454 THE DIGESTIVE AFPARATUS IN MAMMALIA. 



the cfecum and the second flexure of the colon, which constitute the meso-coecum 

 and meso-colon. 



The great mesentery is detached from around the large mesenteric artery, and 

 projects into the abdominal cavity to reach the small intestine at the lesser 

 curvature, and to envelop that viscus. 



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

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

 duodenal frjenum, and the posterior border, the longest, with the meso-colon, its 

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

 layers that compose it, are the blood-vessels and lymphatics, as well as the nerves, 

 of the small intestine. 



The colic mesentery is formed 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 ctecum, from the origin to the termination 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-ccmum ; another layer, comprised between the second 

 and third portion of the colon — the shape of which is that of a battledore, is 

 named the meso-colon. 



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

 wards, 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 lateral walls of the abdomen. 



TMs serous membrane covers the fundus of the bladder, and at this point it 

 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 fundus ; they have on their free border the obliterated umbilical 

 arteries. In the male, the peritoneum is prolonged from the upper face of the 

 bladder to the enlargement of the deferent ducts, between which it sends a trans- 

 verse 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, and to the cornua of that organ, where it forms three folds 

 named the broad ligaments, ligamefits 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 peritoneal serous 

 membrane. 



Structuee. — 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 an endothelial layer (the cells of Avhich are flat and polygonal, and about ^-^ 

 of an inch in diameter). Many blood-vessels are found on the adherent surface ; 



