CHAPTER XXXIII 



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 

 or proteoclastic enzyme 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 fistulae 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. 



Artificial gastric juice is made by mixing weak hydrochloric acid 

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

 killed animal. This acts like the normal juice. 



When examined with a lens, the internal or free surface of the 

 stomach presents a peculiar honeycomb appearance, produced by 

 shallow polygonal depressions. In the bottom of these little pits, and 

 to some extent between them, minute openings are visible, which 

 are the orifices of the ducts of perpendicularly arranged tubular 

 glands (fig. 354), imbedded side by side in the substance of the 

 mucous membrane. 



The glands of the mucous membrane are of three varieties, 

 (a) Cardiac, (&) Fundus, and (c) Pyloric. 



(a) Cardiac glands; these are simple tubular glands lined by 

 short columnar granular cells, and are only found quite close to the 

 cardiac orifice. 



* 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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