacilli, cause them to gather in clumps or masses. If the serum is sufficiently diluted, it will not cause this clumping in other species closely related to the typhoid bacillus or of any other species of bacteria. Blood Cultures—For making blood cultures it is necessary to obtain some blood from the patient. This may be done very easily and with very little annoyance to the patient. The blood may be taken from the finger or the lobe of the ear. Precaution should be taken to prevent contamination of the blood through other microdganisms present on the surface of the part from which the blood is taken. It is better to take a larger quantity of blood than can be easily obtained from the finger or lobe of the ear. The usual source from which the blood is obtained in larger quantity (5-10 e. e.) is the large vein at the bend of the elbow. After thoroughly cleaning the surface over the por- tion of the vein from which the blood is to be taken, a little diluted tincture of iodin, or some other disinfectant, is applied. A sterile hypo- dermic needle, which should have a sharp point, is now introduced into the vein. By gentle suction with a sterile syringe from 5-10 ec. e. of blood is withdrawn and placed in sterile culture media. The cultures are placed in the incubator, at body temperature, for 24 hours, at the end of which time development of any germs which may be present in the blood will have taken place. From the cultures further labora- tory tests are made to determine if any of the organisms which may be present are typhoid bacilli. Instead of using a syringe some other Diseases Spread Through Intestinal Discharges 127 especially prepared form of apparatus may be used for securing the blood. The taking of the blood is a simple procedure, and gives the patient very little annoyance. No other laboratory or clinical method of diagnosis will give positive results as soon as will blood cultures. If typhoid bacilli are found in the blood, it may be said with positiveness that the patient has typhoid fever. No other method is so certain. Blood taken from the patient suffering from typhoid fever will show positive cultures in about 90 per cent. of the cases during the first week of the disease. From the second week on the percentage of positive findings continuously decreases. Cultures from the Feces—Only occasionally are typhoid bacilli found in the feces before the middle of the second week of the disease. Between the seventh and twenty-first day of the disease they may be found in about 25 per cent. of the cases; repeated examinations show positive cultures in about 75 per cent. The examination of the feces is of even greater value in carriers than in the diagnosis of typhoid fever. About a third of the typhoid cases continue to discharge typhoid bacilli in the feces for three weeks after the beginning of convalescence, more than 10 per cent. for two to three months; these are known as temporary convalescent carriers. It is esti- mated that from 1-5 per cent. of all those who have had typhoid fever continue to harbor typhoid bacilli in the intestinal tract and to dis- charge them constantly or intermittently for an indefinite period. Such carriers are known as chronic or permanent convalescent carriers. Ac- cording to Albert, 25 per cent. of the chronic carriers have never had typhoid fever. These are called healthy or passive chromic carriers. During excessive exposure to typhoid infection the number of healthy carriers is much increased. Such individuals usually carry the bacilli for a short time only and might, therefore, be very properly called tem- porary healthy carriers. Of especial importance is the fact that women outnumber men as carriers in the ratio of 4-1. The explanation for this increased number in women is found in the greater frequency of gall-bladder lesions, such as inflammatory processes and gall-stones in women, the latter usually arising from typhoid infection of the gall-bladder. Special attention should, therefore, be given to troubles of the gall-bladder and liver in women. This is of particular importance since women come into such intimate contact with the articles of food which they handle and prepare. Of much less importance than the fecal carrier is the urinary carrier, since very few outbreaks of typhoid fever have been traced to this source. The discovery of urinary carriers should be relatively easy, since the typhoid bacillus may be isolated without much difficulty by making cultures of the urine. Blood cultures are obviously of no value in the examination of typhoid carriers, since the germ is not present in the blood of carriers. Cultures of the feces and Widal examinations are the 128 Disease Prevention best, and, at the same time, most reliable methods of detecting typhoid carriers. Medical treatment has had very little effect upon the elimination of typhoid bacilli from the feces of carriers. In some cases the surgical removal of the gall-bladder has eliminated the condition. Urotropin (hexamethylenamin) has been found useful in clearing up urinary car- riers, but it is of no value in fecal carriers. Typhoid carriers should not be allowed to engage in any occupa- tion which directly or remotely has to do with the production, handling, or preparation