Shape.—Bacteria are composed of single cells and are consequently called unicellular organisms. Under the microscope individual cells are seen to differ in size, shape, and structure. In shape bacteria show three different types; the rod-shaped (bacillus), the spherical (coccus), and the spiral (spirillum). The organisms causingtyphoid fever for example are a variety of bacilli, those causing pneumonia are cocci, while those causing Asiatic cholera are spirilla.
—Bacteria are composed of single cells and are consequently called unicellular organisms. Under the microscope individual cells are seen to differ in size, shape, and structure. In shape bacteria show three different types; the rod-shaped (bacillus), the spherical (coccus), and the spiral (spirillum). The organisms causingtyphoid fever for example are a variety of bacilli, those causing pneumonia are cocci, while those causing Asiatic cholera are spirilla.
Fig. 1.—Bacilli of Various Forms.(Williams.)
Size.—Bacteria vary greatly in size. Average rod-shaped bacteria are about1/25000of an inch long, but there are undoubtedly organisms so small that they cannot be seen, even by means of the strongest microscopes we now possess.
—Bacteria vary greatly in size. Average rod-shaped bacteria are about1/25000of an inch long, but there are undoubtedly organisms so small that they cannot be seen, even by means of the strongest microscopes we now possess.
Staphylococci. Streptococci. Diplococci. Tetrads. Sarcinæ.Fig. 2.—(Williams.)
Motion.—The power of motion in certain species of bacteria is due to hair-like appendages called flagella. These flagella by a lashing movement somewhat resembling the action of oars enable the organisms to move through fluids.
—The power of motion in certain species of bacteria is due to hair-like appendages called flagella. These flagella by a lashing movement somewhat resembling the action of oars enable the organisms to move through fluids.
Multiplication.—After bacteria have fully developed, each cell divides into two equal parts; the process of division is called fission. Eachof these two parts rapidly grows into a full-sized organism. Then fission again takes place, so that four bacteria replace the original one. In each of the four, fission occurs again, and so the process of multiplication continues. As bacteria develop they group themselves in characteristic ways. Some, like the streptococci, arrange themselves in chains; the diplococci, in pairs; the tetrads, in groups of four; others in packets called sarcinæ, and still others, the staphylococci, form masses supposed to resemble bunches of grapes.
—After bacteria have fully developed, each cell divides into two equal parts; the process of division is called fission. Eachof these two parts rapidly grows into a full-sized organism. Then fission again takes place, so that four bacteria replace the original one. In each of the four, fission occurs again, and so the process of multiplication continues. As bacteria develop they group themselves in characteristic ways. Some, like the streptococci, arrange themselves in chains; the diplococci, in pairs; the tetrads, in groups of four; others in packets called sarcinæ, and still others, the staphylococci, form masses supposed to resemble bunches of grapes.
Fig. 1.—Bacilli of Various Forms. (Williams.)Fig. 3.—Spirilla of Various Forms.(Williams.)
Fig. 4.—Bacteria showing Flagella.(Williams.)
Under favorable conditions fission occurs rapidly; in some types a new generation may appear as often as every 15 minutes. Enormousmultiplication would result if nothing occurred to check the process. But in nature such increase never continues unhindered, and bacteria, acting upon their food substances, produce acids and other materials injurious to themselves. Furthermore, lack of proper food, moisture, or favorable temperature, and competition with other organisms tend to prevent their unrestricted growth and multiplication.
Fig. 5.—Bacteria with Spores.(Williams.)
Spores.—Most bacteria die if conditions become unfavorable to their growth, but some enter into a resting stage. This stage is characterized by the development of round or oval glistening bodies called spores, which are of dense structure and possess an extraordinary power to withstand heat, chemicals, and unfavorable surroundings. Except in rare instances a single cell produces but one spore. As soon as favorable conditions of temperature, moisture, and food supply are restored, the spore develops into the active form of the germ; it may, however, remain dormantfor months or years. Spore formation, however, occurs in only a very few varieties of pathogenic bacteria.
—Most bacteria die if conditions become unfavorable to their growth, but some enter into a resting stage. This stage is characterized by the development of round or oval glistening bodies called spores, which are of dense structure and possess an extraordinary power to withstand heat, chemicals, and unfavorable surroundings. Except in rare instances a single cell produces but one spore. As soon as favorable conditions of temperature, moisture, and food supply are restored, the spore develops into the active form of the germ; it may, however, remain dormantfor months or years. Spore formation, however, occurs in only a very few varieties of pathogenic bacteria.
Distribution.—Bacteria are very widely distributed in nature; they are in fact found practically everywhere on the surface of the earth. They are present in plants and water and food; on fabrics and furniture, walls and floors; and they are found in great numbers on the skin, hair, many mucous surfaces, and other tissues of the body.
—Bacteria are very widely distributed in nature; they are in fact found practically everywhere on the surface of the earth. They are present in plants and water and food; on fabrics and furniture, walls and floors; and they are found in great numbers on the skin, hair, many mucous surfaces, and other tissues of the body.
