26 



DISSECTION OF THE DOG 



It is noteworthy that there is a series of anastomoses along the course of 

 the colon between the ileo-cwco-colic, right colic, and middle colic arteries. 



A. MBSENTEEiCA CAtTDALis. — The caudal mesenteric artery can be most 

 readDy found by dissecting between the two layers of the descending mesocolon 

 about the level at which the duodenum crosses the middle line. Very much 

 smaller than the cranial mesenteric artery, it leaves the aorta opposite the 

 fifth or sixth lumbar vertebra. From its point of origin the artery runs 

 towards the pelvis in the attached border of the mesocolon and divides into 

 two branches — left colic and cranial hoemorrhoidal arteries. 



Colon transveTsum 

 Colon ascendens 

 a. colica dextra 

 a. Ueo-cmco-colica , 



a. colica media 



a. pancrealico 

 duodenalis '. 



aa. intestinales 



^Colon descenders 

 -Intestinum tenue 



Duodenum 

 Iniestinum coscum 



I-nlesiinum ileum 



colica sinistra ^ " 



Fig. 8. — Diagram of the cranial mesenteric artery. 



A. colica sinistra. — The left colic artery runs towards the thorax along 

 the descending colon. This it helps to supply, and finally ends by anastomosing 

 with the middle colic arterj'. 



A. hcemorrhoidalis cranialis. — The cranial haemorrhoidal artery follows the 

 direction of the parent vessel and ends in the pelvis where it supplies the terminal 

 part of the colon and anastomoses Avith the middle haemorrhoidal artery. 



Ganglion me?entericum CAtrDALB. — As was seen to be the case with 

 the cranial mesenteric artery, so in association with the root of the caudal 

 vessel of the same name a small sympathetic ganglion is developed. From 

 this filaments arise Avhich follow the mesenteric artery, so forming the caudal 

 mesenteric plexus (plexus mesentericus caudalis). 



