THE DTOESTU'F. SYSTEM 



265 



running in the long axis of the \illus. A single lymph or ch\Ie vessel 

 (Fig. i66, /; 167, ch) with distinct endothelial walls traverses the 

 centre of each villus, ending at its tip in a slightly dilated blind 

 extremity. As it is usually seen collapsed, it appears as two closely 

 approximated rows of Hat cells with bulging nuclei. The capillaries 

 of the villus lie for the most part away from the chyle vessel, just 

 beneath the basement membrane (Fig. 166, e\ 167, g). 



From the depths of the depressions 

 between the villi, simple tubular glands 

 — glands or crypts of Lieberkiihn (Figs. 

 165 and 168) — extend down through the 

 stroma as far as the muscularis mucosas. 

 These crypts are lined with an epithelium 

 similar to and continuous with that 

 covering the villi. The cells are, how- 

 ever, lower, have no striated borders, 

 and there are fewer goblet cells. In 

 addition to these cells there are also 

 found in the depths of the crypts of 

 Lieberkiihn pecuhar coarsely granular 

 cells, the cells of Paneth (Fig. 168, k). 

 They are found in man and in rodents, 

 but do not occur in the carnivora. 

 They probably produce a specific secre- 

 tion, the nature of which is unknown. ^^^ i68.-Longitudinal Section 



In contrast with the stomach, where of Fundus of Crypt of Lieberkuhn. 



. , : . XS30. (Kolliker.) b, Goblet cell 



most active mitosis is at the junction showing mitosis; e, epithelial cell; 



of the neck and body of the gland (page f ■ iSlV:°'„,f ^miio'sis 'S^piSdial 



256), the most active cell proliferation cell. Surrounding the crypt IS 

 ,, . , . , -,1 T • . ,1 seen the stroma of the mucous 



in the intestinal epithenum is at the membrane. 



bottoms of the crypts whence the cells 



are gradually pushed toward the surface, the oldest, cells thus being 



found at the crests of the villi. 



The stroma, besides forming the centres of the villi, fills in the 

 spaces between the crypts of Lieberkuhn and between the latter and 

 the muscularis mucosae. In places the lymphoid cells are closely 

 packed to form distinct nodules or "solitary folHcles," such as are 

 found in the stomach (see page 259). 



Peyer's Patches (agminated follicles) (Fig. 169). — These are 

 groups of lymph nodules found mainly in the ileum, especially near 



