THE GLANDS OF THE STOMACH 263 



3. THE GLANDS OF THE STOMACH 

 A. SECRETORY NERVES 



Early observations on the secretion of gastric juice for the most part 

 tended to show that this process scarcely came within the control of the 

 central nervous system. Some few observations there were, it is true, which 

 indicated such an influence, but they were rather scattered and were outnum- 

 bered by other observations which made it more likely that the extrinsic nerves 

 to the stomach had no influence of a direct kind upon its secretory activity. 

 In the year 1889, however, Pawlow and Schumow-Simanowsky demonstrated 

 that the vagus contains secretory fibers for the gastric glands. 



Richet had found in the case of a man with an oesophageal stricture and 

 upon whom a stomach fistula had been made, that chewing strongly sapid foods 

 produced immediately a flow of gastric juice from the fistula. It was natural 

 to regard this secretion as a reflex. 



The above-named authors undertook to establish this conclusion experiment- 

 ally, and for the purpose made on dogs an cesophageal fistula besides the usual 

 stomach fistula. When the animal received something to eat and swallowed a 

 bolus, it of course came out through the opening in the neck without ever reach- 

 ing the stomach ("fictitious feeding")- Nevertheless, after a latent period of 

 five to six minutes a copious secretion of gastric juice made its appearance. In 

 this way it was proved that the secretion can in fact be called out reflexly. 



The efferent nerves concerned in this reflex are the vagi. If the vagi be 

 cut, the reflex fails. If they be stimulated a clear fluid begins to trickle from 

 the fistula, which in comparison with the normal gastric juice shows a lower 

 acidity, but digests proteids. In addition to these the vagus appears to 

 contain also fibers which inhibit the glands of the stomach. 



But the secretion of gastric juice is not dependent alone upon the vagus. 

 There are perfectly trustworthy statements in the literature which show that 

 the secretion does not cease after section of the vagi, although the reflex from 

 the mouth be excluded; but that animals thus operated upon digest their 

 food in the stomach. Besides, analysis of the urine reveals no products of 

 abnormal putrefaction in the alimentary canal of such animals, and we may 

 conclude that a real gastric juice is secreted which contains just as much 

 hydrochloric acid, but considerably less pepsin, than the normal juice. 



Thus there are two modes of gastric secretion, namely, one under the 

 influence of the secretory nerve fibers which traverse the vagus, and the other 

 independent of those fibers. 



(1) The Secretion under the Influence of the Vagus. Neither excitation of 

 the nerves of taste, nor the act of chewing, nor the movements of deglutition 

 have of themselves any power to cause a reflex secretion of gastric juice. Only 

 when the animal exhibits some desire for food does secretion result. The imagi- 

 nation of savory substances would seem therefore to be of special importance, 

 and this is confirmed by the fact that gastric secretion occurs when one merely 

 offers a dog a piece of meat without giving it to him. This " psychical " secre- 

 tion is at times very abundant; but if not, the amount of secretion is consider- 

 ably increased by fictitious feeding. From these and similar facts it appears 

 that although excitation of the afferent nerves from the mouth and the cesopha- 



