Page:Popular Science Monthly Volume 15.djvu/835

Rh One result of these researches has been to demonstrate that the consumption of proteine in the body is determined by the amount of it present in the food. If the food contains but little proteine, but little is oxidized in the body; if more be added, the consumption of it in the vital processes promptly increases, and within at the most three or four days comes into equilibrium with the supply, or very nearly so.

Another important point is the distinction, first introduced by Voit, between what he calls circulatory and organized proteine. He has shown, by experiments which it would take too much space to describe, that the proteine of the body exists in two states: first, as organized proteine, which is comparatively stable; and, second, circulatory proteine, which exists in much smaller amount than the other, and undergoes a much more rapid decomposition in the body. The first effect of albuminoids in the food is to increase the amount of this circulatory proteine and the rapidity of its decomposition, and it is in this way that the consumption of proteine in the body is, as has just been stated, determined by the supply of albuminoids in the food. The production of organized proteine, which Voit supposes to constitute the muscular tissue, is, on the contrary, much less rapid, it being slowly formed from the circulatory proteine under proper conditions.

Some authorities dispute the correctness of the names circulatory and organized proteine, but there is no dispute as to the fact, shown by his experiments, that most of the proteine of the body exists in a comparatively stable form, while a small portion, dependent in amount upon the supply in the food, is being continually and rapidly oxidized and furnishes most of the nitrogen eliminated through the kidneys. We might compare the stock of circulatory albuminoids in the body to a mass of water contained in a vessel with a small aperture in the bottom. If there is no supply, it quickly runs out. If a small stream of water be let in at the top, a small supply of water may be maintained in the vessel. If a larger stream be admitted, the depth of water in the vessel will at once begin to increase, but at the same time the pressure on the bottom, and consequently the rapidity of the outward flow through the aperture, increases, and outflow and inflow soon come into equilibrium. If the supply be diminished, the level of the water sinks till the hydrostatic pressure causes the outflow to again equal the inflow.

Voit's results have been abundantly confirmed by other observers in experiments on various animals, including man, and must be regarded as fully established, whatever view we may take of the interpretation put upon them by their author. In Professor Flint's book, however, we fail to find any reference to these discoveries, though they have, as we shall see, a most important bearing on his own experiments. He does, indeed, mention the similar but less complete results