of food. They should not be employed as cooks, waiters, nurses, in dairies or any other occupation concerned in the handling of milk or any of its products, meats, groceries, or other articles of food. The following quotation from Rosenau’s ‘‘Preventive Medicine and Hygiene’’ is an illustration of the importance of carriers in the trans- mission of typhoid fever:? “The story of ‘Typhoid Mary’ was the first of its kind to be re- ported 2 in America, and has become a classic. Mary Mallon was a cook in a family for three years, and in 1901 she developed typhoid fever. About the same time a visitor to the family had the disease. One month later the laundress in this family was taken ill. “In 1902, Mary obtained a new place, and two weeks after her arrival the laundress was taken ill with typhoid fever. In a week, a second case developed, and soon seven members of the household were sick. “In 1904, the cook went to a home on Long Island. There were four in the family, besides seven servants. Within three weeks after her arrival, four servants were attacked. “In 1906 Mary went to another family, and six of the eleven mem- bers of this family were attacked with typhoid between August 27th and September 3rd. At this time, the cook was first suspected. She entered another family on September 21st, and on October 5th the laundress developed typhoid fever. “In 1907, she entered a home in New York City and two months after her arrival two cases developed, one of which proved fatal. During these five years, ‘Typhoid Mary’ is known to have been the cause of twenty-six cases of typhoid fever. ‘“She was virtually a prisoner by the New York Department of Health in a hospital from March 19, 1907. Cultures taken every few days showed bacilli on and off for three years. Sometimes the stools contained enormous numbers of typhoid bacilli, and again for days none could be found. ““ ‘Typhoid Mary’ then escaped from observation until 1914. In October of that year, she was engaged as cook in the Sloane Hospital for Women in New York. In January and February of 1915, an out- 1D. Appleton & Co., 1922, p. 114. ?J.AM.A., June 15, 1907; Military Surgeon, July, 1919—a review of the facts by Geo. A. Soper, Diseases Spread Through Intestinal Discharges 129 break of typhoid occurred, principally among the doctors, nurses and help of the institution, involving twenty-five cases. The cook was sus- pected, but she left the premises on a few hours’ leave, and did not return or leave her address. She was, however, located by the Health Department under an assumed name, and an investigation established her identity as the famous ‘Typhoid Mary.’ : “A subsequent study of her career showed that she had infected still other individuals beyond those. already mentioned, and that she may have given rise to the well-known water-borne outbreak of typhoid in Ithaca, New York, in 1903, involving over 1,300 cases (1,350 cases, 82 deaths). The fact is that a person by the name of Mary Mallon had been employed as a cook in the vicinity of the place where the first ease appeared, and from which contamination of the water supply occurred.’’ An interesting account of an outbreak of typhoid fever caused by a carrier, was reported by Sawyer in 1914. This outbreak occurred in Hanford, California, during the latter part of March, 1914. In all 93 persons were infected, the source of infection being Spanish spaghetti, prepared and cooked by a typhoid carrier, for a church dinner. The spaghetti was baked after it had been infected with typhoid bacilli, the - heat used in baking not being high enough to destroy the bacilli, which were located in the center of the spaghetti. Many similar outbreaks, which have had their origin in a typhoid carrier, have been reported. It is, therefore, obvious that the spread of typhoid fever can never be completely controlled until the carrier problem is solved. Modes of Transmission of the Typhoid Bacillus.—Typhoid fever is transmitted both directly and indirectly from patients and carriers. Water, milk, butter, cheese, and other milk products, oysters and other shell-fish, vegetables which are eaten raw, fruits, other foods, flies, fin- gers, and fomites may serve as vehicles of indirect transmission. The ultimate source of infection is man, and infection always arises through the entrance of the discharges of a case of typhoid fever or a carrier into the body of another individual. Water—Budd believed that sewage-contaminated water caused typhoid fever, and suggested human feces as the source of the contam- ination of the water as early as 1856. Numerous epidemics of typhoid fever have been traced to infected water supplies. Schiider collected statistics on 640 typhoid epidemics in 1901 and found that 72 per cent. of them were directly traceable to contaminated water. Although water- borne epidemics of typhoid fever are still of not infrequent occurrence, the proportion of water-borne typhoid epidemics has constantly decreased since 1901. At one time it was thought that nearly all typhoid fever was due to contaminated water. Today we know that this is not so; however, water is still an important source of infection, especially in rural districts. In 1908 Whipple estimated that polluted water was responsible for