THE INTESTINES. I9I 
Its first portion, the blind intestine or caecum (intestinum 
caecum), distinguished by its great size, is connected with the 
large intestine proper only in the region of the sacculus rotundus. 
The organ (Fig. 43) consists of three limbs, and terminates in the 
narrow but thick-walled vermiform process (processus vermi- 
formis) or appendix. The latter lies in a dorsal position, and is 
directed backward. 
The second portion, the colon, comprising the major portion 
of the large intestine proper, leaves the caecum in the region of the 
sacculus rotundus, in which position it is distinguished by its greatly 
sacculated walls. 
The third portion, the straight intestine, or rectum (intes- 
tinum rectum) is a small terminal division situated in the middle 
line and enclosed for the most part by the pelvis. It is scarcely 
distinguishable from the related portion of the colon. 
5. In the caecum the following features may be distinguished: 
(a) The wall, which is otherwise smooth, is divided by a spirally 
arranged constriction, the latter denoting the position, 
internally, of a fold of the mucous tunic, the spiral valve. 
(b) The vermiform process is a narrow, light-colored tube of 
about five inches in length, the wall patterned externally 
by lymph follicles, in the same way as that of the sacculus 
rotundus, and greatly thickened in comparison with that of 
the caecum proper. 
6. The colon is divisible into ascending, transverse, and de- 
scending portions, the relations of which may be traced as follows: 
(a) The ascending colon (colon ascendens) passes from its 
origin on the caecum to a point forwards on the right side of 
the dorsal body-wall. This portion is greatly elongated in 
the rabbit, and instead of passing directly forward (i.e., 
in man, upward (see Fig. 40), follows more or less closely 
the course of the caecum. It is composed of five principal 
limbs, united by flexures. Three of the limbs are directed 
for the most part forward, the remaining two backward. 
The first limb of the colon bears three rows of small saccu- 
lations, the haustra, separated by three longitudinal 
muscle stripes, distinguished as the bands of the colon 
