CHAPTER II. 



GASTRIC DIGESTION. 



SECT. 1. INTRODUCTORY. ON THE STRUCTURE OF THE STOMACH 

 OF MAN AND CARNIVOROUS ANIMALS. 



THE stomach consists of a muscular bag, the greater part of 

 which is covered with a peritoneal investment which constitutes its 

 serous coat, and which is lined by a mucous membrane in which are 

 imbedded the glands whose mixed products give rise to the peculiar 

 secretion, the gastric juice. 



The mucous membrane of the stomach is a thin membrane, 

 presenting prominent folds or rugce, most abundant at its pyloric 

 end, and which disappear when the organ is distended. With a 

 magnifying glass the mucous membrane is seen to present innu- 

 merable pits or alveoli, which are separated from one another by 

 intervening ridges, at the bottom of which are the open mouths 

 of the gastric glands, which are tubular glands, simple or compound, 

 occupying nearly the whole thickness of the mucous membrane. 



In some animals, typically in the dog, the mucous membrane 

 does not present one uniform appearance to the naked eye, nor is its 

 structure identical in all parts. In the pyloric region it is less 

 vascular, and appears thicker, though it is here much poorer in 

 glandular structures than at the fundus. 



In the stomach of all animals there are observed two sets of 

 glands, which formerly used almost invariably to be classified by 

 English writers, as (a) peptic, and (6) mucous glands, to indicate the 

 view, then held, that the first secreted gastric juice, whilst the 

 second merely secreted mucus. In the dog, the former are absent 

 from the pyloric region, but occupy the mucous membrane of the 

 fundus and curvatures ; they are therefore often spoken of as the 

 glands of the fundus. On the other hand, the other glands are 

 spoken of as the pyloric glands. In animals where, as in the dog, 

 these two structurally different regions of the stomach are observed, 

 an intervening region, with transitional forms between these two sets 

 of glands, has been described. 



