An Improved Procedure for Metabolism

There are two general types of metabolism experiments: those of relatively short duration covering several periods, each from a few days to a week in length; and those carried out over as long a period as possible. As examples of the first type we have such investigations as the study of the effect of a given substance upon the nitrogenous equilibrium, or the study of the ability of the animal body to divert urea or other excretory nitrogen for the synthesis of special conjugate radicles of interest in intermediary metabolism; other examples will doubtless suggest themselves to the reader. As illustrations of metabolism experiments extending over months rather than days may be cited the investigations of Abderhalden and his collaborators into the ability of completely digested protein to maintain nitrogenous equilibrium over long periods and to replace adequately the intact protein molecule in nutrition. Some of Abderhalden’s experiments lasted over a period of 74 days. Examination of the protocols presented in Abderhalden’s paper (1912) discloses the fact that loss of the desire to eat on the part of the experimental animals presented quite an obstacle to the complete success of the experiments. This failure of appetite appeared anywhere from the 7th to the 21st day of the experiment, a fact that is striking in its similarity to the behavior of our own animals which were fed diets adequate in all respects except vitamin B (and vitamin C?). Examination of Abderhalden’s diets makes it