LARGE INTESTINE. 461 



of Lieberkiihn, and into the ducts of the glands of Brunner, and gives them 

 a lining. 



Dissection. To demonstrate the areolar tissue between the coats of the 

 intestine, a piece of the bowel turned inside out is to be inflated forcibly ; 

 and to insure the success of the attempt, a few cuts may be previously 

 made through the peritoneal coat. The air enters the wall of the intes- 

 tine where the peritoneal covering is injured, and spreads through the 

 whole gut ; but opposite the solitary glands, and the patches of Peyer, the 

 mucous coat is more closely connected with the contiguous structures, and 

 the subjacent portion will not be distended with the air. The piece of the 

 intestine may be examined when it is dry. 



Vessels .of the intestine. The branches of arteries ramify in the sub- 

 mucous layer, and end in a network of small twigs in the mucous mem- 

 brane, which supplies the folds, the villi, and the glands. Opposite 

 Peyer's patches the intestine is most vascular ; and the vessels form circles 

 around the follicles, before supplying offsets to them. The veins have 

 their usual resemblance to the companion arteries. 



The absorbents consist of a superficial set (lymphatics) in the muscular 

 coat ; and of a deep plexiform set (lacteals) in both the mucous and sub- 

 mucous layers. The two sets join, and all end in larger trunks in the 

 mesentery. 



Nerves of the small intestine come from the upper mesenteric plexus, 

 and entering the coats by the side of the arteries, form plexuses with in- 

 terspersed ganglia. One such plexus is contained in the muscular coat 

 between the longitudinal and circular h'bres (Auerbach) ; and another is 

 placed in the submucous layer (Meissner) : they join freely by branches 

 through the intestinal coats, and reach from the pylorus to the extremity 

 of the alimentary tube. 



Structure of the common bile duct. The bile duct consists of an exter- 

 nal or strong fibrous layer, and of an internal or mucous coat which is 

 lined by columnar epithelium. On the surface of the inner membrane are 

 the openings of numerous branched mucous glands, which are imbedded 

 in the fibrous coat ; some of them are aggregated together, and are visible 

 with a lens. 



LARGE INTESTINE. 



The large intestine is the part of fhe alimentary canal between the 

 termination of the ileum and the anus.- 1 Its division and its attachment 

 by peritoneum to the abdominal wall, have been described (p. 4JJ3). 



In length this part of the alimentary canal measures about five or six 

 feet one-fifth of the length of the intestinal tube. The diameter of the 

 colon is largest at the commencement in the caecum, and gradually de- 

 creases as far as the rectum, where there is a dilatation near the end. 



When compared with the small intestine, the colon is distinguished by 

 the following characters : It is of greater capacity, being in some parts as 

 large again, and is more fixed in its position : it is also free from convolu- 

 tion, except in the left iliac fossa, where it forms the sigmoid flexure. 

 Instead of being a smooth cylindrical tube, the colon is sacculated, and is 

 marked by three longitudinal muscular bands, which alternate with as 

 many rows of dilatations ; but at the lower part of the large intestine 

 (rectum), the surface is smooth, and the longitudinal bands have disap- 

 peared. Attached to the surface at intervals, especially along the trans- 