The protozoa are the lowest group of the animal kingdom. Like bacteria they are composed of single cells so small as to be visible only under the microscope. They play an important part in causing certain diseases of man, especially in the tropics. Among the well-known human diseases of protozoan origin are malaria, amoebic dysentery, and sleeping-sickness. Protozoa also cause several wide-spread and serious plagues of domestic animals.
A few diseases are caused by parasites large enough to be seen with the naked eye. One of the most important is hookworm disease. Thisdisease is caused by a tiny worm which penetrates the victim's skin and ultimately finds its way into the intestine. Other diseases also are caused by parasitic worms, such as tapeworms, pinworms, and trichinæ. The latter are acquired as a result of eating infected meat, particularly infected pork that has not been thoroughly cooked.
Pathogenic or disease producing organisms need for their development food, moisture, darkness, and warmth, conditions that exist within the human body. When one or more of these factors is unfavorable, development of germs is checked; if unfavorable conditions are extreme or long continued, the organisms begin to die. It is difficult to say at exactly what moment they will die if deprived of moisture or exposed to extremes of temperature or other unfavorable conditions, just as it would be impossible to state at exactly what moment a collection of house plants would all be dead if water were withheld, or if the room temperature were greatly reduced.
Most pathogenic organisms, however, do not flourish long outside the body, and owe theircontinued existence to a fairly direct transfer from person to person. They gain access to the body through mucous surfaces such as the respiratory and digestive tracts, and through breaks in the skin, such as cuts, abrasions, and the bites of certain insects. They leave the body chiefly in the nasal and mouth discharges, as in coughing, sneezing, and spitting, in the urine and bowel discharges, and in pus or "matter."
Flow chart depicting spread of typhoid fever.Fig. 6.(L. H. Wilder.)
The problem of controlling communicable diseases, consequently, lies in preventing the bodily discharges of one person from travellingdirectly into the body of another. If a person is not expelling pathogenic germs, it is clear that he cannot pass diseases on to others. But both pathogenic and harmless germs follow the same routes from person to person, so that safety as well as decency lies in preventing so far as possible all exchanges of bodily discharges.
There are five routes by which the bodily discharges most frequently travel from one person to another. Four of these routes of infection are called public, because in most cases efforts of individuals alone are not sufficient to control them. The public routes are water, milk, food, and insects. The fifth, or private route, includes all means by which fresh discharges of one person are passed to another, as when nose and mouth discharges are carried in coughing, sneezing, and kissing, or when bowel and bladder discharges are carried by the hands. These five routes in a given case differ greatly in relative importance, but the fifth, or direct route plays an immense part, although its importance in causing sickness has only lately been recognized. It cannot be too strongly emphasized that the chief agent in the spread of human diseases is man himself, and the human hand is the great carrier of disease germs both to and from the body. If unclean hands could be kept away from the orifices of the body,particularly the mouth, many diseases would soon cease to exist.
In view of all the dangers from disease-producing germs it may seem surprising that the human race has not long ago succumbed to its invisible enemies. But the body has various defenses by means of which it may prevent invasion, or successfully combat its enemies in case they do gain access.
The unbroken skin is usually impassable to bacteria. Virulent organisms are often found upon the skin of perfectly healthy persons, where they appear to be harmless unless an abrasion occurs which affords entrance into the deeper tissues. Most bacteria breathed in with the air cling to the moist surfaces of the air-passages and never reach the lungs.
Mucous membranes lining the mouth and other cavities of the body would prove favorable sites for the growth of bacteria if the mucus secreted by them were not frequently removed. The mouth of a healthy person may contain bacteria of many kinds, but the saliva has a slight disinfectant power and serves as a constant wash to the membranes. The normal gastric (stomach) juice is decidedly unfavorable to the growth of bacteria,although it does not always kill them; they often pass through the stomach and are found in large numbers in the intestines. Other bodily secretions, such as the tears and perspiration, tend to discourage bacterial growth.
Tissues of the body vary greatly in their power to resist invading germs, so that the route by which germs enter influences the severity of their effects. Typhoid bacilli and the spirilla of Asiatic cholera when taken with food or water produce far more serious disturbances than when injected under the skin; infections from pus germs through an abrasion of the skin may result in a slight local disturbance, while the same amount introduced into a deeper wound might cause a fatal infection. Certain germs nourish in certain tissues only; even tuberculosis, which attacks practically all tissues, has its favorite locations.
Immunity.—In addition to its mechanical defenses against disease, the body shows a varying degree ofimmunity, or the power possessed by living organisms to resist infections. Immunity or resistance is the opposite of susceptibility. It is exceedingly variable, being greater or less in different people and under different conditions, but the exact ways in which it is brought about are still in many cases far from clear.
