THE INTESTINE 59 



clear that ordinary reflex action was out of the question. 

 Popielski concluded, therefore, that the secretion is due to a 

 local, a peripheral, reflex action, the centres for which are 

 situated in the scattered ganglia found throughout the 

 pancreas. 



Wertheimer and Le Page, however, made a very interesting 

 discovery namely, that secretion of the pancreatic juice 

 could also be induced by the injection of acid into the lower 

 portions of the small intestine, the effect, however, gradually 

 diminishing as the injection was made nearer and nearer the 

 lower end of the small intestine, so that no effect at all was 

 produced from the lower two feet of the ileum. Secretion could 

 be excited from a loop of jejunum entirely isolated from the 

 duodenum. They concluded that, in this latter case, the reflex 

 centres are situated in the ganglia of the solar plexus, but they 

 did not perform the obvious control experiment of injecting 

 acid into an isolated loop of jejunum after extirpation of these 

 ganglia. 



About this time Bayliss and Starling were engaged upon 

 investigations into the local nervous reflexes concerned with 

 movements of the intestine. These observers made numerous 

 experiments to test the validity of a hypothesis such as that of 

 Wertheimer and Le Page, but soon found that in the case of 

 the pancreatic secretion they were dealing with an entirely 

 different order of phenomena, and that the secretion of the 

 pancreas is normally called into play, not by nervous channels 

 at all, but by a chemical substance which is formed in the 

 mucous membrane of the upper parts of the small intestine 

 under the influence of acid, and is carried thence by the blood- 

 stream to the gland cells of the pancreas. 



The experiments of Bayliss and Starling confirmed those of 

 previous observers in so far as they found that, after exclusion 

 of all nerve centres except those in the pancreas, a secretion of 

 pancreatic juice is obtained by the introduction of acid into the 

 duodenum. But, as pointed out above, the experimentum 

 crucis of taking an isolated loop of intestine, dividing the 

 mesenteric nerves supplying it, and then injecting acid into it, 

 had not been performed. 



Bayliss and Starling found that when this was carried out a 

 well-marked flow of pancreatic juice was brought about. They 

 next cut out the loop of jejunum, scraped off the mucous 



