DIGESTION IN THE STOMACH 779 



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 introduced 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 hydrochloric 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 peptone 

 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 dis- 

 tinctly acid in its reaction and to possess proteolytic properties. 

 The injection of these substances had therefore caused the secretion 

 of a certain amount of gastric juice containing both hydrochloric 

 acid and pepsin. In order to produce this positive effect, it was 

 necessary to employ pyloric mucous membrane, extracts made by 

 infusing or boiling cardiac mucous membrane with any of these 

 substances being without effect. Edkins concludes therefore that 

 the secondary secretion of gastric juice is determined, not, as Pawlow 

 and Popielski imagined, by a local stimulation of the reflex nervous 

 apparatus in the gastric wall, but by a chemical mechanism. The 

 first products of digestion act on the pyloric mucous membrane, and 

 produce in this membrane a substance which is absorbed into the 

 blood stream, and carried to all the glands of the stomach, where it 

 acts as a specific excitant of their secretory activity. This substance 

 may be called the gastric secretin or gastric hormone. It is noteworthy 



