222 PHYSIOLOGY OF ALIMENTATION. 





3. The Relation of the Nervous System to Pancreatic 

 Secretion. The secretion of juice by the pancreas is in- 

 fluenced by the vagus nerve in much the same way as the 

 secretion from the stomach. In this chapter of physiology 

 also, PAWLOwand his coworkers have done most within recent 

 years to advance the state of our knowledge. The following 

 experiment shows unequivocally that the vagus nerve con- 

 tains fibres which influence the secretion of the pancreatic 

 juice. A dog in which a permanent pancreatic fistula has 

 been made after the fashion described above is employed. The 

 vagus nerve is divided in the neck on one side, the peripheral 

 end is laid bare, and after having a ligature passed around 

 it, is preserved under the skin. On the fourth day after 

 division the severed nerve is carefully pulled out of the 

 wound without hurting the dog in any way. No juice flows 

 from the pancreatic fistula. But one or two minutes after 

 the peripheral end of the vagus is stimulated by an induc- 

 tion current a drop of juice appears at the orifice of the 

 pancreatic duct, which is soon followed by another and 

 another in rapid succession. If the induction current is 

 interrupted the pancreatic juice continues to flow for four 

 or five minutes and then ceases. If now the stimulation be 

 renewed juice appears a second time, and so on. 



The reason why the older observers never obtained a flow 

 of pancreatic juice when they stimulated the vagus is due to 

 the fact that in their experiments performed at one sitting 

 peripheral stimuli initiated by anaesthetic, pain due to opera- 

 tion, etc., acted upon the pancreas and produced a reflex 

 inhibition. That such sensory stimuli exert an inhibitory ef- 

 fect upon the pancreatic gland has been shown by BERNSTEIN, 

 PAWLOW, and others. Circulatory disturbances also inter- 

 fere with pancreatic activity. In the experiment described 

 above such peripheral stimuli are carefully avoided, first 

 by utilizing an animal which has recovered from the effects 

 of anaesthetic and operation, arfd secondly by stimulating 

 the vagus at a time when its cardiac fibres have degenerated 