about 35 per cent. of all typhoid fever. Today (1925) it is probable that water is responsible for not over 20 per cent. of the 130 Disease Prevention cases. This reduction is due to better sanitation of water supplies secured chiefly through filtration and disinfection. Epidemics of typhoid fever, due to a polluted water supply, occur most frequently in the late fall, winter and early spring; summer epidemics are not common. Ice—In some of the water-borne epidemics of typhoid fever, the evidence is convincing that the pollution of the water has arisen from frozen typhoid excreta, deposited along some water-shed. A classical example of such an epidemie, which occurred in Plymouth, Pennsylvania, was reported by Taylor in 1886. On January 2, 1885, a man living near the bank of a stream, which served as one of the sources from which the water supply of Plymouth was obtained, returned home from a visit in Philadelphia, suffering from typhoid fever. This illness con- tinued until early in March when he was first able to leave his bed. In the middle of March he suffered a relapse from which he did not recover until about the middle of April. Throughout this illness his excreta was thrown out on the snow, on the bank of the stream where the accumula- tion remained in a frozen condition until some time between March 25 and April 1. At this time there was a thaw which carried the dis- charges into the stream. An epidemic soon broke out in which 1,104 of the population, which was estimated to be about 8,000, contracted the disease, with 114 deaths. Relatively few epidemics of typhoid fever have been traced directly to ice, and when they have occurred, the number infected has been relatively small. In some instances, however, the evidence is convincing that the source of infection was ice. It is only under exceptional cir- cumstances that ice is a source of danger. If ice is stored, and allowed to remain for several months before it is used, the danger from its use is not great, since the longer it remains in the frozen condition the greater the destruction of the bacteria which were present when it was har- vested. Nevertheless ice should never be harvested from a polluted water, or from any source where there is a potential danger of pollution. Milk.—Milk may become contaminated at the dairy through the local water supply, or from a case or a carrier. It may be contaminated in transportation, at the local distributing plant, or in the home. Milk epidemics are characterized by an explosive outbreak which usually sub- sides almost as rapidly as it has arisen. It especially attacks women and children; its onset is sudden and the incubation period is short. It is more prevalent among the well-to-do, since they consume more milk than do those in poorer circumstances. The cases are usually mild and frequently more than one case occurs in a household. If two or more cases of typhoid fever arise simultaneously in the same house, or within a few days of one another, milk should be investigated, especially if the water supply is good. The cases are distributed along a single milk route, and are not found along the routes of other distributors. Milk epidemics are usually circumscribed but may be extensive. If all the milk from a large plant is infected, the more extensive will Diseases Spread Through Intestinal Discharges 131 be the outbreak. If only a small part of the total supply, or the supply of a small distributor, is involved, the outbreak will be small. Proper inspection of dairies, including buildings, water supply, exam- ination of milkers, and of all others who handle the milk, exclusion of all carriers of typhoid and of other diseases, and finally pasteurization of all market milk, would prevent milk-borne typhoid epidemics. Milk Products—Milk products, such as cream, ice cream, butter, buttermilk, and cheese, may contain typhoid bacilli if made from a con- taminated milk, if handled by a person suffering from a mild attack of typhoid fever, or by a convalescent or carrier. This is more apt to occur the more recently the product has been made. Oysters and Other Shellfish—The first outbreak from oysters was reported by Conn. in 1894. In this epidemic 25 students from Wesleyan University, Middletown, Conn., were made ill from eating infected raw oysters. Four of those who were infected died. However, oysters and other shellfish play a minor role as a source of typhoid infection. Legislation has been the means of lessening the danger, through laws which prevent the growing or fattening of oysters in polluted beds. Fruits and Vegetables—Minor epidemics due to contaminated fruit or vegetables have been reported. Fruits and vegetables which are eaten raw, such as lettuce, radishes, celery, and water cress, if handled by typhoid contaminated hands, or grown in soil fertilized by human - excreta, may give rise to an occasional case or a small outbreak. Such outbreaks may be prevented to a large extent by close inspection of the producers and purveyors of raw fruits and vegetables, and the pro- hibition of human excreta as a fertilizing agent unless they have been sterilized. Flies—It has been conclusively demonstrated that the common house- fly may act as a carrier in typhoid fever. In well sewered