Fig. 2.—Records of carotid blood pressure and flow of pancreatic juice on intravenous injection of secretin prepared by us according to the Beveridge method. X, injection of 10 c.c. of the secretin; b, record of flow of pancreatic juice in drops. Tracing A, the 10 c.c. of Beveridge’s secretin injected had been digested for five minutes with 3 c.c. of human gastric juice. Tracing B, injection of 10 c.c. of the same secretin preparation not subjected to gastric digestion. Showing rapid and complete destruction of Beveridge’s secretin by human gastric juice.
It will be seen that the rate of deterioration (oxidation or decomposition) of the secretin is practically the same whether prepared according to Bayliss and Starling or according to Beveridge (Figure 3). In both preparations the rate of deterioration is most rapid the first few days after preparation. It is scarcely necessary to point out that secretin preparations not kept constantly at low temperature and in the dark, as in the above experiments, will deteriorate more rapidly.
Fig. 3.—Records of carotid blood pressure and flow of pancreatic juice on intravenous injection of secretin preparations. X, injection of 10 c.c. secretin; b, record of flow of pancreatic juice in drops. Tracing A, secretin prepared according to the Beveridge method September 30. I, injection of 10 c.c. October 2. II, injection of 10 c.c. November 30. Tracing B, secretin prepared by the Bayliss-Starling method September 30. III, injection of 10 c.c. October 2; IV, injection of 10 c.c. November 30. Showing no greater stability of Beveridge’s secretion over that of Bayliss and Starling.
Why can we hope that the addition of serum or any solution of protein will render secretin more stable? In the intact man or animal under normal conditions of digestion, secretin reaches the pancreas by way of the blood, that is, it is in solution in blood. Does that fact render the secretin stable? By no means. The reader is familiar with the fact that the response of the pancreas to a single intravenous administration of secretin is very transitory (5–15 min.). The cessation of activity is due, not to fatigue of the pancreas, as a second injection of secretin gives a prompt response of pancreatic secretion, but to the disappearance of active secretin from the blood. In fact, secretin left in the test tube or in the bottle remains active over a much longer period of time than when introduced into the blood stream.
IV. Beveridge’s Secretin Given by Mouth to the Intact Animal Has No Specific Action on the Pancreas.—Active secretin prepared according to the method of Beveridge was fed on an empty stomach to a small dog (5 kilo) with permanent fistula of one of the pancreatic ducts. On control days we gave the dog (a) equal quantities of n/10 HCl, and (b) bread and milk. The Beveridge secretin was prepared with 0.3 per cent. HCl and the addition of 0.2 per cent. serum. The results may be stated by the following summary:
GIVING BEVERIDGE’S SECRETIN BY MOUTH