ing the liquids as much as possible. In this way, as the loss by perspiration is not supplied, the weight of the body must diminish. The deficient quantity of water seems to prevent the full supply of reparative matter to the muscles, while it does not interfere so much with their disassimilation. At all events, it is evident that the loss of weight involves the muscles almost exclusively, and this is probably due primarily to the excessive exercise. With this violent exercise, the muscular system might be reduced in weight by restricting the quantity of nitrogenized food; but experience has shown that this course involves much greater loss of strength than the reduction of weight by restricting the quantity of liquids.

Practically, it has been found to be very difficult to keep the weight of the body much below the normal standard for any considerable length of time; and an increase in the quantity of liquids taken will add several pounds to the weight in the course of a few hours. Such reduction of weight, however, has its limit; and it has very often occurred that men have miscalculated the effects of this severe course of training, and, although they have gone into the ring at the proper weight, and apparently in very "fine condition," they have been utterly incapable of making a contest.

Some persons, whose muscles are small, and who have no tendency to the accumulation of fat, increase very considerably in weight under the ordinary course of training.

A steam-engine is not "trained" to accomplish a certain amount of work. A machine of this kind is perfected in all of its parts, and is so constructed as to be of sufficient strength to overcome such resistance as it is likely to meet. It is simply an apparatus for transforming heat furnished by fuel into useful force, and it is nothing without fuel. Man, on the other hand, is a living being, developed from a fecundated ovum of microscopic size, by a process which we have hardly begun to comprehend. In his growth, the various tissues and organs have the power of appropriating materials for development, when they are presented in an appropriate form and under proper conditions. There is no reason to suppose that the nature of this process of nutrition radically changes when the being reaches adult life, and there is no single reasonable argument in favor of such a view. A man may take a certain quantity and kind of food, and still, without training, be able to perform only a certain amount of work. After proper training, with precisely the same food, he can develop greatly-increased power. His span of life is definitely fixed, and no amount of care can

prevent those retrograde organic changes which result in death.

Assuming that a proper system of training is essential to perfect development of the machinery of the muscular system, the simple question is whether, in the perfected muscular system of the adult, force be generated by changes of the muscular substance or whether the force be due to the direct transformation of elements of food. In other words, is the muscular substance an apparatus for transforming the force locked up in food into power, or are the muscles themselves consumed, the elements of food being used for their repair? These questions may be resolved by little more than a single experimental line of inquiry: Does physiological exercise of the muscular system increase the elimination of nitrogenized excrementitious principles?

Relations of the Muscular System to the Elimination of Nitrogen.

There seems, at the first blush, to be good ground for supposing that the elimination of nitrogen is closely related to the physiological wear of muscular tissue, for several reasons. The muscular system may be, under certain circumstances, the only part of the body that is materially affected by exercise. In a

man of ordinary development, the muscular system constitutes at least two-fifths of the total weight.' Fat may disappear almost entirely from the body, and the food may be restricted to nitrogenized matters, without disturbing nutrition. These matters. are never discharged from the body as albuminoids, but the nitrogen is eliminated mainly in the urea. Under such conditions, and with a varying amount of exercise, it is the muscular system only which presents any considerable changes in weight.

Supposing the fat of the body to be reduced to its minimum proportion-and it usually constitutes but about one-twentieth of the total weight-there are no other parts that can be affected by exercise; for there is no reason to suppose that the nervous system, the abdominal, thoracic, or pelvic viscera, the skin, bones, or tendons, present any immediate changes in weight as the result of muscular exertion. Take the case of Weston, the pedestrian, who was under my observation in 1870, and who weighed a little more than one hundred and nineteen pounds just before he began a walk of five consecutive days. He must have had at least forty-eight pounds of muscular tissue, and he was reduced in weight, dur

1 SAPPEY, Traité d'anatomie, Paris, 1868, tome ii., p. 6.

2 CARPENTER, Principles of Human Physiology, Philadelphia, 1876, p. 66.

ing a walk of two hundred and seventy-seven miles in four consecutive days, to one hundred and fourteen pounds. During this time, he probably consumed five pounds of muscular tissue which could not be repaired by food, or about ten per cent. of the total weight of muscle. It might be assumed that he consumed this amount of muscular substance because the food taken was insufficient to produce the force exerted; but it is more reasonable to suppose that he lost muscular weight because the food could not repair the excessive waste engendered by the extraordinary amount of work accomplished. However this may be, our views must rest upon the experimental answer to the question whether or not muscular exercise increase the elimination of nitrogen from the body, irrespective of theoretical considerations relative to the force-value of food, which are derived solely from physical and chemical observations and which do not take into account the complex and imperfectly-understood processes of nutrition, the mysterious influences of the nervous system, or the intricate series of phenomena which are intermediate between the appropriation of oxygen and the production of carbonic acid by the tissues.

In discussing the various experiments that have

1 This was the greatest loss of weight observed at any time during the walk of five days.