Chapter 23

"To cure was the voice of the Past: to prevent is the divine whispering of To-day."

As stated in the introduction to our study, the fundamental law of hygiene is the law of harmony: _Habits of living must harmonize with the plan of the body._ Having acquainted ourselves with the plan of the body, we may now review briefly those conditions that help or hinder its various activities. The hygiene already presented in connection with the study of the various organs may be condensed into general rules, or laws, as follows:

1. Of exercise: Exercise daily the important groups of muscles.

2. Of form: Preserve the natural form of the body.

3. Of energy: Observe regular periods of rest and exercise and avoid exhaustion.

4. Of nutriment: Eat moderately of a well-cooked and well-balanced diet and drink freely of pure water.

5. Of respiration: Breathe freely and deeply of pure air and spend a part of each day out of doors.

6. Of nervous poise: Suppress wasteful and useless forms of nervous activity, avoid nervous strain, and practice cheerfulness.

7. Of cleanliness: Keep the body and its immediate surroundings clean.

8. Of restraint: Abstain from the unnecessary use of drugs as well as from the practice of any form of activity known to be harmful to the body.

9. Of elimination: Observe all the conditions that favor the regular discharge of waste materials from the body.

Obedience to these laws is of vast importance in the proper management of the body. They should, indeed, be so thoroughly impressed upon the mind as to become fixed habits. There are, however, other conditions that relate to this problem, and it is to these that we now turn. These conditions have reference more specifically to

*The Prevention of Disease.*--While the average length of life is not far from thirty-five years, the length of time which the average individual is capable of living is, according to some of the lowest estimates, not less than seventy years. This difference is due to disease. People do not, as a rule, die on account of the wearing out of the body as seen in extreme old age, but on account of the various ills to which flesh is heir. It is true that many people meet death by accident and not a few are killed in wars, but these numbers are small in comparison with those that die of bodily disorders. The prevention of disease is the greatest of all human problems. Though the fighting of disease is left largely to the physician, much is to be gained through a more general knowledge of its causes and the methods of its prevention.

*Causes of Disease.*--Disease, which is some _derangement of the vital functions_, may be due to a variety of causes. Some of these causes, such as hereditary defects, are remote and beyond the control of the individual. Others are the result of negligence in the observance of well-recognized hygienic laws. Others still are of the nature of influences, such as climate, the house in which one lives, or one's method of gaining a livelihood, that produce changes in the body, imperceptible at the time, but, in the long run, laying the foundations of disease. And last, and most potent, are the minute living organisms, called microbes or germs, that find their way into the body. Although there are two general kinds of germs, known as _bacteria_ (one-celled plants) and _protozoa_ (one-celled animals), most of our germ diseases are caused by bacteria.

*Effects of Germs.*--While there are many kinds of germs that have no ill effect upon the body and others that are thought to aid it in its work, there are many well-known varieties that produce effects decidedly harmful. They gain an entrance through the lungs, food canal, or skin, and, living upon the fluids and tissues, multiply with great rapidity until they permeate the entire body. Not only do they destroy the protoplasm, but they form waste products, called _toxins_, which act as poisons. Diseases caused by germs are known as infectious, or contagious, diseases.(129) The list is a long one and includes smallpox, measles, diphtheria, scarlet fever, typhoid fever, tuberculosis, la grippe, malaria, yellow fever, and others of common occurrence. In addition to the diseases that are well pronounced, it is probable that germs are responsible also for certain bodily ailments of a milder character.(130)

*Avoidance of Germ Diseases.*--The problem of preventing diseases caused by germs is an exceedingly difficult one and no solution for all diseases has yet been found. One's chances of avoiding such diseases, however, may be greatly enhanced:

1. By strengthening the body through hygienic living so that it offers greater resistance to the invasions of germs.

2. By living as far as possible under conditions that are unfavorable to germ life.

3. By understanding the agencies through which disease germs are spread from person to person.

*Conditions Favorable and Unfavorable for Germs.*--Conditions favorable for germ life are supplied by animal and vegetable matter, moisture, and a moderate degree of warmth. Hence disease germs may be kept alive in damp cellars and places of filth. Even living rooms that are poorly lighted or ventilated may harbor them. Water may, if it contain a small per cent of organic matter, support such dangerous germs as those of typhoid fever. Fresh air, sunlight, dryness, cleanliness, and a high temperature, on the other hand, are destructive of germs. The germs in impure water, as already noted (page 165), are destroyed by boiling.

*How Germs are Spread.*--Some of the more common methods by which the germs of disease are spread, and by so doing find new victims, are as follows:

1. _By Means of Foods._--Foods, on account of the locality in which they are produced or the method of gathering or of handling-them, may become contaminated with germs, which are then transported with the foods to the consumer.

2. _By Means of Dust._--Material containing germs, _e.g._, discharges from the throat and lungs, will on drying form dust. This is lifted with other fine particles by the air and may be carried quite a distance. The dust from public halls and other places where people congregate is the kind most likely to contain disease germs. Dust should be breathed as little as possible and only through the nostrils. Where one is compelled, as in sweeping, to breathe dust-laden air for some time, he should inhale through a moistened sponge, or cloth, tied in front of the nostrils.

3. _By Means of Domestic Pets and Different Kinds of Household Vermin._--Germs sticking to the bodies of small animals are carried about and may be easily communicated to people. By this means, rats, mice, bedbugs, etc., where such exist, are frequently the means of spreading disease; and particularly dangerous, on this account, is the common house fly. Feeding as it does on filth of all kinds, it is easy for it to transfer the bacteria that may stick to its body to the food which is supplied to the table. The proper screening of houses and the destruction of material in which flies may develop, such as the refuse from stables, are necessary precautions.

Germs are spread also by the clothing of people, by railroad and steamship lines, by the mails, and by the natural elements. In fact, any kind of carrier, in or upon which germs can live, may serve as a means of spreading those of certain kinds.

*Public Sanitation.*--The general conditions under which germs may thrive and some of the means by which they are scattered, emphasize the practical value of measures which have for their purpose the making of one's surroundings more wholesome and hygienic. Such measures may be directed both toward one's immediate surroundings--the home--and toward the neighborhood, town, or city in which one lives. The hygienic conditions of primary importance in every city or town are as follows:

1. An adequate public supply of pure water.

2. An efficient system of underground pipes for the removal of sewage.

3. An efficient system for removing from the streets and alleys everything of the nature of waste.

4. Prevention, by enforcement of ordinances, of spitting upon sidewalks and the floors of public halls and conveyances.

5. A hospital or sanitarium in which people can be cared for when sick with infectious diseases.

In the larger cities other hygienic measures demand attention, such as provisions for parks and playgrounds, the proper housing of the poor of the city, and the suppression of the smoke and dust nuisances. Crowded together as people are in the cities, the welfare of each individual depends in a large measure upon the welfare of all. Hence the problems of public sanitation are matters in which all are vitally concerned.

*Sanitary Conditions of the Home.*--The home, being the feeding and resting place for the entire family, is the most important factor in one's physical, as well as moral, environment. For this reason there is no place where careful attention to hygienic requirements will yield better results. Much of the danger from germs may be prevented by instituting and maintaining proper sanitary conditions in and about the home.

One of the first requisites of the home is a suitable location for the house. The house should be built upon ground that is well drained, and if natural drainage be lacking, artificial drainage must be supplied. It should not be situated nearer than a quarter of a mile to any marsh or swamp and, if so near as that, it ought to be on the side from which the wind usually blows. A stone foundation should be provided, and at least eighteen inches of ventilated air space should be left between the ground and the floor. Ample provisions must be made for pure air and sunlight in all the rooms. The cellar, if one is desired, needs to be constructed with special care. It should be perfectly dry and provided with windows for light and ventilation. Adequate means must also be provided, by sewage pipes and other methods, for the disposal of all waste. Where drainage pipes are provided, care must be taken to prevent the entrance of sewer gas into the house and also the passage of material from these pipes into the water supply. The placing and connecting of sewer pipes should, of course, be under the direction of a plumber.

*The Water Supply.*--Since water readily takes up and holds the impurities with which it comes in contact, it should be exposed as little as possible in the process of collecting. Where cistern water is used, care must be taken to prevent filth from the roof (Fig. 168), water pipes, or soil from getting into the reservoir. Water should be collected from the roof only after it has rained long enough for the roof and pipes to have been thoroughly cleaned. The cistern should have no leaks (Fig. 169), and the top should be tightly closed to prevent the entrance of small animals and rubbish.

[Fig. 168]

Fig. 168--*Contamination of cistern water* by birds nesting in the gutter trough.

Shallow wells are to be condemned, as a rule, because of the likelihood of surface drainage (Fig. 169), and water from springs should, for the same reason, be used with caution. Deep wells that are kept clean usually may be relied on to furnish water free from organic impurities, but such water often holds in solution so much of mineral impurities as to render it unfit for drinking. The presence in water of any considerable quantity of the compounds of iron or calcium makes it objectionable for regular use.

[Fig. 169]

Fig. 169--*Sources of contamination of cistern and well water.* Illustration shows liability of contamination from surface drainage and from entrance of filth at top.

*Hygienic Housekeeping.*--However carefully a house has been constructed from a sanitary standpoint, the constant care of an intelligent housekeeper is required to keep it a healthful place in which to live. Daily cleaning and airing of all living rooms are necessary, while such places as the kitchen, the cellar, and the closets need extra thoughtfulness and, at times, hard work. Moreover, the problem is not all indoors. The immediate premises must be kept clean and sightly, and all decaying vegetable and animal matter should be removed. Home sanitation consists, not of one, but of many, problems, all more or less complex. None of these can be slighted or turned over to a novice.

*Destruction of Infectious Material.*--At times the housekeeping has to be directed especially toward hygienic requirements, such an occasion being the sickness of one of the inmates with some contagious disease. Unless special precautions are taken, the disease will spread to other members of the household and may reach people in the neighborhood. Not only must great care be exercised that nothing used in connection with the sick shall serve as a carrier of disease, but germs passing from the patient should, as far as possible, be actually destroyed. All discharges from the body likely to contain bacteria, should be burned or treated with disinfectants and buried deeply at a remote distance from the water supply to the house.

After recovery all clothing, bedding, and furniture used in connection with the sick should be disinfected or burned. The room also in which the sick was cared for should be thoroughly disinfected and cleaned; in some instances the woodwork ought to be repainted and the walls repapered or calcimined. The purpose is, of course, to destroy all germs and prevent, by this means, a recurrence of the disease.

*Fumigation.*--To destroy germs in the air or adhering to the walls of rooms, furniture, clothing, etc., fumigation is employed. This is accomplished by saturating the air of rooms with some vapor or gas which will destroy the germs. Fumigation is quite generally employed in the general cleaning after the patient leaves his room. This, to be effective, must be thorough. Formaldehyde is considered the best disinfectant for this purpose, and it should be evaporated with heat in the proportion of one half pint of the 40 per cent solution to 1000 cu. ft. of space. Since formaldehyde is inflammable and easily boils over, it has to be evaporated with care. It should be boiled in a tall vessel (a tin or copper vessel which holds about four times the quantity to be evaporated) over a quick fire, the room being tightly closed (openings around windows and doors plugged with cotton or cloth). After three or four hours the room may be opened and thoroughly aired. Since formaldehyde is most disagreeable to breathe, one should not attempt to occupy the room until it is free from the gas. This will require a day or more of thorough ventilation.

*Facts Relating to the Spread of Certain Diseases.*--The problem of preventing disease in general often resolves itself into the problem of preventing the spread of some particular disease. It is then of vital importance to know the special method by which the germs of this disease leave the body of the patient and are conveyed to the bodies of others. Some of these methods are novel in the extreme, and are not at all in accord with prevailing notions. Particularly is this true of that disease known as

*Malaria, or Malarial Fever.*--This disease, so common in warm climates and also prevalent to a large extent in the temperate zones, is due to animal germs (protozoa), which attack and destroy the red corpuscles of the blood. These germs, it is found, pass from malarial patients to others through the agency of a variety of mosquitoes known as _Anopheles_. In sucking the blood of a malarial patient, the mosquito first infects her own body.(131) In the body of the mosquito the germs undergo an essential stage of their development, after which they are injected beneath the skin of whomsoever the mosquito feeds upon. For the spreading of malaria, then, two conditions are necessary: first, there must be people who have the disease; and second, there must be in the neighborhood the special variety of mosquito that spreads the disease. If either condition be lacking, the disease is not spread. The malarial mosquito (_Anopheles_) may be distinguished from the harmless variety (_Culex_) by the position which it assumes in resting, as shown in Fig. 170.

