Page:Popular Science Monthly Volume 72.djvu/406

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point of view, viz., that the processes of animal metabolism are peculiar and are by no means always concomitant with ordinary oxidation. Outside the animal body, the customary components of our daily food, the proteins, fats and carbohydrates, are not affected by oxygen even at the body temperature or by long exposure to the gas. Catalytic action is a necessary prelude to their oxidation, and it is the smaller molecules resulting from the action of enzymes working through catalysis that are mainly burned up or broken down with liberation of their contained energy.

The processes of nutrition are truly complicated, and we can readily conjecture that their harmonious working is dependent in large measure upon the integrity of many closely related operations. Enzymes must be elaborated in due proportions, both in digestive secretions and in tissue cells; proper conditions for enzymolysis must prevail at the places where the reactions take place, since enzymes are extremely sensitive to their environment and fail to work unless all the requirements are fully met; proper conditions of circulation of blood and lymph must be maintained, in order to supply fresh pabulum and to prevent undue accumulation of the products of enzymolysis. In short, there are a multitude of accessory reactions to be preserved in their proper sequence and normal rhythm if perversions of nutrition are to be avoided. Many a substance known to have a deleterious effect upon nutrition does so in virtue of its action upon some one or more enzymes with which it may be brought in contact in the body. Take, for example, the well-known influence of alcohol as a factor in the causation of gout. In this disease, there is an increased amount of uric acid in the system, due in part to an inhibition of its oxidation and consequent destruction. When alcoholic fluids are taken, together with an excess of meat or kindred animal foods, the kidneys at once excrete increased amounts of uric acid, in harmony with the increased content in the blood. It is a well-known fact that alcohol interferes with the oxidative processes in the liver. It is equally well known to-day that the liver and other organs contain an enzyme, or more specifically an oxidase, which has the power of oxidizing uric acid to urea and other products. After the ingestion of alcohol and animal foods rich in uric acid precursors, the notable increase of uric acid in the blood and urine is considered as due to the inhibitory action of alcohol on this oxidase, which under normal conditions causes more or less destruction of uric acid. The failure of the enzyme to accomplish its ordinary duty naturally results in an accumulation of uric acid in the system, although the kidneys plainly endeavor to meet the new conditions by increased elimination. Hence, we see that the predisposition to the development of gout caused by the ingestion of a high protein diet reinforced by alcohol is to be explained in part at least by the direct