DISSECTION OF THE ABDOMEN. 307 



crook of the caecum. In this disposition the suprasternal and diaphrag- 

 matic flexures are obliterated, and the 1st and 4th portions are seen to 

 be closely adherent to one another, and, in like manner, the 2nd and 

 3rd portions, except just at the pelvic flexure, where, in the angle of the 

 flexure, a small space is bridged over by a racket-shaped piece of 

 peritoneum. It will be noticed also that the intestine varies greatly in 

 calibre at different points. Its greatest diameter is in its 4th portion, 

 and its smallest about the centre of the 3rd. This narrow portion of the 

 intestine is further distinguished from the rest by being not puckered, 

 but plain, when distended. 



The Small or Floating Colon succeeds the double colon. It is much 

 narrower than that bowel ; indeed, in calibre it does not greatly exceed 

 the small intestine, from which, however, its coils are readily distin- 

 guished by their puckered appearance. In a medium-sized animal it is 

 about ten feet in length. It is disposed within the abdomen after the 

 manner of the small intestine, being suspended at the free edge of a 

 dependency of the peritoneum, termed the meso-colon or colic mesentery. 

 It has a convoluted disposition, and occupies the left lumbar and iliac 

 regions. Its last coil passes into the pelvic cavity, and is continued as 

 the rectum. 



The Rectum is the terminal portion of the intestine, and is about two 

 feet in length. It derives its name from its approximately straight 

 course through the pelvic cavity, in connection with which it will be 

 more fully described. 



Dilutions. — The coils of the jejunum and ileum should be arranged 

 in the left flank after the manner of Plate 41. To get a view of the 

 duodenum, the caecum should be thrown across the abdomen, with its 

 point towards the left side. The duodenum will then be seen encircling 

 the crook of the caecum on its outer side. Should the large intestine 

 contain much ingesta, that should be evacuated through an incision 

 across the pelvic flexure of the double colon and another at the point of 

 the caecum. When the ingesta have been expelled the bowels should be 

 moderately inflated, and the cut ends ligatured. 



The Duodenum (Plate 44) is the first segment of the small intestine. 

 Its length is about two feet, but it cannot be very well seen in its 

 entirety at this stage of the dissection. It begins at the pyloric aper- 

 ture of the stomach, where it is related to the posterior surface of the 

 liver. It curves upwards and backwards across the lower face of the 

 right kidney, and then, sweeping round the crook of the caecum to its 

 outer side, it crosses the spine behind the anterior mesenteric artery, and 

 is continued as the jejunum. It is maintained in position by a narrow 

 band of peritoneum, and in this fixity of position it is distinguished from 

 the rest of the small intestine. 



The Jejunum and Ileum. These comprise the remaining portion of 



