THE ABDOMEN 7^7 



The gastro-splenic omentum extends between the posterior 

 surface of the cardiac end of the stomach and the gastric surface 

 of the spleen just in front of the hilum. It is composed of two 

 layers, anterior and posterior, which are continuous with the t^vo 

 anterior layers of the great omentum. The anterior layer is formed 

 by peritoneum belonging to the great sac, and the posterior layer 

 by that belonging to the small sac. The fold contains between its 

 two layers the vasa brevia of the splenic artery. 



Mesenteries. — The mesentery proper is the fold of peritoneum 

 which attaches the jejunum and ileum to the vertebral column. 

 Its vertebral border is called the root, and is comparatively 

 short, measuring from 5 to 6 inches in length. Its line of attach- 

 ment extends from the commencement of the jejunum on the 

 left side of the body of the second lumbar vertebra, at the anterior 

 border of the pancreas, to the termination of the ileum in the right 

 iliac fossa, near the right sacro-iliac articulation. This line of 

 attachment passes obliquely from left to right, and in this course 

 the root of the mesentery proper crosses in succession the third part 

 of the duodenum, aorta, infeiior vena cava, and right psoas magnus. 

 The other border of the mesentery proper is called the intestinal 

 border, and is attached to the jejunum and ileum throughout their 

 whole length. This border is of considerable length, and equals 

 that of the jejunum and ileum. The widening of the mesentery 

 proper takes place gradually, so that it is thrown into a number of 

 folds, an arrangement which accounts for the coils of the jejunum 

 and ileum. I to average breadth, from the root to the intestinal 

 border, is about 8 inches. The fold is composed of two layers of 

 peritoneum, right or superior, and left or inferior. The right or 

 superior layer is continuous with the inferior layer of the transveise 

 meso-colon, and with the peritoneum which covers the ascending 

 colon, whilst the left or inferior layer is continuous with the peri- 

 toneum which covers the descending colon. Both layers are 

 formed by peritoneum belonging to the great sac. The two layers 

 contain between them the following structures: (i) the superior 

 mesenteric vessels, and the rami intestini tenuis ; (2) the superior 

 mesenteric plexus of sympathetic nerves, and its secondary off- 

 shoots ; (3) the lacteal vessels ; and (4) the mesenteric lymphatic 

 glands. 



In some cases the mesentery proper presents one or more openings, 

 known as mesenteric holes, which may be congenital or traumatic. 

 If a portion of intestine slipped through one of these holes a mesen- 

 teric hernia wovild result, and, if the hole is situated in one layer 

 only^ the herniated portion of intestine would take up a position in 

 the space between the two layers. These openings are liable to 

 be met with in that portion of the mesentery proper which is 

 attached to the lower part of the ileum, within the arch formed 

 by the ileo-colic branch of the superior mesenteric arterv and the 

 last ramus intestini tenuis (Treves). 



The appendicular mesentery or meso-appendix is a fold of 



