284 INFLUENCE OF THE 



that no food or saliva passes from the mouth to the stomach, upon 

 the importance of which Pawlow himself lays great stress and 

 against which the cesophageal fistula was intended to guard. 



The absence of such a precautionary measure seriously in- 

 validates the result of many of the earlier experiments of Pawlow 

 and his collaborators on the effects of vagal stimulation upon 

 pancreatic secretion. Thus, while Pawlow invariably obtained a 

 positive effect upon pancreatic secretion as a result of vagus stimu- 

 lation after certain preliminary procedures, which will presently 

 be described, had been carried out, Bayliss and Starling were quite 

 unable to find any result upon pancreatic secretion from stimula- 

 tion of the peripheral end of the vagus. It must hence be regarded 

 as a possibility that in Pawlow' s experiments, as a result perhaps 

 of stimulation of movement of the stomach by the vagal excita- 

 tion, that acid which had escaped from the stomach set free secretin 

 from the duodenal mucous membrane, and this in turn directly 

 stimulated the pancreatic cells. Bayliss and Starling, while not 

 explicitly denying a control of secretion by the vagus, state that 

 they have not in several experiments been able experimentally 

 to demonstrate the fact, and certainly regard the chemical stimulus 

 as the adequate and efficient one. 



Hence judgment must be reserved regarding the control of 

 the pancreatic secretion upon the nervous side. Still the methods 

 used may here be described from their interest as leading up to 

 the discovery of the chemical control, and as the experimental 

 basis of any future attempts at a study of the influence of the gland 

 nerves, when the additional safeguard has been provided of a fistula 

 between pylorus and duodenum, or the separation of these by 

 ligation. 



In preparing the permanent pancreatic fistula in the dogs used 

 for the experiments, Pawlow employed a modification of the method 

 used by Heidenhain. Heidenhain, in preparing his fistulse, had 

 completely resected the intestine in order to obtain a short piece of 

 the intestine into which the pancreatic duct opened, and which 

 was then, after splitting open, attached to the abdominal wall, 

 the continuity of the intestine having of course been restored 

 by suturing together the two ends of the intestine after the removal 

 of the short piece containing the opening of the pancreatic duct. 

 Pawlow improved upon this by merely cutting out a small oval 

 patch of the intestinal wall around the entrance of the pancreatic 



