THE GASTRIC JUICE 323 



The influence of the higher nerve centers on gastric digestion, as in the 

 case of emotions, is too well known to need more than a reference. 



Immediately on the introduction of food or other stimulating substance, 

 the mucous membrane, which was previously quite pale, becomes slightly 

 turgid and reddened with the influx of a larger quantity of blood, and the gas- 

 tric glands commence actively to secrete. An acid fluid is poured out in minute 

 drops and the secretion may continue for hours. 



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 investigated 

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

 gastric fistula. The mucous membrane was excited to action by the intro- 

 duction 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 1002 to 1010. 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 two enzymes, pepsin and rennin, with possibly a third, maltase. The 

 gastric juice of dogs and other animals obtained from gastric fistulas shows 

 some difference in composition. 



CHEMICAL COMPOSITION OF GASTRIC JUICE. 



Dogs. Human. 



Water 9 7 1 . 1 7 994-4 



Solids 28.82 5.60 



Solids- 

 Ferment Pepsin 17.5 3-19 



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 Acid of Gas'ric 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 



