190 GASTRIC DIGESTION 



(parietal cells), in the secreting portion of the glands of the greater 

 pouch. 



The acid-glands are found throughout the stomach except near the 

 pylorus. The secreting portion of these glands contains peptic cells, 

 but near the tubular membrane are rounded cells, larger than the peptic 

 cells, darker and more granular, which are the acid, or parietal cells. 

 These are strongly stained when treated with osmic acid. It is prob- 

 able that the so-called acid-glands secrete propepsin as well as an acid, 

 while the pyloric glands secrete propepsin but no acid. In accordance 

 with the views just stated, in the glands of the greater pouch, the acid 

 is secreted by the rounded acid-cells, while the propepsin is secreted by 

 cells (peptic cells) similar to those lining the secreting portion of the 

 pyloric glands. During the intervals of digestion, propepsin is in pro- 

 cess of formation by the peptic cells, and no acid is produced; but acid 

 begins to be secreted soon after food is received into the stomach. The 

 peptic cells, therefore, do not produce pepsin directly, but a substance 

 sometimes called zymogen, but more properly propepsin or pepsinogen, 

 which is changed into pepsin, possibly by the action of hydrochloric acid. 



The glands of the stomach have an excretory portion and a secreting 

 portion, the latter presenting two or more branches. The excretory 

 portion is lined with cells nearly like those found on the surface of the 

 mucous membrane. The secreting portion is lined with the peptic and 

 the acid-cells already described (see Plate IV, Fig. 3). 



Closed Follicles. In the substance of the mucous membrane, be- 

 tween the tubes and near their caecal extremities, are occasionally found 

 closed follicles, like the solitary glands and patches of Peyer of the 

 intestines. These are not always present in the adult but frequently are 

 found in children. They usually are most abundant over the greater 

 curvature, though they may be found in other situations. In their 

 anatomy they are identical with the closed follicles of the intestines and 

 do not demand special consideration in this connection. 



Gastric Juice. The observations of Beaumont on Alexis St. Martin, 

 the Canadian who had a large fistulous opening into the stomach, gave 

 the first definite knowledge of the most important of the physiological 

 properties of the gastric juice. The following was the method employed 

 in collecting the secretion : The subject was placed on the right side in 

 the recumbent posture, the valve of mucous membrane partially closing 

 the fistula was pressed into the stomach, and a gum-elastic tube, of the 

 size of a large quill, was passed in to the extent of five to six inches 

 (12 to 15 centimeters). On turning him upon the left side until 

 the opening became dependent, the stimulation of the tube caused the 

 secretion to flow, sometimes in drops and sometimes in a small stream. 



