THE PERITONEUM. 



897 



above the symphysis pubis ; the rectum lies in the concavity of the sacrum, but 

 is usually obscured by the coils of the small intestine. 



If the stomach is followed from left to right it will be found to be continuous 

 with the first part of the small intestine, or duodenum, the point of continuity being 

 marked by a thickened ring which indicates the position of the pyloric valve. 

 The duodenum passes toward the under surface of the liver, and then curving 

 downward, is lost to sight. If, however, the great omentum be thrown upward 

 over the chest, the terminal part of the duodenum will be observed passing across 

 the spine toward the left side, where it becomes continuous with the coils of the 

 small intestine. These measure some twenty feet in length, and if followed down- 

 ward will be seen to end in the right iliac fossa by opening into the caecum or 

 commencement of the large intestine. From the caecum the large intestine takes 

 an arched course, passing at first upward on the right side, then across the middle 

 line and downward on the left side, and forming respectively the ascending, trans- 

 verse, and descending parts of the colon. In the left iliac region it makes still 

 another bend, the sigmoid flexure, and then follows the curve of the sacrum as 

 the rectum. 



FIG. 487. The regions of the abdomen and their contents. (Edge of costal cartilages in dotted outline.) 



The spleen lies behind the stomach in the left hypochondriac region, and may 

 be in part exposed by pulling the stomach over toward the right side. 



The glistening appearance of the deep surface of the abdominal "wall and of 

 the exposed viscera is due to the fact that the former is lined and the latter more 

 or less completely covered by a serous membrane, the peritoneum. 



The Peritoneum. 



The peritoneum is the largest serous membrane in the body, and consists, in 

 the male, of a closed sac, a part of which is applied against the abdominal parietes, 

 while the remainder is reflected over the contained viscera. In the female the 



57 



