Protein differing from the normal one by the content of S-S-bonds and by the amount of the carbohydrate component was found in the acid-soluble fraction of skin collagen in rats which were fed the protein-free diet and the protein-free diet with the glycine loading for 3 and 14 days and tryptophan for 1, 2 and 3 days. The result testifies to the fact that under extremal states in the animal skin there occurs the synthesis of collagen the structure of which differs from that in the normal animal skin.