FOOD AND DIGESTION. 359 



tected during the most active secretion ; the thermometer introduced into 

 the stomach always stood at 37.8 C. (100 F.) except during muscular 

 exertion, when the temperature of the stomach, like that of other parts 

 of the body, rose one or two degrees higher. 



The chemical composition of human gastric juice has been also inves- 

 tigated by Schmidt. The fluid in this case was obtained by means of an 

 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 introduction 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 

 to 1010. It contained a few cells, seen with the microscope, and some 

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

 given below. Essentially it is a weakly acid fluid containing hydro- 

 chloric acid and two enzymes, pepsin and rennin, with possibly a third 

 (glucase) . The gastric juice of dogs and other animals obtained by the 

 introduction into the stomach of a clean sponge through an artificially 

 made gastric fistula, shows a decided difference in composition, but pos- 

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



CHEMICAL COMPOSITION OP GASTRIC JUICE. 



Dogs. Human. 



Water . . , . ,. . . . V . . 971.17 994.4 

 Solids ..... .. . . .. . . . . 28.82 5.60 



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 infrequently to be found therein as products of 

 gastric digestion or abnormal fermentation. In healthy gastric juice the 

 amount of free hydrochloric acid is usually about 0.2 per cent, but may 

 be as much as 0.3 per cent. In pathological conditions it may be en- 

 tirely absent, or may amount to 0.5 per cent, or even more. 



There is but little doubt that hydrochloric acid is the proper acid of 

 healthy gastric juice, and various tests have been used to prove this ; 

 most of these depend upon changes produced in aniline colors by the 



