DIGESTION. 180 



the pyloric valve. PLANER found in the stomach-gases of a dog 

 66-68$ N, 25-33$ C0 8 , and only a small quantity, 0.8-6.1$, of 

 oxygen. 



According as the food is finely or coarsely divided it passes 

 sooner or later through the pylorus into the intestines. From 

 BUSCH'S observations on a human intestinal fistula, it required 

 generally 15-30 minutes after eating for undigested food, such 

 as pieces of meat, to pass into the upper part of the intestines. 

 Among the cases of duodenal fistula in human beings observed by 

 KUHNE, one is mentioned in which he saw, ten minutes after eat- 

 ing, uncurdled but still coagulable milk and small pieces of meat 

 pass out of the fistula. The time in which the stomach unburdens 

 itself of its contents depends, however, upon the rapidity with 

 which the quantity of hydrochloric acid increases, for it seems to 

 act as a sort of irritant and causes the opening of the pylorus 

 (EwALD and others). Many other conditions also come into play, 

 namely, the activity of the gastric juice, the quantity and character 

 of the food, etc., etc., and therefore the time required to empty the 

 stomach must be variable. BICHET observed in a case of stomach 

 fistula that in man the quantity of food which is in the stomach 

 the first three hours is not essentially changed, but that in the 

 course of a quarter of an hour nearly all is driven out, so that only 

 a small residue remains. KUHNE has made about the same obser- 

 vations on dogs and human beings. He found, indeed, in dogs that 

 in the first hour small quantities of meat passed into the intestines 

 every ten minutes ; but he also observed that in dogs, on an ave- 

 rage, about five hours after eating, in man somewhat earlier, a free 

 emptying into the intestines takes place. According to other 

 investigators (EwALD and BOAS), the emptying of the human 

 stomach does not take place suddenly, but gradually. BEAUMONT 

 found in his extensive observations on the Canadian hunter, ST. 

 MARTIN, that the stomach, as a rule, is emptied li-5 hours after 

 a meal, depending upon the character of the food. 



The time in which different foods leave the stomach depends 

 upon their digestibility. In regard to the unequal digestibility in 

 the stomach of foods rich in proteids, which really form the object 

 of the action of the gastric juice, a distinction must be made be- 

 tween the rapidity with which the proteids are converted into 



