CHAPTER XXX PUBLIC HEALTH. INFECTIOUS AND CONTAGIOUS (Part 1)

CHAPTER XXX PUBLIC HEALTH. INFECTIOUS AND CONTAGIOUS DISEASES. MICROBES 1. The Public Health. — The environment of man con- sists of two principal, and very different, parts: one near, and chiefly personal, domestic, or private, including his clothing, house, family, and estate; the other more remote, impersonal, and public, including his neighborhood, village, town or city, state, and country (p. 299). In sparsely settled districts little attention is paid to any health beyond that of the person or the family; and the family, as we have shown (p. 425), is really a small and private community; but in thickly settled regions, such as cities and towns, conditions and problems arise involv- ing numbers of families, and public hygiene and sanitation become necessities. In the country each family generally has its own private water supply, milk supply, food sup- ply, and drains; but in cities and towns mutual conven- ience, economy, and safety require public supplies and public drains. Instead of private roads we find public streets; instead of private estates, public parks. Public gardens and public markets furnish flowers and vegetables ; public conveyances, such as cars, steamboats, and car- riages, serve public needs; public institutions arise, such as hospitals, schools, almshouses, and jails; and public buildings, such as halls, hotels, churches, schoolhouses, shops, factories, stores. 463 464 THE HUMAN MECHANISM In all such cases numbers, groups, or masses of individ- ual families — called collectively the people, or the publie — are at times and as a whole exposed to unfavorable condi- tions, such as a general want of muscular exercise, lack of sleep, a too sedentary life, and overwork; or to germs of infectious and contagious diseases in public supplies of water, milk, etc.; or to foul air, overheating, defective lighting, gas poisoning, noise, dust, smoke, or impure food ;_ some of which conditions are chiefly personal, affecting more or less directly the bodies of the people, while others are more remote, or environmental. By the public health we mean the health of the public, i.e. of the people as a whole; and the health of the pub- lic depends — just as the health of the individuals who compose that public depends — on a great variety of con- ditions, some of which, as just stated, are chiefly internal, or in intimate relation with the persons of the people, and ~ may conveniently be called hygiene; while others are chiefly external, or at least not in intimate relation with the persons of the people but rather in their environment, and may be described as sanitary (pp. 301, 302). The applications of the various branches of science, such as physiology, chemistry, bacteriology, vital statistics, clima- tology, medicine, engineering, etc., to the control of these various hygienic and sanitary conditions, and thereby to the protection and promotion of the public health, consti- tute the science of public health ; and of this, as indicated in the last paragraph, there are two grand divisions, namely, hygiene and sanitation. 2. Public Health Rules and Regulations. — For the regu- lation and control of those conditions which are personal and domestic we must look, even in large communities, chiefly to individuals and families; but even if individuals and families always obeyed the laws of personal hygiene and domestic sanitation, the protection of the public health would 4h hak bod iG hd oe ce | INFECTIOUS DISEASES. MICROBES 465 still require special supervision and control of public sup- plies, public drains, public vehicles, public institutions, and the like, because these things are outside and beyond the control of private individuals or families and stand in a class by themselves. In point of fact, however, private ‘persons and families are often negligent in matters of this kind, inflicting damage upon their neighbors by maintain- ing nuisances of one kind or another, or else by their care- lessness in respect to filth or in respect to the spread of infectious or contagious diseases. Hence it has come to pass that sanitary and hygienic rules and regulations have been adopted by the citizens of most civilized communi- ties for mutual benefit. 3. Public Health Authorities. — For the enforcement of these rules and regulations (sanitary laws) special public officials are usually elected or appointed, such as boards of health, health officers, city physicians, sanitary in- spectors, medical inspectors, quarantine officers, school nurses, sanitary police, vaccinating physicians, etc. By common consent of the majority of the citizens these officers are authorized and required under the laws to prepare, publish, and enforce needful sanitary rules and ‘regulations for the protection and promotion of the public health. 4. Public Health Problems. — In this and the following chapters we can touch upon only a few of those more elementary and important problems of the public health of which every educated citizen should have some knowledge. Such problems are almost all fundamentally concerned with the control of infectious diseases, to the nature of which we shall therefore at once turn our attention. Much of what follows was formerly the exclusive pos- session of the medical profession and has only recently become a part of the common knowledge of mankind. Much of it also is comparatively new, and among the best 466 THE HUMAN MECHANISM fruits of the splendid advances of the last half century in the sciences of pathology, hygiene, and sanitation. 