cities, and in other communities where provision is made for the exclusion of flies from contact with typhoid excreta, fly transmission is of no practical impor- tance. On the other hand, where provisions for the exclusion of the fly have not been made, it may become an important factor in the spread of typhoid fever. Reed, Vaughan and Shakespeare, appointed on a special commission to investigate typhoid fever during the Spanish- American War, concluded from their investigations of the Army camps in 1898 that about 15 per cent. of all the cases could be reasonably at- tributed to fly transmission. In certain sections of the United States no provision is made for the disposal of the discharges from the body; in others privy contents are freely exposed to flies and other vermin. To some extent fly transmission may be prevented by campaigns devoted to the destruction of the fly and its breeding places, but of infinitely greater importance is the construec- tion of sanitary privies, from which flies are excluded by screening and fly-tight construction, combined with the disposal of the contents of these privies and of all excreta, in such a manner that flies and other vermin cannot subsequently come in contact with this material. Safe 132 Disease Prevention disposal of excreta is practical and it may be done at an expense which is not beyond the means of those with small incomes. Only too fre- quently shiftlessness is responsible for the careless exposure of excreta. If those who live under such unsanitary conditions could be brought to the realization of the dangers which such practices involve, they might be stimulated to correct these conditions. Exereta exposed to flies may be, and often are, a source of typhoid infection; excreta protected from an access to flies and other vermin absolutely prevent transmission through these vehicles. The extermination of flies and their breeding places is an important sanitary measure for the prevention of typhoid fever and other diseases, but is subordinate to the safe disposal of excreta in the prevention of fly-borne typhoid fever. Dust, Fomates, Soil, etc.—Dust has sometimes been accused of being the agent which served as a means of carrying typhoid fever. That such a mode of conveyance may occur is certainly possible, but such conveyance must be exceedingly rare and, therefore, of little practical importance. Fomites is a rather indefinite term which includes many objects, such as clothing, bed linen, napkins, towels, sheets, blankets, etc. Any of these articles may be the means of spreading infection through being soiled with excreta from typhoid patients. Such transmission is most apt to occur in army camps and where large bodies of men are closely aggregated if scrupulous care is not taken to prevent such transmission. In private homes typhoid fever is frequently transmitted in this way. Soil is one of the less important factors in the spread of typhoid fever. Direct infection certainly occurs very rarely from the soil unless the pollution has been recent and the infection has occurred in some unusual way. Indirectly flies, fomites, and dust may carry the bacillus to some article of food and in this way cause infection. Of more im- portance than the above-given modes of transmission is that which arises from the pollution of water through the discharges being carried by surface washings, or in some other way, into a well, stream, reservoir, or some other domestie water supply. Contact Infection.—It is probable that more than 65 per cent. of all cases of typhoid fever are conveyed by some form of contact. Contact infection does not mean that actual physical contact must occur, though this is perhaps the most frequent way in which it is brought about. The transfer of infectious material, however, must be short in time and space. As illustrations of contact infection through intermediate objects, soiled articles, such as food, eating utensils, clothing, fingers, flies, etc., might be mentioned. It would be an impossible task to enumerate all the various ways in which contact infection might take place. However, the transfer must usually be the result of rather close personal associa- tion with the patient, or with some one who has been in contact with him. Summary. —The prevention of typhoid fever depends upon the care- ful observance of the following measures: Isolation, early diagnosis, Diseases Spread Through Intestinal Discharges 133 concurrent disinfection of all discharges (feces, urine, vomitus, sputum, pus, or any other discharge), of all articles of clothing which have come in contact with the patient, and all other articles, such as eating utensils, remains of food, ete., the hands and any other part of the body or cloth- ing of attendants which have or may have come in contact with the pa- tient. At the present time contact infection is of much greater impor- tance than infection through water, milk and other foods. Nevertheless the same vigilance should be observed in keeping sanitary conditions at a high level as was exercised in inaugurating them. In the country there is much need of improving sanitation; in some places of introducing sanitary measures, since they are at present practically non-existent. Anti-typhoid vaccination has