124 Anatomy of the Rabbit. 



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. 



Fig. 44. Plan of the connections of the large and small 

 intestines: c, ascending colon; cae., caecum; h., haustra; 

 i., ileum; s.r., sacculus rotundus; t.c, band of the colon; 

 v.s., spiral valve. 



6. The colon is divisible into ascending, transverse, and descending 

 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 follows a 

 tortuous course. 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 (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. 



(b) The transverse colon (colon transversum)' is a short segment, 

 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. 



