432 ARTERIES OF THE ABDOMEX. 



these two branches passes upwards alonjr the colon, and inosculates 

 with the descending branch of the middle colic ; whilst the other 

 descends towards the sigmoid flexure, and anastomoses with the sigmoid 

 artery. 



(b) The sifimoid artery runs obliquely downwards to the sigmoid 

 flexure of the colon, where it divides into branches ; some of which 

 incline upwards and form arches with the preceding vessel, while othei's 

 turn downwards to the rectum and anastomose with the following 

 branch. Instead of a single sigmoid artery, two or three branches are 

 sometimes present. 



(f) The superior lucmorrlwidal artery, the continuation of the inferior 

 mesenteric, passes downwards over the common iliac artery and vein 

 into the pelvis behind the rectum, lying at first in the meso-rectum, and 

 then divides int<> two l)ranches which extend one on each side of the 

 intestine toward the lower end. About five inches from the anus these 

 subdivide into branches, about a line in diameter, which pierce the 

 muscular coat two inches lower down. In the intestine, these arteries, 

 about seven in number, and placed at regular distances from each other, 

 descend between the mucous and muscular coats to the end of the 

 gut, where they communicate in loops opposite the internal sphincter, 

 and end by anastomosing with the middle and inferior ha^morrhoidal 

 arteries. 



Varieties. — Absence of this ai-tery has been noted, its branches being given 

 off by the superior mesenteiic. It has abo been found suppl\-ing access^ory 

 branches to the liver and kidneys. 



Anastomoses on the intestinal tube.— The arteries distributed to the 

 alimentary canal communicate freely •u-ith each other over the v\-holc length of 

 that tube. The arteries of the great intestine derived from the t-^'O mesenteric 

 arteries, form a range of vascular arches along the colon and rectum, at the 

 lower end of which they anastomose with the middle and inferior hajmorrlioidal 

 arteries, given from the internal iliac and pudic arteries. The brandies from 

 the left side of the superior mesenteric form another series of arches along the 

 small intestine, which is connected with the former by the ileo-colic artery. 

 Farther, a branch of the superior mesenteric joins upon the duodenum with the 

 superior pancreatico-duodenal artery. The latter, at its commencement, is in a 

 manner continuous with the pyloric artery ; and so likewise, through the 

 coronary artery of the stomach and its ascending branches, a siniUar connection 

 is formed with the oesophageal arteries, even up to the pharynx. 



The suprarenal or capsular arteries are two very small vessels which 

 arise fi'om the aorta on a level with the superior mesenteric artery, and 

 incline obliquely outwards upon the crura of the diaphragm to reach 

 the suprarenal capsules, to which bodies they are distributed, anasto- 

 mosing at the same time with the upper and lower capsular branches 

 derived respectively from the phrenic and the renal arteries. In the 

 foetus these arteries are of larger size. 



Varieties. — This middle suprarenal artery is often very small, its place being 

 supplied by the superior and inferior suprarenals. The middle suprarenal some- 

 times gives ofE the spermatic artery. This occurs usually on the left, but it 

 also occui'S, though rarely, on the right side (Henle). 



The renal or enxulgent arteries, of large diameter in proportion to 

 the size of the organs which they sup.ply, arise from the sides of the 



