The transverse mesocolon, formed of two layers of peritoneum, derived as described above, is about six inches broad in the middle, and gradually narrows off on each side. It retains the transverse portion of the colon in situ, and transmits the veins, arteries, and nerves to this part of the intestine. At its root its two layers separate, leaving a prismoid space, which gives passage to the transverse portion of the duo denum..
The mesentery is the peritoneal fold that connects the small intestine to the posterior abdominal parietes, g,iving transit to the vessels and nerves of that part of the intestinal tube. Numerous lymphatic glands, called mesenteric glands, are also included between its layers. It is eight inches in breadth at its widest part, and ntirrows off towards each end, where the small intestine becomes adherent to the parietes. Its parietal attachment, as mentioned above, is only a few inches in extent, whilst its visceral border is usually twenty feet long.
The ascending mesocolon, descending meso colon, and mesoccecum, when they exist, and the iliac or sigmoideal mesocolon and mesorectum, which always exist, perform all the offices of mesenteries to those parts, respectively, of the intestinal tube which are indicated in their names.
The appendices epiploica are numerous small masses of fat, somewhat pyriform, and having a peritoneal investment, attached along the large intestine. Their use is not known ; perhaps they serve as packing to the sacculated bowel on which they are placed.
The recto-resical folds give transit to some vesical vessels and the umbilical arteries of the fcetus. The cellular tissue enclosed by them is very lax, so that they are easily unfolded by distention of the bladder.
The brood liganients of the uterus are two folds of peritoneum passing from the lateral borders of the uterus to the opposite abdominal parietes. The line of their summits is about level with that of the superior border of the unimpregnated uterus. This summit or supe rior border of the broad ligament is defined by the Fallopian tube which it encloses ; a little lower down on its posterior aspect the ovary is sessile upon it, invested in a secondary fold of its posterior layer : and the round ligament of the uterus passing between its layers from the side of the uterus to the inguinal canal carries out another little secondary fold in front of it.
The broad ligament, then, and its secondary folds, enclo-se the ovary with its ligament, the Fallopian tube, the round ligament of the ute rus, and the spermatic vessels and nerves. The layers of the broad ligament itself, but not those of its secondary folds, are connected together by loose areolar tissue, and are separated (the broad ligament itself becoming effaced) by the enlargement of the uterus in pregnancy.
There are a pair of recto-uterine peritoneal folds in the female and a pair of vesico-uterine folds ; the former pass across from the sides of the rectum to the sides of the uterus, and repre sent the recto-vesical folds of the male ; the latter pass across from the sides of the uterus to the sides of the bladder. The layers of both pairs are very loosely connected together.
There is a slight median fold and two slight lateral folds of the peritoneum lining the ante rior abdominal parietes, converging from the fundus and sides of the bladder to the navel ; they enclose the remains of the urachus and of the two umbilical arteries of the fatus.
At the point corresponding with each inter nal abdominal ring. in the male subject, there is a little infundibuliform depression or dimple of the peritoneal surface ; it indicates the point from which a portion of peritoneum, being car ried down with the testicle in its descent, was separated to form the tunica vaginalis—in the female; from the same points a cylindrical sheath of peritoneum accompanies the round ligament a little way into the inguinal canal ; this sheath has been called the canal of Nuck.
With regard to our third proposition,—THE