DISSECTION OF THE ABDOMEN. 305 



artery to form an arch. From the convexity of these arches smaller 

 vessels pass to each side of the intestine, and anastomose ronnd it. At 

 the anterior part of the tube two sets of superposed arches are formed 

 before the ultimate vessels to the intestine are detached. The branch 

 which is most anterior in point of distribution anastomoses with the 

 duodenal branch of the cocliac axis, while the one which is most pos- 

 terior anastomoses with the ileo-ceecal artery from the right branch of 

 the anterior mesenteric. 



2. The Right Branch of the anterior mesenteric artery divides into 

 four vessels, viz., the ileo-csecal, the superior csecal, the inferior ceecal, 

 and the direct colic arteries. 



a. The Ileo-ccecal Artery (Plate 41, for ilio-ccecal read ileo-ccecal) sup- 

 plies the terminal poilion of the ileum (about two feet in length), and 

 inosculates with the last of the arteries from the left branch. 



b. The Superior C cecal Artery, in the present inverted position of the 

 intestines, passes beneath the termination of the ileum to run along one 

 of the longitudinal muscular bands of the caecum. It sometimes gives 

 off the ileo-csecal artery as a collatei-al branch, and at the point of the 

 caecum it anastomoses with the next vessel. It gives off branches right 

 and left to the walls of the csecum. 



c. The Inferior Ccecal Artery, in the present position of parts, passes 

 above the termination of the ileum to run along another of the muscular 

 bands of the caecum. Besides collateral branches to the main portion of 

 the bowel, it gives off the artery of the arch, which follows the concavity 

 of the csecal crook and terminates on the beginning of the double 

 colon. 



d. The Direct or Eight Colic Artery. — This is a large vessel, receiving 

 the first of these designations because the course of its blood stream is 

 the same as that of the alimentary matters in the bowel. It supplies, 

 by right and left collateral branches, the 1st and 2nd portions of the double 

 colon, and anastomoses at the pelvic flexure Avith the retrograde colic 

 artery. 



3. The Anterior Branch of the anterior mesenteric artery divides after 

 a very short coiu-se into two vessels of unequal size, viz., the retrograde 

 colic artery and the first artery of the small colon. 



a. The Retrograde or Left Colic Artery, much the larger of the two, 

 supplies successively the 4th and 3rd portions of the double colon, run- 

 ning parallel to the direct colic artery, but carrying its blood in a direc- 

 tion counter to the course of the alimentary matters in the intestine. 



h. The First Artery of the Small Colon supplies a short piece at the 

 beginning of that bowel. It is included between the layers of the colic 

 mesentery, and auostomoses with the first branch of the posterior 

 mesenteric artery. 



Directions. — To display the posterior mesenteric artery, the small 



X 