been shown to be of great value and should be one of the principal methods of preventing and controlling typhoid fever, particularly when men are gathered together in large bodies, as in camps and public institutions. Vaccination should not supplant sanitary measures in any degree whatever. It is not a substitute for sanitation, nor should it be so regarded. It should not be considered of more im- portance than sanitary measures, but as an adjuvant to them. In the discussion of typhoid fever the method of administering anti-typhoid vaccine was described, and will not be further considered. The vaec- cine which should be used by preference is the ‘‘triple vaccine,’’ since it not only protects against typhoid but also paratyphoid A and B infections. Within recent years it has been discovered that certain cases of disease, with clinical symptoms which cannot be distinguished from those of typhoid fever, though usually less severe, are due to organisms, which, though they resemble the typhoid bacillus, are nevertheless dis- tinct types or species. These organisms are divided into two groups, designated as paratyphoid bacillus A and B. The paratyphoid bacillus A resembles the typhoid bacillus more closely than does the paratyphoid bacillus B. The paratyphoid bacillus B is more closely related to the B. enteritidis, Gaertner’s bacillus, which frequently causes epidemics of food-poisoning. Strictly speaking, the B. enteritidis causes a food-infec- tion rather than a food-poisoning, since the germ present in the food develops in the body after the food is eaten. It is probable that para- typhoid infections are frequently due to food-infections; however, infection through water is not uncommon. The prevention of these diseases is based upon measures similar in all respects to those used in the prevention of typhoid fever. Preventive vaccination against paratyphoid- infections has the same value as vac- cination in typhoid fever. The ‘‘triple vaccine’’ is now given to pro- tect against the three diseases, typhoid, paratyphoid A and B infections. The prevention of food-infections consists in avoiding the consumption of food from diseased animals and by handling food as little as possible after it is prepared, especially if it is allowed to stand for some time before it is eaten. Another group of diseases of intestinal origin, characterized by fre- 134 Disease Prevention quent diarrhceal discharges containing blood, commonly spoken of as the ‘‘bloody flux,’’,caused by an organism which very closely resembles the typhoid bacillus, and giving rise to dysentery in adults and summer diarrheeas in infants, is due to an infection by the B. dysenterie. Infec- tion occurs in the same way as it does in typhoid fever. Water, contact and flies are the most frequent agents of transmission. Carriers may also be of importance in spreading the infection. Since the germs leave the body through the intestinal discharges, pre- vention should be directed to the disinfection of all excreta, especially the intestinal discharges, since this infection seems to be limited to the intestinal tract. Some benefit seems to have been derived from the administration of dysentery vaccines, and they should, therefore, be used as a preventive measure whenever an epidemic prevails. Asiatic Cholera.— This disease is caused by a spiral shaped bacterium, the Spirillum cholere asiatice. Water, polluted with the discharges of cholera patients and carriers, is an important source of infection. Other important modes of spreading the infection are through contaminated food, contact, and flies. It is estimated that from 7-10 per cent. of those who come in contact with cholera patients become carriers. This condition lasts for a short time only, a few days or weeks. Carriers are probably an important means of spreading the infection. Many important epidemies have occurred in the past. Cholera is endemic in several places in India, the most important focus being in Burmah. During recent years important epidemics have occurred in the period from 1879 to 1910. Koch, in 1883, isolated the cause of Asiatic cholera, the Spirillum cholere asiatice, while engaged in the study of the epidemic which broke out in Egypt in 1879. This epidemic spread over Asia and into Europe. At times cholera epidemics have been so widespread that they might be regarded as pandemic. The epidemic which began in 1891 is said by Castellani to have had its origin in India, at the celebration of a religious festival, during which those who had gathered for the ceremonies bathed in the Ganges River and polluted it with cholera discharges. In 1892 it had spread to Europe and Africa, a violent epidemic occurring in Hamburg, Germany, from whence a few cases came to the Port of New York. In Russia 400,000 are said to have died as a result of this epidemic. It prevailed in the armies during the Balkan War in 1912, and in the World War in the Austrian Army in Galicia, and there were outbreaks in Mesopotamia, Greece and Turkey. Quarantine regulations have kept the disease out of the United States almost completely for the past fifty years. In 1873 it broke out in New Orleans and spread for some distance up the Mississippi River valley. A few cases occurred in New York in 1892, having been brought there from Hamburg, Germany, where the disease was then prevailing. The germ is restricted to the intestinal tract, and prevention is chiefly based on the concurrent disinfection of the bowel discharges. All things which are, or may have been contaminated, should be disinfected, and all the measures used in preventing typhoid fever should be Diseases Spread Through Intestinal Discharges 135 employed in Asiatic cholera. Preventive vaccination is of considerable value, but is less effective than antityphoid vaccination. Hookworm Disease.