CH. XXVII.] 



THE yiLLI. 



449 



same animal, and differ according as the lymphatic vessels or 

 lacteals which they contain are empty or full ; being usually, in 

 the former case, flat and pointed at their summits, in the latter 

 cylindrical. 



Each villus consists of a small projection of mucous mem- 

 brane ; its interior consists of 

 fine adenoid tissue, which forms 

 the framework in which the 

 other constituents are con- 

 tained. 



The surface of the villus is 

 clothed by columnar epithelium, 

 which rests on a fine basement 

 membrane ; while within this are 

 found, reckoning from without 

 inwards, blood-vessels, fibres of 



Fig. 381. Vertical section of duode- 

 num, showing a, villi ; b, crypt* 

 of Ldeberkuhn, and c, Brunnor's 

 glands in the submucosa , with 

 aucta, d ; muncularifl mucosw, m ; 

 and circular muscular coat/. 

 (Sehofleld.) 



Fig. 382. Vertical section of a villus of 

 the small intestine of a cat. a, 

 striated border of the epithelium ; 

 b, columnar epithelium; c, goblet 

 cells ; d, central lymph-vessel ; r, 

 smooth muscular fibres; /, adenoid 

 stroma of the villus in which lymph 

 corpuscles lie. (Klein.) 



the muscularis mucogce, and a single lymphatic or lacteal vessel 

 sometimes looped or branched (fig. 383). 



The epithelium is continuous with that lining the other parts 

 of the mucous membrane. The cells are arranged with their long 

 axis radiating from the surface of the villus (fig. 382), and their 

 smaller ends resting on the basement membrane. The free 

 surface of the epithelial cells of the villi, like that of the cells 



K.P. 



o a 



