456 DIGESTION. 



in the interior of the same the food may remain for hours without coming 

 in contact with a trace of gastric juice. 



What has been said above applies at least to solid food. We have no 

 extensive observations on the behavior of fluids or semifluid food. Accord- 

 ing to GRUTZNER, in these cases, as well as in the above-mentioned 

 experiments, the swallowed foodstuffs are not irregularly mixed together. 

 Fluids quickly leave the stomach, which is also the case with a mixture 

 of solid and fluid food. 



The fact that only that part of the ingesta lying on the mucous mem- 

 brane is mixed with gastric juice, while the mass in the interior is not 

 acid in reaction, is of special importance for the digestion of starches 

 in the stomach. By this we can explain why the salivary diastase, 

 although sensitive toward acids, can continue its action for a long time 

 in the contents of the stomach. That this is true was first found by 

 ELLENBERGER and HOFMEISTER and then by CANNON and DA.Y 1 by 

 special experiments upon animals. The occurrence of sugar and dextrin 

 in the contents of the human stomach has been repeatedly observed. 

 In carnivora, whose saliva shows scarcely any diastatic action, it is a 

 priori not expected that there should be a diastatic action in the stomach, 

 but the conditions are different in herbivora, where an abundant digestion 

 of starch takes place in the various stomachs, due to the different species. 



The gastric contents which have been prepared in the pylorus part 

 are passed through -the pylorus into the intestine intermittently. This 

 material is generally fluid, but it is possible that pieces of solid food may 

 also occur, and this has often been observed. Thin or plastic food leaves 

 the stomach earlier than solid food, and it is obvious that the time in which 

 the stomach unburdens itself depends naturally upon the coarseness or 

 fineness of the food. This depends essentially upon the reflex action of 

 the stomach or intestine, causing an opening oc closing of the pylorus, 

 which action is dependent upon the quantity and character of the food, 

 the amount of fat, and the degree of acidity in the contents of the stomach 

 and intestine. The emptying of the food into the small intestine causes, 

 as shown by PAWLOW, a closing of the pylorus by chemo-reflex in which 

 the hydrochloric acid and the fat take part, and we thus find in this regard 

 an alternate action between the stomach and duodenum. 



This alternate action, according to CANNON 2 is due to the fact that 

 the acid in the pylorus which acts upon the sphincter and makes possible 

 the passage of the fluid chyme by the contraction of the muscles of the 

 stomach. In the intestine the acid has a reverse stimulation upon the 

 sphincter and causes a contraction of the same. As soon as the acid 



1 Ellenberger and Hofmeister, Maly's Jahresb., 15 and 16; Cannon and Day, Amer. 

 Journ. of Physiol., 9. 



2 Amer. Journ. of Physiol., 20. 