—The cause, source and mode of infestation in this disease have already been described. The measures which should be employed in preventing the disease are obvious, but it is difficult to put them into practice, since it is not an easy task to convince many of those who are afflicted that the disease can be prevented by following a few simple procedures. The essential things to be observed in the prevention of hookworm disease are all directed against contact with fecal discharges. If all intestinal discharges were deposited in sanitary privies, or buried at some depth when deposited in the open, the disease would be greatly limited in prevalence. Under present conditions it would be an impossible task to disinfect the excreta of the infested since the number of the latter is so great. The custom of going bare- footed should be entirely abolished where hookworm disease prevails. Shoes should be constantly worn, especially outside the house. Miners and others, whose occupation is such that the hands may become infected through contact, should wear gloves as a means of protection. Frequent washing of the hands should also be an important factor in hookworm regions. If the water is not above suspicion it should be boiled, and even if it is not suspected it does no harm to boil it. The hands should always be washed after answering the call of nature, and this is impera- tively necessary where hookworm disease prevails. The chief mode of transmission is through the skin. About 90 per cent. of all infection takes place in this way, the majority being infected through the skin of the feet. Anything which has become polluted with hookworm discharges, such as water, food, clothing, or any other article, may serve as a source of infection. The treatment of all persons suffering from hookworm disease is not alone of benefit to the infected individual; it is likewise a most important preventive measure. Thymol has been used extensively for the purpose of eradication. Since the World War greatly reduced the supply of thymol, oil of chenopodium has come prominently into use. Its effec- tiveness is about the same as that of thymol. Neither of them can be administered without some danger. They should, therefore, be given by a physician or some one who has been especially trained for this par- ticular purpose. One treatment of either of these drugs rarely removes all hookworms. In some of the more obstinate cases it may be necessary to give 20 or more treatments. In 1921 Hall first called attention to the value of carbon tetrachlorid for the removal of parasitic worms, especially hookworms. He first worked with dogs. Later other animals were treated, including the monkey. By using 0.3 c.c. of the drug for every kilogram of body weight he found that he could expel all the hookworms without subse- quent purgation. With no other drug was he able to accomplish such favorable results. When used with thymol or chenopodium equally good results followed. Post-mortem examination of monkeys, swine and 136 Disease Prevention horses, several months after treatment with carbon tetrachlorid, showed no pathologic changes which could be attributed to its action. Dr. Hall took 3 c.c. of the drug without ill effects. Dr. W. M. Lambert, Medical Officer, Bureau of Ankylostomiasis, Colony of Fiji, Suva, Fiji, has reported the results of the treatment of more than 20,000 cases of hookworm disease in man during the period from Feb. 14 to May 30, 1922. Dr. Lambert gives the drug in the fol- lowing dosage: The increase per year of age is 0.2 c.c. The dose given is begun at the age of two years. Each year the dose is increased 0.2 c.c. up to the 15th year. From this time on 3 to 4 c.c. is administered. The large dose is given to large individuals. For administration the drug is placed in a tablespoon or small glass and is covered with water. It has a little odor but no appreciable taste. It may produce a sensation of heat when swallowed. Often no symptoms follow the administration of the drug. When they do occur they are invariably mild. In many there is a sleepiness for several hours. A very limited number have a headache which may last for several days. Only two small children, of more than 20,000 persons treated, vomited. It was found that most symptoms are eliminated if 1 ounce of magnesium sulphate is given three hours before the drug is administered. The best results are obtained when carbon tetrachlorid is given on an empty stomach. In those who are afflicted with constipation, a mild laxative, given on the day preceding the administration of carbon tetrachlorid, aids in its action. It is advisable that the patient should remain at rest for a day following this treatment. The