CH. xxxi.] THE GASTRIC JUICE. 479 



CHAPTER 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 proteo- 

 lytic 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 fistula? 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 physio- 

 logy of the stomach and its secretion. 



We now make artificial gastric juice by mixing weak hydro- 

 chloric acid (o - 2 per cent.) with the glycerine 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. 443, 444- We may, however, repeat that the 

 cardiac glands arc 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 pyloric glands, in the 

 pyloric part of the stomach, have long ducts and short tubules 

 lined with cubical granular cells. There are no parietal cells. 



The central cells of the cardiac glands and the cells of 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. 



