Nitrogen Retention on Casein Digests

1. Continuous daily nitrogen balances covering 140 days have been made on rats restricted to a nitrogen-low basal diet, supplemented for various periods with casein, and an acid or an enzymic digest of casein. 2. The enzymic digest fed in comparison with casein, resulted in nitrogen retention of approximately the same magnitude as the unhydrolyzed protein. 3. The acid digest, supplemented with 0.2% tryptophane likewise gave positive nitrogen balances, but without the addition of the essential tryptophane, was refused by the animals. 4. When both the unsupplemented acid digest, and the enzymic digest were administered by stomach tube, the latter was well retained, but the former gave a slight negative balance with some indication that it was partially effective in supplying animal requirement for nitrogen.