CHAPTER VIII. 

 PANCREATIC DIGESTION. 



As soon as the food mixture leaves the stomach it comes into 

 intimate contact with the bile and the pancreatic juice. Since these 

 fluids are alkaline in reaction there can obviously be no further 

 peptic activity after they have become intimately mixed with the 

 chyme and have neutralized the acidity previously imparted to it by 

 the hydrochloric acid of the gastric juice. The pancreatic juice 

 reaches the intestine through the duct of Wirsung which opens into 

 the intestine near the pylorus. 



Normally the secretion of pancreatic juice is brought about by the 

 stimulation produced by the acid chyme as it enters the duodenum. 

 This secretion is probably not due to a nervous reflex as was believed 

 by Pawlow but rather, as Bayliss and Starling have shown, is de- 

 pendent upon the presence, in the epithelial cells of the duodenum 

 and jejunum of a body known as prosecretin. This body is changed 

 into secretin 1 through the hydrolytic action of the acid present in the 

 chyme. The secretin is then absorbed by the blood, passes to the 

 pancreas and stimulates the pancreatic cells, causing a flow of 

 pancreatic juice. The quantity of juice secreted under these con- 

 ditions is proportional to the amount of secretin present. The ac- 

 tivity of secretin solutions is not diminished by boiling, hence the 

 body does not react like an enzyme. Further study of the body 

 may show it to be a definite chemical individual of relatively low 

 molecular weight. It has not been possible thus far to obtain secre- 

 tin from any tissues except the mucous membrane of the duodenum 

 and jejunum. 



The juice as obtained from a permanent fistula differs greatly 

 in its properties from the juice as obtained from a temporary fistula, 

 and neither form of fluid possesses the properties of the normal 

 fluid. Pancreatic juice collected by Glaessner from a natural fistula 

 has been found to be a colorless, clear, strongly alkaline fluid which 

 foams readily. It is further characterized by containing albumin, 



1 Secretin belongs to the class of substances called hormones or chemical 

 messengers. 



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