348 



FOOD AND DIGESTION 



products with the pyloric end of the stomach, where they are slightly ab- 

 sorbed, gives rise to some chemical substance a gastric hormone or secre- 

 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. 



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



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 