[Fig. 170]

Fig. 170--*Mosquitoes* in resting position. (From Howard's _Mosquitoes_.) On left the malarial mosquito (_Anopheles_); on the right the harmless mosquito (_Culex_).

*Remedies against Mosquitoes.*--The natural method of preventing the spread of malaria is, of course, the destruction of mosquitoes. This is accomplished by draining pools of water where they are likely to breed, and by covering pools of water that cannot be drained with crude petroleum or kerosene. The kerosene, by destroying the larvae, prevents the development of the young. In communities where such measures have been diligently carried out, the mosquito pest has been practically eliminated. Other methods are also under investigation, such as the stocking of shallow bodies of water with varieties of fish that feed upon the mosquito larvae.

[Fig. 171]

Fig. 171--*Stegomyia*, the yellow-fever mosquito (after Howard).

*Yellow Fever.*--This scourge of the tropics is, like malaria, caused by animal germs. It is also propagated in the same manner as malaria, but by a different variety of mosquito (_Stegomyia_, Fig. 171). The stamping out of yellow fever in Havana, the Panama Canal Zone, and other places, through the destruction of this variety of mosquito, affords ample proof of the correctness of the "mosquito theory."

[Fig. 172]

Fig. 172--*Consumption germs* from the spit of one having the disease. Highly magnified and stained. (Huber's _Consumption and Civilization_.)

*Consumption*, or tuberculosis of the lungs, spoken of as the "white plague," was among the first diseases shown to be due to bacteria. Consumption is now recognized as an infectious disease, though not so readily communicated as some other diseases. Several methods are recognized by which the germs are passed from the sick to the well, the most important being as follows:

1. By personal contact of the sick with the well, especially in kissing.

2. By the sputum, or spit, which, if allowed to dry, is blown about as dust and breathed into the lungs(132) (Fig. 172).

3. By means of objects (drinking cups, tableware, etc.) that have been handled by consumptives.

4. By infectious material associated with houses or rooms in which consumptives have lived.

These methods of spreading consumption suggest the necessity for the greatest care, on the part of both the patient and those having him in charge.(133) The material coughed up from the lungs and throat should be collected on cloths or paper handkerchiefs and afterwards burned. The house where a consumptive has lived should be disinfected, repapered or calcimined, and thoroughly cleaned before it is again occupied. The inside woodwork should also be repainted. The approaches to the house where the patient may have expectorated should be disinfected and cleaned. Since the germs are able to live in the soil, fresh lime or wood ashes should be spread around the doorsteps and along the walks.

*Typhoid Fever*, one of our most dangerous diseases, is caused by germs (bacteria) that enter the body through the food canal. They attack certain glands in the walls of the small intestine, where they produce toxins that pass with the germs to all parts of the body. Typhoid fever germs spread from those having the disease to others, chiefly through the discharges from the bowels and the kidneys. The germs contained in these, if not destroyed by disinfectants, find their way into the soil, or into sewage, where they may be picked up by water and widely distributed. Finding suitable places, such as those containing decaying material, the germs may rapidly increase in number, and from these sources find their way into the bodies of new victims. They are likely, on account of manures, to get on vegetables; on account of uncleanly methods of milking, to get into the milk supply; and from sewerage outlets, to get into the oysters that grow in bays and harbors near seaboard cities; but they are most frequently introduced into the body through the drinking of impure water.

*Diphtheria*, also known as "membranous croup," is caused by germs that attack the membranes of the throat. This most dangerous of children's diseases is spread chiefly by discharges from the mouth and throat. These should be collected on cloths and burned, or rendered harmless with disinfectants. The disease may be spread also by objects brought into contact with the mouth, such as cups, toys, pencils, etc. Children are known to have diphtheria germs in the mouth for some time after recovering from the disease, and should, for this reason, be kept away from other children until pronounced safe by the physician.

The _antitoxin method_ of treating diphtheria has robbed this disease of much of its terror, yet it not infrequently happens that the physician is called too late to administer this remedy to the best advantage. Since certain cases of diphtheria are likely to be mistaken for croup, the parent frequently does not realize the serious condition of the child. A croupy cough _that lasts through the day_, or a sore throat which shows small white patches, are indications of diphtheria.

*Scarlet Fever, Measles, Chicken Pox, and Smallpox*, on account of the eruptions of the skin which attend them, are classed as eruptive diseases. As the eruptions heal, scales separate from the skin, and these are supposed to be the chief means of spreading the germs. Attention must be given to the destruction of these scales by burning or thoroughly disinfecting all objects, such as clothing, bedding, etc., that may serve as carriers of them. Those having eruptive diseases should be confined to their rooms as long as the scales continue to separate from the body.

*Vaccination.*--The method of preventing smallpox known as vaccination, which has been practiced since its discovery in 1796 by Jenner, has always proved effective. In some instances the sore arm causes considerable inconvenience, but this generally results from neglect to cleanse the arm thoroughly before applying the virus, or from contact of the sore with the clothing later. The virus should be applied by a physician and the wound should be protected after the operation. If discomfort is felt when it "takes," medical advice should be sought.

*Isolation*, or quarantining, is a most important method of combating contagious diseases. By removing the sick from the well many outbreaks of disease are quickly checked. Isolation of individual patients, and sometimes of infected neighborhoods, is absolutely necessary; and while this works a hardship to the few, it is frequently the only safeguard of the many. The community, on the other hand, should make ample provision for the care of the afflicted in the way of hospitals, or sanitaria, and if it is deemed necessary to remove people from their homes, they should not be subjected to unnecessary hardship.

Where one is sick from some contagious disease in the home and there is liability of communicating it to the other members of the family, _room isolation_ should be practiced. Infection cannot spread through solid walls, and where the doors, and the cracks around the doors, are kept completely closed and the usual precautions are observed by those attending the patient, the other inmates of the house can be protected from the disease.

*The Physician and His Work.*--In combating disease the services of the physician are a prime necessity. The special knowledge which he has at his command enables the conflict to be carried on according to scientific requirements and vastly increases the chances for recovery. He should be called early and his directions should be carefully followed. Everything, however, must not be left to the physician, for recovery depends as much upon proper nursing and feeding as upon the drugs that are administered. Of great importance is _the saving of the energy of the patient_, and to accomplish this visitors should, as a rule, be excluded from the sick room.

*Precautions in Recovery from Disease.*--Many diseases, if severe, not only leave the body in a weakened condition, but may, through the toxins which the germs deposit, cause untold harm if the patient leaves his bed or resumes his usual activities too soon. Especially is this true of typhoid fever,(134) diphtheria, scarlet fever, and measles. Rheumatism and affections of the heart, lungs, kidneys, and other bodily organs frequently follow these diseases, as the result of slight exposure or exertion before the body has sufficiently recovered from the effects of the toxins. To guard against such results, certain physicians require their patients to keep their beds for a week, or longer, after apparent recovery from diseases like typhoid fever, diphtheria, and scarlet fever.

*Relation of Vocation to Disease.*--With a few exceptions, the pursuit of one's vocation, or calling in life, does not supply either the quantity or the kind of activity that is most in harmony with the plan of the body. Especially is this true of work that requires most of the time to be spent indoors, or which exercises but a small portion of the body. The effect of such vocations, if not counteracted, is to weaken certain organs, thereby disturbing the functional equilibrium of the body--a result that may be brought about either by the overwork of particular organs or by lack of exercise of others. Herein lies the explanation of the observed fact that people of the same calling in life have similar diseases.

*A Special Problem for the Brain Worker.*--Farthest removed from those forms of activity which harmonize with the plan of the body, and which therefore are most hygienic, is that class of workers known as the professional class, or the "brain workers." This class includes not only the members of the learned professions--law, medicine, and the ministry--but a vast army of business men, engineers, teachers, stenographers, office clerks, etc., a class that is ever increasing as our civilization advances. It is this class in particular that must give attention to those conditions that indirectly, but profoundly, influence the bodily well-being and must seek to obviate if possible such weaknesses as the occupation induces.

*The Remedy* lies in two directions--that of spending sufficient time away from one's work to allow the body to recover its normal condition, and that of counteracting the effect of the work by special exercise or other means. In many cases the first symptoms of weakness indicate a suitable remedy. Thus exhaustion from overwork suggests rest and recreation. The diverting of too much blood from other parts of the body to the brain suggests some form of exercise which will equalize the circulation. If feebleness of the digestive organs is being induced, some natural method of increasing the blood supply to these organs is to be looked for. And effects arising from lack of fresh air and sunlight are counteracted by spending more time out of doors.

*Exercise as a Counteractive Agent.*--In counteracting tendencies to disease and in the maintenance of the functional equilibrium of the body, no agent has yet been discovered of greater importance than physical exercise, when applied systematically and persistently. This may consist of exercises that call into play all the muscles of the body, or which are concentrated upon special parts. When general tonic effects are desired, the exercise should be well distributed; but when counteractive or remedial effects are wanted, it must be applied chiefly to the parts that are weak or that have not been called into action by the regular work. Unfortunately, health is sometimes confused with physical strength and exercise is directed toward the stronger parts of the body with the effect of making them still stronger. Not only is health not to be measured by the pounds that one can lift or by some gymnastic feat that one can perform, but the possession of great muscular power may, if the heart and other vital organs be not proportionally strong, prove a menace to the health. This being true, one having his health primarily in view will use physical exercise, in part at least, as a means of building up organs that are weak. Since the body, like a chain, can be no stronger than its weakest part, this is clearly the logical method of fortifying it against disease.

*Value of Work.*--Although there may exist in one's vocation certain tendencies to disease, it must not be inferred that work in itself is detrimental to health. Health demands activity, and those forms of activity that provide a regular and systematic outlet for one's surplus energy and compel the formation of correct habits of eating, sleeping, and recreating best serve the purpose. Work furnishes activity of this kind and serves also as a safeguard against the unhealthful and immoral habits contracted so often from idleness. Even physical exercise which has for its purpose the reenforcement of the body against disease may frequently consist of useful work without diminishing its hygienic effects.

*The Mental Attitude.*--While a proper thoughtfulness and care for the body is both desirable and necessary, it is also true that over-anxiety about, or an unnatural attention to, the needs of the body reacts unfavorably upon the nervous system. Observance of the laws of health, therefore, should be natural and without special effort--a matter of habit. The attention should never be turned with anxiety upon any organ or process, but the mental attitude should at all times be that of _confidence in the power of the body organization to do its work_. Fear and morbidity, which are disturbing and paralyzing factors, should be supplanted by courage, cheerfulness, and hopefulness.

Let it be borne in mind that hygienic living requires nothing more than the application of the same intelligence and practical common sense to the care of the body that the skillful mechanic applies to an efficient, but delicate, machine. And, just as in the case of the machine, care of the body keeps its efficiency at the maximum and lengthens the period that it may be used. This end and aim of hygienic living is best attained by cultivating that attitude of mind toward the body that avoids interference in the vital processes and permits the natural appetites, sensations, and desires to indicate very largely the body's needs.

*Attitude toward Habit-forming Drugs.*--Among the different substances introduced into the body, either as foods or as medicines, are a number which have the effect of developing an artificial appetite or craving which leads to their continued use. Since the effect of such substances is usually harmful and since they tend to engraft themselves upon communities as social customs, they present a twofold relation to the general problem of keeping well. The individual may be injured through the personal use which he makes of them, or he may be injured through the effect which they have upon relatives or friends or upon society at large. Since our social environment is a factor in health little less important than our physical environment, the conditions that make for their continuance should be more generally understood.

*How Social Agencies perpetuate the Use of Habit-forming Drugs.*--When the use of some habit-forming drug has risen to the importance of a general custom, a number of conditions arise which tend to continue its use, even though the fact may be quite generally known that the substance does harm. In the first place, those who have formed the habit suffer inconvenience and distress when deprived of its use. In the second place, a number of people will have become interested in the production and sale of the substance, and these will lose financially if it is discontinued. In the third place, those of the rising generation will, from imitation or persuasion, be constantly acquiring the habit before they are sufficiently mature to decide what is best for them. Thus may the use of a substance most harmful, such as the opium of the Chinese, be indefinitely continued--a species of slavery from which the individual finds it hard to escape.

