1006 



THE ORGANS OF DIGESTION. 



brown color over the rest of its surface. In infancy it is of a brighter hue, the 

 vascular redness being more marked. It is thin at the cardiac extremity, but 

 thicker toward the pylorus. During the contracted state of the organ it is thrown 

 into numerous plaits or rugse, which for the most part have a longitudinal direc- 

 tion, and are most marked toward the lesser end of the stomach and along the 

 greater curvature. These folds are entirely obliterated when the organ becomes 

 distended. 



Structure of the Mucous Membrane. When examined with a lens the inner 

 surface of the mucous membrane presents a peculiar honeycomb appearance, 

 from being covered with small shallow depressions or alveoli of a polygonal 

 or hexagonal form, which vary from y^-g to -^-^ of an inch in diameter, and 

 are separated by slightly elevated ridges. In the bottom of the alveoli are 

 seen the orifices of minute tubes, the gastric follicles, which are situated 

 perpendicularly side by side throughout the entire substance of the mucous mem- 

 brane. 



The gastric glands are of two kinds, which differ from each other in structure, 



FIG. 629. Pylorio gland. 



FIG. 630. Peptic gastric gland. 



and it is believed also in the nature of their secretion. They are named respectively 

 pyloric and peptic glands. They are both tubular in character, and are formed of 

 a delicate basement membrane, supporting epithelium. The basement membrane 

 consists of flattened transparent endothelial cells, with processes which extend and 

 support the epithelium. The pyloric glands (Fig. 629) are most numerous at the 

 pyloric end of the stomach, and from this fact have received their name. They were 

 formerly termed mucous glands, and were supposed to secrete mucus ; but, as Klein 

 points out, " the cells are serous, not mucous, and the secretion of the glands cannot 

 therefore be mucus." They consist of two or three short closed tubes opening 

 into a common duct, the external orifice of which is situated at the bottom of an 

 alveolus. The caeca! tubes- are wavy, and are of about equal length with the duct. 

 The tubes and duct are lined throughout with epithelium, the duct being lined 

 by columnar cells continuous with the epithelium lining the surface of the mucous 