—In addition to its mechanical defenses against disease, the body shows a varying degree ofimmunity, or the power possessed by living organisms to resist infections. Immunity or resistance is the opposite of susceptibility. It is exceedingly variable, being greater or less in different people and under different conditions, but the exact ways in which it is brought about are still in many cases far from clear.
Immunity may benaturaloracquired. Bynatural immunity is meant an inherited characteristic by which all individuals of a species are immune to a certain disease. The natural immunity of certain species of animals to the diseases of other animals is well known. Man is immune to many diseases of lower animals, and they in turn are immune to many diseases of man. Cattle, for instance, are immune to typhoid and yellow fever, while man shows high resistance to rinderpest and Texas fever; both, however, are susceptible to tuberculosis, to which goats are immune. There are all gradations of immunity within the same species. Moreover, certain individuals have a personal immunity against diseases to which others of the same race or species are susceptible.
Immunity may beacquiredin several ways. It is commonly known that one attack of certain communicable diseases renders the individual immune for a varying length of time, and sometimes for life. Among these diseases are smallpox, measles, whooping-cough, scarlet fever, infantile paralysis, typhoid fever, chicken-pox, and mumps; erysipelas and pneumonia on the other hand appear to diminish resistance and to leave a person more susceptible to later attacks.
Again, in some cases immunity may be artificially acquired by introducing certain substancesinto the body to increase its resistance. Examples of this method include the use of antitoxin as a protection against diphtheria, of sera in pneumonia and other infections, and vaccination against smallpox and typhoid fever whereby a slight form of the disease is artificially induced. Laboratory research goes on constantly, and doubtless many more substances will eventually be discovered that will reduce human misery as vaccines and antitoxin have already reduced it.
Vaccination and inoculation have saved thousands of lives. Smallpox, once more prevalent than measles, was the scourge of Europe until vaccination was introduced. During the 18th century it was estimated that 60,000,000 people died of it, and at the beginning of the 19th century one-fifth of all children born died of smallpox before they were 10 years old. In countries where vaccination is not practised the disease is as serious as ever; in Russia during the five years from 1893-97, 275,502 persons died of smallpox, while in Germany where vaccination is compulsory, only 8 people died of it during the year 1897. Death rates from diphtheria and typhoid fever have been greatly reduced by the use of antitoxin and antityphoid vaccine. Thus in New York State in 1894, before antitoxin was generally used, 99 out of every 100,000 of the population died ofdiphtheria, while only 20 out of 100,000 died of it in 1914. In 1911 a United States Army Division of more than 12,000 men camped at San Antonio, Texas, for four months. All of these men were vaccinated against typhoid fever and only a single case occurred during the summer, although conditions of camp life always tend to spread the disease.
While many and various factors tend to lower resistance rather than to increase it, the idea that these factors act equally in all kinds of infection is erroneous.
"The principal causes which diminish resistance to infection are: wet and cold, fatigue, insufficient or unsuitable food, vitiated atmosphere, insufficient sleep and rest, worry, and excesses of all kinds. The mechanism by which these varying conditions lower our immunity must receive our attention, for they are of the greatest importance in preventive medicine. It is a matter of common observation that exposure to wet and cold or sudden changes of temperature, overwork, worry, stale air, poor food, etc., make us more liable to contract certain diseases. The tuberculosis propaganda that has been spread broadcast with such energy and good effect has taught the value of fresh air and sunshine, good food, and rest in increasing our resistance to this infection."There is, however, a wrong impression abroad that because a lowering of the general vitality favors certain diseases, such as tuberculosis, common colds, pneumonia, septic and other infections, it plays a similar rôle in allcommunicable diseases. Many infections, such as smallpox, measles, yellow fever, tetanus, whooping-cough, typhoid fever, cholera, plague, scarlet fever, and other diseases, have no particular relation whatever to bodily vigor. These diseases often strike down the young and vigorous in the prime of life. The most robust will succumb quickly to tuberculosis if he receives a sufficient dose of the virulent micro-organisms. A good physical condition does not always temper the virulence of the disease; on the contrary, many infections run a particularly severe course in strong and healthy subjects, and, contrariwise, may be mild and benign in the feeble. Physical weakness, therefore, is not necessarily synonymous with increased susceptibility to all infections, although true for some of them. In other words, 'general debility' lowers resistance in a specific, rather than in a general, sense."—(Rosenau: Preventive Medicine and Hygiene, pp. 403 and 404.)
"The principal causes which diminish resistance to infection are: wet and cold, fatigue, insufficient or unsuitable food, vitiated atmosphere, insufficient sleep and rest, worry, and excesses of all kinds. The mechanism by which these varying conditions lower our immunity must receive our attention, for they are of the greatest importance in preventive medicine. It is a matter of common observation that exposure to wet and cold or sudden changes of temperature, overwork, worry, stale air, poor food, etc., make us more liable to contract certain diseases. The tuberculosis propaganda that has been spread broadcast with such energy and good effect has taught the value of fresh air and sunshine, good food, and rest in increasing our resistance to this infection.