physiologic effects of the drug are apparently due to the absorp- tion of a part of the dose which is administered. Constipation and a full stomach seem to be responsible for the absorption. When the stomach is empty and the bowels are not constipated, the drug acts as a purge with no symptoms developing. Food should not be eaten just before or after giving the drug. The administration of magnesium sul- phate before giving the carbon tetrachlorid almost completely eliminates the symptoms of headache. Even more rarely do symptoms occur when magnesium sulphate is given following the administration of the drug. Alcohol should not be taken for some time before or after the drug is given, since the most severe symptoms occur when this precau- tion is disregarded. If symptoms do appear the best treatment seems to be a dose of magnesium sulphate. With the exception of the Ozyuris vermicularis, which it usually completely removes, it does not, in the dosage given, dispel more than 40 per cent. of the Ascarids and very few of the Trichocephalus dispar. The conclusions of Dr. Lambert, after having administered the drug to more than 20,000 persons, are as follows: * “1. Carbon tetrachlorid is a vermifuge and vermicide of great power. “2. Tt gives little discomfort to the patient. * Lambert, Carbon Tetrachloride in the Treatment of Hookworm Disease, Jour. Amer. Med. Assoc., 1922, p. 2057. Diseases Spread Through Intestinal Discharges 137 ‘3. It permits of rapidly treating, at a low cost, vast populations suffering from hookworm disease. ‘‘4. Reéxamination of the feces of 823 treated patients indicated that one treatment administered to each individual in a given area had lowered the original infection rate of 100 per cent. to less than 9 per cent. “5. Clinically, the standard of health of the community is immedi- ately raised.” From this report and others which have been given on the use of carbon tetrachlorid, there is no doubt of its superiority to other drugs which have been used. It is more uniformly effective; it is easier to administer; its by-effects are less frequent and less severe; the cost of its administration is remarkably low; in the more than 20,000 cases treated by Dr. Lambert no untoward results occurred. Amebic Dysentery.— Amebiasis, tropical dysentery or amebic dysen- tery, is caused by another animal organism, the Entameba histolytica. It is a chronic disease of the large bowel, from which area there is not infrequently an involvement of the liver with the formation of abscesses. The disease comes on insidiously, relapses occur after the patient has apparently recovered, and acute attacks are of occasional occurrence. The organism which causes the disease is a protozoon. It enters the body through the mouth and leaves in the intestinal discharges. Infection occurs whenever anything which has come in contact with the encysted form of the parasite enters the mouth. The contact must be rather direct and intimate. Water, milk and other articles of food, soiled hands, ete., are the usual vehicles of infection. Outbreaks of amebic dysentery do not occur as in typhoid fever and bacillary dysentery. The disease is endemic but it very rarely reaches epidemic proportions. Its greatest prevalence is in tropical countries. It has been known to occur in the arctic regions, is not of infrequent occurrence in subtropical and tem- perate regions. For the treatment of the disease ipecac and its alkaloid, emetin, have been extensively used. The effectiveness of emetin in amebic dysentery is comparable to that of quinine in malaria. It relieves the patient of his symptoms but does not destroy the encysted parasite. It cannot, there- fore, be relied upon as a means of prevention. In places where the disease is prevalent, search should be made for carriers as well as for those suffering from the infection. Some substance should be introduced into the large bowel which will destroy the encysted parasite. Injections of solutions of quinine, kerosene or some other amebicide; emetin, bis- muth iodide, oil of chenopodium, and bismuth subnitrate have been given internally with fair results. None of the measures yet tried have cleared up all cases. The same measures should be employed to destroy the amebse in the intestinal discharges as are used for typhoid fever and the bacillary dysenteries. CHAPTER VI DISEASES TRANSMITTED THROUGH THE RESPIRATORY TRACT DiseAsEs of the respiratory tract are responsible for more illness and death than any other group of diseases. They are more prevalent in temperate climates, of frequent occurrence in cold climates and in regions where there are marked variations in temperature. In the warmer climates they are of less frequent occurrence; however, the tropics are not wholly free from respiratory infections. Respiratory diseases are endemic throughout the world. From these endemic foci epidemics of certain of these diseases frequently arise, and at periodic intervals, varying in length, pandemics spread over the entire world. The best illustration of respiratory pandemics of recent times is that of influenza, which was prevalent during the latter part of the World War in 1918. The respiratory diseases still prevail with the same morbidity rate as existed a century