352 On the so-called "Peripheral Beflex Secretion " of the Pancreas. 



" On the Causation of the so-called ' Peripheral Eeflex Secretion ' 

 of the Pancreas. (Preliminary Communication.)" By W. M. 

 BAYLISS, D.Sc., and ERNEST H. STARLING, M.D., F.RS. Re- 

 ceived January 22, Read January 23, 1902. 



(Prom the Physiological Laboratory, University College, London.) 



Introduction. 



It has long been known that the introduction of acid into the 

 duodenum causes a flow of pancreatic juice, and it has been shown 

 recently by Popielski, and by Wertheimer and Le Page, that this flow 

 still occurs after nervous isolation of duodenum and pancreas. 



Wertheimer also mentions that the flow can be excited by injection 

 of acid into the jejunum, but not by introduction of acid into the loAver 

 part of the ileum. 



These authors conclude that the secretion is a local reflex, the 

 centres being situated in the scattered ganglia of the pancreas, or, in 

 the case of the jejunum, in the ganglia of the solar plexus (Wertheimer). 



Results. 



The secretion excited by introduction of acid into the jejunum 

 cannot be reflex, since it occurs after extirpation of the solar plexus 

 and destruction of all the nervous filaments passing to the isolated 

 loop of jejunum. It also occurs after intravenous injection of O01 

 gramme atropin sulphate. It must therefore be due to direct excita- 

 tion of the gland cells by a substance or substances conveyed to the 

 gland from the bowel by the blood stream. 



The exciting substance is not acid. Wertheimer has shown that 

 injection of 0'4 per cent. HC1 into the blood stream has no excitatory 

 influence on the pancreas. 



The secretion must therefore be due to some substance produced in 

 the intestinal mucous membrane under the influence of the acid, and 

 carried thence by the blood stream to the gland. 



This conclusion was at once confirmed by experiment. 



When the mucous membrane of the jejunum or duodenum is exposed 

 to the action of 0'4 per cent. HC1 a body is produced which, when 

 injected in minimal doses into the blood stream, produces a copious 

 secretion of pancreatic juice. This body, which for the present we 

 may term secretin, is associated with another body with a pronounced 

 lowering effect on the blood pressure. The two bodies are not identical, 

 since acid extracts of the lower end of the ileum produce the pressure- 

 lowering effect, but have no excitatory influence on the pancreas. 



The action of the acid is to split off the secretin from a precursor, 



