DIGESTION IN THE STOMACH. 481 



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

 the acid in the pylorus which acts upon the sphincter and makes pos- 

 sible 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 is neutralized the contractions of the sphincter cease and the 

 passage of new portions of the chyme occur. If the flow of bile and pan- 

 creatic juice is prevented, and the neutralization of the acid contents 

 of the stomach in the intestine is retarded, then the stomach does not 

 eject its contents so often. The duration of gastric digestion varies 

 according to conditions, and in consequence the reports of observers are 

 widely divergent. BEAUMONT 2 found in his extensive observations 

 on the Canadian hunter St. MARTIN that the stomach, as a rule, is 

 emptied 1J-5J hours after a meal, depending upon the character of the 

 food. 



The time in which different foods leave the stomach also depends 

 upon their digestibility. Respecting the unequal digestibility in the 

 stomach we must differentiate between the rapidity with which the food- 

 stuffs are chemically transformed and that with which they leave the 

 stomach and pass into the intestine. This distinction is especially 

 important, and it is evident that the main factors governing speed of 

 digestion and the time required before the food leaves the stomach are the 

 kind of food and the fineness of its subdivision, and its action upon the 

 gastric secretion, upon the pyloric reflexes, etc. 



The observations of BOLDYREFF and others 3 on the action of fats 

 and fatty acids and not too dilute hydrochloric acid (stronger than 0.2 

 per cent) are conclusive concerning the manner in which the properties 

 of the food act upon the gastric secretion and upon the digestion in the 

 stomach as a whole. Irrespective of the reducing action of the fats 

 upon the extent and digestive power of the gastric juice BOLDYREFF 

 found after food very rich in fat that the bile, pancreatic juice and intes- 

 tinal juice migrate from the intestine into the stomach so that the diges- 

 tion in the stomach in these cases is essentially brought about by the 

 pancreatic juice. 



We have numerous investigations on the rapidity with which the 

 food is digested in the stomach of dogs, but we must especially mention 



1 Amer. Journ. of Physiol., 20. 



2 The Physiology of Digestion, 1833. 



3 Boldyreff, Pfluger's Arch., 121, 140; Migay, Maly's Jahresb. 39; Best and 

 Cohnheim, Zeitschr. f. Physiol. Chem. 69; Cathcart, Journ. of Physiol. 42. See 

 also Abderhalden and Medigreceanu, Zeitschr. f. physiol. Chem., 57. 



