THE LARGE INTESTINE 433 



to it, on the iliacus, internal to it, on the pelvic brim, or entirely 

 within the pelvis. In any of these positions it is entirely sur- 

 rounded by peritoneum. 



The vermiform appendix conies off from the inner and back 

 part of the cecum, near its lower end, and extends upward 

 and inward behind it. This is a piece of gut of the diameter 

 of a goose-quill, varying from 3 to 6 inches in length, curved 

 upon itself, and ending in a blind extremity. It tapers gradually 

 to its end, which is blunt, is completely invested by the peri- 

 toneum, which forms for it a mesentery (mesoappendix), and 

 at its connection with the cecum is guarded by an imperfect 

 valve (valve of Gerlach). This is not always constant. 



The ileocecal valve guards the opening of the small intestine 

 into the large gut. This junction is oblique and situated about 

 1\ inches above the lower extremity of the cecum. It is a 

 double fold lying transversely to the long axis of the colon. 

 Each fold of the valve is made up of the mucous and submucous 

 coats, reinforced by some circular fibers from the muscular 

 coat, of each portion of the gut, and is covered on the side 

 toward the ileum with villi. At each end of the opening these 

 folds run together and are prolonged some distance around 

 the gut, forming the retinacula. 



The ascending colon runs from the cecum, above the ileo- 

 cecal valve, upward to the under surface of the liver on the 

 right side of the gall-bladder, and then turns forward and 

 to the left to form the hepatic flexure. The peritoneum .rarely 

 forms for it a mesocolon; generally it covers only the front 

 part and the sides. It occupies the right lumbar and hypo- 

 chondriac regions. 



The transverse colon arches across the abdomen, the con- 

 vexity looking toward the belly wall, and makes a sudden 

 turn backward and downward beneath the spleen, forming 

 the splenic flexure, and is completely invested by the peri- 

 toneum, which holds it to the anterior aspect of the pancreas 

 and second portion of the duodenum; by two layers of peri- 

 toneum called the transverse mesocolon, the upper surface of 

 which fuses with the posterior layer of the great omen turn. 

 It occupies the right hypochondriac, upper part of umbilical, 

 and left hypochondriac regions. At the splenic flexure is 

 attached the phrenocolic ligament, a fold of peritoneum extending 

 to the diaphragm opposite the tenth or eleventh rib. 

 28 



