CH. XXVII.] THE INTESTINES 455 



intestinal mucous membrane, thickly distributed over the whole 

 surface both of the large and small intestines. In the small intestine 

 they are visible only with the aid of a lens ; and their orifices appear 

 as minute dots scattered between the villi. They are larger in the 

 large intestine, and increase in size the nearer they approach the / 

 anal end of the intestinal tube ; and in the rectum their orifices may ( 

 be visible to the naked eye. In length they vary from T f F to gV of 

 an inch. Each tubule (fig. 386) is constructed of a fine basement 



FIG. 384. A. Villus of sheep. B. Villi of man. (Slightly altered from Teichmann.) 



membrane, lined by a layer of columnar epithelium, many of the cells 

 of which are goblet cells. 



Urunner's glands (fig. 382) are confined to the duodenum ; they 

 are most abundant and thickly set at its commencement, and diminish 

 gradually as the duodenum advances. They are situated beneath the ' 

 muscularis mucosae, imbedded in the submucous tissue ; each gland 

 is a branched and convoluted tube, lined with columnar epithelium. 

 In structure they are very similar to the pyloric glands of the 

 stomach, but they are more branched and convoluted, and their ducts 

 are longer. The duct of each gland passes through the muscularis 

 inucosae, and opens on the surface of the mucous membrane. 



