192 
(b) 
(c) 
ANATOMY OF THE RABBIT. 
(taeniae coli). Two of these bands are free, while the third 
is enclosed by the supporting peritoneum, the mesocolon. 
The two free bands run together toward the anterior end 
of the first limb. 
The transverse colon (colon transversum) is a short seg- 
ment, beginning forwards on the right and crossing ‘the 
middle line transversely to the left, where it bends sharply 
backward, and is replaced by the descending colon. 
The descending colon (colon descendens) passes backward 
to a point in front of the pelvis, where it is replaced by the 
rectum. 
The descending mesocolon, which connects this por- 
tion with the dorsal body-wall, should be noted on account 
of its relation to the inferior mesenteric artery and sympathe- 
tic plexuses. It is connected for a considerable distance with 
the mesentery of the ascending limb of the duodenum. _ 
————— z 
7. Displace the caecum, turning it over to the right side of the 
animal. Lay out the mesenterial small intestine, so that the mesen- 
tery and its bloodvessels are exposed. Remove the lymph glands 
from about the base of the superior mesenteric artery, first noting 
their position at the root of the mesentery. They receive afferent 
lymphatic vessels from the wall of the intestine, and send off efferent 
vessels to one another and to the lymphatic trunks. 
Trace the branches of the superior mesenteric artery as follows: 
(a) 
(b) 
The middle colic artery (a. colica media), a small vessel 
(frequently two) arising from the left wall and passing to the 
transverse colon. 
The inferior pancreaticoduodenal artery (p. 189) arises at 
the same level, but from the right wall. 
(c) The ileocaecocolic artery (a. ileocaecocolica), a large 
branch, equalling in size the superior mesenteric trunk, is 
distributed to the terminal portion of the ileum, the caecum 
(including the vermiform process), and the ascending colon. 
Its branches are arranged in two series, a proximal group 
being given off near the point of origin of the main vessel, 
and a distal group, including the terminal portion of the 
vessel, at about two inches from the point of origin. 

