DIGESTION AND ABSORPTION IN THE INTESTINES 



99 



from without inward that is, from the surface of the villus 

 inward to its center is (i) a layer of columnar epithelium 

 resting upon a delicate basement membrane; (2) lymphoid 



FIG. 40. Portion of the wall of the small intestine laid open to 

 show the valvulae conniventes. (From Yeo after Brinton.) 



tissue containing abundant capillaries and connective tissue 

 cells; (3) a thin layer of plain muscle fibers continuous from 



FIG. 41. Vertical section of a villus of the small intestines of a cat. 



a, striated border of the epithelium; b, columnar epithelium; c, goblet cells; 

 d, central lymph-vessel; e, smooth muscular fibers; f, adenoid stroma of the 

 villus in which lymph corpuscles lie. (Kirkes after Klein.) 



the intestinal wall; (4) the lacteal, whose endothelial wall 

 contains many stomata. 



3. The glands of Brunner and the crypts of Lieberkuhn, 

 or intestinal tubules, are supposed to produce the succus en- 



