OF THE ALIMENTARY CANAL 119 



membrane of the duodenum, a soluble chemical 

 substance is formed called " secretin," which passes 

 into the rootlets of the portal vein, is carried to the 

 liver and heart, and thence all over the body. Some 

 of it in due course reaches the pancreas, and a flow of 

 pancreatic juice is at once instituted and continues 

 as long as the acid contents of the stomach continue 

 to enter the duodenum. The secretion acts chemi- 

 cally on the pancreatic cells, hberating steapsin from 

 pro-steapsin, amylopsin from pro-amylopsin, and 

 trypsinogen from pro-trypsinogen. There is some 

 evidence that secretin stimulates also the activity of 

 the hver cells, thus pouring into the bowel not only 

 pancreatic juice but bile. 



We find in this mechanism a clear indication for 

 the administration of hydrochloric acid in cases 

 where that of the gastric juice is deficient. At least 

 we may be able to preserve for the patient the 

 activity of his pancreatic juice, which is hkely to be 

 suppressed when the usual stimulus is lacking. The 

 exhibition of secretin itself has so far been a failure ; 

 it is not absorbed from the bowel, and giving it 

 subcutaneously produces dangerous depression, due 

 apparently to other substances, which we do not 

 know how to separate, extracted along with it from 

 the duodenal mucous membrane. 



Pawlow and his followers have described a mar- 

 vellous adaptation of the various pancreatic ferments 

 to the work in hand ; thus, they thought that a 

 meat diet called forth much trypsin, and a starchy 

 diet much amylopsin. These statements were made 

 before we knew that the flow of pancreatic juice 



