Page:Popular Science Monthly Volume 60.djvu/518

510 consumed by the salmon in accomplishing the distance, it would be easy to reach fairly exact conclusions in terms of distance traveled, weights transported and fuel expended by the salmon, and to compare these results with those accomplished by a steamship; or to calculate the resistance of the water overcome by the salmon, and from this compare the relative advantages of the 'lines' of a salmon and those of a racing yacht. There can be little doubt that in the first case the advantages would be heavily on the side of the salmon, and that the yacht would show little if any superiority. But leaving aside such theoretical considerations—for which, it is only just to say. Dr. Noël Paton and his coworkers are in no way responsible—the investigations on the Scottish salmon show that eighty to ninety per cent, of the energy liberated by them in the muscular work of swimming is derived from the fats. The hungering salmon, like a hungering man or dog, reduces to a minimum the waste of protoplasm—that peculiar jelly of albuminous substances which constitutes the chemical framework and essential mechanism of the living cells of the body. In the salmon ascending a river, as in a man ascending a mountain, the energy liberated in the work done is supplied by a vigorous oxidation, and this is evidenced by an increased absorption of oxygen and excretion of carbonic acid. The elimination of nitrogenous substances from the waste of the tissue proteids is, however, only slightly increased.

No less interesting are the processes by which the genitalia develop, since they afford an example of constructive activity almost without parallel among animals; processes so characteristic of plants, on the contrary, that they were long supposed to exhibit the generic differences in the vital mechanism in the plant and animal kingdoms. Modern research has, indeed, shown that these great apparent differences are matters of degree, not kind. Plants can not now be considered as devoted solely to absorbing carbonic acid, and by means of the heat and light of the sun synthesizing carbonaceous material. They can, and when need arises, they do draw on their store of fuel, exhale carbonic acid, and even liberate measurable quantities of heat. On the other hand, physiologists have come to admit that the cells of the animal body, although wholly dependent on the vegetable kingdom for their materials and energy, yet possess wide powers of transforming the food substances to their needs. Uncertainty has, however, attended the efforts of the investigator of metabolism in man and the higher animals. Generally when the subject of the experiment fasts, growth stops. If on the other hand the subject is fed, the origin of the substances shown to appear or increase in any tissue—for instance the fats—may be assigned with almost equal chances to any one of the constituents of the food, or to a transportation from other tissues of the body itself. In the salmon, on the contrary, the conditions are of extreme simplicity