THE INNERVATION OF GLANDULAR STRUCTURES 127 



pointed out that the secretion of gastric juice which can be evoked 

 by the presence or smell of food does not occur after section of 

 the vagi nerves, and that stimulation of the peripheral end of the 

 cut vagus nerve will cause a flow of gastric juice provided that 

 too much anaesthetic has not been given. There is no evidence 

 that the splanchnic nerves have any effect on the secretion of 

 gastric juice. 



The innervation of the pancreatic glands is not so clear as 

 that of the gastric glands, because the stimulation of such a 

 nerve as the vagus, which causes a flow of pancreatic juice, 

 causes at the same time a secretion of gastric juice, and Bayliss 

 and Starling have shown that the presence of the acid of the 

 gastric juice in the duodenum causes an internal secretion from 

 the cells of the duodenal mucous membrane of a substance, 

 secretin, which on reaching the pancreatic gland produces a 

 flow of pancreatic juice. For this reason it is not so certain that 

 stimulation of the vagus nerve produces pancreatic secretion 

 as the result of the excitation of nerve cells which send secretory 

 fibres to the pancreas. Pawlow however has shown that, if the 

 stomach be ligatured off and its contents made alkaline, stimula- 

 tion of the vagus will still cause a secretion of pancreatic juice, 

 which is very much less in extent than that seen when there is 

 free access of gastric juice to the duodenal membrane. We must 

 conclude that there are secretory nerves for the pancreas which 

 arise from nerve cells connected with vagus connector nerve 

 fibres. As to the splanchnic nerves, the evidence that they 

 contain secretory fibres for the pancreas is still more doubtful. 



I have already referred to the prostate gland in connexion 

 with the muscular tissues surrounding it. According to Barring- 

 ton there is some evidence that in the case of this gland as well 

 as in that of Bartolini's and Cowper's glands, the same question 

 of double innervation occurs, as has already been discussed at the 

 anterior end of the body. He shows that the mucous secretion 

 of Cowper's glands and of Bartolini's glands is controlled by the 

 hypogastric nerves, the secretory nerve cells being situated peri- 

 pherally and not in the inferior mesenteric ganglion, since the 

 effect of stimulation of the hypogastric nerve is abolished by 

 degenerative section of the inferior splanchnic nerves. He also 

 finds that these glands are made to secrete by stimulation of the 

 pelvic nerve, but to a much less extent than by stimulation of the 



