Inability of Thymine to Substitute for Folic Acid in the Rat

Abstract
Thymine had no curative or preventive effect on the course of folic acid deficiency in the rat with respect to growth or to any part of the blood picture, when it was fed daily in amts. equivalent to 2.1, 3.5, 4.2, and 7.2 [gamma] of folic acid as detd. microbiologically. Thymine is thus not a true substitute for folic acid, and when folic-acid-like activity is shown by thymine, pyrimidines, or other prepns., some indirect mode of action must be operating.