226 Anatomy Applied to Medicine and Surgery. 



a rule, after the second year, so that it is impossible in the 

 adult to distend it by introducing air through the foramen 

 of Winslow. The nerves of the transverse colon are de- 

 rived from the cseliac plexus of the sympathetic. The de- 

 scending colon begins above at the splenic flexure and runs 

 downwards and slightly inwards to terminate below in the 

 left iliac fossa as the sigmoid flexure. It averages eight 

 and a half inches in length and is attached, at its upper 

 part, to the diaphragm, by the phreno-colic ligament a 

 concave fold of peritoneum, which acts as a stay or sup- 

 port for the spleen as well. Relations : The descending 

 colon lies in front of the left kidney, the diaphragm, the 

 outer margin of the psoas and the quadratus lumborum 

 muscle, and has a meso-colon thirty-six times out of one 

 hundred subjects (Treves). The sigmoid ftexure, about 

 seventeen inches long, begins where the descending colon 

 ends, viz., in the left iliac fossa, and passes from left to 

 right towards the pelvis, in which most of its length is con- 

 tained, to end at the middle of the third piece of the sacrum 

 in the median line. As it crosses the psoas muscle it lies gen- 

 erally at right angles to it and often midway between the 

 lumbo-sacral angle and Poupart's ligament, and its shape 

 is such that it resembles the Greek letter Omega. It is 

 almost completely surrounded by peritoneum and is at- 

 tached to the fossa by means of a meso-colon the sigmoid 

 meso-colon. The longitudinal muscular bands of the 

 large intestine are three in number one on the posterior ; 

 a second on the anterior, and a third on the internal sur- 

 face of the ascending and the descending colon and on the 

 lower border of the transverse colon. They all start at 

 the appendix and are lost as bands over the rectum, since 

 they spread out and blend with one another on this por- 

 tion of the intestine. 



