REGULATION OF THE PANCREATIC SECRETION 229 



still purer state, the filtrate may be treated with absolute 

 alcohol and ether, which precipitates certain impurities but 

 allows the secretin to remain in solution. Secretin is there- 

 fore a substance which is unaltered by boiling and is soluble 

 in alcohol. It cart moreover be shown that it is diffusible. 

 It is not necessary that the mucous membrane from which 

 the pancreatic secretin is to be obtained should be living. 

 It can be obtained just as well from an intestine which has 

 been killed by boiling. Pancreatic secretin has, therefore, 

 none of the ordinary characteristics of a ferment, and recent 

 experiments seem to indicate that it belongs to the class of 

 the peptones. It is possible, therefore, that secretin repre- 

 sents nothing but a product of proteolytic activity. 



A few cubic centimeters of the secretin-containing filtrate 

 obtained as described above when injected into the veins of 

 an animal call forth a plentiful secretion of clear pancreatic 

 juice, which may be collected by means of a cannula placed 

 in the pancreatic duct. The pancreatic secretin obtained 

 from one animal is not specific for that class alone, but will 

 when injected into the veins of any other vertebrate call 

 forth a copious pancreatic flow. It is well to add that the 

 pancreatic juice obtained after the injection of secretin is to 

 all appearances identical with that obtained after an ordinary 

 meal. 



BAYLISS and STARLING'S findings alter somewhat our con- 

 ception of the events which follow each other in the intestinal 

 canal. A consideration of the facts which have been out- 

 lined above makes us imagine the changes which occur here 

 to be somewhat as follows: The acid gastric contents enter 

 the duodenum and bring about the formation of pancreatic 

 secretin. This is absorbed into the circulation and, passing 

 with the blood-current through the pancreas, causes a secre- 

 tion of pancreatic juice. Since the pancreatic juice is able to 

 neutralize free acids, it will decrease little by little the acidity 

 of the gastric contents which have come into the duodenum. 

 Little by little also will the rate of production of secretin be 