"There is, however, a wrong impression abroad that because a lowering of the general vitality favors certain diseases, such as tuberculosis, common colds, pneumonia, septic and other infections, it plays a similar rôle in allcommunicable diseases. Many infections, such as smallpox, measles, yellow fever, tetanus, whooping-cough, typhoid fever, cholera, plague, scarlet fever, and other diseases, have no particular relation whatever to bodily vigor. These diseases often strike down the young and vigorous in the prime of life. The most robust will succumb quickly to tuberculosis if he receives a sufficient dose of the virulent micro-organisms. A good physical condition does not always temper the virulence of the disease; on the contrary, many infections run a particularly severe course in strong and healthy subjects, and, contrariwise, may be mild and benign in the feeble. Physical weakness, therefore, is not necessarily synonymous with increased susceptibility to all infections, although true for some of them. In other words, 'general debility' lowers resistance in a specific, rather than in a general, sense."—(Rosenau: Preventive Medicine and Hygiene, pp. 403 and 404.)
Well persons who carry in their bodies pathogenic germs but who themselves have no symptoms of disease are called carriers. Thus typhoid carriers have typhoid bacilli in the intestinal tract, while they themselves show no symptoms of typhoid fever; diphtheria carriers have bacilli of diphtheria in the throat or nose, but have themselves no symptoms of diphtheria, and so on. It has now been proved that many patients harbor bacteria for weeks, months, or even years following an infection, and are dangerous distributors ofdisease; also, some healthy individuals without a history of illness harbor living bacteria which may infect susceptible persons in the usual ways. Transmission by healthy carriers goes far to explain the occurrence of diseases among persons who have apparently not been exposed. This explanation has greatly clarified the whole problem of the spread of communicable diseases. Carriers, unfortunately, exist in large numbers, and render the ultimate control of disease exceedingly difficult. They can usually be identified by bacteriological tests. To some extent they can be supervised; food handlers at least should be legally obliged to submit to physical examinations, and should be licensed only when proved free from communicable disease.
Diseases are also spread by persons suffering from them in a form so mild or so unusual that they pass unrecognized. These persons are known as "missed" cases. Carriers of disease and "missed" cases go freely about the community, handling food, using common drinking cups, travelling in crowded street cars, standing in crowded shops; in various ways coming into close contact with other people, coughing and sneezing and kissing their friends no less often than normal individuals. It is consequently clear that the bodily discharges of supposedly normal personsmay be hardly less a menace than those of persons known to be infected.
Diseases that depend for transmission upon milk, water, food, and insects may be controlled by public action, that is, by specific measures taken by a large group of people in order to protect the individual. Such action constitutespublic sanitation. There is, however, a large group of diseases, chiefly sputum-borne, that cannot be controlled except by individual action. Such individual action constitutes a large part ofpersonal hygiene.
The whole problem of controlling infections sounds simple, depending as it does for the most part upon unpolluted water, milk, and food, extermination of certain insects, and cleanliness in personal behaviour. In practice the problem is not so easy. Public sanitation has performed miracles in the past, and will do much in the future; behaviour, however, will continue to be influenced by many factors, social and economic as well as personal. Ignorance of the laws of health is an obstacle to progress, but in modern conditions even the instructed may be unable to control their ways of living and working. Indeed, such control is at present limited to the privileged few. On the ignorant and the poor, those least able to bear it, society loads the heaviest burden of sickness. Only when ignorance and poverty areabolished, as one day they will be, can the final stage be reached in the fight for public health.
In this group is included a great variety of maladies. Of some the causes are known, while in the case of others, origin, prevention, and remedy are still obscure. Here belong defects in structure of the body, both hereditary and acquired; insanity and other nervous diseases; new growths, like tumors and cancer; disturbances of bodily processes, as malnutrition and gout; and the important class of degenerative diseases, like arteriosclerosis, in which tissues become hardened and fibrous and hence less able to perform their normal functions.
The degenerative diseases are playing a menacing part in national health. The average length of life in the United States has shown a marked increase it is true, during the last 40 years. But this gain represents chiefly the saving of life through prevention of communicable diseases, especially among babies and children; among people who have passed the 30th year on the other hand, death rates are actually increasing. This increase is most marked after the age of 45, and is caused chiefly by the increase of cancer, and of degenerative diseases of the heart, blood vessels, andkidneys. Degeneration of tissues is normally a condition typical of old age, and in aged persons it may occur in any tissue. There is no elixir of youth, and for old age there is no cure. But the important facts in this connection are that degenerative changes now occur prematurely, and that among a vast number of people, in various classes of society and various occupations, the vital organs show a marked tendency to break down after the age of 45.
This condition is not inevitable. Before the beginning of the present war, death rates at all ages were decreasing in England, Sweden, and other European countries. In America also degenerative diseases can be checked or prevented to a large extent, and it is highly important that their causes should be generally understood.
