246 HAND-BOOK OF PHYSIOLOGY. 



accidental gastric fistula, which existed for several years below the left 

 mammary region of a patient between the cartilages of the ninth and 

 tenth ribs. The mucous membrane was excited to action by the introduc- 

 tion of some hard matter, such as dry peas, and the secretion was removed 

 by means of an elastic tube. The fluid thus obtained was found to be acid, 

 limpid, odorless, with a mawkish taste with a specific gravity of 1002, 

 or a little more. It contained a few cells, seen with the microscope, and 

 some fine granular matter. The analysis of the fluid obtained in this is 

 given below. The gastric juice of dogs and other animals obtained by 

 the introduction into the stomach of a clean sponge through an artifi- 

 cially made gastric fistula, shows a decided difference in composition, but 

 possibly this is due, at least in part, to admixture with food. 



CHEMICAL COMPOSITION OF GASTRIC JUICE. 



Dogs. Human. 



Water 971-17 994-4 



Solids 28-82 5 "39 



Solids- 

 Ferment Pepsin . . . 17'5 3*19 

 Hydrochloric acid (free} ....2*7 -2 



Salts- 

 Calcium, sodium, and potassium, chlorides; and 

 calcium, magnesium, and iron, phosphates . 8*57 2 '19 



The quantity of gastric juice secreted daily has been variously esti- 

 mated; but the average for a healthy adult may be assumed to range from 

 ten to twenty pints in the twenty-four hours. The acidity of the fluid is 

 due to free hydrochloric acid, although other acids, e.g., lactic, acetic, 

 butyric, are not unfrequently to be found therein as products of gastric 

 digestion. The amount of hydrochloric acid varies from 2 to '2 per 1000 

 parts. In healthy gastric juice the amount of free acid may be as much 

 as *2 per cent. 



As regards the formation of pepsin and acid, the former is produced 

 by the central or chief cells of the peptic glands, and also most likely by 

 the similar cells in the pyloric glands; the acid is chiefly found at the 

 surface of the mucous membrane, but is in all probability formed by the 

 secreting action of the parietal cells of the peptic glands, as no acid is 

 formed by the pyloric glands in which this variety of cell is absent. 



The ferment Pepsin (p. 246) can be procured by digesting portions 

 of the mucous membrane of the stomach in cold water, after they have 

 been macerated for some time in water at a temperature 80 100 F. 

 (27 37 '8 C.). The warm water dissolves various substances as well 

 as some of the pepsin, but the cold water takes up little else than pepsin, 

 which is contained in a greyish-brown viscid fluid, on evaporating the 



