The human body requires about three thousand cubic feet per hour, and the great problem of ventilation is to give this amount of pure air, moving, and with the proper amount of moisture.

It is a common belief that with each breath we take we are filling our lungs with fresh air.  This is not the case, for we never do get our lungs filled with fresh air.  What really happens is that we ventilate a long tube which has no intercommunication whatever with the blood.  Most of the time our lungs are filled with impure air, and we simply exchange a part of it for fresh air.

THE VALUE OF DEEP BREATHING

Deep breathing is undoubtedly extremely beneficial.  Most of us, due largely to the fact that Nature leaves a considerable margin of safety, are able to carry on our ordinary activities without the requisite ventilation of the lungs, especially if we do not exercise.  This, however, is injurious to the lungs, for it allows the blood to stagnate in them.  Exercise is Nature’s method of compelling ventilation in the lung area.  Deep breathing may be used as a substitute, but the other beneficial effects of exercise are lost.

The skin and the various glands connected with it form a complex organism, the functions of which play a very important part in the work which the body has to do.  The skin aids the lungs in their work of respiration; and, like the lungs, it throws off water and carbon dioxide and absorbs oxygen.  The respiratory work of the skin, however, is only a minute fraction of that which the lungs do.

The skin is a heat regulator, and in this, its most important work, it is aided by the two million or more sweat-glands which are distributed over almost the entire surface of the body.  The skin and the sweat-glands work together to keep the blood at an even temperature, either by giving off heat or in preventing this process in case the outside air is too cool.  The body temperature, as a rule, is higher than that of the outside air, so that heat is generally being given off by the skin.  We are perspiring constantly, but usually to such a slight extent that the fact is hardly noticeable.  The amount of heat which is thrown off at any time is proportional to the amount of the tissue burned up by muscular action.

CHAPTER V

Health, strength, and efficiency!  Surely every man in this great Republic of ours wants to be healthy, strong, and efficient, but how is he to obtain and maintain this threefold blessing?  It has been stated that scientific physical exercise, preferably taken in group association, will accomplish it.  Now to consider some of the practical details involved.

THE ORGANIZATION

The organization may be composed of any number from sixteen to one hundred men, and about the smallest unit that should be undertaken is that of sixteen men.  On the other hand, when the number gets above one hundred (or preferably ninety-six, in order that it may be divided into four companies of twenty-four each) it is better to start a second group under a separate leader.