THE LARGE INTESTINE. 



171 



the epithelium. The veins within the submucosa accompany the arteries 

 through the muscular coat and unite into the emergent venous channels that 

 course with the arteries between the peritoneal folds. 



The lymphatics of the small intestine, long known as the lacteals on 

 account of their milky appearance when containing finely divided particles 

 of fat, begin as the absorbent vessels of the villi. In addition, lymph-chan- 

 nels form a plexus within the tunica propria in the neighborhood of the 

 muscularis mucosae, from which tributaries pass to the larger submucous 

 plexus. The latter is characterized by irregular contours, due to the dila- 

 tations associated with the numerous valves. The emergent lymphatics 

 penetrate the muscular coat and, within the serous tunic, unite into larger 

 trunks that pass to the lymph-nodes between the peritoneal folds; from these 

 smaller nodes lymphatics converge to the larger mesenteric lymph-nodes. 



The nerves supplying the small intestine are derived from the solar 

 plexus, and include both medullated and nonmedullated fibres, the last being 

 chiefly from the sympathetic. In their distribution, they closely follow the 

 arrangement observed in the stomach (page 163), including the plexus of Auer- 

 bach and of Meissner and, additionally, a plexus of nonmedullated fibres 

 within the villi. ^ 



THE LARGE INTESTINE. 



The large intestine, subdivided into the caecum, the colon and the rectum, 

 measures about i . 6 meters or about 5 ft. in length. As other parts of the intesti- 



Lieberkiihn's glands 



Solitary lymph-nodul 



Mucous coat 



Submucous 

 coat 



ml- : : ; S1 



- '' ..; ~- 



;>>*" ^ ; ^i2-? 



FIG. 213. Longitudinal section of large intestine (ascending colon), showing the general arrangement of 

 the coats and a solitary lymph-nodule. X 30. 



naltube, it consists of four coats the mucous, submucous, muscular and serous. 



The mucous coat of the large intestine agrees in its essential structure 



with that of the small gut, consisting of a tunica propria, resembling lymphoid 



tissue, covered by a single layer of columnar epithelium exhibiting a cuticular 



