Abstract
1. A toxic constituent is present in the fresh pancreas of dogs before trypsinogen can have been activated. 2. The toxic fraction is present in the beta-nucleoprotein, and therefore is thermostable. 3. It is gradually destroyed by autolysis but can be obtained in concentrated form from a gland which has autolyzed 24 hours. 4. The toxic material is probably protein in nature. 5. Intravenous or intraperitoneal injection of from 0.05 to O.I gm. per kilo of body weight is usually fatal and elicits in dogs symptoms comparable to those of spontaneous hemorrhagic necrosis of the pancreas. 6. Dog pancreas differs from that of beef or pig in that guanylic acid and toxic protein combined with it are slowly broken down by autolysis. 7. After autolysis of dog pancreas the toxic protein and guanylic acid may be separated and obtained in relatively pure form.