Such is human nature and such are the forces and influences of human society, that the freeing of a people from the bondage of some habit-forming drug cannot be accomplished without strenuous and persistent effort. Education, persuasion, the good example of abstainers, and legal restrictions must be pitted against the forces that make for its continuance. Such a struggle is now in progress in all civilized countries relative to the use of alcoholic beverages.(135)

*How the Use of Alcohol became a Social Custom.*--The general use of alcohol as a beverage may be accounted for by three facts. Alcohol is a habit-forming drug; it has a stimulating effect which many have found agreeable; and being a product of the fermentation of fruit juices and other liquids containing sugar, it is easily obtained. Through the operation of these causes the human family became habituated very early to the use of alcohol. The "wine" of primitive man, however, did little harm as compared with the alcoholic liquors of modern times. It was a weak solution and on account of the crude methods of manufacture and storage could only be produced in limited quantities. Perhaps the worst effect of its early use was the establishment of a general belief in its power to benefit, since this laid the foundation for excess in its use when the developments of a later period made it possible.

During the eleventh century the method of making alcoholic drinks from starch-producing substances, such as wheat, barley, and potatoes, became quite generally known, and also the method of concentrating them by distillation. This knowledge made possible the manufacture of alcoholic drinks in large quantities and in considerable variety. Alcoholic indulgence was now no longer the pastime of the few, but the privilege of all. Its evil effects followed as a matter of course; and as these became more and more apparent, there began the struggle to restrict the consumption of alcohol which has continued with varying success to the present time.

*Counts against Alcohol.*--The statements found in different parts of this book relative to the effects of alcohol upon the body may here be summarized as follows:--

1. Alcohol has an injurious effect upon the white corpuscles of the blood and lessens the power of the body to resist attacks of disease (pages 35, 98).

2. Alcohol injures the heart and the blood vessels (page 56).

3. Alcohol causes diseases of the liver and kidneys and interferes with the discharge of waste through these organs (pages 210, 212).

4. Alcohol interferes seriously with the regulation of the body temperature (page 271).

5. Alcohol is one of the worst enemies to the nervous system (pages 326, 332-334. 336, 337).

6. Through its effect upon the nervous system and through its interference with the production of bodily energy (page 195), alcohol greatly diminishes the efficiency of the individual.

7. The taking of alcohol in amounts that apparently do not harm the tissues is, nevertheless, liable to produce a habit which leads to its use in amounts that are decidedly harmful.

*Alcohol and the Social Environment.*--Our social environment includes the people with whom we are directly or indirectly associated. The presence in any community of those who are immoral, inefficient, or defective, places a burden upon those who are mentally and physically capable and renders them liable to results which are the outgrowth of weakness or viciousness. The fact that alcohol causes pauperism, crime, and general inefficiency, thereby rendering the social environment less conducive to what is best in life, is plainly evident. To realize how alcohol harms the individual through its effects upon society in general, one has only to take into account his dependence upon society for intellectual and moral stimuli, for industrial and economic opportunity, for protection, and for general conditions that make for health and happiness. As we strive to improve our physical environment, so should we also strive for the betterment of social conditions.

*Industrial Use of Alcohol.*--Interesting and instructive in this connection is the fact that alcohol is, after all, a substance capable of rendering great service to humanity. The injury which it causes is the result of its misuse. Though unfit for introduction into the human body, except in the most guarded manner, it is adapted to a great variety of uses outside of the body. A combustible substance which is readily convertible into a gas, it may be substituted for gasoline in the cooking of food, lighting of dwellings, and the running of machinery. As a solvent for gums, resins, essential oils, etc., it is used in the preparation of varnishes, extracts, perfumes, medicines, and numerous other substances of everyday use. Through its chemical interactions, it is used in the manufacture of ether, chloroform, explosives, collodion, celluloid, dyestuffs, and artificial silk. In fact, alcohol is stated by one authority to be, next to water, the most valuable liquid known.(136)

Opposed to an extensive use of alcohol for industrial purposes is the guard which the government must keep over its manufacture on account of its use in beverages. Though alcohol may be profitably manufactured and sold at thirty cents per gallon, the government revenue stamp of $2.08 per gallon practically prohibits its use for many purposes. A step toward a wider application to industrial purposes has been taken by the law permitting the sale of so-called "denatured"(137) alcohol without the tax for revenue. This law has proved beneficial to some extent, though the practical solution of the problem is still remote.

*Nicotine and Social Custom.*--The influences which brought about a general use of tobacco are similar to, though not identical with, those that engrafted alcohol upon society. The drug nicotine is a habit-forming substance and the plant producing it is easily cultivated.(138) Its immediate effect upon the user is generally agreeable, acting as a stimulant to some, but having a soothing effect upon the nerves of others. Moreover, a strong deterring factor in its use is lacking, since its harmful effects are not readily discernible and by many are avoided through moderation in its use.

As with alcohol, tobacco is conveniently used to promote sociability among men, a fact which has much to do with its very general use. If it could be limited to social purposes, it would likely do little harm, but the habit, once started, is continued without reference to sociability--a matter of selfish indulgence. In fact, one effect of tobacco is to cause the user to become less sensitive to the rights of others, this being evidenced by smokers who do not hesitate to make rooms and public halls almost unbearable to those unaccustomed to tobacco.

*Counts against Nicotine.*--The physiological objections to the use of tobacco, as already stated (pages 56, 92, 326, 333, 336), are the following:--

1. The use of tobacco before one reaches maturity stunts the growth. The boy who uses it cannot develop into so strong and capable a man as he would by leaving it alone.

2. Tobacco injures the heart.

3. Tobacco injures the air passages, especially when inhalation is practiced.

4. Tobacco injures the nervous system and by this means interferes in a general way with the bodily processes. For the same reason it interferes with mental and moral development, the cigarette being a chief cause of criminal tendencies in boys.

5. In some cases tobacco injures the vision.

6. The tobacco habit is expensive and is productive of no good results.

*Tobacco and the Rising Generation.*--The problem of limiting the use of tobacco to the point where it would do slight harm, in comparison to what it now does, would be solved if those under twenty years of age could be kept from using it. But few would then acquire the habit, and those who did would not be so seriously injured. In our own country it lies within the province of the home and the school to bring about this result. The fact that parents use tobacco is no reason why the boys should also indulge. The decided difference in effects upon the young and upon the mature makes this point very clear. Laws protecting boys from the evil effects of tobacco, not only cigarettes, but other forms as well, are both just and necessary.

*Social Custom and the Caffeine Habit.*--By suitable processes a white, crystalline solid, easily soluble in water, can be separated from the leaves of tea, and from the berry of the coffee plant. This is the drug caffeine, the substance which gives to tea and coffee their stimulating properties, but not their agreeable flavors. Less injurious, on the whole, than either alcohol or tobacco, caffeine has come into general use in much the same way as these substances. In a sense, however, caffeine is more deceptive than either alcohol or nicotine, because the usual mode of preparing tea and coffee gives them the appearance of real foods. The housewife who would feel condemned in purchasing caffeine put up as a drug somehow feels justified when she extracts it from plant products in the regular preparation of the meal.

*Counts against Caffeine.*--People of vigorous constitutions and of active outdoor habits are injured but slightly, if at all, by either tea or coffee when these are used in moderation. As already stated (pages 56, 167, 326, 329), they do harm when used to excess and, in special cases, in very small amounts, in one of the following ways:--

1. By stimulating the nervous system, thereby causing nervousness and insomnia and interfering with vital organs.

2. By introducing a waste which forms uric acid into the body, thereby throwing an extra burden upon the organs of elimination.

In this connection it may also be stated that there appears to be little, if any, real advantage to the healthy body from the use of either tea or coffee, beyond that of temporary stimulation and the gratification of an appetite artificially acquired. Hence the large sums of money expended for these substances in this country yield no adequate returns.

*Caffeine Restrictions Necessary.*--Though with many the cup of tea or coffee at breakfast does no harm, but gives an added pleasure to the meal, there is no question but that the use of caffeine beverages should be greatly curtailed. Children should not be permitted to drink either tea or coffee. Brain workers and indoor dwellers generally should use these substances very sparingly, and people having a tendency to indigestion, nervousness, constipation, rheumatism, or diseases of the heart, kidneys, or liver frequently find it best to omit them altogether.

*Caffeine and "Soft" Drinks.*--Recently the practice has sprung up of using caffeine as a constituent of certain drinks supplied at the soda-water fountains. Such drinks usually purport to be made from the kola nut, which contains caffeine, or to consist of extracts from the plants which yield cocoa and chocolate, when in reality they consist of artificial mixtures to which caffeine has been added. Those using these beverages are stimulated as they would be by tea or coffee and soon acquire the habit which makes them regular customers. Chief harm comes to the children who frequent the soda fountains and to those who, on account of constitutional tendencies, should avoid caffeine in all of its forms. It is generally understood that the so-called "soft" drinks are harmless. If this reputation is to be maintained, those containing caffeine must be excluded.

*Danger from Certain Medicinal Agents.*--Among the most valuable drugs used by the physician in the treatment of disease are several, such as morphine, chloral, and cocaine, which possess the habit-forming characteristic. Sad indeed are the cases in which some pernicious drug habit has been formed through the reckless administration of such medicines. Even the taking of such a drug as quinine as a "tonic" tends to develop a dependence upon stimulation which is equivalent to a habit. In the same list come also the drugs that are taken to relieve a frequently recurring indisposition, such as headache. The so-called headache powders are most harmful in their effects upon the nervous system and should be carefully avoided.(139)

*Stimulants in Health Unnecessary.*--Stimulants have been aptly styled "the whips of the nervous system." The healthy nervous system, however, like the well-disposed and well-fed horse, needs no whip, but is irritated and harmed through its use. Even in periods of weakness and depression, stimulants are usually not called for, but a more perfect provision for hygienic needs. Rest, relaxation, sleep, proper food, and avoidance of irritation, not stimulants, are the great restorers of the nervous system. A surplus of nervous energy gained through natural means is more conducive to health and effective work than any result that can possibly be secured through drugs. Then withal comes the satisfaction of knowing that one has the expression of his real self in the way in which he feels and in what he accomplishes--not a "whipped-up" condition that must be paid for by weakness or suffering later on.

*Summary.*--To solve the problem of keeping well, one must live the life which is in closest harmony with the plan of the body. Such a life, because of differences in physical organization, as well as differences in environment and occupation, cannot be the same for all. All, however, may observe the conditions under which the body can be used without injuring it and the special hygienic laws relative to the care of different organs. Causes of disease, whether they be in one's environment, vocation, in his use of foods or drugs, or in his mode of recreation, must either be avoided or counteracted.

While the problem is beset with such difficulties as lack of sufficient knowledge, inherited weakness, and time and opportunity for doing what is known to be best for the body, yet study and work that have for their aim the preservation or improvement of the health are always worth while. _Health is its own reward._ The expression of the poet,

"Each morn to feel a fresh delight to wake to life, To rise with bounding pulse to meet whate'er of work, of care, of strife, day brings to me,"

suggests the _joy_ of being well. But the ultimate realization of one's aims and ambitions in life and the actual prolongation of one's period of usefulness are _higher and more enduring rewards_.

*Exercises.*--1. Summarize the different laws of hygiene. Upon what one fundamental law are these based?

2. State the important differences between a condition of health and one of disease.

3. In what general ways may disease originate in the body?

4. Describe a model sanitary home. With what special hygienic problems has the housekeeper to deal?

5. Describe a method of collecting a wholesome supply of cistern water. State possible objections to well and spring water.

6. What means may be employed in preventing the spread of contagious diseases?

7. By what means are malaria, typhoid fever, diphtheria, and tuberculosis spread from one individual to another?

8. Why are extra precautions necessary in the recovery from certain diseases, as typhoid fever, diphtheria, and scarlet fever?

9. How may one's vocation become a cause of disease? What conditions in the life of a student may, if uncounteracted, lead to poor health?

