368 FOOD AND DIGESTION 



The Gastric Juice. The first analysis of gastric juice was made by 

 Prout on a small and impure specimen. Beaumont made an elaborate and 

 classic series of observations on the gastric secretion of Alexis St. Martin, 

 in whom there existed, as the result of a gunshot wound, an opening leading 

 directly into the stomach near the upper extremity of the great curvature 

 and three inches from the cardiac orifice. The introduction of any mechan- 

 ical irritant, such as the bulb of a thermometer, into the stomach through 

 this artificial opening excited the secretion of gastric fluid. This was drawn 

 off, and was often obtained to the extent of nearly an ounce. 



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

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

 accidental gastric fistula. 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 obtained was found to be 

 acid, limpid, odorless, with a specific gravity of i . 002 to i . oio. It contained 

 a few cells 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 

 hydrochloric acid and enzymes, of which pepsin and rennin are the chief, 

 though lipase and maltase are both present. The gastric juice obtained 

 from gastric fistulas of dogs and other animals shows some difference in 

 composition. 



CHEMICAL COMPOSITION OF GASTRIC JUICE (SCHMIDT). 



Dogs. Human. 



Water 97 1 - 1 ? 994-4 



Solids 28.82 5.60 



Solids- 

 Ferment pepsin * 7 5 3 J 9 



Hydrochloric acid (free) 2.7 0.2 



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 estimated; 

 but the average for a healthy adult may be assumed to range from 2,000 to 

 3,000 cubic centimeters in the twenty-four hours. 



The Nature and Origin of the Acid of Gastric Juice. 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 entirely absent, or may 

 amount to 0.5 per cent., or even more. 



Hydrochloric acid is the proper acid of healthy gastric juice, and various 

 tests have been used to prove this. The tests depend upon changes produced 



