These facts furnish an important clew to the source of muscular power. The experiments of Voit and Pettenkofer show that while storing up oxygen during rest the organism is laying up a store of force to be used later; while those of Henneberg connect this storing up of oxygen with the supply of albuminoids in the food, and render it highly probable that it is accomplished by their means.
Two hypotheses as to the function of the albuminoids as agents in the production of muscular power at once suggest themselves. The first is, that they simply serve as reservoirs of oxygen, which latter is used at will to burn the non-nitrogenous parts of the food, the result being work, heat, and an increased excretion of carbonic acid and water. This would be the view of those who consider the carbhydrates and fats as the source of muscular power, and its simplicity renders it attractive. It must be noted, however, that it requires us to look upon the non-nitrogenous materials oxidized as part of the muscle, since the latter can perform work independently of the circulation of blood through it.
A second hypothesis, however, less simple and easily grasped than the first, is considered by many high authorities to accord more closely with the facts of the case and with our general conceptions of vital activity.
This hypothesis supposes that during rest some of the substances of the muscle-cells decompose into simpler compounds, and in so doing set free their latent energy, which energy, instead of appearing as heat, etc., is used to build up out of other constituents of the cell a still more complex compound containing more potential energy than its components, just as one portion of society may acquire wealth at the expense of another portion, with no increase of the total wealth of the community.
The substances which are thus "synthesized" are proteine, an unknown non-nitrogenous matter from the blood and oxygen; the hypothetical compound thus formed accumulates to a certain extent in the muscle, and, when the latter is called on to perform work, splits up, yielding carbonic acid, water, and other non-nitrogenous matters, and proteine or some similar compound, and giving forth the amount of force which was required to form it. The non-nitrogenous substances which are formed are supposed to be rapidly excreted; while the nitrogenous product, instead of undergoing further decomposition, is used over again to re-form the hypothetical substance.
This view has much in its favor. Various syntheses like that above outlined are known to take place in the body; and, moreover, all the facts seem to indicate that muscular force originates in a splitting up of some substance in the muscle, accompanied by the liberation of force, rather than by any process of oxidation in the ordinary sense of the word.
The hypothesis explains the object of the storing up of oxygen in
