THE STRUCTURE OF THE STOMACH 143 



The mucous membrane is a soft, thick layer, generally somewhat 

 corrugated in the empty condition of the organ. Its thickness is 

 mainly due to the fact that it is made up of long tubular glands, which 

 open upon the inner surface. Between the glands the mucous mem- 

 brane is formed of areolar with much lymphoid tissue. Externally it 

 is bounded by the muscularis mucosce, which consists of an external 

 longitudinal and an inner circular layer of plain muscular fibres. The 

 glands are formed of a basement-membrane lined wiih epithelium. 

 Each gland consists of three or four secreting tubules, which open* 

 towards the surface into a larger common tube, the duct of the gland. 

 The duct is in all cases lined by columnar epithelium of the same 

 character as that which covers the inner surface of the mucous mem- 

 brane, but the epithelium of the secreting tubules is somewhat different 

 from this, and, moreover, differs somewhat in the glands of the cardiac 

 and pyloric regions of the organ. 



In the cardiac glands (fig. 173) the secreting tubules are long, and 

 the duct short. The epithelium of the tubules is composed of two kinds 

 of cells. Those of the one kind, which form a continuous lining to the 

 tubule, are somewhat polyhedral in shape, and in stained sections look 

 clearer and smaller than the others, but in the fresh glands, and in 

 osmic preparations, they appear filled with granules (fig. 174). 1 These 

 cells are believed to secrete the pepsin of the gastric juice, and are termed 

 the chief cells of the cardiac glands, or, from their relative position in 

 the tubule immediately surrounding the lumen, the central cells. Scat- 

 tered along the tubule, and lying between the chief cells and the base- 

 ment membrane, are a number of other spheroidal or ovoidal cells, 

 which become stained by logwood and other reagents more darkly than 

 the central cells. These are the superadded or parietal cells (oxyntic 2 

 cells of Langley). 



In the pyloric glands (fig. 175) the ducts are much longer than in 

 the cardiac glands, and the secreting tubules possess cells of only one 

 kind. These correspond to the chief cells of the cardiac glands. They 

 are of a columnar or cubical shape, and in the fresh condition of a 

 granular appearance, and quite unlike the columnar epithelium-cells 

 of the surface, which are long tapering cells, the outer part of which 

 is filled with mucus. At the pylorus itself the pyloric glands become 

 considerably lengthened, and are continued into the submucous tissue, 

 the muscularis mucosae being here absent ; they thus present transi- 

 tions to the glands of Brunner, which lie in the submucous tissue of 

 the duodenum, and send their ducts through the mucous membrane 

 to the inner surface. 



The blood-vessels of the stomach (fig. 176) are very numerous, and 



1 The granules are most numerous at the inner part of the cell, a small outer 

 zone being left clear. After prolonged activity this outer zone increases in size 

 while the granules diminish in number as in the analogous cases of the pancreas 

 and parotid glands. 



2 So called because they produce the acid of the gastric secretion. 



