190 
ANATOMY OF THE RABBIT. 
3. In the mesenterial small intestine the following features may 
be identified: 
(a) 
(b) 
(c) 
(d) 
(e) 
(f) 
The lighter coloration, due to the thicker wall and greater 
vascularity, of the first or duodenal portion, thus distin- 
guished as the jejunum (intestinum jejunum). 
The darker coloration, due to the thinner wall, which allows 
the contents to show through, and diminished vascularity of 
the terminal or caecal portion, thus distinguished as the 
ileum (intestinum ileum). The two portions are not 
distinctly separable. The circular folds (plicae circulares), 
or valvulae conniventes, of the mucous tunic, which in many 
mammals contribute to the thickness of the wall in the 
duodenum and jejunum, are, in the rabbit, not definitely 
expressed. 
The mesentery, the peritoneal support of the mesenterial 
small intestine, is distinguished in its major portion by its 
broad frill-like character, which allows great freedom of 
movement to this portion of the digestive tube. Its terminal 
portion, however, beginning at a point where the intestine 
turns sharply forward on its way to the caecum, is adherent 
to the mesocolon. 
The mesenteric lymph glands (lymphoglandulae mesen- 
tericae) are aggregated at the dorsal root of the mesentery, 
where they form a compact mass surrounding the base of the 
superior mesenteric artery. 
The wall of the sacculus rotundus shows externally a fine 
hexagonal pattern on account of the presence in it of a large 
number of lymph follicles. Similar structures, forming ovai 
areas about 3 mm. in diameter and 5 mm. in length, may be 
found along the intestinal wall (aggregated lymph nodules 
of Peyer). 
The finger-like processes, or villi, of the mucous tunic of the 
small intestine may be seen by making an incision of the 
wall and examining its internal surface. A small portion of 
the wall may be excised and examined under water. 
4. Trace the course of the large intestine, beginning at the 
sacculus rotundus, as follows: 
