INTESTINAL DIGESTION 



THE products of gastric digestion, after being worked up in the 

 pyloric half of the stomach, are passed at intervals into the first part 

 of the duodenum. Here they meet the secretions of three glands, 

 namely, the pancreas, the liver, and the tubular glands of the intes- 

 tine. In addition to these must be mentioned the secretion of 

 Brunner's glands, which are situated at the very beginning of the 

 duodenum. The glands of Brunner extend only over about half to 

 one and a half inches in the carnivora, such as the dog or cat, but 

 in the herbivora they may be found occupying the upper six inches 

 of the intestine. The secretion of these various juices is practically 

 simultaneous and is aroused by the very act of entry of the acid 

 chyme into the duodenum. Although they co-operate in their action 

 on the food-stuffs, it will be convenient to deal separately with each 

 both as regards their action and the mechanism of their secretion. 



SECTION V 

 THE PANCREATIC JUICE 



PUEE pancreatic juice can be obtained either from an animal 

 with a permanent fistula or from one with a temporary fistula by the 

 injection of secretin into the animal's veins. A flow of pancreatic 

 juice may also be produced by the administration of pilocarpine. 

 This drug acts, however, as a poison on many tissues of the body, not 

 confining its action to the pancreas or even to the secreting glands. 

 It is not to be wondered at therefore that the pancreatic juice 

 obtained by its injection differs in quality from that obtained by the 

 more natural method of injection of secretin. The average com- 

 position of pancreatic juice is shown in the Table on p. 789. 



It is a clear or slightly opalescent fluid, strongly alkaline from 

 the presence of sodium carbonate, its alkalinity varying between 

 N N 



and Na^COg. It is therefore about as alkaline as gastric 



juice is acid, and it will be found that equal quantities of gastric 

 juice and pancreatic juice when added together practically neutralise 



one another. The proteins of the juice may be roughly divided 



788 



