THE SMALL INTESTINE. 129 



villi, and contain two kinds of secretory glands, intestinal and 

 duodenal, lymphoid structures, bloodvessels, lymphatics, and 

 nerves. 



The mucous membrane is thrown into transverse and 

 oblique folds, the valvulce conniventes. Its free surface is 

 raised in papillary projections, called vitti, between the bases 

 of which the intestinal glands dip down. The mucosa con- 



FIG. 55. 





f -^--^ 





* rt in i B ; M 



. 



& 



- - 



m \ i.&o 1 



Axial section of villus (Kultschitzky). a, epithelium ; b, gob'.et-cell ; d, C9nnective- 

 tissue cell of basement-membrane ; e, smooth muscle-cells ; /, reticulum of 

 tunica propria ; g, central lacteal. 



sists of a lining of simple columnar epithelium, which differs 

 somewhat in the villi and the glands ; subepithelial connec- 

 tive tissue ; adenoid tissue ; blood and lymph vessels, and 

 the muscularis mucosse. 



The villi (Fig. 55) are minute club-shaped papillaB about a 



9 Hist. 



