4)8 ABDOMEN 



aorta to the left common iliac artery, where it becomes the superior haemor- 

 rhoidal artery. Before it becomes the superior hsemorrhoidal it gives off 

 the left colic branch, and one or more sigmoid branches. The left colic 

 branch passes to the left, towards the descending colon, and divides into an 

 ascending and a descending branch which run towards the upper and the 

 lower parts of the descending colon respectively. The sigmoid branches 

 run downwards and laterally towards the lower part of the iliac colon. 

 To the left of the inferior mesenteric artery is the inferior mesenteric vein, 

 which ascends, crossing behind the left colic artery, to the root of the transverse 

 meso-colon where it disappears behind the lower border of the pancreas, 

 which is exposed in the upper part of the area under consideration. To 

 the left of the inferior mesenteric vein are the internal spermatic vessels 

 which pass behind the sigmoid and left colic arteries, or their branches, and 

 also disappear above, behind the pancreas. In the upper and left angle 

 of the area, in the concavity of the splenic flexure of the colon, is the lower 

 part of the left kidney, and, descending along its medial border, the left 

 ureter, which passes downwards, behind the internal spermatic vessels and 

 the left colic and sigmoid arteries, to the lower end of the left common iliac 

 artery. Running downwards and laterally behind the left ureter, on the 

 front of the left psoas magnus muscle, is the left genito-femoral nerve, and 

 beyond the lateral border of the left psoas is the fascia on the front of the 

 medial part of the left quadratus lumborum. Along the anterior border 

 of the psoas, at the left of the aorta, is the left sympathetic cord. The 

 right sympathetic cord is concealed by the inferior vena cava. 



When the dissector has found and defined all the structures mentioned 

 he should commence the study of the superior and the inferior mesenteric 

 arteries and their branches. He will find that the superior mesenteric 

 supplies the terminal portions of the duodenum, the whole of the jejunum 

 and the ileum, the caecum, the ascending colon and the greater part of the 

 transverse colon. That the inferior mesenteric supplies the left part of the 

 transverse colon, the left colic flexure, the descending colon, the iliac colon, 

 and the pelvic colon, and that it also furnishes the greater part of the 

 blood supply of the rectum, by means of its continuation the superior 

 hremorrhoidal artery. He will find also that there is a very free anasto- 

 mosis between the left colic branch of the inferior mesenteric artery and 

 the middle colic branch of the superior mesenteric artery. At a later 

 period he will find that an inferior pancreatico-duodenal branch of the 

 superior mesenteric anastomoses with the superior pancreatico-duodenal 

 branch of the gastro-duodenal artery, and when he recalls to mind the fact 

 that the latter artery is a branch of the hepatic, and that it furnishes the 

 right gastro-epiploic, which passes to the stomach and anastomoses on its 

 surfaces with the other arteries which supply that viscus, he will recognise 

 that a complete chain of arterial anastomoses runs along the wall of the 

 abdominal part of the 'alimentary canal, providing for the continuance of 

 the blood supply to the wall of the gut in the event of one or more of 

 the bigger trunks being temporarily or permanently occluded. 



Arteria Mesenterica Superior. The superior mesenteric 

 artery springs from the front of the abdominal aorta about a 

 quarter of an inch below the coeliac artery. At its origin 

 it is covered by the neck of the pancreas, and crossed by 

 the splenic vein. Emerging from under cover of the pan- 

 creatic neck it proceeds downwards, in front of the lower 

 portion of the head of the pancreas, crosses the third part of 



