128 ORGANS OF DIGESTION. 



four layers of peritoneum, two of which descend from the stomach, one from 

 its anterior, the other from its posterior surface, and, uniting at its lower border, 

 descend in front of the small intestines, as low down as the pelvis; they then 

 turn upon themselves, and ascend again as far as the transverse colon, where 

 they separate and inclose that part of the intestine. These separate layers may 

 be easily demonstrated in the young subject; but, in the adult, they are more 

 or less inseparably blended. The left border of the great omentum is continu- 

 ous with the gastro-splenic omentum ; its right border extends as far only as 

 the duodenum. The great omentum is usually thin, presents a cribriform ap- 

 pearance, and always contains some adipose tissue, which, in fat subjects, accu- 

 mulates in considerable quantity. Its use appears to be to protect the intestines 

 from cold, and to facilitate their movement upon each other during their 

 vermicular action. 



The gastro-splenic omentum is the fold which connects the concave surface of 

 the spleen to the cul-de-sac of the stomach, being continuous by its lower border 

 with the great omentum. It contains the splenic vessels and vasa brevia. 



The Mesenteries are, the mesentery proper, the meso-csecum, the ascending, 

 transverse, and descending meso-colon, the sigmoid meso-colon, and the meso- 

 rectum. 



The mesentery (niaov lvr*por), so called from being connected to the middle of 

 the cylinder of the small intestine, is the broad fold of peritoneum which con- 

 nects the convolutions of the jejunum and ileum with the posterior wall of the 

 abdomen. Its root, the part connected with the vertebral column, is narrow, 

 about six inches in length, and directed obliquely from the left side of the 

 second lumbar vertebra to the right sacro-iliac symphysis. Its intestinal border 

 is much longer ; and here its two layers separate, so as to inclose the intestine, 

 and form its peritoneal coat. Its breadth, between its vertebral and intestinal 

 border, is about four inches. Its ripper border is continuous with the under 

 surface of the transverse meso-colon; its lower border, with the peritoneum 

 covering the caecum and ascending colon. It serves to retain the small intes- 

 tines in their position, and contains between its layers the mesenteric vessels 

 and nerves, the lacteal vessels, and mesenteric glands. 



The meso-csecum, when it exists, serves to connect the back part of the caecum 

 with the right iliac fossa ; more frequently, the peritoneum passes merely in 

 front of this portion of the large intestine. 



The ascending meso-colon is the fold which connects the back part of the 

 ascending colon with the posterior wall of the abdomen ; and the descending 

 meso-colon retains the descending colon in connection with the posterior abdomi- 

 nal wall : more frequently, the peritoneum merely covers the anterior surface 

 and sides of these two portions of the intestine. 



The transverse meso-colon is a broad fold, which connects the transverse colon 

 with the posterior wall of the abdomen. It is formed by the two ascending 

 layers of the great omentum, which, after separating to surround the transverse 

 colon, join behind it, and are continued backwards to the spine, where they 

 diverge in front of the duodenum, as already mentioned. This fold contains 

 between its layers the vessels which supply the transverse colon. 



The sigmoid meso-colon is the fold of peritoneum which retains the sigmoid 

 flexure in connection with the left iliac fossa. 



The meso-rectum is the narrow fold which connects the upper part of the 

 rectum with the front of the sacrum. It contains the lueinorrhcmlal vessels. 



The appendices epiploicse are small pouches of the peritoneum filled with fat, 

 and situated along the colon and upper part of the rectum. They are chiefly 

 appended to the transverse colon. 



THE STOMACH. 



The Stomach is the principal organ of digestion. It is the most dilated part 

 of the alimentary canal, serving for the solution and reduction of the food, 