5. Plagues, Pestilences, and Epidemics are the most strik- ing examples of influences affecting both personal and public health. Only wars, riots, and great conflagrations are capable of throwing communities into such terror as° has often been caused by plagues or pestilences of some swiftly fatal disease. Such was the plague in London described by Defoe in his Journal of the Plague Year, a story which has been well called “ that truest of all fic- tions.” History is full of similar instances. Even as late as 1892 the rich and powerful city of Hamburg, Germany, was terrorized by a severe epidemic of Asiatic cholera due _ to a polluted public water supply, while still more recently the cities of Ithaca in New York and Butler in Pennsyl- vania have been ravaged by the plague of typhoid fever. Plagues and pestilences are simply older names for great: epidemics of much dreaded diseases, such as smallpox, yel- low fever, Asiatic cholera, or the bubonic plague, and the pesthouse which formerly existed in many towns and cities was a remote and isolated shelter, or primitive hospital, often of the crudest and poorest kind, to which the vic- tims of pestilence were taken (or driven) by a frightened: public. The true sources of epidemics, plagues, and pesti- lences have only recently become known. Savages often attribute these to supernatural causes, such as evil spirits or demons, and even for civilized people pestilences were until recently mysterious in origin and incomprehensible in behavior. It is now known, however, that. such out- breaks are simply extensive epidemics of contagious or in- fectious diseases, which may often be controlled and even prevented; but in order that control or prevention shall be effective, the intelligent cobperation of all good citizens is essential. It is one of our first duties to acquaint our- selves with the nature and the methods of prevention of RMT ¥ bid d “paps ip bie tg rik areas i Lace ideal wer INFECTIOUS DISEASES. MICROBES 467 contagious and infectious diseases, and thus at the same time of plagues, pestilences, and epidemics. 6. What are Infectious and Contagious Diseases ? —The discoveries of Pasteur, Koch, and their successors in the last half of the nineteenth century have brought to light the remarkable fact that those “fevers ”— typhoid fever, malarial fever (malaria), diphtheria, smallpox, cholera, tuberculosis, etc., and probably also measles, chicken pox, scarlet fever, and many “ colds ”— which attack apparently healthy persons and cause a severe but brief sickness that seems to run its course and then cease, are due to invasions of the body by microparasites! called microbes. Each of these contagious or infectious diseases has its own special microbe to which it owes its origin ; and it is customary to speak of the microbes of diphtheria, of typhoid fever, of the bubonic plague, of Asiatic cholera, etc., as the cause of these diseases. Although in some contagious and infec- tious diseases the microbe has not yet been discovered, all these diseases are nevertheless so much alike, and causa- »tive microbes have been found in so many cases, that all are believed to have a similar microbie origin. The view or theory just outlined is known as the germ theory of infectious and contagious diseases, and the causa- tive microbes are known as disease germs. It is easy, on this theory, to see why these diseases are “catching.” It is, 1 Microparasites. — A parasite is a plant or animal which feeds upon another plant or animal (called its host), and renders it no services in return. Some parasites, like fleas, lice, the pork worm (Trichina) and ‘ringworm,’ are visible or nearly visible to the naked eye; but many others are invisible and may be called microparasites. Of these the most important belong among the microbes (see p. 468) ; but, as the microbes form an enormous group of plants and animals, most of which are in no way parasitic or harmful to mankind, but on the contrary are highly use- ful, we must,be careful not to regard as parasites more than a very few of the microbes. Those that do not lead a parasitic life are usually scavengers and lead a saprophytic life; that is, they feed upon dead organic matters, often helping greatly to clean and to keep clean the surface of the earth. 468 THE HUMAN MECHANISM of course, not the disease but the parasitic microbes which can be “ caught” or “taken,” as fleas can be “ taken” from a dog, or bedbugs carried from place to place in bedding or clothing, or lice “caught” by children from lousy play- mates. It is easy, also, to understand how destructive epi- demics, plagues, and pestilences can occur, if public food supplies, water supplies, milk supplies, carriages, steamers, caravans, cars, or other conveyances have become infected with infectious microbes or disease germs. An infectious disease is one in which the disease germs infect (that is, invade) the body from without. Such are diphtheria, typhoid fever, tuberculosis, trichinosis, scarlet fever, smallpox, measles, chicken pox, and all the more common “fevers.” Among these some are ordinarily con- veyed quite directly and quickly from person to person, and to such infectious diseases the term “contagious” is often applied. Formerly a sharp line was drawn between infection and contagion, but to-day it is recognized that no such line exists. Typhoid fever, for example, is still sometimes said to be “infectious but not contagious.” If by this is meant that it is not as often spread through the air or by mere “contact” as are smallpox and some other diseases, then it is true. But if the saying means that it cannot be transmitted by mere contact with the patient or his excreta, then it is false (see p. 485). It would be better to drop altogether the term “contagious,” for its use is antiquated and misleading. 