THE ABDOME}i '/*7 



quinary arches. The minute vessels arising from the arches of the 

 last tier enter the wall of the jejunum and ileum along the mesen- 

 teric border, where each divides into two branches, which encircle 

 the bowel beneath its serous covering. From the rings thus formed 

 branches penetrate deeply to reach the mucous coat. Each ramus 

 intestini tenuis, as well as its various branches, conducts to the 

 bowel an offshoot of the superior mesenteric sympathetic plexus. 



Right Branches — Ileo-colic Artery. — ^This vessel is the lowest of 

 the right branches, and in many cases it arises in common with the 

 right colic. Its course is downwards and out\vards towards the 

 right iliac fossa behind the peritoneum, and it divides into two 

 branches, colic and ileo-caecal. The colic branch passes upwards and 

 forms an arch with the descending branch of the right colic, from 

 which branches proceed to the lower part of the ascending colon. 

 The ileo-ccecal branch passes to the upper part of the ileo-caecal 

 junction, where it furnishes the following branches: ileal, to the 

 terminal part of the ileum, where it anastomoses with the last 

 ramus intestini tenuis ; appendicular, which, descending behind the 

 terminal part of the ileum, passes between the two layers of the 

 meso-appendix, and so reaches the vermiform appendix; anterior 

 ccecal, to the front of the caecrim ; and posterior ccecal, to its posterior 

 aspect. 



Right Colic Artery.— This is the second branch in order from below 

 upwards, and in many cases it arises in conmion with the ileo-colic. 

 Its course is transversely to the right behind the peritoneum, and it 

 divides into two branches, descending and ascending. The descend- 

 ing branch anastomoses with the colic branch of the ileo-colic, and 

 the ascending branch with the right branch of the middle colic. The 

 arches thus formed furnish branches to the ascending colon, which 

 in their course form secondary and tertiary arches. 



Middle Colic Artery. — ^This vessel arises from the right side and 

 front of the main trunk about 2 inches above the right colic, on a 

 level with the lower border of the third part of the duodenum. Its 

 course is forwards between the two layers of the transverse meso- 

 colon, and it divides into a short right and a long left branch. 

 The right branch anastomoses with the ascending branch of the 

 right colic, and the left branch with the ascending branch of the left 

 colic from the inferior mesenteric. The arches thus formed fuirnish 

 branches to the middle colon, which in their course form secondary 

 and tertiary arches. 



Inferior Pancreatico-duodenal Artery. — ^This small vessel usually 

 arises from the right side of the main trunk opposite the upper 

 border of the third part of the duodenum, but it may spring from 

 the first ramus intestini tenuis. Its course is to the right behind 

 the superior mesenteric vein, and between the head of the pancreas 

 and the third part of the duodenum. Thereafter it ascends for a 

 little between the head of the pancreas and the second part of 

 the duodenum, and anastomoses with the superior pancreatico- 

 duodenal of the gastro-duodenal from the hepatic. It supplies the 