10. Of what special value are the parks and pleasure grounds in a city to the health of its inhabitants?

11. Discuss the hygienic value of work.

12. What conditions lead to the continuance of habit-forming substances after their use has become general?

13. How is it possible for one not using alcohol to be injured by this substance?

14. Discuss the effect of alcoholic abuse upon social environment.

15. Summarize the rewards of hygienic living.

SUMMARY OF PART II

For the maintenance of life the needs of the cells must be supplied and _the body as a whole must be brought into proper relations with its surroundings_. The last-named condition requires that the body be moved from place to place; that its parts be controlled and cooerdinated; and that it be adjusted in its various activities to external physical conditions. To accomplish these results there are employed:

1. The skeleton, or bony framework, which preserves the form of the body and supplies a number of mechanical devices, or machines, for causing a variety of special movements.

2. The muscular system, which supplies the energy necessary for executing the movements of the body.

3. The nervous system, which (_a_) controls and cooerdinates the various activities and (_b_) provides for the _intelligent_ adjustment of the body to its environment. (Review Summary of Part I, page 215, and consult Fig. 92, page 214.)

APPENDIX

*Equipment.*--Nearly all of the apparatus and materials called for in this book may be found in the physical, chemical, and biological laboratories of the average high school. There should be ready, however, for frequent and convenient use, the following: One or more compound microscopes with two-thirds and one-fifth inch objectives; a set of prepared and mounted slides of the various tissues of the body; a set of dissecting instruments, including bone forceps; a mounted human skeleton and a manikin or a set of physiological charts; a set of simple chemical apparatus including bottles, flasks, test tubes, and evaporating dishes; and a Bunsen burner or some other means of supplying heat.

The few chemicals required may be obtained from a drug store or from the chemical laboratory. Access to a work bench having a set of carpenter's tools will enable one to prepare many simple pieces of apparatus as they are needed.

*Physiological Charts* are easily prepared by teachers or pupils by carefully enlarging the more important illustrations found in text-books or by working out original sketches and diagrams. These, if drawn on heavy Manila paper, may be hung on the wall as needed and preserved indefinitely. By the use of colors, necessary contrasts are drawn and emphasis placed on parts as desired. The author has for a number of years used such home-made charts in his teaching and has found them quite satisfactory. His plan has been to draw on heavy Manila paper, cut in sizes of two by three feet, the general outline in pencil and then to mark over this with the desired colors. There is of course an opportunity for producing results that are artistic as well as practical, and if one has time and artistic skill, better results can be obtained. Many of the cuts in this book are excellently suited to enlargement and, if properly executed, will provide a good set for general class purposes.

*Models.*--The use of prepared models of the different bodily organs is strongly urged. These may be so used in elementary courses as to obviate much of the dissections upon lower animals. Although the actual tissues cannot be so well portrayed, the general form and construction of organs are much better shown. Models well adapted to class or laboratory work are easily obtained through supply houses. Illustrations of several of these are shown in connection with the "Practical Work."

INDEX

Abdomen; dissection of, 169.

Abdominal cavity, 7, 138, 152.

Absorption, 173-186. Defined, 18, 173.

Accommodation, 379. To illustrate, 391.

Acid reactions, 171.

Acquired reflexes, 314.

Adipose tissue, 5, 178.

Afferent neurons, 296.

Air, 76. Changes it undergoes in lungs, 101. Complemental, 89, 103. Reserve, 89, 103. Residual, 89, 103. Tidal, 88, 103.

Air passages, 80.

Albuminoids, 119. Purpose served by, 121.

Alcohol, A cause of crime, 333. Effects on circulation, 55, 56. Effects on digestion, 167. Effects on energy supply, 195. Effects on respiratory organs, 98. Effects on social environment, 413. Effect on temperature regulation, 271. Effects on waste elimination, 212. General considerations, 412-415.

Alimentary canal, coats of, 138.

Alimentary muscles, work of, 159.

Alkaline reactions, 171.

Alveoli, 82.

Amylopsin, 155, 156.

Anatomy, defined, 1.

Animal heat, 192.

Anopheles, 401.

Antiseptic ointment, 275.

Antitoxin, 405.

Appetite, natural, 163.

Aqueous humor, 377.

Arachnoid, 299.

Arteries, 47. Bronchial, 84. Functions of, 51. Pulmonary, 84. Renal, 202. To illustrate elasticity of, 62. Why elastic, 48.

Articulations, 230-232. Kinds of, 230.

Assimilation, 18, 182.

Astigmatism, 384.

Atlas, 223.

Atoms, defined, 105.

Attraction sphere, 15.

Auditory canal, 358.

Auricles, 42.

Axis, 223.

Axis cylinder, 284.

Axon, 283. Form and length of, 284. Function of, 306. Structure of, 284.

Bacteria, 394.

Ball-and-socket joint, 231.

Basement membrane, 197.

Basilar membrane, 363.

Bathing, 272, 274.

Biceps muscle, action of, 263.

Bicuspids, 143.

Bile, 154, 155.

Binocular vision, 381.

Blind spot, 377. To prove presence of, 390.

Blood, 24-39. Changes in, 34. Checking flow from wounds, 58. Coagulation of, 31. Experiments with, 37-39. Flow of, how regulated, 50. Functions of, 33. Hygiene of, 34-36. Physical properties of, 24. Quantity of, 33. Supply to lungs, 82. Velocity of, 54. Where found, 24.

Blood platelets, 25.

Blood pressure, 52, 70.

Blood pressure and velocity, 52.

Blood vessels, to strengthen, 57.

Body, organization of, 19.

Bone groups, 223-229.

Bones, 216-242. Adaptation of, 228. Composition, 217. Gross structure of, 218. Minute structure of, 219. Observation on gross structure, 241. Properties of, 217. Table of, 229. To show composition of, 241. To show minute structure of, 242.

Bowels, rules for care of, 166.

Brachial plexus, 302.

Brain, 280, 288-291. Disturbed circulation, 327. Protection of, 299.

Brain workers, 408.

Breathing, _see_ Respiration. Causes of shallow, 92. Illustrated, 87. To prevent shallow, 92.

Breathing exercises, 93.

Bronchus, 80.

Bulb, 291.

Caecum, 151, 158.

Calcium carbonate, 122.

Calcium phosphate, 122.

Calorie, defined, 126.

Cane sugar, 120.

Canines, 143.

Capillaries, 50, 64, 249. Blood pressure at, 70. Functions of, 51. Work of, 174.

Carbohydrates, 119, 125. Purpose served by, 121. Storage of, 177. Tests for, 135.

Carbon, 134.

Carbon dioxide, Final disposition of, 111. Preparation, 115. Pressure, 110. Properties, 110, 115.

Cardiac cycle, 46.

Cardiac orifice, 147.

Carpals, 227.

Carpus, 228.

Cell body, 283. Functions of, 305.

Cell-division, 16.

Cell nucleus, 14.

Cell reproduction, 16.

Cell structure, 14.

Cell surroundings, 17.

Cell wall, 15.

Cells, 13-23. Bone, how nourished, 220. Ciliated epithelial, 81. Food supply to, 180. General work of, 17. Importance of, 15. Passage of materials to, 183. Relation to nutrient fluid, 20. Specialized, 197. Special work of, 18. Striated muscle, 244.

Cerebellum, 290. Functions of, 317.

Cerebral functions, localization of, 318.

Cerebral hemispheres, 289.

Cerebral peduncles, 290.

Cerebrum, 288. Functions of, 317.

Chlorine, 135.

Cholesterine, 155.

Chordae tendineae, 43.

Choroid coat, 375.

Chyme, 150.

Cigarettes, 333.

Cilia, 81. To observe, 101.

Ciliary muscle, 375.

Ciliary processes, 375.

Circulation of blood, 40-64. Causes of, 54. Discovery of, by Harvey, 40. Divisions of, 51, 52. Effects of exercise upon, 63. Effects of gravity upon, 64. In a frog's foot, 64. Organs of, 40-54. Routes to, 174.

Coagulation, Causes of, 31. Purpose of, 32. Time required for, 33.

Cochlea, 362.

Coffee, Effects on complexion, 274. Effects on digestion, 167. Effects on heart, 56.

Colds, 193. Serious nature of, 94. To cure, 94.

Colon, parts of, 158.

Complexion, care of, 273.

Compound, defined, 104.

Conduction pathways, 286.

Conductivity, 304.

Condyloid joint, 232.

Conjunctiva, 373.

Consumption, _see_ Tuberculosis.

Control of arteries, 319.

Convolutions, 289.

Cooerdination, defined, 279.

Cornea, 375.

Corpora quadrigemina, 290.

Corpora striata, 289.

Corpus callosum, 289, 293.

Cortex, 288, 294.

Coughing, 81.

Cranial cavity, 7, 225.

Cranial nerves, 296.

Crura cerebri, 290.

Crystalline lens, 380.

Culex, 402.

Cytoplasm, 15.

Defects in focusing, 383.

Deformities of skeleton, 233-236. Correction of, 236. Prevention of, 235.

Deglutition, 145. Steps in, 146.

Dendrites, 283, 306.

Dentine, 143.

Dermis, 264.

Dextrose, 30, 120, 150.

Diaphragm, 88. To illustrate action of, 102.

Diastole, 46.

Diaxonic neuron, 283.

Diet, one-sided, 124.

Diffusion, 371.

Digestion, 130-172. Hygiene of, 160. Nature of, 130. Not a simple process, 131. Of fat, 156. Purpose of, 177. Stomach, 148.

Digestive fluids, 132.

Digestive organs, 160. Table of, 138.

Digestive processes, 130, 141. Illustrated, 137.

Diphtheria, 94, 405. Care after, 211.

Disaccharides, 120.

Disease, 392-412. Causes of, 393. Eruptive, 405. Precautions in recovery from, 407. Prevention of, 393.

Dislocations, 239.

Dorsal-root ganglia, 295.

Drill, "setting up," 237.

Drugs, effects of, 35, 55, 129, 332.

Duodenum, 151.

Dura, 299.

Ear, 358. Hygiene of, 365. To demonstrate, 369.

Ear drum, 359.

Efferent neurons, 296.

Element, defined, 104.

Elevators of the ribs, 87.

Emetics, 151.

Emotional states, effects of, 330.

End bulbs, 342.

Endocardium, 42.

Endolymph, 361.

End-plate, 244.

End-to-end connections, 286.

Energy, 107, 186-196. Bodily control of, 192. From sun to cells, 191. How plants store sun's, 189. Increasing one's bodily, 194. In food and oxygen, 190. Kinds of, 186. Methods of storing, 187, 188. Transformation of, in muscle, 248, 249.

Enzymes, 132, 155. Of the tissues, 184.

Epidermis, 264, 266.

Epiglottis, 80, 354.

Epithelium, 139.

Eruptive diseases, 405.

Esophagus, 146.

Eustachian tube, 359.

Excessive reading, 331.

Excitant impulse, 305.

Excretion, 197-213. Defined, 18. Necessity for, 201.

Exercise, 256, 257, 328, 409. General rules for, 259. Results of, 257.

Exhaustion, nervous, 211. Results of, 195.

External ear, 358.

External stimuli, action of, 307.

Eye, 370-391.

Eyeball, 373. Chambers of, 377. Focusing power of, 378. Movements of, 381.

Eyelids, 373.

Eyes, Care of, 386. Removal of foreign bodies from, 387, Strong chemicals in, 388.

Eye strain, 211. And disease, 385.

Fat, 30, 149, 162. Digestion of, 156. Emulsification of, 157. Purpose served by, 121. Route taken by, 175. Tests for, 137. Where stored, 178.

Fatty acid, 156.

Fenestra ovalis, 361.

Fenestra rotunda, 363.

Ferments, _see_ Enzymes.

Fibrin, 31.

Fibrin ferment, 32.

Fibrinogen, 30, 31.

Fissures, 289.

Food, 117-137. Advantages of coarse, 167. Classes of, 118, 119. Composition of, 124. Dangers from impure, 165. Defined, 117. Elements supplied by, 134. Excess of proteid, 208. Frequency of taking, 165. Materials, table of, 126, 126. Nitrogenous, 119. Order of taking, 161. Preparation of, 164. Purity of, 128. Quantity of, 164. Simple, 118. Variety, 128. With reference to digestive changes, 132.

