364 



VETERINAEY PHYSIOLOGY 



last causes a moderate production of trypsin, little diastase, 

 and a comparatively large amount of lipase. 



As to the mode of production of these enzymes, it is known 

 that trypsin is not formed as such in the cells, for the secretion 

 direct from the acini has no tryptic action. A forerunner of 

 trypsin trypsinogen is produced, and this changes into 

 trypsin after it is secreted. The intestinal secretion contains 



FIG. 161. To show the mode of action of secretin and the action of the 

 vagus nerve, on the secretion of the pancreas and the activation of 

 trypssinogen by enterokinase. 



something of the nature of an enzyme which has been termed 

 enterokinase, which has the power of bringing about this change. 



It is doubtful whether the pancreatic secretion contains 

 any true rennin, although it produces a modified clotting of 

 milk, under certain conditions. 



3. Physiology of Pancreatic Secretion. The secretion of 

 pancreatic juice is not constant, but is induced when the acid 

 chyme passes into the duodenum. This occurs even when all 

 the nerves to the intestine have been cut, and it appears from 



