384 THE DIGESTIVE APPARATUS IN MAMMALIA. 



Its shape is that of an irregular triangle, whose summit corresponds to the 

 mesenteric artery, the very short anterior border being continuous with the 

 duodenal fraenum, and the posterior border, the longest, with the meso-colon, 

 its convex festooned base being as long as the intestine itself. Between the 

 two laminae that compose it are the blood-vessels and lymphatics, as well as 

 the nerves, of the small intestine. 



The colic mesentery is constituted like the great mesentery. Its inferior 

 border, plane or plicated, is fixed to the small curvature of the floating colon 

 and the commencement of the rectum ; its upper border extends from the 

 great mesenteric artery as far as the entrance to the pelvic cavity. 



Around the cross of the caecum, from the origin and the termina- 

 tion of the great colon, the peritoneum is reflected to cover these viscera ; 

 a layer passes from the anterior border of the caecum on to the ileum 

 and the second flexure of the colon : this is the meso-ccecum ; another layer, 

 comprised between the second and third portion of the colon, and whose 

 shape is that of a battledore, is named the meso-colon. 



If, again, the peritoneum is taken at the umbilical region and followed 

 backwards, it will be found to insinuate itself into the inguinal canals, cover 

 the organs contained in the pelvis, and become reflected at the bottom of 

 that cavity, to be continued either with the peritoneum of the sublumbar 

 region, or with that on the abdominal walls. 



This serous membrane covers the anterior cul de sac of the bladder, and 

 at this point has three ligaments. The middle ligament, falciform in shape, 

 leaves the large extremity of the bladder, is attached to the anterior border 

 of the pubis, and insensibly disappears on the inferior abdominal wall ; on 

 its free border is a small fibrous cord, which is supposed to be the remains 

 of the urachus. The two lateral ligaments are more developed, and extend 

 from the entrance to the pelvic cavity to the vesical cul-de-sac ; they have on 

 their free border the obliterated umbilical arteries. In the male, the peri- 

 toneum is prolonged from the upper face of the bladder to the enlargement of 

 the deferent ducts, between which it sends a transverse fold to the anterior 

 extremity of the vesiculse seminales, and is then reflected around the 

 rectum. 



In the female, it is carried from the bladder to the terminal portion 

 of the vagina, to the uterus, arid to the cornua of that organ, where it 

 forms three folds named the broad ligaments, ligaments of the ovary, and the 

 round ligament; then it re-descends on the upper face of the vagina, and 

 thence envelops the rectum, around which it is reflected from behind forwards. 



According to this arrangement, we see that the termination of the 

 digestive canal, and the parts of the genito-urinary organs situated altogether 

 at the posterior portion of the pelvic cavity, are placed outside the peri- 

 toneal serous membrane. 



STRUCTURE. Like all the serous membranes, the peritoneum is formed 

 by a membrane of connective tissue, rich in elastic fibres, and covered on its 

 free face by a simple tesselated layer of epithelium (the cells of which are flat 

 and polygonal, and about T ^Vo" ^ an ^ ncn ^ n diameter). Many blood-vessels 

 are found on the adherent surface, while lymphatics are abundant in the 

 visceral layer. Its nerves come from the diaphragmatic, lumbar, and inter- 

 costal branches, and the great sympathetic. 



DIFFERENTIAL CHARACTERS IN THE ABDOMINAL CAVITY OF OTHER THAN SOL1PED 

 * ANIMALS. 



In the Carnivnra, the abdominal cavity is very narrow ; while in Buminants it is 



very vast, its capacity being in direct relation to the volume of the viscera it contains. 



