60 



ABSORPTION. 



gut. Each villus is covered by an epithelial layer, and within, sup- 

 ported by areolar tissue, is a delicate capillary n-etwork of blood- 



FIG. 11. 



FIG. 12. 



X/fyV^ 



m&wm 



w^:v>:^-^i 



$y/-. / 



j^*B^ ?; 



h&tAifW 



FIG. 11. An Intestinal Villus: a, layer of cylindrical epithelium, with its external trans- 

 parent striated portion; bb, blood-vessels entering and leaving the villus; c, lym- 

 phatic vessels, occupying its central axis (Leydig). 



FIG. 12. Patch of Peyer's Glands, from the lower part of the ileum, showing villi (mag- 

 nified). 



vessels, a muscular layer (nmscularis mucosse), and a more or less 

 branched ending of a lacteal vessel (Figs. 11 and 12); The ileo- 

 caecal valve sho.ws the absolute alteration which is apparent in the 

 mucous membrane of the small as compared with the large intes- 

 tine. On the side toward the ileum are found villi in great num- 

 bers, while its csecal side shows none. 



Where does the absorption occur in the intestine ? 



Probably throughout its length in some degree. In the stomach 

 and large intestine the absorption is very much less than in the 

 small intestine, but there is reason to think that there is consider- 

 able activity of absorption from the entire gut so long as digestion 

 continues. 



