THE GASTRIC JUICE 



367 



tagogue which acts as a powerful stimulus to gastric secretion when it is 

 introduced into the circulation. Such food substances are dextrins, maltose 

 and dextrose, proteoses, and above all meat extract. 



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. 



FIG. 260. Table to show the Secretion of Gastric Juice by the Dog. (Lliffine.) 



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. 



