428 



DIGESTIVE SYSTEM OF THE HORSE 



have a diameter of about twenty inches (50 cm.)- This is succeeded by a funnel- 

 shaped terminal contraction. 



The right ventral part of the great colon is attached to the lesser curvature of 

 the caecum by two layers of peritoneum which form the caeco-colic fold (Plica 

 csecocolica) . The right parts are united by peritoneum on either side and also by 

 areolar tissue and muscular fibers, the surface of contact being about four or five 

 inches (ca. 10 to 12 cm.) wide; the left parts are attached to each other in a similar 

 fashion near the anterior flexures, but further back the connection is by a peritoneal 

 fold which gradually becomes wide enough to allow them to be drawn apart about 



six inches (ca. 15 cm.) near the pelvic 

 flexure. The terminal part of the colon 

 is attached by peritoneum and areolar 

 tissue to the ventral surface of the pan- 

 creas dorsally and to the base of the 

 caecum laterally. It is connected in- 

 directly with the diaphragm and liver 

 by means of a fold derived from the 

 right lateral ligament of the liver. 



The relations are complex, but the 

 more important facts are as follows: 

 The ventral parts have extensive con- 

 tact with the abdominal wall ventrally 

 and laterally. On the right side the 

 colon is almost entirely excluded from 

 contact with the flank by the caecum; 

 on the left side it has no contact with 

 the upper part of the flank, being ex- 

 cluded here by coils of the small colon 

 and small intestine. Dorsally the chief 

 relations are to the stomach, duodenxim, 

 liver, pancreas, small colon, small intes- 

 tine, aorta, posterior vena cava, and- 

 portal vein. Since there are no trans- 

 verse attachments of the right and left 

 parts, and the latter have no attach- 

 ment to the wall, they are subject to 

 considerable displacement.^ The pel- 

 vic flexure is variable in position, but 

 usually it is directed against the poster- 

 ior part of the right flank or lies in the 

 right inguinal region.^ 



The longitudinal bands (Taeniae 



coli) vary in number on the different 



parts. The ventral parts have four bands. The pelvic flexure has a band along 



its lesser curvature. The left dorsal colon has at first only one band, which is 



a continuation of the preceding one; further forward two other bands appear, and 



1 Abnormal displacement, e. g., torsion of the left parts, is not rare, and is liable to produce 

 death if not promptly reduced. 



' The length of the left parts varies and this appears partly to account for the differences to 

 be found in the arrangement of their posterior parts and the pelvic flexure. In subjects in which 

 these parts of the colon are relatively long, their posterior ends are usually bent to the right across 

 the peh-ic inlet so that the pelvic flexure lies to the right of the inlet. In few cases the left parts 

 of the colon seem relatively short and the pelvic fiexure hes at the pelvic inlet. Other dispositions 

 are encountered. 



Fig. 368. — Posterior Portion of Left Parts of Colon 



OF Horse; Dorsal View. 

 1, Left dorsal part; 2, left ventral part; 3, pelvic flexure. 



