CHYME AND DIGESTION IN THE STOMACH. 479 



juice occurs, which gradually mixes with the swallowed food, and digests 

 it more or less strongly. The material in the stomach during digestion, 

 which has a pasty or thick consistency, and is called chyme, is not a 

 homogeneous mixture of the ingesta with the various digestive fluids, 

 gastric juice, saliva, and gastric mucus, but the conditions seem to 

 be more complicated. 



From the investigations of several workers, 1 on the movements of 

 the stomach, we conclude that this organ in carnivora and also in man 

 consists of two physiologically different parts, the pylorus and the 

 fundus. The greater fundus part, which serves essentially as a reservoir, 

 may be a rhythmic, strong contraction of the muscle, acting like a 

 sphincter between it and the pylorus part, be separated from the latter, 

 and according to some observers so completely so that during contrac- 

 tion scarcely anything passes from the fundus to the pylorus part. 

 Differing from the fundus part the pylorus is the seat of very powerful 

 contractions by which its contents are intimately mixed with gastric 

 juice and are also driven through the pyloric valve into the intestine. 



The contents of the pylorus part have an acid reaction, and a strong 

 pepsin digestion takes place in the contents, which are thoroughly mixed 

 with gastric juice. The contents of the fundus, on the contrary, show 

 a different behavior, for here, as ELLENBERGER first showed, a special 

 stratification of the various solid food-stuffs takes place. 



By very instructive investigations on different animals (frogs, rats, 

 rabbits, guinea-pigs, and dogs) GRUTZNER 2 later showed that when 

 the aminals are fed with food having different colors, and the stomach 

 removed after a certain time, and the contents frozen, the frozen sec- 

 tions show a regular stratification of the contents. These layers are 

 so arranged that the food first taken is found in direct contact with the 

 mucosa, while the food taken later is enclosed by that partaken of first, 

 and this prevents contact with the walls of the stomach. The empty 

 stomach, whose walls touch each other, is so filled that, as a rule, the 

 foodstuffs taken later are in the middle of the older food. 



Because of this fact only the foodstuffs which lie close to the surface 

 of the mucous membrane undergo the process of peptic digestion, and 

 it is principally these ingesta, which lie on the surface and are laden with 

 pepsin and mixed with gastric juice, which are shoved to the pylorus 

 end, here mixed and digested, and finally moved into the intestine 



1 Hofmeister and Schiitz. Arch. f. exp. Path. u. Pharm., 20; Moritz. Zeitsehr. f. 

 Biologic, 32; Cannon, Amer. Journ. of Physiol., 1; Schemiakine, 1. c.; Cathcart, 

 Journ. of Physiol., 1911, 42. 



2 See Eilenberger, Pfluger's Arch., 114, and Scheunert, ibid., 144; Griitzner, ibid., 

 106. 