ago. The reason for failure in their control is prin- cipally due to two factors. Our limited knowledge of the manner in which they are actually spread, and the present impossible task of com- pelling or inducing those affected with respiratory infections to so take care of their discharges as to render them as harmless as possible. In respiratory diseases, infection most frequently occurs through the direct transference of infectious material from the respiratory tract of an ill person to others, by means of the droplets which are expelled in sneezing, coughing and talking. Infection occurs more or less readily if the dis- tance through which the droplets must travel is not more than three feet. As the distance increases, the danger decreases, yet infection may occur through a distance of several feet. Anything which has come in contact with the respiratory discharges may transmit the infection. It is very probable that the hands are responsible for many infections, perhaps standing close to droplet infec- tions. Food and drink, eating utensils, dust from floors and other sur- faces, clothes which have been soiled with sputum or other respiratory discharges, are also not infrequently sources of infection. In only one of the respiratory diseases, tuberculosis, has much been accomplished in either prevention or control. With this one exception, the mortality and morbidity rate is essentially the same as it was fifty years ago. As yet none of the preventive vaccines or sera have had much influence on these diseases. 138 Diseases Transmitted Through the Respiratory Tract 139 TUBERCULOSIS Within recent times tuberculosis was responsible for more deaths than any other communicable disease. It is a bacterial disease of world- wide distribution. The organism which causes it, the Bacillus tuber- culosis, was discovered and isolated by Robert Koch in 1882. After a long and careful investigation he announced his discovery. This an- nouncement was not made until he had isolated it from all parts of the body. His original work was of so exhaustive a nature that very little has since been added concerning the various tissues and organs in which it may be found. The history of this disease begins in the distant past. The deserip- tions which appear in the writings of the Greeks leave no doubt that they recognized and differentiated it from other diseases, especially the pulmonary form, which was even then called consumption. Hippoe- rates, Galen, Areteus, Herodotus, Aristotle, Isocrates, and others have left unmistakable records of a knowledge of some of the more character- istic features of pulmonary tuberculosis. Among the Romans contributions were also made which point to a knowledge of the fundamental characteristics and symptoms of the dis- ease. Celsus, early in the Christian era (about 50 A. D.), advised change of climate, rest, milk, and certain remedies, to relieve the symptoms, particularly the cough. He also observed that the disease usually develops at the age when the individual is most vigorous, from the eight- eenth to the thirty-fifth year. Pliny, Horace, Seneca, and others, describe some of its more striking features, and advocate the use of cer- tain medicines in treatment. The Hindus recognized that there were stages in the disease which could be roughly separated from one another. They treated the disease in its early stages, but when it became advanced they regarded treat- ment as hopeless. Consumptives were supplied with an abundance of fat which was chiefly obtained from the milk of the cow, goat and other animals. It is probable, too, that consumptives were allowed to con- sume wine and the flesh of various animals, a privilege which was denied the Hindus in general by their legal code. Until within recent times tuberculosis has stood at the head of the list of all of the communicable diseases, both in the number of those who are infected and of those who die. Some years ago it was estimated that one out of every seven deaths was due to some form of tuberculosis, the pulmonary form or consumption being responsible for the large ma- jority of these deaths. At the present time the death rate is much less, and there is possibly some decrease in the number of infections which occur, but it is reasonably certain that the decrease in death rate has been much greater than the decrease in infection. Today tuber- culosis is responsible for about one out of every ten deaths which occur in the United States. The following figures, compiled by the Bureau of the Census of the 140 Disease Prevention United States, give the death rate from tuberculosis per 100,000 of the population. DEATHS PER 100,000 Tuberculosis Tuberculosis Year (All Forms) Year (All Forms) AS70-1880 vis. eieincns even 326.2 1031 a a 159.1 ASSOIS00. secs coi vs 264.4 OND is ei 149.7 A800 nels biel 205.2 101300, La Dn a, 147.9 900. oa 201.9 i513 em GA BR 147.2 21000. a a ere 196.9 YOIS iin, sail 146.4 B00. eis ii sn 184.5 £10 SR ROR er Ce EY 142.1 A903 he at ar anos 188.5 BOLT isiainis niin ni vinteibabainlain's 147 FOOL on, niki ie 200.7 JOAS: is eae dase 150 O05. iso sciineinvioininwein os 192.3 1? 11. A RP SRE fl 125.7 006 2s seats sienna 180.2 020. saa eres 114.2 BOD nies it hie ens 178.5 OB ete sss eis apes 99.4 1008