Foot lever, diagram of, 253.

Foot-pound, 196.

Foot-wear, hygienic, 238.

Fractures, treatment of, 239.

Fumigation, 400.

Furniture, school, 236.

Gall bladder, 154.

Ganglia, 281. Dorsal-root, 295. Sympathetic, 298.

Gastric glands, 147.

Gastric juice, to illustrate action of, 172.

Gelatine, 218.

Germ diseases, avoidance of, 394.

Germs, 29, 394, 395. How spread, 395.

Glands, 197-213. Digestive, 140. Ductless, 208. Excretory, work of, 201. Gastric, 147. Kinds of, 197, 198. Lymphatic, 68, 208. Perspiratory, 206. Salivary, 144. Structure of, 197. Thymus, 208. Thyroid, 208.

Gliding joint, 232.

Glottis, 355.

Glycogen, 120, 177.

Grape sugar, tests for, 120, 136.

Gross anatomy, defined, 1.

Gullet, 146.

Gustatory pore, 345.

Gustatory stimulus, 345.

Habits, 315, 334.

Hair, 267. Care of, 276.

Hair cells, 363.

Hair follicle, 267.

Haversian canals, 219.

Hearing, defective, 366.

Heart, 41. Care of, 55. Connection with arteries and veins, 45. Difference in parts of, 44. How it does its work, 45. Observations on, 60, 61, 62. Sounds of the, 47. Valves of, 43.

Heart muscle, structure of, 247.

Heat and cold, effects of, 330.

Hemoglobin, 26.

Hepatic artery, 154.

Hepatic veins, 154.

Hindbrain, 290.

Hinge joint, 231.

Histology, defined, 1.

Humerus, 227.

Hyaloid membrane, 378.

Hydrochloric acid, 149, 150.

Hydrogen, 134.

Hygiene, Defined, 2. General aim of, 2. General laws of, 2, 392. Of digestion, 160. Of skeleton, 238. Relation of physiology and anatomy to, 3.

Hygienic housekeeping, 399.

Hypoglossal nerves, 298.

Ileo-caecal valve, 151.

Ileum, 151.

Images, Diagram illustrating, 372. Formation of, 371.

Incisors, 143.

Incus, 359.

Infectious diseases, 394.

Infundibula, 80, 84.

Inhibitory impulse, 305.

Insomnia, 329.

Inspiratory force, 70.

Intercellular material, production of, 13, 18.

Internal ear, 360.

Intestinal juice, 152, 157.

Iris, 375.

Iron, 135.

Irritability, 6, 243, 304.

Isolation, 406.

Jejunum, 151.

Joints, 230-232, 242.

Kidneys, 201. Blood supply to, 204. Cortex of, 204. Inflammation of, 211. Pelvis of, 202. Structure, 202. Symptoms of diseased, 211. Work of, 205.

Knee jerk reflex, 322.

Lachrymal glands, 383.

Lacteals, work of, 174.

Lacunae, 220.

Laminae, 220.

Large intestine, 157. Division of, 158. Work of, 159.

Larynx, 80, 353-357. To show plan of, 368.

Lever, 251. Application to the body, 251. Classes of, in body, 251. Producing motion, diagram of, 252. To show action of, 252.

Leucocytes, 27.

Levulose, 120, 150.

Life, maintenance of, 20.

Light, 370, 371. Simple properties, illustrated, 389.

Light waves, diagram illustrating passage of, 370.

Lime water, to prepare, 101.

Liver, 52, 152-155, 178. Protection of, 210. Work of, 206.

Lockjaw, 276.

Longsightedness, 384.

Lung capacity, diagram illustrating, 89.

Lung diseases, out-door cure for, 98.

Lungs, 77-103. Capacity of, 88. Changes air undergoes in, 101. Excretory work of, 207. Interchange of gases in, 88. Observations of, 100. Supply of blood to, 82. To estimate capacity of, 103. Weakest portions of, 92.

Lymph, 65-75. Composition, 66. Movements at the cells, 71. Origin of, 65. Physical properties, 66. Where it enters the blood, 70.

Lymph movements, causes of, 69.

Lymph spaces, 66.

Lymph vessels, 66. Variable pressure on the walls of, 70.

Magnesium, 135.

Malarial fever, 401.

Malleus, 359.

Malpighian capsules, 203.

Maltose, 120.

Massage, 259.

Mastication, Muscles of, 144. Slow, 145. Thorough, 160. To show importance of, 171.

Matrix, 267.

Measles, 94. Care after, 211.

Median fissures, 289.

Medulla oblongata, 291.

Medullary sheath, 284.

Membrana tympani, 358.

Membrane, Active, 173. Basement, 197. Basilar, 363.

Membranous capsule, 377.

Membranous labyrinth, 361.

Mesentery, 152.

Metacarpals, 227.

Midbrain, 289.

Middle ear, 359. Purposes of, 360.

Milk sugar, 120.

Mineral salts, 30. Uses, 121.

Moderate drinkers, 333.

Molars, 143.

Molecules, defined, 105.

Mon-axonic neuron, diagram of, 282.

Mono-saccharides, 120.

Mosquitoes, 401-403. Remedies against, 402.

Mouth, 141.

Movable joints, Kinds of, 231. Structure of, 230.

Mucous membrane, 80, 264.

Mucus, 139.

Muscle organ, 245.

Muscles, 243-263. Alimentary, 189. Important, 254-256. Intercostal, 87. Of mastication, 144. Properties of, 243.

Muscular force, plan of using, 249.

Muscular sensations, 344.

Muscular stimulus, 248.

Muscular stimulus and contraction, to illustrate, 261.

Muscular tissue, kinds of, 243, 244.

Nails, 267. Care of, 276.

Nasal duct, 383.

Neck exercise, 328.

Nerve cells, 281, 282.

Nerve fibers, 282, 293, 294.

Nerve path, diagram of, 286.

Nerve pathways, to demonstrate, 322.

Nerves, 281.

Nerve skeleton, 280. Diagram of, 281.

Nerve stimuli, 306.

Nerve trunks, 281.

Nervous activity, wasteful forms of, 325.

Nervous control of, Body temperature, 320. Circulation of blood, 318. Respiration, 320.

Nervous energy, economizing of, 315.

Nervous impulse, 248, 305.

Nervousness, 326.

Nervous system, 279-337. Diagram of, 287. Dissection of, 302. Divisions of, 287. Hygiene of, 324-337. Nature of, 287. Physiology of, 304-323. Work of, 280.

Neural arch, 224.

Neurilemma, 284.

Neurons, 281, 282. Arrangement of, 284, 293. Diagram, illustrating, 285. Properties of, 304.

Nicotine, Effects of, 333. Relation of age to effects, 333.

Nitrogen, 134.

Non-striated cells, to show, 261.

Non-striated muscles, Purpose of, 246. Structure of, 246. Work of, 247.

Normal temperature, 269.

Nosebleed, 58.

Nucleoplasm, 14.

Nutrients (_see_ Foods), Composition of, 135. Relative quantity needed, 123. Routes taken by, 175. Tests for, 136.

Nutriment, storage of, 177-180.

Olfactory stimulus, 347.

Opsonins, 34.

Optic thalami, 289.

Orbit, 373.

Organ, defined, 7.

Organism, defined, 19.

Organization, defined, 10.

Osmosis, 72. At the cells, 72. To illustrate, 75.

Ossein, 218.

Overstudy, 211.

Oxidation, defined, 106.

Oxygen, 104-117. Combined, 105, 113. Free, 105, 113. How it unites, 105. Main uses of, 108. Movement a necessity, 106, 108, 115. Movement in body, 106, 108, 115. Nature of, 104. Passage of, from cells, 110. Passage of, through blood, 109. Passage of, toward cells, 109. Preparation of, 113. Pressure, 109. Properties of, 113. Purpose of, in the body, 106.

Oxyhemoglobin, 27.

Pacinian corpuscles, 342, 343. To demonstrate, 348.

Pancreas, 155.

Pancreatic juice, 155.

Papillae, 266.

Patent medicines, 166.

Pelvic girdle, 226.

Pepsin, 149.

Peptones, 149, 176.

Pericardium, 41.

Perilymph, 361.

Perimysium, 245.

Periosteum, 218.

Peritoneum, 180.

Perspiration, 207.

Pharynx, 145. Openings into, 145, 146.

Phosphorus, 135.

Phrenic nerve, 302.

Physiological salt solution, 38.

Physiology, defined, 2.

Pia, 299.

Pigment granules, 266.

Pinna, 358.

Pitch, detection of, 365.

Pivot joint, 232.

Plasma, 25, 29.

Pleura, 84.

Plexus, 281.

Pneumonia, 94.

Pons, 290.

Pons Varolii, 290.

Portal vein, 154.

Primitive sheath, 284.

Proteids, 161. Circulating, 179. Kinds of, 118. Purposes of, 119. Supplied by, 125. Tests for, 135, 136. Tissue, 179.

Proteoses, 149, 176.

Protoplasm, 14.

Protozoa, 394.

Ptyalin, 145.

Public sanitation, 396.

Pulp cavity, 143.

Pupil, 375.

Pure food law, 128.

Pus, 28, 29.

Pyloric orifice, 147.

Pyramids, 202.

Quarantine, 406.

Radius, 227.

Reaction time, to determine, 323.

Reading glasses, 386.

Receptacle of the chyle, 68, 170.

Rectum, 158.

Red corpuscles, 25. Disappearance of, 27. Function of, 26. Origin of, 27. To examine, 38. To prepare models of, 39.

Red marrow, 219.

Reenforcement of sound, 352, 356, 368.

Reflection, kinds of, 371.

Reflex action, 308. Diagram illustrating, 310. In circulation of blood, 311. In digestion, 310. Purposes of, 311.

Reflex action and mind, 308.

Reflex action pathway, 309.

Refraction, 371.

Rennin, 149.

Respiration, 76-103. Artificial, 97. Internal, 89. Lung, 76.

Retina, 376.

Retinitis, 333.

Rheumatism, Effects on the heart, 56. Sequel to other diseases, 407.

Right lymphatic duct, 67.

Rods and cones, 377.

Rods of Corti, 364.

Sacrum, 224.

Saliva, 145. Composition of, 145. Uses of, 145. To show action on starch, 171.

Salivary glands, 144. Kinds of, 144. Reflex action of, 323.

Sanitation, defined, 2.

Sarcolemma, 244.

Sarcoplasm, 244.

Scala media, 363.

Scala tympani, 363.

Scala vestibula, 363.

Scarlet fever, care after, 211.

Sciatic nerve, 302.

Sclerotic coat, 374.

Secondary reflex action, 314.

Secretions, 197. Kinds of, 200.

Secretory process, nature of, 199.

Seeing, problem of, 372.

Self-control, 326, 334. Habit of, 325.

Semicircular canals, 362.

Semilunar valves, 44.

Sensations, 338-349. Classes of, 339. Production of, 338, 349. Purposes of, 340. Special, 340.

Sensations (_continued_). Steps in production of, 341.

Sensation stimuli, 339.

Sense organs, simple forms of, 341, 342

Serous coat, 140, 148.

Serous membrane, 264.

Serum albumin, 30.

Serum globulin, 30.

Shortsightedness, 384.

Shoulder girdle, 226.

Sight, organs of, 373.

Sigmoid flexure, 158.

Simple life, 410.

Skeleton, 216-243. How deformed, 234. Hygiene of, 233. Plan of, 221. Purpose of, 221.

Skin, 264-277. As regulator of temperature, 270. Experiments on, 349. Functions of, 267, 268. Observations on skin, 278.

Skin wounds, treatment of, 275.

Skull, 225.

Sleep, 329.

Small intestine, 151. Mucous membrane of, 151. Muscular coat of, 152. As organ of absorption, 173. Parts of, 151. Serous coat of, 152. Work of, 157.

Smell, Sensation of, 346. Value of, 347.

Sneezing, 81.

Sodium, 135.

Sodium carbonate, 155.

Sodium chloride, 122.

Soft palate, 141.

Solution, 131. Kinds of, 73.

Solution theory, 156.

Solvents, 131.

Sound, To illustrate origin of, 367. To show transmission of, 367.

Sound waves, As stimuli, 331. Nature of, 350. Reenforcement of, 352. To show effects of, 368. Value of, 353.

