PHYSIOLOGY OF THE DIGESTIVE GLANDS 



463 



the latter hormone, much doubt existed as to the correctness of Pavlov's 

 claim. As in many other fields of physiological science, investigators at- 

 tempted to show that one or the other mechanism obtained, and they were 

 not inclined to consider the possibility that both mechanisms might exist 

 side by side. That such is the case, however, is clear from the most recent 

 work, in which it has been found that if proper precautions are taken, 

 repeated stimulation of the vagus nerve does call forth a secretion of 

 pancreatic juice which, besides being less copious than that following 



II. III. 



Fig. 147. Three preparations of pancreatic acini stained by eosin orange toluidin blue. The 

 acini of Fig. I were from a gland after vagus stimulation, and it is noted that besides free ex- 

 trusion of the granules, globules staining with orange (and appearing in deep black in the photo- 

 graph) have formed and may be present in the ductules. Some of the globules, however, change 

 in their staining properties, becoming light red (dark gray in photograph). The acini in II and III 

 were from glands excited by secretin. No globules appear; the granules remain, and fine canaliculi 

 appear in the clear protoplasm. (From Babkin, Rubaschkin and Ssawitsch.) 



secretin injection, differs from it in the important fact that it contains 

 not trypsinogen but active trypsin. Since the normal pancreatic juice 

 contains trypsinogen, this last mentioned fact would appear to indicate 

 that vagus control of the normal secretion can not be an important affair. 

 The vagus secretion of pancreatic juice is, moreover, paralyzed by atro- 

 pine, which has no action on the secretin mechanism (cf. Bayliss). 



