THE ALIMENTARY APPARATUS. 237 



but only partially the others,, being absent in the posterior sur- 

 faces of the ascending and descending portions, and on the 

 middle portion of the rectum. The lower portion of the rectum 

 is without peritoneal covering. The appendices epiploicce are 

 folds of serous membrane filled with fat and attached chiefly 

 to the transverse colon, depending from it. 



The muscular coat consists of longitudinal fibres arranged 

 into three flat bands, shorter by nearly one-half than the intes- 

 tine itself, and the circular, distributed more evenly, but accumu- 

 lated at points, producing with the former a sacculated condition. 



The cellular coat connects the mucous with the muscular 

 coat beneath. 



The mucous coat is smooth, destitute of villi and valvulse 

 conniventes, and thrown into numerous folds, two to four of 

 which, situated in the rectum, have received the name of Hous- 

 ton's folds. 



It contains crypts of Lieberkiihn, more numerous here than 

 in the small intestine, and solitary glands scattered throughout, 

 but most numerous in the appendix and caecum, where some of 

 them are accumulated into Pe} r er's patches. 



The arteries of the caecum and colon are from the mesen- 

 teric. The lymphatics empty into the mesenteric glands, and 

 -the nerves are derived from the mesenteric plexus of the sym- 

 pathetic system. 



The arteries of the rectum are the haamorrhoidal branches 

 of the inferior mesenteric, internal iliac, and internal pudic. 

 The veins form the haBmorrhoidal plexus, and empty into the 

 inferior mesenteric and internal iliac veins. 



The lymphatics go to the sacral and lumbar glands, and the 

 nerves are from the hypogastric plexus of sympathetic and con- 

 tiguous spinal nerves. 



THE PANCREAS. 



The pancreas is an oblong compound racemose gland, about 

 six to eight inches in length, one and one-half inches in breadth, 

 and one-half to one inch in thickness, situated across the back 

 part of the epigastric and left hypochondriac regions. Its weight 

 varies from two to six ounces. 



It consists of a head, body, and tail: 



The head, or right extremity, is received into the concavity 

 of the duodenum. The lesser pancreas, a detached portion of 

 the gland, lies behind it. 



The tail, or lesser end , terminates above the left kidney and 

 suprarenal capsule, in contact with the spleen. 