Speech, production of, 357.

Spinal column, 223-225. Hygiene of, 233.

Spinal cord, 280. Protection of, 299.

Spinal nerves, 295. Double nature of, 295.

Spitting, 403.

Spleen, 208.

Sprains, 239, 240.

Stapes, 359.

Starch, 162. Action of, on saliva, 171. Animal, 120. Tests for, 136.

Steapsin, 155, 156.

Stegomyia, 403.

Sternum, 225.

Stomach, 147. Mucous membrane of, 147. Muscular action of, 150. Muscular coat, 148.

Serous coat, 148.

Storage of nutriment, 177-179.

"Strenuous life," 410.

Striated fibers, to show, 261.

Striated muscles, to show, 261.

Stroma, 25.

Sugars, kinds, 120.

Sulphur, 135.

Supra-renal bodies, 208.

Suspensory ligament, 377.

Sutures, 230.

Sympathetic ganglia and nerves, 298. Work of, 316.

Synovial fluid, 231.

Synovial membrane, 231.

System, defined, 20.

Systole, 46.

Taste buds, 345.

Tea, Effects on digestion, 167. Effects on heart, 56.

Tears, 383.

Teeth, 142. Care of 163. Kinds of, 143.

Temperature, Body, 207. Corpuscles, 271, 345. Sensation, 343.

Tendon of Achilles, 256.

Tendons, 246.

Tests for foods, 136, 137.

Tetanus, 262, 275.

Thoracic cavity, 7, 85, 100, 102.

Thoracic duct, 67, 170.

Thorax, 85. Bones of, 225.

Tissue enzymes, 182.

Tissues, 4. Complex nature of, 13. Defined, 20. General purposes of, 5. Kinds of, 5, 6. Observations on, 12. Properties of, 6.

Tobacco, effect on heart, 56.

"Tobacco heart," 56, 333.

Tongue, 143.

Tonic bath, 273.

Touch, 343.

Touch corpuscles, 342.

Toxins, 394.

Trachea, 80.

Trypsin, 155, 156.

Tuberculosis, 90, 92, 94, 98. How communicated, 403. Outdoor treatment, 98. To prevent, 404.

Tympanum, 359.

Typhoid fever, 404, 407.

Ulna, 227.

Urea, 110, 205, 207, 210.

Ureters, 170.

Uriniferous tubules, 203.

Vaccination, 406.

Valves, Advantages of, in veins, 49, 63. Mitral, 43. Position of, in veins, 63. Purposes of, 49, 63. Tricuspid, 43.

Veins, 47. Functions of, 51. Renal, 202.

Ventilation, 94. Rules for, 95, 96.

Ventricles, 42. To illustrate action of, 62.

Vermiform appendix, 158.

Vertebrae, 223-225. Interlocking of, 225. Joining of, 224. Kinds, 223.

Vestibule, 361.

Villi, 152. Parts of, 173, 174.

Visual perceptions, 382.

Visual sensations, 382.

Vitreous humor, 378.

Vocal cords, 355.

Voice, 353-357. How produced, 356. Pitch and intensity, 356.

Voluntary action, 311, 312.

Voluntary action pathways, 312.

Vomiting, 151, 152.

Waste material, passage from body, 210.

Wastes, 30.

Water, Importance of, 123. Supply of, 398. Value of, 210.

Water-vapor, 208.

White corpuscles, 27, 28. Functions of, 29. To examine, 39.

Work, Hygienic value of, 328, 409.

Worry, 211.

Yellow fever, 403.

Yellow marrow, 218.

Yellow spot, 377.

FOOTNOTES

1 The body is affected by what it does (exercise, work, sleep), by things taken into it (food, air, drugs), and by things outside of it (the house in which one lives, climate, etc.). That phase of hygiene which has for its object the making of the surroundings of the body healthful is known as _sanitation_.

2 When classified according to their essential structure, the tissues fall into four main groups: epithelial and glandular tissue, muscular tissue, nervous tissue, and connective tissue. According to this system the osseous, cartilaginous, and adipose tissues are classed as varieties of connective tissue. See page 18.

3 The properties of substances are the qualities or characteristics (color, weight, etc.) by means of which they are recognized.

4 Certain of these cells also form deposits of fat, giving rise to the adipose, or fatty, tissue.

5 Any organized structure, such as the body, whose parts are pervaded by a common life, is known as an _organism_. The term "organism" is frequently applied to the body.

6 In birds, reptiles, amphibians, and fishes the red corpuscles have nuclei (Fig. 9).

7 The micron is the unit of microscopical measurements. It is equal to 1/1000 of a millimeter and is indicated by the symbol {~GREEK SMALL LETTER MU~}.

8 The peculiar shape of the red corpuscle has no doubt some relation to its work. Its circular form is of advantage in getting through the small blood vessels, while its extreme thinness brings all of its contents very near the surface--a condition which aids the hemoglobin in taking up oxygen. If the corpuscles were spherical in shape, some of the hemoglobin could not, on account of the distance from the surface, so readily unite with the oxygen.

9 The coloring matter of the bile consists of compounds formed by the breaking down of the hemoglobin; the spleen contains many large cells that seem to have the power first of "engulfing" and later of decomposing red corpuscles. A further evidence that the spleen aids in the removal of worn-out corpuscles is found in the fact that during diseases that cause a destruction of the red corpuscles, such as the different forms of malaria, the spleen becomes enlarged.

10 An infected part of the body, such as a boil or abscess, should never be bruised or squeezed until the time of opening. Pressure tends to break down the wall of white corpuscles and to spread the infection. Pus from a sore contains germs and should not, on this account, come in contact with any part of the skin. (See treatment of skin wounds, Chapter XVI.)

11 Coagulation is not confined to the blood. The white of an egg coagulates when heated and when acted upon by certain chemicals, and the clabbering of milk also is a coagulation.

12 If the blood be stirred or "whipped" while it is coagulating, the clot may be broken up and the fibrin separated as fast as it forms. The blood which then remains consists of serum and corpuscles and will not coagulate. It is known as "defibrinated" blood.

13 Certain substances, called _opsonins_, have recently been shown to exist in the plasma, that aid the white corpuscles in their work of destroying germs. The opsonins appear to act in such a manner as to weaken the germs and make them more susceptible to the attacks of the white corpuscles.

14 Some of the changes in the blood are very closely related to our everyday habits and inclinations. For example, a lack of nourishment in the blood causes hunger and this leads to the taking of food. If the fluids of the body become too dense, a feeling of thirst is aroused which prompts one to drink water.

15 Metchnikoff, _The New Hygiene_.

16 A physiological salt solution is prepared by dissolving .6 of a gram of common salt in 100 cc. of distilled water or pure cistern water. This solution, having the same density as the plasma of the blood, does not act injuriously upon the corpuscles.

17 The term "circulation" literally means moving in a circle. While the blood does not move through the body in a circle, the term is justified by the fact that the blood flows out continually from a single point, the heart, and to this point is continually returning.

18 The heart at first glance seems to bear little resemblance to the pumps in common use. When it is remembered, however, that any contrivance which moves a fluid by varying the size of a cavity is a pump, it is seen that not only the heart, but the chest in breathing and also the mouth in sucking a liquid through a tube, are pumps in principle. The ordinary syringe bulb illustrates the class of pumps to which the heart belongs. (See Practical Work.)

19 The contraction of the heart is known as the _systole_ and its relaxation as the _diastole_. The systole plus the diastole forms the so-called "cardiac cycle" (Fig. 18). This consists of (1) the contraction of the auricles, (2) the contraction of the ventricles, and (3) the period of rest. The heart systole includes the contraction of both the auricles and the ventricles.

20 Martin, _The Human Body_.

21 The pressure maintained by the left ventricle has been estimated to be nearly three and one half pounds to the square inch--a pressure sufficient to sustain a column of water eight feet high. The pressure maintained by the right ventricle is about one third as great. In maintaining this pressure the heart does a work equal to about one two-hundredth of a horse power.

22 The location of the heart in the thoracic cavity causes movements of the chest walls to draw blood into the right auricle for the same reason that they "draw" air into the lungs.

23 Active exercise through short intervals, followed by periods of rest, such as the exercise furnished by climbing stairs, or by short runs, is considered the best means of strengthening the heart.

24 Nosebleed in connection with any kind of severe sickness should receive prompt attention, since a considerable loss of blood when the body is already weak may seriously delay recovery.

25 Newton, _Practical Hygiene_.

26 On account of its position in the body, the lymph is not easily collected for examination. Still, nearly every one will recall some experience that has enabled him to see lymph. The liquid in a water blister is lymph, and so also is the liquid which oozes from the skin when it is scraped or slightly scratched. Swelling in any part of the body is due to the accumulation of lymph at that place.

27 In certain small animals of the lowest types a single liquid, serving as a medium of exchange between the cells and the body surface, supplies all the needs of the organism. In larger animals, however, where materials have to be moved from one part of the cell group to another, a portion of the nutrient fluid is used for purposes of transportation. This is confined in channels where it is set in motion by suitable organs. The portion which remains outside of the channels then transfers material between the cells, on the one hand, and the moving liquid, on the other.

28 Surgeons in opening veins near the thoracic cavity have to be on their guard to prevent air from being sucked into them, thereby causing death.

29 Oxygen forms about 21 per cent of the atmosphere, nitrogen about 78 per cent, carbon dioxide about .03 per cent, and the recently discovered element argon about 1 per cent. The oxygen is in a _free_, or uncombined, condition--the form in which it can be used in the body.

30 The peculiar work devolving upon the organs of respiration necessitates a special plan of construction--one adapted to the properties of the atmosphere. Being concerned in the movement of air, a gaseous substance, they will naturally have a structure different from the organs of circulation which move a liquid (the blood). All the organs of the body are adapted by their structure to the work which they perform.

31 In ordinary inspirations the force that causes the air to move through the passages is scarcely an ounce to the square inch, while in forced inspirations it does not exceed half a pound. On this account the closing of any of the air passages by pressure, or by the presence of foreign substances, would keep the air from reaching some part of the lungs.

32 Coughing, which is a forceful expulsion of air, has for its purpose the ejection of foreign substances from the throat and lungs. Sneezing, on the other hand, has for its purpose the cleansing of the nostrils. In coughing, the air is expelled through the mouth, while in sneezing it is expelled through the nostrils.

33 The amount of dust suspended in what we ordinarily think of as pure air is shown when a beam of direct sunlight enters an otherwise darkened room.

34 Some children find it difficult to breathe through the nostrils on account of growths (called adenoids) in the upper pharynx. Such children should have medical attention. The removal of these growths not only improves the method of breathing, but in many instances causes a marked improvement in the general health and personal appearance.

35 The weakest portions of the lungs appear to be the tiny lobes at the top. As they occupy the part of the thorax most difficult to expand, air penetrates them much less freely than it does the lobes below. In most cases of consumption (some authorities give as high as eighty per cent), the upper lobes are the first to be affected. Flat chests and round shoulders, by increasing this natural difficulty in breathing, have long been recognized as causes which predispose to consumption.

36 The following exercise, from Dudley A. Sargent's _Health, Strength, and Power_, will be found most beneficial: "Stand with the feet together, face downward, arms extended downward, and backs of the hands touching. Raise the hands, arms, and elbows, keeping the backs of the hands together until they pass the chest and face. Then continue the movement upward, until the hands separate above the head with the face turned upward, when they should be brought downward and outward in a large circle to the starting point. Begin to inhale as the arms are raised and take in as much air as possible by the time the hands are above the head, then allow the breath to go out slowly as the arms descend."

37 Colds may frequently be broken up at their beginning by taking a prolonged _hot_ bath and going to bed. After getting a start, however, they run a course of a few days, a week, or longer, depending upon the natural vigor of the individual and the care which he gives his body during the time. In throwing off a cold, the following suggestions will be found helpful:

1. Dress warmly (without overdoing it) and avoid getting chilled. 2. Diminish the usual amount of work and increase the period for sleep. If very weak, stay in bed. Save the energy for throwing off the cold. 3. If able to be about, spend considerable time in light exercise out of doors, but avoid getting chilled. 4. Keep the bowels active, taking a cathartic if necessary. 5. To relieve pain in the chest, apply a mustard plaster or a flannel cloth moistened with some irritating substance, such as turpentine or a mixture of equal parts of kerosene and lard. Keep up a mild irritation until the pain is relieved, but avoid blistering.

