COURSE OF COLON IN THE HORSE. 57 



what is known in human anatomy. Its capacity is estimated 

 at four gallons. Its contents after death are generally found 

 to be fluid. 



At the junction of the ilium with the great intestine there 

 is a valve termed the ilio-colic valve. It appears to be formed 

 by a doubling of the mucous coat, in the fold of which muscu- 

 lar fibres are contained. It has a half-moon shape. 



The caecum occupies the right side of the abdomen, and 

 appears immediately on opening the cavity of the peritoneum. 

 Commencing from the colon and ilium in the right iliac 

 region, it extends forward towards the right side, with its 

 pocket-like part applied towards the diaphragm and liver, near 

 the ensiform cartilage. It is sometimes said that the ilium 

 in the horse enters the caecum only. This statement refers to 

 what is sometimes regarded as the rudiment of a second 

 caecum, a kind of elbow of the great intestine, between which 

 and the caecum proper the ilium is inserted, the colon being 

 represented as arising from this rudimentary caecum. The 

 colon, then, at its junction with this rudimentary caecum, is 

 narrowed, but immediately enlarges into a capacious canal. It 

 makes nearly the circuit of the abdomen, and is again con- 

 tracted in a slighter degree. It then once more enlarges, and 

 again passes round the abdomen, when, lessening a third time, 

 it ends in the rectum. The colon is distinguished from the 

 small intestines not only by its greater size in the chief part 

 of its course, but also by longitudinal bands, namely, three dis- 

 tinct in the first part of its course, two in the latter part. 

 These bands contract the colon into cells which are deep and 

 capacious in the first part of its course, shallower as the rectum 

 is approached. 



The rectum is more capacious in its posterior than in its 

 anterior extremity. It exhibits no longitudinal muscular 

 bands like the colon, yet is highly muscular throughout. Its 