7, Microbes. — Brief references have frequently been made on previous pages to microbes and their work, but we must now give them special consideration. As the word implies, microbes (micros, small; bios, life) are little living things, and they have been described: as ‘all forms of life, whether animal or vegetable, invisible or barely visible to the naked eye.” It is customary to regard them as the smallest of all living things, and sometimes che INFECTIOUS DISEASES. MICROBES 469 as identical with microdrganisms, germs, or bacteria. All bacteria, however, are plants, so that a broader term, such as “germs,” “‘microdrganisms,” or “ microbes,” is required if the lowest forms of animal life are also to be covered. In these pages we shall use the term microbes for those forms of life, . either plant or animal, which are invisible or barely visible Fie. 118. Microbes (rod-shaped bacteria, or bacilli). (All very highly magnified) 1, bacilli, some very large and some very small; 2, other forms of bacilli; 3, bacilli forming threads or filaments; 4, dead or dying bacilli (énvolu- tion forms) to the naked eye, and of interest or importance in physiology, hygiene, and sanitation. For our purposes microbes may be divided into bacteria, or vegetable microbes, and protozoa, or animal microbes. The bacteria are unicellular plants of the simplest struc- ture and of three principal forms, viz. rods, berries or balls, and spirals. The rods form the group bacilli (Fig. 118), the balls the cocci (pronounced cock’s eye) (Fig. 119), and the spirals the spirilla (Fig. 120). Bacteria often grow and multiply (by simple cell division) very rapidly, and some are HS 470 THE HUMAN MECHANISM capable of producing within themselves smaller cells, called spores, which have thick walls and possess great powers of resistance (see Fig. 121). The protozoa are unicellular animals, also of the simplest _structure, and among them one group, the sporozoa, is of Fie. 119. Microbes (ball-shaped bacteria, or cocci). (All very highly magnified) 1, cocci single, and cocci united in a jelly mass or zodglea; 2, in twos and fours (diplococci and tetrads); 3, in clusters (staphylococci); 4, in chains or necklaces (streptococci) especial interest because it certainly includes the microbes of malaria, and probably also those of smallpox and of scarlet fever (see Fig. 126). Microbes are of interest and importance to the physiolo- gist, hygienist, and sanitarian, first, because they are na- ture’s scavengers, i.e. removers of organic waste matters ; second, because they are the ordinary agents of the decom- position, putrefaction, and decay of foods and other valu- able organic matter; and third, and especially, because among them are found many microparasites, and especially those germs which cause infectious and contagious diseases such as consumption, typhoid fever, diphtheria, and malaria. ete. f Lael cee pal beet eee INFECTIOUS DISEASES. MICROBES 471 1. Microbes as Scavengers. — Whenever the dead body of a plant or animal, or any part of it, is left upon the ground, or in water, or is buried in the earth, it soon crumbles or decays and disappears, turning, as we say, to dust and ashes. It was formerly universally believed that this Fic. 120, Microbes (spiral or screw-shaped bacteria, or spirilla), (All very highly magnified) 1, spirilla from the human mouth; 2, microbes of Asiatic cholera; 3, spirilla of relapsing fever; 4, large spirilla from ditch water change was a slow combustion or oxidation caused by the direct action of the oxygen of the atmosphere. It is now known, however, that this oxidation is due to the influence of microbes which abound in the upper layers of the earth, and to a less extent in air and water. These oxidize the waste organic matters to carbon dioxide, water, etc., much 472, THE HUMAN MECHANISM as the muscle fiber oxidizes the food brought to it by the blood (see Chapter IV). It is now established that scavenging is one of the prin- cipal functions of microbes, for they abound in sewage, which they readily decompose and, under favorable cir- cumstances, completely purify; in excrement, which they. work over and change to harmless, inoffensive, and even useful mineral matters; and in many organic wastes, which they reduce to simple and harmless chemical compounds (Figs. 120, 4, and 122, 4). 2. Microbes as Agents of Decomposition and Decay. — The peculiar property which makes microbes destroyers of waste organic matters, and therefore useful as scavengers, makes them also troublesome, if not dangerous, agents of the decomposition, decay, and consequent destruction of useful organic substances, such as foods. Milk, for exam- ple, may be spoiled by lactic acid microbes which feed” upon its sugar and, by producing lactic acid in the course of their feeding, cause the milk to turn'sour; but, on the other hand, this very change wrought by the microbes, though dreaded by the milkman, may be desired by the cheese-maker, in whose work the souring of the milk is necessary. The spoiling of meat, fish, fruit, and many other forms of food is due almost wholly to the vital actiy- ity of microbes, and we have to use cold and heat for protection against their inroads. Cold, by chilling and benumbing them, checks their growth and multiplication ; while heat, if sufficiently intense, destroys them altogether. Upon the former fact are based the important arts of refrigeration and cold storage; upon the latter the great modern industry of canning. Microbes have a wide and useful employment in the arts and industries, — such as the souring of milk in cheese- making, the flavoring of cheese and butter, the preparation of hides for tanning, the ripening of manures, the fixation Pe Ue INFECTIOUS DISEASES. MICROBES 473 of free nitrogen in agriculture, and many other processes depending upon their vital activity. But, on the other hand, spoiled foods — especially meat, eggs, and fish — may be not only disagree- able but also dangerous, owing to the formation by microbes of poisonous by-products known as pto- maines, to whose agency have been attributed severe outbreaks of acute disease. Ptomaines are bodies of un- certain chemical composi- tion, which cause intense general prostration and ; : 5 : Fic. 121. Diagram of the growth, sometimes death. It is a multiplication, and spore forma- good rule to avoid carefully __ tion of a bacterial microbe all meat or fish which is 1-4, growth and multiplication by cell “tainted,” or suspected of Svslm(eion): eg, fomation ib putrefactive decomposition. At the same time there is reason to believe that some out- breaks of obscure poisoning have been charged to this rather uncertain source largely because no other explana- tion could be as easily given. 3. Microbes as Disease Germs. — But it is as disease