INFLUENCE OF NERVES ON PANCREATIC SECRETION. 549 



secretion is still fairly marked, a further stimulation will result in 

 inhibition of the secretion, which inhibition ends with the stimulation 

 provoking it. The spontaneous secretion that is sometimes observed 

 before the experiment begins, is stopped by cutting both vagi, and is 

 therefore due to impulses proceeding from the upper portion of the 

 cervical spinal cord or the medulla oblongata. Pawlow also points out 

 the importance of the circulation in general for the secretion. A brief 

 stoppage of the blood stream caused a cessation of the flow, and an 

 anaemic condition of the gland resulting from reflex nervous influence 

 caused a similar cessation. The latent period relapsing before the 

 secretion resulting from stimulation becomes obvious, is, according to 

 Pawlow, two to three minutes, but later observers such as Mette 1 and 

 Kudrewetzky 2 regard it as somewhat longer, namely, from four to six 

 minutes. Mette in addition found that, though previous observers 

 (Lewaschew, Heidenhain) had stated that the proteolytic ferment failed 

 in the pancreatic juice of dogs which had fasted five or six days, yet it 

 was continuously obtainable by stimulation of the vagus. Gottlieb 3 

 confirms the old observation, that stimulation of the divided vagus at the 

 central end causes inhibition of the secretion, and he refers this result to 

 general spasm of the abdominal blood vessels. Another contribution to 

 the study of the inhibitory influences on the pancreatic secretion has 

 recently been made by Popielski. 4 It had been previously noticed by 

 Mette and Kudrewetzky that the secretion caused by stimulating one 

 vagus could frequently be stopped by stimulating the other vagus. 

 Hence it was inferred that antagonistic fibres passed in these nerves. 

 Stimulation of such fibres may bring about sometimes a lengthened 

 latent period, sometimes total inhibition of the flow. Mette regarded 

 this as due to the existence of vaso-constrictor fibres, Kudrewetzky 

 to the presence of specific fibres inhibiting the secretion. Popielski 

 endeavoured to elucidate this point. He found that a secretion evoked 

 by peripheral stimulation of the vagus could later, by a repetition of 

 the stimulation of the same nerve, be interrupted. The interruption 

 started some seven seconds after the stimulation commenced, and 

 lasted about the same interval beyond the cessation of stimulation. 

 This inhibition also follows from stimulation of the other vagus, as 

 previously observed, and is best shown when the exciting current 

 is not too strong. The branch of the vagus which lies behind the 

 oesophagus in the thoracic cavity is that concerned with changes in 

 the secretory activity of the pancreas. Dolinski 5 had previously 

 observed that the introduction of acids into the duodenum produces 

 a flow of pancreatic juice (see next section). Popielski made use of 

 this fact to see how far the secretion thus excited could be inhibited 

 by nerve stimulation. He found that a secretion so produced 

 was inhibited with perfect regularity by stimulation of the vagus. 

 Stimulation of the vagus, after secretion evoked by pilocarpine, pro- 

 duced the same result. Popielski points out that there are three 

 ways in which inhibition of the flow of pancreatic juice can be brought 

 about 



1. By stimulation of vaso-constrictor fibres. 



1 Arch.f. Physio!., Leipzig, 1894, Supp. Bd. 2 Ibid., 1894. 



3 Arch. f. exper. Path. u. PharmakoL, Leipzig, 1895, Bd. xxxiii. 



4 CentralU.f. PhysioL, Leipzig u. Wien, 1896, Bd. x. 



5 Arch, de ac. bioL, St., P^tersbourg, 1895, vol. iii. 



