INFERIOR MESENTERIC. 



503 



which vessels are distributed to the ascending colon. The branches of this 

 vessel are covered with peritoneum only on their anterior aspect. 



The colica media arises from the upper part of the concavity of the superior 

 mesenteric, and, passing forwards between the layers of the transverse meso- 

 colon, divides into two branches ; the one on the right side inosculating with 

 the colica dextra; that on the left side, with the colica sinistra, a branch of the 

 inferior mesenteric. From the arches formed by their inosculation, branches 

 are distributed to the transverse colon. The branches of this vessel lie between 

 two layers of peritoneum. 



INFERIOR MESENTERIC ARTERY. (Fig. 293.) 



In order to expose this vessel, draw the small intestines and mesentery over to the right side 

 of the abdomen, raise the transverse colon towards the thorax, and divide the peritoneum cover- 

 ing the left side of the aorta. 



The Inferior Mesenteric Artery supplies the descending and sigmoid flexure 

 of the colon, and the greater part of the rectum. It is smaller than the supe- 



Fig. 293. The Inferior Mesenteric Artery aud its Branches. 



Infenor Unnvrrhoiilal 



rior mesenteric ; and arises from the left side of the aorta, between one and two 

 inches above its division into the common iliacs. It passes downwards to the 

 left iliac fossa, and then descends, between the layers of the meso-rectum, into 

 the pelvis, under the name of the superior hsemorrhoidal artery. It lies at first 