38 Not only do the lungs remove oxygen from the air and add carbon dioxide to it, but they separate from the body considerable moisture and, according to some authorities, a small amount of an impurity referred to as "animal matter." Odors also arise from the skin, teeth, and clothing which, if not dangerous to the health, are offensive to the nostrils. If on going into a room such odors are detected, the ventilation is not sufficient. This is said to be a reliable test.

39 E.A. Schaffer, "Artificial Respiration in its Physiologic Aspects," _The Journal of the American Medical Association_, September, 1908.

40 Testing the prone-posture method by suitable apparatus, Professor Schaffer has found it capable of introducing more air per minute into the lungs than any of the other methods of artificial respiration, and more even than is introduced by ordinary breathing.

41 Osier, _The Principles and Practice of Medicine_.

42 Huber, _Consumption and Civilization_.

43 To prepare limewater some small lumps of _fresh_ lime (either slacked or unslacked) are added to a large bottle of water and thoroughly shaken. This is put aside until the lime all settles to the bottom and the water above is perfectly clear. This is now ready for use and may be poured off as needed. When the supply is exhausted add more water and shake again.

44 An _element_ is a single kind of matter. Those substances are classed as elements which cannot be separated into different kinds of matter. Two or more elements combined in definite proportions by weight form a _compound_. The elements are few in number, only about eighty being known. Compounds, on the other hand, are exceedingly numerous.

45 The term _energy_, as used here, has the same general meaning as the word _power_. See Chapter XII.

46 The oxygen pressure of the atmosphere is that portion of the total atmospheric pressure which is due to the weight of the oxygen. Since oxygen comprises about one fifth of the atmosphere, the pressure which it exerts is about one fifth of the total atmospheric pressure, or, at the sea level, about three pounds to the square inch (15 x 1/5 = 3). This is the oxygen pressure of the atmosphere. The low oxygen pressure in the tissues is due to its scarcity, and this scarcity is due to its entering into combination at the cells.

47 See footnote on oxygen pressure, page 109.

48 The impression prevails to some extent that carbon dioxide, on account of its weight, settles out of the atmosphere, collecting in old wells and at the floor in crowded rooms. Any such settling of the carbon dioxide is prevented by the rapid motion of its molecules. This motion not only prevents a separation of carbon dioxide and air after they are mixed, but causes them to mix rapidly when they are separated, if they still have surface contact. The carbon dioxide found in old wells is formed there by decaying vegetable or animal matter. In rooms it is no more abundant at the floor than in other parts.

49 On account of the formation of carbon dioxide in places containing decaying material, the descent into an old well or other opening into the earth is often a hazardous undertaking. Before making such a descent the air should always be tested by lowering a lighted lantern or candle. Artificial respiration is the only means of restoring one who has been overcome by this gas (page 97).

50 While awaiting oxidation at the cells, the carbohydrates and fats are stored up by the body, the carbohydrates as glycogen and the fats as some form of fat. In this sense they are sometimes looked upon as serving to build up certain of the tissues.

51 The following table shows the main elements in the body and their relation to the different nutrients:

[Nutrient Table]

52 The recently advanced theory that the molecules of the mineral salts, by dissolving in water, separate into smaller divisions, part of which are charged with positive electricity and part with negative electricity, has suggested several possible uses for sodium chloride and other mineral salts in the body. The sodium chloride in the tissues is in such concentration as to be practically all separated into its sodium and chlorine particles, or ions. It has recently been shown that the sodium ions are necessary for the contraction of the muscles, including the muscles of the heart. There is also reason for believing that the different ions may enter into temporary combination with food particles, and in this way assist in the processes of nutrition.

53 Chittenden, _The Nutrition of Man_.

54 Compiled from different sources, but mainly from Atwater's _Foods: Nutritive Value and Cost_, published by the U.S. Department of Agriculture.

55 The calorie is the adopted heat unit. As used in this table it may be defined as the quantity of heat required to raise 1 kilogram (2.2 pounds) of water, 1 degree centigrade. The calories also show the relative amount of energy supplied by the different foods.

56 While alcohol cannot be classed as a food, it is believed by some authorities to contain _food value_ and, in the hands of the physician, to be a substance capable of rendering an actual service in the treatment of certain diseases. It might, for example, be used where one's power of digestion is greatly impaired, since alcohol requires no digestion. But upon this point there is a decided difference of opinion. Certain it is that no one should attempt to use alcohol as food or medicine except under the advice and direction of his physician.

57 A layer of connective tissue between the mucous membrane and the muscular coat is usually referred to as the _submucous_ coat. This contains numerous blood vessels and nerves and binds the muscular coat to the mucous membrane.

58 The saliva may continue to act for a considerable time after the food enters the stomach. "Careful examination of the contents of the fundus (large end of the stomach) by Cannon and Day has shown that no inconsiderable amount of salivary digestion occurs in the stomach."--FISCHER, _The Physiology of Alimentation_.

59 Perhaps the simplest method of inducing vomiting is that of thrusting a finger down the throat. To make this method effective the finger should be held in the throat until the vomiting begins. An emetic, such as a glass of lukewarm salt water containing a teaspoonful of mustard, should also be taken, and, in the case of having swallowed poison, the vomiting should be repeated several times. It may even be advantageous to drink water and then vomit it up in order to wash out the stomach.

60 Hammerstein, _Text-book of Physiological Chemistry._

61 Amylopsin is absent from the pancreatic juice of infants, a condition which shows that milk and not starch is their natural food.

62 The fact that butter is more easily digested than other fatty substances is probably due to its consisting largely of a kind of fat which, on splitting, forms a fatty acid (butyric) which is soluble in water.

63 Fischer, _Physiology of Alimentation._

64 Beginning the meal with a little soup, as is frequently done, may be of slight advantage in stimulating the digestive glands. To serve this purpose, however, and not interfere with the meal proper, it should contain little greasy or starchy material and should be taken in small amount.

65 Dr. William Beaumont, an American surgeon of the last century, made a series of observations upon a human stomach (that of Alexis St. Martin) having an artificial opening, the result of a gunshot wound. Much of our knowledge of the digestion of different foods was obtained through these observations. In spite of the protests of his physician, St. Martin would occasionally indulge in strong drink and always with the same result--the lining of the stomach became much inflamed and very sensitive, and the natural processes of digestion were temporarily suspended.

66 The lacteals (from the Latin _lacteus_, milky) are so called on account of their appearance, which is white, or milk-like, due to the fat droplets.

67 Peptones and proteoses, when injected directly into the blood, are found to act as poisons.

68 The soluble double sugars (maltose, milk sugar, and cane sugar) are reduced to the simple sugars (dextrose and levulose). Furthermore the action on the proteids does not stop with the production of peptones and proteoses, but these in turn are still further reduced.

69 Energy, which is defined as _the ability to do work_, or _to cause motion_, exists in two general types, or forms, known as kinetic energy and as potential energy. _Kinetic_ energy is energy at work, or energy in the act of producing motion; while _potential_ energy is reserve, or stored, energy. All moving bodies have kinetic energy, and all stationary bodies which have within them the _capability_ of causing motion possess potential energy. A bent bow, a piece of stretched rubber, a suspended weight, the water above a mill dam, all have the capability of causing motion and all have potential energy. Examples of kinetic energy are found in the movements of machinery, in steam and electricity, in winds, and in currents of water. Kinetic is the active, and potential the inactive, form of energy.

70 As the atoms of hydrogen and oxygen that make up the molecules of water separate, they unite with atoms of their own kind--the hydrogen with hydrogen and the oxygen with oxygen atoms. Since these combinations are weaker than those of the water molecules, energy is required to bring about the change. But when hydrogen burns in the oxygen, the change is from a weaker to a stronger combination. The stored-up energy is then given up or becomes active.

71 In the evaporation of water, the energy of the sun is stored with reference to the force of gravity. In evaporating, water rises as a gas, or vapor, above the earth's surface, but on condensing into a liquid, it falls as rain. It then finds its way through streams back to the ocean. All water above the sea level is in such a position that gravity can act on it to cause motion, and it possesses, on this account, potential or stored-up energy. It is because of this energy that rapids and waterfalls are such important sources of power.

72 Energy, like matter, can neither be created nor destroyed. It can, however, be transferred from one body to another and transformed from one form to another form. Whenever work is done, energy is transferred from the body doing the work, to the body upon which the work is done. During this process there may, or may not, be a transformation of energy. In turning a grindstone, kinetic energy is passed to the stone and used without transformation, but in winding a clock, the kinetic energy from the hand is transformed into potential energy in the clock spring. Then as the clock runs down this is retransformed into kinetic energy, causing the movements of the wheels.

Not only is kinetic transformed into potential energy and _vice versa_, but the different forms of kinetic energy (heat, light, electricity, sound, and mechanical motion) are readily transformed the one into the other. With suitable devices, mechanical motion can be changed into heat, sound, or electricity; heat into motion and light; and electricity into all the other forms of energy. These transformations are readily explained by the fact that the different varieties of kinetic energy are but different forms of motion (Fig. 84).

73 The simplest arrangement of the parts of a gland is that where they are spread over a plain surface. This arrangement is found in serous membranes, such as the pleura and peritoneum. These membranes, however, are not called glands, but secreting surfaces.

74 In the oxidations that occur in the body it is not supposed that the nutrients are immediately converted to carbon dioxide, water, and urea. On the other hand, it is held that their reduction takes place gradually, as the reduction of sugar by fermentation, and that the wastes leaving the body are but the "end products" and show only the final results.

75 Alcohol, if used in considerable quantity, leads to cirrhosis of the liver and Bright's disease of the kidneys, both very dangerous diseases. Dr. William Osler in his treatise, _The Practice of Medicine_, states that alcohol is the chief cause of cirrhosis of the liver. Dr. T.N. Bogart, specialist in kidney diseases, asserts that one third of all the cases of Bright's disease coming under his observation are caused by alcohol.

76 Hall, _The Purin Bodies_.

77 Review "Main Physiological Problems," page 21.

78 In the production of motion in the body, as well as in the production of any kind of _purposeful_ motion outside of the body, three conditions must be fulfilled. There is required, in the first place, a mechanical device or machine which is so constructed as to produce a certain kind of motion. In the second place, energy is needed to operate this device. And, finally, there must be some controlling force, by means of which the motion is made to accomplish definite results. The driving of a horse hitched to a wagon will illustrate these conditions. The wagon is the mechanical device, the horse furnishes the energy, and the driver supplies the controlling force. In this, as in most cases, the machinery, the source of energy, and the controlling force are disconnected except when at work; but in the body all three occur together in the same structure.

79 The dependence of the outer layers of bone cells upon the periosteum for nourishment causes a destruction of this membrane to affect seriously the bone beneath, producing in many instances a decay of the bone substance.

80 It has been claimed that the introduction of vertical writing has reduced the number of cases of spinal curvature originating in the schoolroom, and statistics appear to prove the claim. It is shown, on the other hand, that unnatural positions also are unnecessary in the slanting system of writing, and that in either system the pupil who is permitted to do so is liable to assume an improper position.

81 Lovett, _Lateral Curvature of the Spine and Round Shoulders_.

82 See "Hygiene of Muscles," Chapter XV.

83 On account of the striations of these cells the muscles which they form are called striated muscles.

84 The striated muscle cells, having many nuclei, are said to be multi-nucleated.

85 Every movement in the body has its opposing movement. This is necessary both on account of the work to be accomplished and for preserving the natural form of the body.

86 The distance from the fulcrum to the power is called the _power-arm_ and the distance from the fulcrum to the weight is called the _weight-arm_ (Fig. 115).

87 The foot in lifting the body on tiptoe appears at first thought to be a lever of the second class, the body being the weight and the toe serving as the fulcrum. However, if the distance which the body is raised is compared with the distance which the muscle shortens, it is found that the _supposed_ weight has moved _farther_ than the power (Fig. 118). It will also be noted that the muscle which furnishes the power is attached at its upper end to the "weight." These facts show clearly that we are not here dealing with a lever of the second class. The foot in this instance acts as a lever of the first class with the fulcrum at the ankle joint and the toe pressing against the earth, which is the _actual_ weight. Since the earth is immovable, the body is lifted or pushed upward, somewhat as a fulcrum support is made to move when it is too weak to hold up the weight that is being lifted. In other words, we have the same lever action in the foot in lifting the body as we have when one lies face downward, and, bending the knee, lifts some object on the toes.