The two groups following include some of the probable causes:
1. Conditions of life which result in continued overwork, and mental overwork in particular; worry, excitement, insufficient recreation and exercise, and other kinds of nervous strain typical of modern life, especially in cities.
2. Irritating substances in the body, including poisonous substances resulting from infectious diseases, and from syphilis in particular; poisons from chronic infections, alcohol, and industrialpoisons such as lead and other metals; overeating and improper eating, especially of meat and other proteins, and rich or highly seasoned food; faulty digestion, constipation, and imperfect elimination through the kidneys.—(See Dr. A. E. Shipley, in bulletin of the N. Y. City Dept. of Health, Feb., 1915.)
The importance of early recognition cannot be overemphasized. In many of these troubles the symptoms are not pronounced, and the victims have no knowledge of their condition until they happen to be examined for life insurance, or until the disease is far advanced. And even when they realize that trouble exists, as for example constipation or overwork, most people absolutely fail to realize how serious the consequences may be. The first step toward remedy is periodic complete physical examination by a competent physician, in order to learn in time how to prevent these degenerative diseases, if present, from growing worse. The custom of undergoing an annual physical examination is becoming more common, and "such a course, conservatively estimated, would add 5 years to the average life of persons between 45 and 50."—(Winslow.)
"Recently, we have been making examinations of the employees of whole institutions, large banks and other industrial concerns in New York City, and wefind almost the same conditions there. Out of 2000 such examinations among young men and women of an average age of 33, just in the early prime of life, men and women supposedly picked because of their especial fitness for work, only 3.14% were found free of impairment or of habits of living which are obviously leading to impairment. Of the remaining persons, 96.69% were unaware of impairment; 5.38% of the total number examined were affected with chronic heart trouble; 13.10% with arteriosclerosis; 25.81% with high or low blood pressure; 35.65% with sugar, casts or albumen in the urine; 12.77% with combination of both heart and kidney disease; 22.22% with decayed teeth or infected gums; 16.03% with faulty vision uncorrected.... The fact of greatest import, however, was that impairment, sufficiently serious to justify the examiner in referring the examinee to his family physician for medical treatment, was found in 59% of the total number of cases, while 37.86% were on the road to impairment because of the use of "too much alcohol," or "too much tobacco," constipation, eye-strain, overweight, diseased mouths, errors of diet, and so forth...."And what is the cause of this appalling increase, in the United States, of these and other degenerative diseases? I believe it can be shown to the satisfaction of any reasonable person that the increase is largely due to the neglect of individual hygiene in United States...."If a man were suddenly afflicted with smallpox or typhoid fever or any other acute malady, he would lose no time in getting expert advice and applying every known means to save his life. But his life may be threatened just as seriously, though possibly not so imminently, by arteriosclerosis, heart disease, or Bright's disease,and he will do nothing to prevent the encroachment of these diseases until it is too late, but will continue to eat as he pleases, drink as he pleases, smoke as he pleases, or overwork, and worry himself into a premature grave."—("Conservation of Life at Middle Age," Prof. Irving Fisher, Am. Journal of Public Health, July, 1915.)
"Recently, we have been making examinations of the employees of whole institutions, large banks and other industrial concerns in New York City, and wefind almost the same conditions there. Out of 2000 such examinations among young men and women of an average age of 33, just in the early prime of life, men and women supposedly picked because of their especial fitness for work, only 3.14% were found free of impairment or of habits of living which are obviously leading to impairment. Of the remaining persons, 96.69% were unaware of impairment; 5.38% of the total number examined were affected with chronic heart trouble; 13.10% with arteriosclerosis; 25.81% with high or low blood pressure; 35.65% with sugar, casts or albumen in the urine; 12.77% with combination of both heart and kidney disease; 22.22% with decayed teeth or infected gums; 16.03% with faulty vision uncorrected.... The fact of greatest import, however, was that impairment, sufficiently serious to justify the examiner in referring the examinee to his family physician for medical treatment, was found in 59% of the total number of cases, while 37.86% were on the road to impairment because of the use of "too much alcohol," or "too much tobacco," constipation, eye-strain, overweight, diseased mouths, errors of diet, and so forth....
"And what is the cause of this appalling increase, in the United States, of these and other degenerative diseases? I believe it can be shown to the satisfaction of any reasonable person that the increase is largely due to the neglect of individual hygiene in United States....
"If a man were suddenly afflicted with smallpox or typhoid fever or any other acute malady, he would lose no time in getting expert advice and applying every known means to save his life. But his life may be threatened just as seriously, though possibly not so imminently, by arteriosclerosis, heart disease, or Bright's disease,and he will do nothing to prevent the encroachment of these diseases until it is too late, but will continue to eat as he pleases, drink as he pleases, smoke as he pleases, or overwork, and worry himself into a premature grave."—("Conservation of Life at Middle Age," Prof. Irving Fisher, Am. Journal of Public Health, July, 1915.)
