Page:Popular Science Monthly Volume 23.djvu/91

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condition of young bone and the manner of its growth at the epiphyses, how easy it is to imagine the advantage of regularly stretching the cartilage in the lines of the most serviceable shape and position of the future bone! We know how easily the thorax-walls, for instance, become misshapen from abnormal pressure within or without, even from lazy slouching; and we know too how quick and lasting is the "setting-up" of the West-Pointers. Their splendid carriage is due simply to the stretching of ligaments and cartilage, maintained till the natural equilibrium of muscular force is regained in the new position. Merely for aesthetic reasons this result is well worth the cost. Of far greater importance are the increase of chest-room and the greater resistance to fatigue thus gained.

In passing now to the theoretical advantages of regularly exercising the voluntary muscles, little consideration need be paid to the supposed advantage of increase in size. Muscles readily respond to increased demands by rapid growth in size, and, for those whose duties do not require large muscles, it is questionable if they are any better off with them. A blacksmith's arm may be considered rather as a superfluity if on a parson. For some sets of muscles the blacksmith and the parson, and in fact all people, have equal need, and, in order to be equally vigorous in their respective stations, the development that the blacksmith gains naturally must, by others leading a sedentary life, be obtained artificially. Of prime importance to all are both the voluntary and the involuntary muscles of respiration. So directly does our physical health depend upon their continued vigor, that nothing short of their highest possible development should satisfy us. Especially is this true of the abdominal muscles, which should give not only most valuable assistance in the mechanism of breathing, but also a support of exceeding value to the viscera. No other set of muscles has suffered more in the change from active to sedentary life. Corsets are proof of this. Fashion is by no means wholly responsible for their almost universal use. They do not come and go, but, in spite of all efforts at dress reform, corsets hold their sway, because their wearers feel better in them. This will continue to be the case until the muscles whose office they partially supply are developed by exercise designed to take the place of what is no longer naturally obtained.

It is not sufficient to have merely large muscles. Like raw troops, their usefulness depends upon constant discipline. This widely-recognized fact is often wrongly explained, as, for instance, by the theory that our nerves need exercising. In this age, nerves need no such stimulus. A much more probable theory is given by Maclaren, of Oxford, namely, that the potential energy of body-substance depends upon its newness, which may be explained by the facts that the potential energy of combustible material is directly proportional, and its chemical stability is inversely proportional, to its molecular com-