_ 88 Walking_ is considered one of the very best forms of counter-active exercise for the brain worker (page 328).

89 The epidermis does not afford complete protection against chemicals, many of them being able to destroy it quickly. The rule of washing the skin immediately after contact with strong chemical agents should always be followed.

90 "Rough calculations have placed the number of sweat glands on the entire body at about 2,000,000." Rettger, _Studies in Advanced Physiology_.

91 Heat also leaves the body by the lungs, partly by the respired air and partly through the evaporation of moisture from the lung surfaces. Respiration in some animals, as the dog, is the chief means of cooling the body.

92 "The story is told of some woodsmen who were overtaken by a severe snowstorm and had to spend the night away from camp; they had a bottle of whisky, and, chilled to the bone, some imbibed freely while others refused to drink. Those who drank soon felt comfortable and went to sleep in their improvised shelter; those who did not drink felt very uncomfortable throughout the night and could get no sleep, but in the morning they were alive and able to struggle back to camp, while their companions who had used alcohol were frozen to death.... This, if true, was of course an extreme case; but it accords with the universal experience of arctic travelers and of lumbermen and hunters in the northern woods, that the use of alcohol during exposure to cold, although contributing greatly to one's comfort for the time being, is generally followed by undesirable or dangerous results."--HOUGH AND SEDGWICK: _The Elements of Hygiene and Sanitation_.

93 Foods that are difficult to digest, or which cause disturbances of the digestive organs (a coated tongue being one indication), have a bad effect upon the skin. It is in this way that the use of tea and coffee by some people induces a sallow or "muddy" condition of the complexion.

94 A most valuable antiseptic ointment is prepared by the druggist from the following formula:

Lanolin, 25 grams. Ichthyol, 6 grams. Yellow vaseline, 20 grams.

This is applied as a thin layer on the surface, except in the case of boils or abscesses. In treating these a heavy layer is spread over the affected part and then covered with absorbent cotton or a thin piece of clean cotton cloth.

95 In a larger sense adjustment includes all those activities by means of which the body is brought into proper relations with its environment, including the changes which the body makes in its surroundings to _adapt them_ to its purposes.

96 Almost to the present time, physiologists have described the nervous system as being made up of two kinds of structural elements which were called _nerve cells_ and _nerve fibers_. The nerve cells were supposed to form the ganglia and the fibers to form the nerves. Recent investigators, however, employing new methods of microscopic study, have established the fact that the so-called nerve cell and nerve fiber are but two divisions of the same thing and that the nervous system is made up of, not two, but one kind of structural element. The term "neuron" is used to denote this structural element, or _complete nerve cell_.

97 Many of the axons in the brain and spinal cord have no primitive sheath. Axons without the medullary sheath are found in the sympathetic nerves. These are known as non-medullated axons and they have a gray instead of a white color.

98 The difference in weight between the brain of man and that of woman is due mainly to the fact that man's body is, as a rule, considerably larger than that of woman's.

99 The nervous tissues present, at different places, two colors--one white, and the other a light gray. Great significance was formerly attached to these colors, because it was supposed that they represented two essentially different kinds of nervous matter. It is now known that the protoplasm in all parts of the neuron proper--cell-body, axis cylinder, and dendrites--has a grayish color, while the coverings of most of the fibers are white. Hence gray matter in any part of the nervous system indicates the presence of cell-bodies, and white matter the presence of nerve fibers.

100 In very early life the spinal cord entirely fills the spinal cavity, but as the body develops the cord grows less rapidly than the spinal column, and, as a consequence, separates at the lower end from the inclosing bony column.

101 Fibers passing between the spinal cord and the cerebrum cross to opposite sides--most of them at the bulb, but many within the cord--so that the right side of the cerebrum is connected with the left side of the body, and _vice versa_. This accounts for the observed fact that disease or accidental injury of one side of the cerebrum causes loss of motion or of feeling in the opposite side of the body.

102 In general, _afferent_ neurons or fibers are those that convey impulses _toward_ the central nervous system (brain and cord), while _efferent_ neurons or fibers are those that convey impulses _from_ the central system.

103 At different times the nervous impulse has been regarded as a current of electricity; as a progressive chemical change, likened to that in a burning fuse; as a mechanical vibration, such as may be passed over a stretched rope; and as a molecular disturbance accompanied by an electrical discharge. The velocity of the nervous impulse, which is only about one hundred feet per second, proves that it is not a current of electricity. It takes place with little or no exhaustion of the cell protoplasm and consequently is not due to chemical action. And the loose, relaxed condition of the nerves prevents their transmission of physical vibrations, like those on a stretched rope. The view that the impulse is a progressive molecular disturbance, accompanied by an electrical discharge, has much evidence in its favor, but it has only recently been proposed and is likely to be modified upon fuller investigation.

104 The surface of the body includes the linings of the air passages, food canal, and certain cavities, as well as the external covering or skin.

105 Derived from the Latin _re_, back, and _flectere_, to turn or bend.

106 A frog from which the brain has been removed is suspended with its feet downward and free to move. If a toe is pinched, the foot is drawn away, and if dilute acid, or a strong solution of salt, is placed on the tender skin, the feet are moved as if to take away the irritating substance. This of course shows that reflex action can take place independently of the brain.

Now if the spinal cord is also destroyed, there is no response when the irritation of the skin is repeated. The animal remains perfectly quiet, because the destruction of the cord has interrupted the reflex action pathway. This shows that some part of the central nervous system is necessary to reflex action.

107 Review description of the spinal nerves, page 295.

108 Where a deep-seated cause for worry exists, there may be occasion for grave concern. Many people have become insane through continued worry about some _one_ thing. In cases of this kind the sufferer needs the aid of sympathetic friends, and sometimes of the physician, in getting the mind away from the exciting cause. A change of scene, a visit, or some new employment is frequently recommended, where the actual cause for the worry cannot be removed.

109 Any part of the body which is overworked or which works at a disadvantage tends to disturb, more or less, the entire nervous system and to produce nervousness. Especially is this true of such delicate and highly sensitive structures as the eyes. If the eyes do not focus properly or if the muscles that move the eyeballs are out of their natural adjustment, extra work is thrown upon these delicate parts. One of the first and sometimes the only indication of eye strain is that of some disturbance of the nervous system. For this reason it is important to carefully test the eyes in determining the cause of nervousness (page 385).

110 One form of neck exercise recommended for this purpose is easily taken on retiring at night. Lying flat on the back, without a pillow, lift the head slowly from the bed and let it as slowly settle back to the level of the body. Repeat several times, lying on the back, and then again on the face and again on each side. Practice these exercises every night during an interval of a month or until relief is secured.

111 Insurance statistics show that habitual _moderate drinkers_ do not live so long as abstainers.

112 Organs very frequently affected by tobacco are the heart and the eyes. It induces, as already stated (page 56), a dangerous nervous derangement called "tobacco heart," and it causes a serious disorder of the retina (retinitis) which leads in some instances to loss of vision. Tobacco smoke also acts as an irritant to the delicate lining of the eyes, especially when the tobacco is smoked indoors.

113 Of 4117 boys in the Illinois State Reformatory, 4000 used tobacco, and over 3000 were cigarette smokers. Dr. Hutchison, of the Kansas State Reformatory, says: "Using cigarettes is the cause of the downfall of more of the inmates of this institution than all other vicious habits combined."

114 The term "mind" is used in this and preceding chapters in its popular, not technical, sense.

115 The problem of social adjustment is but a phase of the general problem of establishing proper relations between the body and its surroundings.

116 A vibrating body is one having a to-and-fro movement, like that of a clock pendulum or the string of a violin on sounding. Bodies to give out sound waves must vibrate rapidly, making not less than sixteen vibrations per second. The upper limit of hearing being about 40,000 vibrations per second, certain bodies may even vibrate too rapidly to be heard.

117 Somewhat as the waves on a body of water impart motion to the sticks and weeds along the shore, sound waves are able to cause bodies that are small or that are delicately poised to vibrate.

118 Some idea of how the movements of the cartilages change the tension of the cords may be obtained by holding the fingers on the larynx, between the thyroid and cricoid cartilages, and making tones first of low and then of high pitch. For the high tones the cartilages are pulled together in front, and for the low tones they separate. As they pull together in front, they of course separate behind and above, where the cords are attached.

119 It is only the central portion of the pinna that aids the entrance of sound into the auditory canal. If by accident the outer portion of the pinna is removed, there is no impairment of the hearing.

120 The middle ear is also called the _ear drum_, and, by the same system of naming, the membrana tympani is referred to as the _drum membrane_.

121 The inner projection of the temporal bone is known as the petrous process.

122 A small opening in the bone at this place is called the _fenestra rotunda_.

123 Consult some work on physics on the different kinds of lenses and their uses.

124 With respect to its adjustments the eye does not differ in principle from various other optical instruments, such as the microscope, telescope, photographer's camera, etc., which, in their use, form images of objects. These all require some adjustment of their parts, called focusing, which adapts them to the distance. The eye's method of focusing, however, differs from that of most optical instruments, in that the adjustment is brought about through changes in the curvature of a lens.

125 The converging power of convex lenses varies as the curvature--the greater the curvature, the greater the converging power.

126 An oculist is a physician who specializes in diseases of the eye.

127 Some of the more common symptoms of eye strain are nervousness, headache, insomnia, irritations of the eyelids, sensitiveness to bright light, and pain in the use of the eyes.

128 Pyle, _Personal Hygiene_.

129 "An infectious disease is one in which disease germs infect (that is, invade) the body from without. Among the infectious diseases are some that are quite directly and quickly conveyed from person to person and to these the term contagious is applied. Formerly a sharp line was drawn between infection and contagion, but to-day it is recognized that no such line exists."--HOUGH AND SEDGWICK, _The Elements of Hygiene and Sanitation._

130 The arctic explorer, Nansen, states that during all the time that his party was exposed to the low temperature of the arctic region, no one was attacked by a cold, but on returning to a warmer climate they were subject to colds as usual. The difference he attributes to the absence of germs in the severe arctic climate. There seems to be no doubt but that most of our common colds are due to attacks of germs.

131 An interesting biological fact is that the female _Anopheles_, and not the male, sucks the blood of animals and is the cause of the spreading of malaria.

132 The habit of spitting upon the floors of public buildings and street cars, and also upon sidewalks, is now recognized as a most dangerous practice. Not only consumptives, but people with throat affections, may do no end of harm in the spreading of disease by carelessness in this respect.

133 For further information on the care of consumptives, consult Huber's _Consumption and Civilization_.

134 As typhoid fever is a disease of the small intestine, great care must be exercised in taking food and in the bodily movements. Solids greatly irritate the diseased lining of the intestine, and the weakened walls may actually be broken through by pressure resulting from moving about.

135 Alcoholic beverages include all the various kinds of drinks that owe their stimulating properties to a substance, ethyl alcohol (C2H5OH), which is made from sugar by the process of fermentation. They include _malt liquors_, such as beer and ale, which contain from three to eight per cent of alcohol; _wines_, such as claret, hock, sherry, and champagne, which contain from five to twenty per cent of alcohol; and _distilled liquors_, such as brandy, whisky, rum, and gin, which contain from thirty to sixty-five per cent of alcohol. Alcoholic beverages all contain constituents other than alcohol, these varying with the materials from which they are made and with the processes of manufacture. The distilled liquors are so called from the fact that their alcohol has been separated from the fermenting substances by distillation.

136 Duncan, _The Chemistry of Commerce_.

137 Alcohol is "denatured" by adding substances to it such as wood alcohol, which render its use as a beverage impossible.

138 The tobacco plant, _Nicotiana tobacum_, is a native of America, and the use of tobacco began with the American Indians. It was taken back to Europe by the early explorers, Sir Walter Raleigh being credited with introducing it to the nobility of England.

139 Most headaches are the result either of eye strain or of digestive disturbances, such as indigestion and constipation, and are to be relieved through the work of the oculist or through attention to the hygiene of the digestive system.