Periodic physical examinations are as necessary for children as for adults, in order to detect physical defects. These defects are known to have such an immense bearing upon health that routine examinations of all children have become an integral part of the work of enlightened public schools.
Prevention of degenerative disease, then, as well as of the enormous numbers of preventable accidents and injuries, depends in large measure upon proper living conditions and proper personal habits. The infectious diseases, according to Dr. Hill, cost us annually at least 10 billion dollars in addition to the loss of life, and he adds: "The infectious diseases in general radiate from and are kept going by women."—(Hill—New Public Health, p. 30.) Women, it is true, can prevent many of the infections, but they can do still more, for hygienic habits to be effective must be acquired early, and mothers and teachers, because they have practically the entire control of children, have the power to prevent many casesof degenerative as well as of communicable disease.
Of all the considerations that determine health, heredity is the one unalterable factor. Although certain characteristics are obviously hereditary,—complexion, height, and mental and physical traits in great variety,—yet in the past heredity has been little understood. In consequence it has served too often as a scape goat for faults and failings not beyond an individual's control. Our first clear understanding of the principles underlying heredity resulted from experiments made by Mendel, an Austrian monk, during the last century, and it is now possible to predict with a high degree of accuracy the inheritance of certain characteristics.
Many diseases, formerly considered hereditary because their actual causes were unknown, are now known to be communicable. Thus, it is now understood that tuberculosis is not hereditary, although little children may be infected by tuberculous parents. No germ diseases are inherited in the strict sense of the word; but ababy may be infected with syphilis before birth if his father or his mother has the disease.
It is true, however, that certain tissue weaknesses of the body seem to be hereditary, and in consequence one family is more susceptible to digestive disorders, another to diseases of the lungs, a third to deafness, and so on. Moreover, general low vitality may be inherited. It should be emphasized, however, that hereditary weakness does not inevitably lead to disease. Many persons have succeeded in preventing the development of active disease by guarding against strain in directions where they are weak by inheritance.
Of all tissue weaknesses that may be inherited, defects of the nervous system are the most serious. Nervous disorders of every degree of severity, from slight nervous instability even to insanity, may result when these tissues are defective; but it is now a recognized fact that nervous disorders in many cases can be prevented from developing. Feeblemindedness, another condition due to defective tissue, is known to be inherited in the majority of cases, and in all cases it is incurable.
By environment is meant everything outside the body that affects it; taken in its completemeaning the word might include everything that is or ever was in the whole universe. It is possible to consider here a few only of the many environmental and personal factors affecting the health of individuals.
The home constitutes the important part of environment for most persons, and for children in particular, since they spend the greater part of their time in or about it, and get there the foundation on which their health in later years depends. For persons employed away from home, industrial and occupational hygiene is hardly less important; but those subjects are too extensive to be considered here.
Most people live where they must, and few have any part in planning the construction of their own houses. In choosing a house, however, one should remember that rooms where sunshine never enters are unfit for continued occupation. For children in particular fresh air and sunshine are essential, and it may be economy in the end to pay a comparatively high rent for an apartment having sunshine during at least a part of the day. Ignorance and carelessness, unfortunately, can spoil the best living conditions, and sometimes even in the country fresh air and sunshine are excluded from sleeping and living rooms.
Ventilation.—Ventilation has a direct bearingon health, although, contrary to former belief, the actual amount of oxygen in the air is not ordinarily the most important factor; even badly ventilated rooms contain more than enough oxygen to support life. The factors of prime importance in ventilation are temperature, humidity, air movement, and the number of persons in a given space since the greater the distance from one another the less is the probability that diseases will be spread.
—Ventilation has a direct bearingon health, although, contrary to former belief, the actual amount of oxygen in the air is not ordinarily the most important factor; even badly ventilated rooms contain more than enough oxygen to support life. The factors of prime importance in ventilation are temperature, humidity, air movement, and the number of persons in a given space since the greater the distance from one another the less is the probability that diseases will be spread.
Room temperature should not be above 70° F. and, except for the aged or sick, it is better to be between 60° and 65°. Some moisture in the air is desirable; the amount needed is from 50% to 55% of the total moisture that the air can hold at a given temperature. We have no apparatus to decrease humidity in the air of houses, and in summer we are obliged to endure humidity, if excessive, no matter how uncomfortable we may be. But in winter the air in most houses is too dry, so that the mucous membranes of the nose and throat often become irritated and susceptible to infection. Most heating systems, particularly in small buildings, make no provision for supplying moisture. Keeping water in open dishes on or near radiators is often recommended, and would greatly improve the condition of the air, if people remembered to keep the dishes filled.
The following is a simple but effective device to increase humidity: Roll an ordinary desk blotter into a cone about 8 inches in diameter at the base, and keep it constantly submerged for about one inch in a dish of water. The water rises to the top of the blotter and a large surface for evaporation is thus afforded.
