234 ANATOMY OF THE ABDOMEN. 



THE INTESTINES. 



The remainder of the ahmentary canal is continued from 

 the pyloric orifice of the stomach to the anus ; forming a 

 long tube, whose varying dimensions have occasioned it to 

 be divided into the large and small intestines, botli of which 

 are very well marked in the horse (see Plate IX. ; compare 

 A, B, C with jD). The length of the tract ranges between 

 twenty-seven and thirty yards ; of which proportions the 

 small intestines occupy from twenty to twenty- two yards, 

 and the large from seven to eight. It is not easy to give a 

 determinate place to the intestines, either individually or 

 generally ; the large, however, may be said to occupy all 

 the anterior and inferior portions of the abdomen ; and the 

 small to range above in the space not already occupied ; 

 both occasionally shifting their positions by reason of the 

 peristaltic motion. They are, however, greatly prevented 

 from an unnatural displacement, by membranous produc- 

 tions of the peritoneum ; which forms bands, that at dif- 

 ferent parts serve to fix portions of the intestines. The 

 first intestinal coat is derived from the peritoneum, which 

 receives the tube between its layers ; at once protecting it, 

 and affording a medium for the transmission of its vessels, 

 and a moistened surface whereupon to move. The second, 

 or muscular coat, presents organic muscular fibres ; by 

 the contraction of which the peristaltic action is per- 

 formed, the longitudinal slightly shortening them, and the 

 circular diminishing their diameter. Of these two coats of 

 muscular fibre, the circular is much the most powerful, as 

 is proved by the intestines always being found contracted 

 in cases of violent death. The inner tunic of the intestinal 

 canal is mucous or villous, and is very vascular and sensi- 

 tive ; its villi presenting an increased surface for the mucous 

 secretion, as well as more space for the ramification of the 

 terminations of the capillaries and lacteals : but it presents 

 no valvulpe conniventes, as in the human, their place being 

 supplied by the increased length of the tract. 



The duodenum {Plate IV. H), the first portion of the 

 small intestines, commences from the pyloric orifice of the 

 stomach. It hangs loose and pendulous upon the right 

 side, being attached to the concave surface of the liver ; 



