ABDOMINAL CAVITY 481 



caecal junction and sends branches in different directions. 

 Two, termed the anterior and posterior ccecal arteries, pass 

 respectively to the front and back of the caecum ; one, a 

 long slender vessel, the artery to the vermiform process, runs 

 downwards behind the terminal part of the ileum and enters 

 the meso-appendix for the supply of the vermiform process ; 

 whilst a fourth, the Heal artery, turns to the left along the 

 ileum, and forms a loop with the termination of the superior 

 mesenteric trunk. 



The Arteria Colica Dextra arises together with or above 

 the ileo- colic and passes to the right, behind the parietal 

 peritoneum on the posterior wall of the abdomen. It divides 

 into two branches, a superior and an inferior. The superior 

 branch ascends between the two layers of the transverse meso- 

 colon to inosculate with the middle colic ; whilst the inferior 

 branch joins the ascending part of the ileo-colic. From the 

 convexity of these arches twigs proceed to the ascending 

 colon, the right colic flexure, and part of the transverse colon. 



The Arteria Colica Media springs from the upper end of 

 the superior mesenteric. It passes between the two layers 

 of the transverse meso-colon, and divides into a right and a 

 left branch. The right branch joins the superior part of the 

 right colic, whilst the left branch inosculates with the ascending 

 part of the left colic artery, which is derived from the inferior 

 mesenteric. Arterial arcades are thus formed in the transverse 

 meso-colon, from which branches proceed for the supply of 

 the transverse colon. 



Vena Mesenterica Superior. This large vein lies to the 

 right of the superior mesenteric artery, and receives tributaries, 

 which come from those parts of the intestinal canal which are 

 supplied by branches from the superior mesenteric artery, and 

 also the right gastro-epiploic vein from the great curvature 

 of the stomach and the pancreatico-duodenal vein. It passes 

 upwards, in front of the third part of the duodenum, and, 

 leaving the root of the mesentery, disappears under cover 

 of the neck of the pancreas, where it unites with the splenic 

 vein to form the vena portcz. 



Plexus Mesentericus Superior. This is a dense plexus 

 of sympathetic nerve twigs which surrounds the superior 

 mesenteric artery like a sheath. From it filaments are 

 prolonged to the intestine along the various branches of the 

 artery. As the nerves approach the bowel some of the twigs 



VOL. i 31 



