DIGESTION IN THE STOMACH 739 



the injection of bouillon directly into the circulation has no effect, this author 

 concludes that the second phase of secretion is determined by the stimulation 

 of the local nerve plexus, and that we have here, in short, a peripheral reflex 

 action, the centres of which are situated in the walls of the stomach 

 itself. There is yet another possible explanation for this second phase of 

 secretion. Although the peptogenic substances, those substances which 

 evoke gastric secretion on introduction into the stomach, have no effect on 

 the gastric glands when injected directly into the blood stream, it is possible 

 that they may have an influence on the cells which line the cavity of the 

 stomach, and that they may produce, in these cells, some other substance 

 which is absorbed into the blood and acts as a specific excitant of the gastric 

 glands. A process of this nature is known to occur in the next segment of 

 the alimentary canal, viz. the duodenum, where it determines the secretion 

 of the pancreatic juice and the bile. 



Edkins has carried out a series of experiments to determine whether such 

 a chemical mechanism may not also account for the secretion of gastric juice, 

 which is excited by the introduction of substances into the stomach. Edkins' 

 experiments were carried out in the following way : The animal, dog or cat, 

 having been anaesthetised, the abdominal cavity was opened, and a ligature 

 passed round the lower end of the oesophagus. so as to occlude the cardiac 

 orifice and effectually crush the two vagus nerves. A glass tube was then 

 introduced through an opening in the abdomen into the pyloric part of the 

 stomach, and fixed in this position by a ligature tied tightly round the 

 pylorus. The glass tube was connected by means of a rubber tube with a 

 reservoir containing normal salt solution at the temperature of the body. 

 By means of this reservoir, a certain amount of fluid was introduced into the 

 stomach and kept there at a constant pressure ; the quantity of fluid intro- 

 duced varied from 30 to 50 c.c. It has been shown by Edkins, as well as by 

 von Mering, that no absorption of water or saline fluid occurs in the stomach. 

 It is therefore possible to recover the whole of the fluid an hour after it has 

 been introduced, by simply lowering the reservoir below the level of the 

 animal's body. If secretion of gastric juice has occurred into the cavity of 

 the stomach, the fluid will be increased in amount and will contain hydro- 

 chloric acid as well as pepsin. In a series of control observations Edkins 

 showed that the mere introduction of this fluid into the stomach caused 

 no secretion of gastric juice, the fluid removed at the end of an hour having 

 the same bulk and the same neutral reaction as the fluid which had been 

 injected. Edkins then tried the influence of injecting substances into the 

 blood stream. The injection of peptone, of acid, of broth, or of dextrin into 

 the blood stream produced no secretion of gastric juice. If however in the 

 course of the hour during which the fluid was allowed to remain in the 

 stomach, a decoction made by boiling pyloric mucous membrane with acid, 

 or with water, or with peptones was introduced in small quantities every ten 

 minutes into the jugular vein, the fluid removed at the end of the hour was 

 found to be distinctly acid in its reaction and to possess proteolytic properties. 

 The injection of these substances had therefore caused the secretion of a 





