142 NORMAL HISTOLOGY. 



3. The (Esophagus (Fig. L20). — The mucous membrane of the 

 oesophagus is composed of three layers. The innermost layer is 

 made up of stratified epithelium. Beneath this is a layer of fibrous 

 tissue, with small papillae extending into the deeper portions of the 

 epithelium (see Fig. 38). Outside of this is a layer of longitudinal 

 smooth muscular tissue, the "muscularis mucosa?." This is but 

 imperfectly represented at the upper part of the (esophagus, but at the 

 lower end forms a continuous layer separating the " tunica propria " 

 (Fig. 120,/) of the mucous membrane from the submucous coat, and 

 becoming continuous with a similar layer of smooth muscular tissue 

 in the mucous membrane of the stomach and intestine. Occasion- 

 ally small, imperfectly defined lymph-follicles are met with in the 

 mucous membrane. 



The submucous coat of loose areolar tissue contains small race- 

 mose glands sparsely distributed through it, the ducts of which 

 penetrate the mucous membrane and open upon the internal surface 

 of the oesophagus. 



The muscular coat consists of an internal circular and an external 

 longitudinal layer, which at the upper end of the oesophagus are 

 composed of striated muscle. This is gradually replaced by smooth 

 muscular tissue further down the oesophagus, and at its lower end 

 only the latter tissue is found. 



The external coat of the oesophagus is represented by a variable 

 amount of areolar tissue which loosely connects it with the sur- 

 rounding structures. 



4. The Stomach. — Nearly the whole thickness of the mucous 

 membrane of the stomach is made up of straight tubular glands 

 (gastric tubules), which lie perpendicular to the surface, and are 

 separated from each other by only a small amount of a delicate, 

 highly vascular areolar tissue. This is a little denser and more 

 abundant below the deep ends of the glands, where it separates 

 them from the muscularis mucosas forming the deepest layer of the 

 mucous membrane. 



The mouths of the gastric tubules open into shallow, polygonal 

 depressions or crypts on the surface of the mucous membrane, 

 several glands opening into each depression. These depressions 

 give the internal surface of the stomach a reticular appearance when 

 viewed with a low power. They, and the ridges which separate 

 them, are covered with a rather tall columnar epithelium. The 

 glands which open into them are of two kinds: the "pyloric" 



