DIGESTION AND ABSORPTION IN THE INTESTINES 



99 



intestinal lymphatic. The structure 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 



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

 valvulae conniventes. (From Yeo after Brinton.} 



membrane; (2) lymphoid tissue containing abundant capillaries 

 and connective tissue cells; (3) a thin layer of plain muscle fibers 

 continuous from the intestinal wall; (4) the lacteal, whose endo- 

 thelial wall contains many stomata. 



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;/, adenoid stroma of the villus in 

 which lymph corpuscles lie. (Kirkes after Klein.) 



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



or intestinal tubules, are supposed to produce the succus entericus. 



