438 INTERNAL SECRETION 



pensation for the suppression of this secretion. Where the 

 function of the pancreas has gradually become completely sup- 

 pressed, the consequent severe diabetes may be unaccompanied 

 by derangement of absorption, and the assimilation of nutriment 

 may at this stage be better than where an active pancreatic fistula 

 is present. 



Lombroso, also, believes the internal secretory function to 

 be the property of both pancreatic tissue formations. 



THE INTERNAL SECRETION OF THE GASTRIC 



AND INTESTINAL MUCOSA. 



Claude Bernard's observation, which later formed the subject 

 of considerable investigation, first showed that the secretion of 

 pancreatic fluid is dependent upon the filling of the duodenum 

 and that it reaches its maximum when the ingesta have passed 

 from the stomach into the duodenum. From the results of 

 numerous experiments, admirable both in conception and tech- 

 nique, Pawlow came to the conclusion that the mechanism by 

 which the pancreatic secretion is elaborated is by a reflex process 

 on the part of the nervous system ; the impulse proceeding from 

 the gastric mucosa is carried by centripetal vagal fibres to a 

 centre in the medulla oblongata, and from this centre stimuli are 

 sent out which, travelling by way of the centrifugal vagus or 

 splanchnic nerve, cause the pancreatic gland to secrete. 



Under Pawlow's direction, Popielski next showed that, if 

 acids are introduced into the duodenum, the pancreatic secretion 

 appears after resection of both the vagus and the splanchnic 

 nerves, after extirpation of the solar plexus, and even after 

 destruction of the spinal cord. Similar findings were observed 

 by Wertheim and Lepage and they, as well as Popielski, con- 

 cluded that the results were the outcome of a local peripheral 

 reflex. 



Bayliss and Starling, however, discovered that the pancreatic 

 secretion is elaborated if acids are introduced into the lumen of 

 a coil of the duodenum which has been freed from all nervous 

 connections. This result showed very clearly that the release 

 of the pancreatic secretion depends upon a chemical substance, 

 and that chemical stimuli are conveyed to the pancreas by way 

 of the blood-stream. According to Wertheim and Lepage, the 

 direct introduction of acids into the blood-stream has no effect 

 upon the pancreatic secretion ; hence the only possible solution 

 was that, by the aid of acids, a substance was formed in the 

 mucous membrane of the intestine. 



Bayliss and Starling obtained an extract by treating mucosa 

 scraped from the upper part of the small intestine with hydrochloric 

 acid, and this extract, when injected into the veins, provoked pro- 



