THE INTESTINAL HORMONE 131 



however, that acid alone introduced into the circu- 

 lation has no effect on the pancreatic secretion, so 

 that the body of which we were in search could not 

 be the acid itself." 



This suggested that there may be a something in 

 the wall of the intestine which was responsible for 

 the action. "The next step in our experiment was 

 plain namely, to cut out the loop of jejenum, 

 scrape off the mucous membrane (tissue covering 

 the surface), rub it up with sand and four-tenths 

 per cent, hydrochloric acid in a mortar, filter 

 through cotton wool to get rid of lumps and sand, 

 and inject the extract into a vein ; . . . After a 

 period of about 20 seconds, we obtained a flow of 

 pancreatic juice at more than twice the rate pro- 

 duced at the beginning of the experiment by intro- 

 duction of acid into the duodenum." 



A pretty variation of this experiment was per- 

 formed by Enriquez and Hallion. They conveyed 

 the blood stream from the vessels of one dog (A) 

 into those of another (B) and found that after in- 

 jecting acid into the small intestine of dog (A), 

 pancreatic juice began to flow in dog (B) ! 



Secretin. Though the hormone responsible for 

 the flow of pancreatic juice has not been isolated in 

 the pure state, its discoverers have given it the 

 name "secretin" (from the Greek "to excite.") 

 Since a watery extract of the mucous membrane of 

 the intestine when injected into the blood stream, 