Cone made of desk blotter sitting in shallow dish of water.Fig. 7.
Stagnant air is harmful. Air should be in constant though not necessarily perceptible motion. Air about the body, if motionless, acts like a warm moist blanket, preventing the passage of heat from the body.
The three factors, heating, humidity, and air motion, must be considered together. Every person requires each hour about 3000 cubic feet of air, and the problem of heating and ventilating is that of providing this amount in gentle motion, at a temperature of about 65° F., and of humidity from 50-55%. Higher temperaturesand stagnant air cause disinclination to work, headache, nausea, restlessness, or sleepiness, and if continued are likely to result in loss of appetite, and anemia. The tuberculosis movement has clearly shown the benefits both for the sick and the well of living in the open air, and has caused great and beneficial changes within a generation. The more time spent in the open air the better; since however most persons who work must spend the greater part of the day indoors, ventilation is a matter of great importance.
Although fresh air enthusiasts are still too few, yet some go to the extreme and think that because cool air in motion is good, the colder the air and more violent the motion the better. On the contrary, chilling the whole body or a part of the body lowers resistance. Draughts of air have no bad effects upon persons in good health, particularly those accustomed to changes in temperature. But draughts are likely to be injurious to aged or sick persons and babies, by diminishing their resistance to such infections as common colds and pneumonia. It should be remembered that draughts or cold alone cannot cause colds; the specific germs must be present.
Lighting.—Amount and direction of light are physiologically important. Defects of the eyes,too prolonged use, and insufficient light are the commonest causes of eye strain. Most eye defects can be relieved by glasses. Children's eyes should be examined upon entering school, and as often afterward as the oculist advises. Prolonged use causes fatigue of the eyes, especially when the illumination is poor; within limits, the amount of light needed depends on the nature of the work. Light should come from the left side of right handed people; never from the front. Light reflected from snow, sand, glazed white paper of books, or other bright surfaces is fatiguing from its intensity, and from the unusual angle at which it enters the eyes. Too much light is harmful, and probably causes some of the effects, such as nausea and headache, commonly attributed to poor ventilation.
—Amount and direction of light are physiologically important. Defects of the eyes,too prolonged use, and insufficient light are the commonest causes of eye strain. Most eye defects can be relieved by glasses. Children's eyes should be examined upon entering school, and as often afterward as the oculist advises. Prolonged use causes fatigue of the eyes, especially when the illumination is poor; within limits, the amount of light needed depends on the nature of the work. Light should come from the left side of right handed people; never from the front. Light reflected from snow, sand, glazed white paper of books, or other bright surfaces is fatiguing from its intensity, and from the unusual angle at which it enters the eyes. Too much light is harmful, and probably causes some of the effects, such as nausea and headache, commonly attributed to poor ventilation.
Almost all blindness is preventable, and blindness due to industrial accidents and processes is no exception to this rule. Surely no individual precautions or legal measures are too great in order to guard against this saddest of all physical defects.
Cleanliness of Houses.—A clean, well-cared for house is desirable from every point of view, but certain kinds of cleanliness affect health more than others.
—A clean, well-cared for house is desirable from every point of view, but certain kinds of cleanliness affect health more than others.
The most scrupulous care should be exercisedwherever food is stored or prepared. The kitchen is in reality a laboratory; in it either intelligently or ignorantly are formed chemical compounds which have a far-reaching effect upon family health. From the standpoint of health no other room in the house is so important. It should be bright, airy, and easy to clean. In cleaning kitchen tables and woodwork water should not be allowed to soak into cracks and dark corners, carrying with it particles of food for the nourishment of bacteria and insects. Linoleum, if used to cover the floor, should be well fitted at the edges to prevent water from running underneath. There should be neither cracks nor crevices in wall or floor, and no dark corners or out-of-the-way cupboards in which dust, food particles, and moisture can accumulate. Such conditions not only attract mice and roaches, but furnish favorable soil for the development of moulds and fungi which by their growth affect food deleteriously. Waging a constant warfare against the development of bacteria constitutes a large part of good housekeeping.
All cooking utensils should be thoroughly washed, scalded, and dried before they are put away; the use of carelessly washed dishes is bad. Enameled or agate ware which has begun to chip should be discarded. Dish-cloths andtowels should be washed and boiled after using, and if possible dried in the sun.
Every place in which food is kept should have constant care. The refrigerator is particularly important. Its linings should be water-tight, and the drain freely open at all times; otherwise the surrounding wood will become foul and saturated with drainings. At least once a week it should be entirely emptied and cleaned in the following way: The racks should be thoroughly washed in hot soapsuds to which a small amount of washing soda has been added, rinsed in boiling water, dried and placed in the sun and air. All parts of the refrigerator should be washed in the same manner, especially grooves and projections where food or dirt may lodge. The drainpipe should be flushed, the whole interior rinsed again with plain hot water, thoroughly dried with a clean cloth, and left to air for at least an hour. The drainage pan should be washed and scalded frequently. Food showing the slightest evidence of spoiling should be removed from the refrigerator at once.
