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 duo- 

 denum. Here they meet the secretions of three glands, namely, the pancreas, 

 the liver, and the tubular glands of the intestine. 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 simul- 

 taneous 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 foodstuffs, 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 



PURE pancreatic juice can be obtained eith&r from an animal with a perma- 

 nent 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. 749. 



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



N N 

 of sodium carbonate, its alkalinity varying between and Na 2 C0 3 . It is 



lliriv.fore 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 into three groups, a small amount of nucleo-protein precipitated 

 on acidification, a protein coagulating at 55 C., and another at about 75 C. 

 The juice tends to become poorer in proteins and richer in alkali as secre- 



748 



