In considering the effect of exercise upon the respiratory system, it is well understood that, in order faster to rid the body of waste gases and to obtain the needed oxygen, the respirations are increased in amount and frequency. Merely from this increased work the lung tissue would be expected to increase; and there is still further influence to this end, from the pressure of air within the lungs, induced by forcibly holding the breath for a moment, as is naturally done at the inception of muscular exertion. This pressure must tend to dilate the alveoli to their full extent, and it also serves to aid the passage of oxygen through the membranes, and its solution by the blood.
Such, then, are some of the theoretical advantages of physical exercise. Let us now examine the results. Unfortunately, exact records of gymnasiums are as yet rare. Although indefinite reports are of comparatively little value, still it is possible to appeal to the personal experience of many to substantiate the claims made for systematic artificial exercise. And, indeed, it is only by this personal testimony that we can get at the indirect, yet perhaps the most valuable, results. No tabulations can represent the after-glow, and the consciousness of increased strength, purified blood, and cleared brain, which delightfully reward such exercise. Equally difficult would it be to describe the body alacrity so acquired, which, without stopping to discuss its origin, is a very valuable result, and never otherwise attainable. We are, however, not entirely dependent upon our own limited experience, nor upon indefinite statements of results. Though strangely few, we still have some unquestionable records of not slight deformities and deficiencies corrected. In searching for measurements that will even approximately represent the vigor of the body, we can not depend upon measurements of muscles, which can never be accurate, and, even if they were so, are no sure guide. The weight and height are also alone useless; but all these measurements taken into account, together with the muscular strength and the general character of the flesh, give a tolerably fair idea of the person's condition. If to these measurements be added the girth and expansive power of the chest, and the lung capacity, a far more accurate idea will be obtained; and the gain in these measurements, after regular terms of exercise, may fairly be assumed to represent its advantages. Taking now the most important measurements, we find reported from various gymnasiums an increase of two inches in passive girth of chest, of four inches in expansive power, and of fifty cubic inches in lung capacity. These gains have been obtained in six months' time, not only in college students, army officers, and school-boys, but also in city girls. Who can properly estimate the advantages of such increased breathing power? In enabling the fortunate gainer more easily to meet the wear and tear of daily duties, or the possible onslaught of acute disease, what invaluable assistance would be rendered by these fifty cubic inches of lung capacity!