Even more attention should be paid to the hands of the cook. They should be washed always before handling food, and always after visiting the toilet, using the handkerchief, or otherwise coming in contact with nose, mouth, or otherbodily secretions. Theoretically coughing and sneezing ought not to occur in the neighborhood of food, especially of food to be eaten raw; and persons with coughs, colds, or other communicable disease, however slight, ought not to handle food. If this rule were observed in practice, more persons would go hungry, but fewer would be sick.
Thorough cleaning of rooms involves soap, water, sunshine, air, and elbow grease, just as it did before germs were discovered. Cleaning means actually removing dirt and dust, not merely stirring it up to settle again; consequently dry sweeping and dusting are ineffectual. Vacuum cleaning, and sweeping and dusting with damp or "dustless" mops and dusters are good. Deodorants and disinfectants do not take the place of ordinary cleanliness.
Dust does not carry living disease germs to an appreciable extent; the fact is now well established that diseases formerly thought to be transmitted by dust or even supposed to travel directly through the air, are carried on tiny particles of moisture and mucus expelled in coughing and sneezing. This mode of transmission is called droplet or spray infection; it is one of the most active agents in spreading certain kinds of communicable diseases.
Nevertheless dust in motion is harmful; it irritates the lining membranes of the nose, throat, bronchial tubes, and lungs, even causing tiny wounds through which disease germs enter. Thus tuberculosis is especially prevalent among stone cutters, felt workers, and others engaged in dusty trades. Metallic dust is especially harmful, because it is harder and sharper than dust from organic substances like wool and cotton. Furthermore, presence of dust indicates a low standard of cleanliness. People who tolerate it generally tolerate uncleanliness in other forms, more serious though less apparent.
Cleaning would not be so great a problem if most houses were not littered with such dust catchers as carpets, so-called ornaments, carved and upholstered furniture, banners, draperies, and a vast collection of articles that can only be classified as Christmas presents. In actual practice things that are difficult or expensive to clean seldom are cleaned; carpets for example are considered unhygienic, not because they cannot be cleaned, but because they are not. William Morris' advice to exclude from houses all articles not known to be useful or believed to be beautiful would, if followed, add years to the lives of housekeepers.
Garbage, has little bearing on health, exceptin so far as it affords a breeding place for flies. If it contains disease germs it may be dangerous, but statistics show that garbage handlers, although they can hardly be called especially careful, are not more subject to sickness than other men of their class. Garbage disposal is chiefly a question of preventing a public nuisance; it is a matter of cleanliness and public decency.
, has little bearing on health, exceptin so far as it affords a breeding place for flies. If it contains disease germs it may be dangerous, but statistics show that garbage handlers, although they can hardly be called especially careful, are not more subject to sickness than other men of their class. Garbage disposal is chiefly a question of preventing a public nuisance; it is a matter of cleanliness and public decency.
Insects.—Flies, cockroaches, and other scavenging insects may carry disease germs on their feet and thus infect food on which they walk. Typhoid, cholera, dysentery, and other diseases have been carried by flies. Flies are always a menace, and should not be tolerated; moreover, the thought of their coming to food directly from manure piles and privy vaults is disgusting. Houses should be thoroughly screened in the fly season, but it is better to destroy the nuisance at its source. The chief breeding places of fliesare garbage cans and manure piles. If the garbage can is water tight, closely covered, frequently emptied, and thoroughly cleaned, flies will not develop in it; about ten days must elapse from the time when the egg is laid until the insect is ready to fly. Fly traps to fit on the garbage can are useful. Manure should be screened and removed frequently, or it can be treated chemically. Methods for treating it are given in "Preventive Medicine and Hygiene."—Rosenau, p. 255, and in Bulletin No. 118, of the U. S. Dept. of Agriculture, July 14, 1914.
—Flies, cockroaches, and other scavenging insects may carry disease germs on their feet and thus infect food on which they walk. Typhoid, cholera, dysentery, and other diseases have been carried by flies. Flies are always a menace, and should not be tolerated; moreover, the thought of their coming to food directly from manure piles and privy vaults is disgusting. Houses should be thoroughly screened in the fly season, but it is better to destroy the nuisance at its source. The chief breeding places of fliesare garbage cans and manure piles. If the garbage can is water tight, closely covered, frequently emptied, and thoroughly cleaned, flies will not develop in it; about ten days must elapse from the time when the egg is laid until the insect is ready to fly. Fly traps to fit on the garbage can are useful. Manure should be screened and removed frequently, or it can be treated chemically. Methods for treating it are given in "Preventive Medicine and Hygiene."—Rosenau, p. 255, and in Bulletin No. 118, of the U. S. Dept. of Agriculture, July 14, 1914.