PERITONEUM. 557 



omentum. The lower or descending layer passes over the 

 small intestines, and round these and their vessels, to form 

 a double lamina, which returns to the spine, forming a very 

 broad and important reflection, termed the mesentery. The 

 mesentery, besides blood-vessels, also encloses numerous 

 lymphatic glands and absorbents. From the root of the 

 mesentery we find its laminae stretching, upon either side, 

 into the lumbar regions upon the right and left colon, con- 

 stituting the right and left mesocolons, into the iliac regions, 

 and thence into the pelvis, upon the rectum, forming the 

 meso-rectum. From the rectum, of which it does not cover 

 more than its upper two-thirds, it is reflected, in the male, 

 upon the posterior and lower part of the bladder, forming 

 two lateral folds, called the posterior ligaments of the blad- 

 der, between which there is a depression or cul-de-sac. 



In the female this reflection passes first to the posterior 

 and upper part of the vagina, then spreads over the uterus 

 and to either side, forming the broad ligaments, which en- 

 close the Fallopian tubes, ovaries, and round ligaments. 

 From the front of the uterus the reflection proceeds to the 

 bladder, and then ascends, as in the male, upon the sides 

 and posterior surface of the bladder, to its fundus, whence 

 it is traced upward, upon the posterior abdominal walls, to 

 the umbilicus the place where it was first opened. 



In this tracing of the peritoneum,, it is seen that it only 

 gives a partial covering to many of the organs as the 

 duodenum, rectum, bladder, kidneys, &c. ; that all the vis- 

 cera, even those having the most complete investment from 

 it, are upon its external surface, and not within its cavity ; 

 and that each organ gets its covering by simply pushing 

 this membrane before it into the peritoneal sac. A famil- 

 iar illustration is found in the double night-cap, showing 

 how a shut sac may invest any thing, yet be on its out- 

 side. The portion of the cap covering the head, resembles 

 the peritoneum, covering the viscera, while the loose part 

 of the cap, above the head, resembles the reflected portion 

 of the peritoneum, upon the abdominal walls. 



About the neck of the gall-bladder, and at the base of 



