324 SPECIAL ANATOMY. 



from the convexity of the last loops, which form a superficial vascular rete 

 (under the peritoneal investment) and a deep upon the mucous membrane 

 of (fifteen to twenty feet long) the small intestines. From one artery 

 arises in the embryo (two to three months) the 



Art. omphalo-mesaraica, which passes from the abdomen through the 

 umbilical cord into the umbilical vesicle, and afterwards becomes imper- 

 vious. 



2. Artt. coliccs pass from the mesenter ium into the mesocolon, divide in the 

 neighbourhood of the large intestines, and unite in larger arches, from 

 which anterior and posterior branches immediately come off; the superfi- 

 cial and deep ramusculi of which supply the parietes of the large intes- 

 tine. There are : 



a. Art. colica dextra superior, passes downwards to colon ascendens, 

 and anastomoses by means of an ascending branch with a. colica me- 

 dia, by a descending branch with a. colica dext. inferior. 



b. Art. colica dextra inferior, s. ileo-colica, arises deeper, about the 

 centre of mesenterica superior; passes downwards, and gives an as- 

 cending branch to colon ascendens (which anastomoses with a.) ; a 

 descending to ccecum (art. coecalis) and ileum (which anastomoses with 

 the termination of mesenter sup. itself); and art. appendicalis for the 

 vermiform process of the caecum. 



c. Art. colica media, arises above from mesent. super, passes forwards 

 to the colon transversum, and anastomoses with art. colica dextra, and 

 to the left with art. colica sinistra. 



3. Mesenterica inferior, smaller than art. mesent. super., supplies the left 

 half of the large intestines. Or. : about two inches above the place of bifurca- 

 tion of the Aorta. Course : at fi,rst downwards upon the Aorta; then before 

 the A. iliaca com. sinistra downwards, and to the left in the mesocolon de- 

 scendens; it divides two inches from the origin, into : 



1. Colica sinistra superior, passes transversely outwards before the left 

 art. spermat. and ureter, then behind the colon sinistrum and peritoneum 

 upwards, divides into a superior and inferior arched branch, and supplies 

 colon sinistr. as far asflexura sigmoidea. 



2. Colica sinistra inferior, supplies theflexur. sigmoidea. 



3. Hcemorrhoidalis superior s. interna, descends in the mesa-rectum to the 

 rectum and on its posterior wall to the sphincter ani, where it anasto- 

 moses with hcemorrhoidahs media (from A. hypogastr.) and the vesical ar- 

 tery. 



573. The lateral branches of the Abdominal Aorta, 

 given off in pairs. 



4. Phrenica inferior, one on either side, arise close under hiatus aorticus 

 (frequently from a. coeliaca, or from a common trunk), pass upwards and out- 

 wards, spread about the hiatus aortic., foram. quadrilat., and reaches with an 

 external branch to the attachments of the diaphragm, where it anastomoses 

 with artt. intercostal, and mammariaint.; it gives off 



