MECHANICAL PHENOMENA. 15 



of the stomach. CANNON was able to show that the food 

 actually moves in this way by mixing with it starch-paste 

 pellets of bismuth subnitrate, the excursions of which could 

 readily be followed among the other food. When the pylorus 

 is closed the food is squirted back through the oncoming 

 constriction with considerable force. A subsequent wave 

 then carries the food toward the pylorus once more. In this 

 way the food is brought in contact with the mucous mem- 

 brane of the stomach over and over again, and thus besides 

 undergoing a certain degree of mechanical division becomes 

 thoroughly mixed with the gastric juice. Interestingly 

 enough, it is from this more active pyloric half of the stomach 

 that the largest secretion of gastric juice occurs. 



While digestion is going on and all the time that the 

 antrum is most busily engaged in kneading and rekneading 

 the food in this portion of the stomach the food in the car- 

 diac half shows no sign of movement. Bismuth-subnitrate 

 balls contained in the food which lies in the fundus keep 

 their relative positions until the fundus begins to contract 

 and then move slowly forward toward the antrum. This 

 observation should settle for all time the question of salivary 

 digestion in the stomach. As is well known l the amylase 

 and maltase of the saliva do not act upon starch or maltose 

 respectively when even a small percent of any acid is pres- 

 ent. Careful examination of the fundus contents after a 

 starchy meal by CANNON and DAY 2 have shown that no 

 inconsiderable amount of salivary digestion occurs in the 

 stomach. Herein we find another fact indicative of the 

 importance of thorough mastication and insalivation of the 

 food before it is swallowed. Food thus prepared can undergo 

 salivary digestion in the cardiac half of the stomach, perhaps 

 even for hours before it is brought to a standstill by becom- 

 ing mixed with the hydrochloric acid of the gastric secre- 

 tion. 



^eep. 103. 



2 CANNON and DAY: American Journal of Physiology. 



