*Counts against Caffeine.*-People of vigorous const.i.tutions 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 appet.i.te 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 const.i.tuent 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 const.i.tutional 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 coordinated; 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 coordinates 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 ill.u.s.trations 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 cla.s.s 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 cla.s.s or laboratory work are easily obtained through supply houses. Ill.u.s.trations of several of these are shown in connection with the "Practical Work."