138 PHYSIOLOGICAL CHEMISTRY 



kinds such as meat and bread, the material instead of passing to the 

 stomach, would invariably find its way out of the animal's body at the 

 upper esophageal opening. Through the medium of the gastric fistula 

 the course of the secretion of gastric juice could be carefully followed. 

 It was found that when the dog ate meat, for example, there was a large 

 secretion of gastric juice notwithstanding no portion of the food eaten 

 had reached the stomach. Further experiments made through the 

 medium of a cul-de-sac formed from the stomach wall have given us 

 many valuable conclusions, among others those regarding the influence 

 of the chemical stimuli. The method followed was to feed the animal 

 certain substances and note the secretion of gastric juice in the miniature 

 stomach while the real process of digestion was taking place in the 

 stomach proper. 



Normal gastric juice is a thin, light colored fluid which is acid in 

 reaction and has a specific gravity varying between i.ooi andi.oio. 

 It contains only 0.5 per cent of solid matter which is made up principally 

 of sodium chlorid, potassium chloride, earthy phosphates, mucin and the 

 enzymes pepsin, gastric rennin, and gastric lipase; the enzymes are of the 

 greatest importance. The acidity of the gastric juice is due to free 

 hydrochloric acid. It was formerly believed that this acid was secreted 

 by the parietal cells of the fundus as well as by the chief cells of both the 

 fundus and pyloric glands. It has been claimed, 1 however, that the 

 parietal cell is the seat of the formation of the hydrochloric acid. This 

 conclusion is based upon the formation of Prussian blue after the subcut- 

 aneous injection of potassium ferrocyanide and ammonium ferric citrate 

 (rabbits and guinea-pigs) and the subsequent (3 to 30 hours) micro- 

 scopical examination of the gastric mucosa. The acid was shown to be 

 present in the lumina of the gland tubules and in the canaliculi of the 

 parietal cells; traces were also apparently present in -the cytoplasm. 

 Later Bensley and Harvey 2 showed by means of dyes which act as vital 

 stains and as indicators very sensitive to alkali that the secretion in the 

 parietal cells is slightly alkaline whereas that in the lumen of the gland 

 proper is very nearly neutral. Therefore, the acid is formed entirely 

 above the level of the gland proper, i.e., in the foveolae and on the sur- 

 face. Hammet 3 and still more recently Macallum and Collip 4 have 

 confirmed Miss Fitzgerald's claim that the acid is formed in the parietal 

 cells. 



It was believed that hydrochloric acid was generally present in the 

 gastric juice of man to the extent of about 0.2 per cent. When the 



1 Fitzgerald: Proceedings Royal Society -(B), 83, 56, 1910. 



2 Bensley and Harvey: Biological Bulletin, 23, 225, 1912. 



3 Hammett: Anatomical Record, 9, 21, 1915. 



4 Reported before Society of Biological Chemists, Boston, Dec. 27, 1915- :^-, 



