CHAPTEE XXXI 



THE GASTRIC JUICE 



THE juice secreted by the glands in the mucous membrane of the 

 stomach varies in composition in the different regions, but the mixed 

 gastric juice, as it may be termed, is a solution of a proteolytic 

 ferment called pepsin in a saline solution, which also contains a little 

 free hydrochloric acid. 



The gastric juice can be obtained during the life of an animal by 

 means of a gastric fistula.* Gastric fistulas have also been made in 

 human beings, either by accidental injury or by surgical operations. 

 The most celebrated case is that of Alexis St Martin, a young 

 Canadian, who received a musket wound in the abdomen in 1822. 

 Observations made on him by Dr Beaumont formed the starting- 

 point for our correct knowledge of the physiology of the stomach and 

 its secretion. 



We now make artificial gastric juice by mixing weak hydrochloric 

 acid (0*2 per cent.) with the glycerin extract of the stomach of a 

 recently -killed animal. This artificial juice acts like the normal 

 juice. 



Two kinds of glands are distinguished in the stomach, which differ 

 from each other in their position, in the character of their epithelium, 

 and in their secretion. Their structure will be found described on 

 pp. 449, 451. We may, however, repeat that the cardiac glands are 

 those situated in the cardiac part of the stomach: their ducts are 

 short, their tubules long in proportion. The latter are filled with 

 polyhedral cells, only a small lumen being left; they are more 

 coarsely granular than the corresponding cells in the pyloric glands. 

 They are called principal or central cells. Between them and the 

 basement membrane of the tubule are other cells which stain readily 

 with aniline dyes. They are called parietal or oxyntic cells. The 



* A gastric fistula is made by cutting through the abdominal wall so as to 

 expose the stomach. The stomach is then attached to the edges of the abdominal 

 wound, and a small orifice is finally made through the wall of the stomach. When 

 the wound heals there is then a free communication between the stomach and the 

 exterior. 



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