Northrop's phenomenon; the digestion of proteins by enzymes in the presence of gelatin

1. Evidence has been found that Northrop's phenomenon (so called by us) is produced in the digestion of casein or hemoglobin brought about by trypsin, papain, and pepsin either crude or crystalline in the presence of gelatin. 2. Anson's and Kunitz' methods permit the measure of proteolytic activity of any protease on casein or hemoglobin substrate in the presence of gelatin, even in very small quantities and with prolonged digestion time.