The Metabolism of Proteins and Amino Acids

This year is an appropriate one for reviewing the evidence which invalidated the classical theory of protein metabolism (in animals) epitomized in the terms "endogenous" and "exogenous" metabolism; the evidence which has established the theory proposed by Borsook & Keighley (1) and confirmed and extended by Schoenheimer and his colleagues (2) and by Tarver & Schmidt (3) will also be reviewed in this context.