NERVOUS SYSTEM UPON SECRETION 181 



and preparation of vagus below the heart, insertion of pancreatic 

 cannula, and slow rhythmic excitation of the nerve. 



In using the acute method, evidence of the presence of inhibitory 

 fibres was obtained similar to that mentioned above in the case 

 of the gastric secretion. Thus it was found that after a steady 

 flow of secretion had been set up by stimulation of one vagus, 

 similar and simultaneous excitation of the other vagus often led 

 after a latent period to a suppression of the flow. 



An inhibitory influence of the sympathetic fibres was also 

 demonstrated in the case of the acute experiment. The first 

 effect of stimulation of the sympathetic by an induced current 

 was a slight increase in flow ; this, however, lasted only for a few 

 seconds, and was followed later, and especially after stopping the 

 stimulus, by a suppression of the secretion. Similar inhibitory 

 results were obtained as a result of mechanical stimulation with 

 the tetanometer, and in a nerve in which degeneration had been 

 allowed to proceed for three or four days a purely inhibitory effect 

 was obtained as a result of electrical stimulation. 



The presence of inhibitory fibres in the vagus was also shown 

 by Popielski, by the employment of another method. This 

 observer caused a continuous flow of pancreatic secretion by 

 injection of dilute hydrochloric acid into the duodenum, and then 

 strongly stimulated the vagus, when a slowing of the secretion 

 was always obtained, often to a complete standstill. Excitation 

 of the sympathetic under like circumstances did not produce such 

 a marked effect, but usually gave rise to decrease in rate of secretion 

 after a long latent period. 



The important fact that the presence of acids in the duodenum 

 gives rise to a copious and long-continued flow of pancreatic juice 

 was established by Dolinski in Pawlow's laboratory in 1894. The 

 whole mental aspect of the workers in Pawlow's laboratory at 

 that period was directed towards the discovery of the innervation 

 of the pancreas, and hence naturally the flow of pancreatic secretion 

 caused by the presence of the acid in the duodenum was looked 

 upon as a reflex act in which the stimulation of the acid upon 

 peripheral nerve-endings in the duodenal mucous membrane give 

 rise to the afferent impulses. 



The secretion set up by the presence of acid in the duodenum 

 was further studied by Popielski and by Wertheimer and Lepage, 

 who showed that secretion was still evoked by the introduction 



