242 HAND-BOOK OF PHYSIOLOGY. 



tabular glands of which the superficial and chief part of the mucous 

 membrane is composed, and passing up between them assists in binding 

 them together. Here and there are to be found in this coat, immediately 

 underneath the glands, masses of adenoid tissue sufficiently marked to 

 be termed by some lymphoid follicles. The glands are separated from 

 the rest of the mucous membrane by a very fine homogeneous basement 

 membrane. 



At the deepest part of the mucous membrane are two layers (circular and 

 longitudinal) of unstriped muscular fibres, called the muscularis mucoscv, 

 which separate the mucous membrane from the scanty submucous tissue. 



When examined with a lens, the internal or free surface of the stomach 

 presents a peculiar honeycomb appearance, produced by shallow polygo- 

 nal depressions, the diameter of which varies generally from ,-} T th to 

 -g-l-g-th of an inch; but near the pylorus is as much as y^-th of an inch. 

 They are separated by slightly elevated ridges, which sometimes, especially 

 in certain morbid states of the stomach, bear minute, narrow vascular 

 processes, which look like villi, and have given rise to the erroneous sup- 

 position that the stomach has absorbing villi, like those of the small in- 

 testines. In the bottom of these little pits, and to some extent between 

 them, minute openings are visible, which are the orifices of the ducts of 

 perpendicularly arranged tubular glands (Fig. 177), imbedded side by 

 side insets or bundles, on the surface of the mucous membrane, and 

 composing nearly the whole structure. 



Gastric Glands. Of these there are two varieties, (a) Peptic, (b) 

 Pyloric or Mucous. 



(a) Peptic glands are found throughout the whole of the stomach except 

 at the pylorus. They are arranged in groups of four or five, which are 

 separated by a fine connective tissue. Two or three tubes often open into 

 one duct, which forms about a third of the whole length of the tube and 

 opens on the surface. The ducts are lined with columnar epithelium. 

 Of the gland tube proper, i.e., the part of the gland below the duct, the 

 upper third is the neck and the rest the body. The neck is narrower 

 than the body, and is lined with granular cubical cells which are continu- 

 ous with the columnar cells of the duct. Between these cells and the 

 membrana propria of the tubes, are large oval or spherical cells, opaque 

 or granular in appearance, with clear oval nuclei, bulging out the mem- 

 brana propria; these cells are called peptic or parietal cells. They do not 

 form a continuous layer. The body, which is broader than the neck and 

 terminates in a blind extremity or fundus near the muscularis mucosae, 

 is lined by cells continuous with the cubical or central cells of the neck, 

 but longer, more columnar and more transparent. In this part are a few 

 parietal cells of the same kind as in the neck (Fig. 177). 



As the pylorus is approached the gland ducts become longer, and the 

 tube proper becomes shorter, and occasionally branched at the fundus. 



