PHYSIOLOGY OF THE DIGESTIVE GLANDS 



427 



enterokinase, an enzyme present in the intestinal juice. By such a mechan- 

 ism the mucosa of the pancreatic duct is protected against autodigestion 

 by trypsin. 



NERVOUS CONTROL OF PANCREAS 



Prior to the discovery of secretin, Pavlov 1 and his pupils had published 

 numerous experiments purporting to show that the secretion of pancreatic 



Fig. 146. Pancreatic acini stained with hematoxylin. The acini at the top and to the left 

 of the figure are from a resting- gland, those to the right being from one that had been secreting 

 for over three hours as a result of acid in the duodenum. The lowermost figure is from a gland 

 the vagus nerve supply of which had been stimulated off and on for several hours. Note that 

 the zymogen granules are extruded only after vagus activity but not after secretin activity. (From 

 Babkin, Rubaschkin and Ssawitsch.) 



juice is controlled through the vagus nerve. The amount of secretion 

 produced by nervous stimulation was, however, never found to be so large 

 as that produced by secretin, and for several years after the discovery of 



