64 



ESSENTIALS OF CHEMICAL PHYSIOLOGY 



The gastric juice can be obtained during the hfe 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. Beavimont 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 a glycerin or aque- 

 ous 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. The 

 cardiac glands are those situated in the 

 cardiac half of the stomach: their ducts 

 are short, their tubules long in proportion. 

 The latter are filled with polyhedial cells, 

 only a small lumen being left ; they are 

 more closely granular than the correspond- 

 ing cells in the pyloric glands. They are 

 called jri rinr.ipn. l ar centrol^eXh,. Between 

 them and the basement membrane of the 

 tubule are other cells which stain readily 

 with aniline dyes. They are called 2^a,rietal 

 or oxyntic {i.e. acid-forming) cells. The 

 injloric glands, in the pj'loric half of the 

 stomach, have long ducts and short tubules 

 lined with cubical cells. There are no 

 parietal cells. 



The central cells of the cardiac glands 

 and the cells of the pyloric glands are 

 loaded with granules. During secretion 

 they discharge their granules, those that 

 remain being chiefly situated near the 

 lumen, leaving in each cell a clear outer zone (see fig. 20). These 

 are the cells that secrete the pepsin. Like secreting cells generally, 

 they select certain materials from the lymph that bathes them ; 

 these materials are worked up by the protoplasmic activity of the 



form from the bat's stomaoli. 

 Osmic acid preparation (Lang- 

 ley) : c, columnar epitlieliuni 

 of the surface ; «, neck of the 

 gland, with central and parietal 

 cells ;/, base or fundus, occupied 

 only by principal or central cells, 

 which exhibit the granules ac- 

 cumulated towards the lumen 

 of the glanil. 



