DIGESTION. 263 



marked in the intervals between the sacculi. Toward the lower end of 

 the rectum they become more numerous, and at the anus they form a 

 strong band called the internal sphincter muscle. 



The mucous membrane of the large, like that of the small intestine, is 

 lined throughout by columnar epithelium, but, unlike it, is quite smooth 

 and destitute of villi, and is not projected in the form of valvulce conni- 

 ventes. Its general microscopic structure resembles that of the small in- 

 testine: and it is bounded below by the muscularis mucosce. 



The general arrangement of ganglia and nerve-fibres in the large in- 

 testine resembles that in the small (p. 255). 



Glands of the Large Intestine. The glands with which the 

 large intestine is provided are of two kinds, (1) the tubular and (2) the 

 lymphoid. 



FIG. 194. Horizontal section through a portion of the mucous membrane of the large intestine, 

 showing Lieberktihn's glands in transverse section, a, lumen of gland lining of columnar cells 

 with c, goblet cells, 6, supporting connective tissue. Highly magnified. (V. D. Harris.) 



(1.) The tubular glands, or glands of Lieberkiihn, resemble those of 

 the small intestine, but are somewhat larger and more numerous. They 

 are also more uniformly distributed. 



(2.) Follicles of adenoid or lymphoid tissue are most numerous in the 

 caecum and vermiform appendix. They resemble in shape and structure, 

 almost exactly, the solitary glands of the small intestine. 



Peyer's patches are not found in the large intestine. 



Ileo-Caecal Valve. The ileo-csecal valve is situate at the place of 

 junction of the small with the large intestine, and guards against any re- 

 flex of the contents of the latter into the ileum. It is composed of two 

 semilunar folds of mucous membrane. Each fold is formed by a doubling 

 inward of the mucous membrane, and is strengthened on the outside by 



