On parenteral protein assimilation

The results of recent work on the fate of protein introduced parenterally led to the conviction that such protein is assimilated and utilized by the organism in the same manner and in accordance with the same laws as protein ingested per os. However, there exists a considerable divergence in the views on the mechanism by which this assimilation is accomplished.

Very recently Freund advanced a theory that protein introduced into the organism subcutaneously or through the circulation is eliminated into the intestinal tract where it undergoes the usual digestion and absorption.

The present investigation aimed to test the correctness of the last theory. An animal deprived of its jejunum and ileum was placed on a standard diet and brought into a condition of nitrogenous equilibrium. On the days of experiments the animal received a subcutaneous injection of horse serum, heated for one half hour at 60° C. The volume of injected serum was equivalent to 1.5 grams of nitrogen. The elimination of additional nitrogen was followed for several days following the days of the serum injection. In all experiments was noted a complete retention of the protein introduced parenterally in the same manner as this occurs in normal animals. Thus the theory of Freund is contradicted by the results of our experiments.