OCR Text |
Show 1873.] ANATOMY OF AULACODUS. 787 few irregular rugae. N o ridges of mucous membrane run along the lesser curvature from the cardiac to the pyloric orifice. The pylorus is large. In the duodenum the pyloric extremity is much dilated pyriformly as in many Rodents. The mucous membrane becomes velvety, with villi on the duodenal surface of the pyloric valve, and continues so along the small intestine. The whole small intestine is 5 | feet long. The bile and pancreatic ducts open by an orifice 2 inches from the pylorus and another a few inches further down. In the large intestine the caecum is 8 inches in length, and the intestine itself an inch over 4 feet. It is peculiar amongst the allied Rodents in that the cascum and colon are directly continuous, no abrupt change of direction occurring at the junction with the ileum ; and what is more, the sacculation on two longitudinal bands observed through the whole length of the caecum is continued for some distance along the colon, without any marked change of character, except size. However, the two longitudinal bands which sacculate the caecum are not those which do the same to the colon; for opposite the ileo-cascalvalve, which is a simple projection of the small into the large intestine for one sixth of an inch, much like that in the horse, one of tbe caecal bands splits into two, part going to join the other band, and part continuing on as an independent band. The small intestine joins the large, not, as is sometimes the case, at one of the bands, but in the middle of one of the sacculi, halfway between two of them. The diameter of the colon is less than that of the caecum, and diminishes gradually till it becomes scarcely greater than that of the ileum. The sacculation continues, getting less and less marked, for about a foot from the ileo-caecal valve; and the rest of the long colon is uniformly cylindrical, presenting the well-known abrupt bend near the middle of its course. The caput of the caecum is situated in the right lumbar region, and the base in the left lumbar, where an abrupt bend backward occurs just before the small intestine enters. The omentum is not large, and does not cover the viscera. There is little or no fat in the abdomen. O n opening the caecum and large intestine along its non-mesenteric longitudinal band, two strongly marked longitudinal ridges are seen to run from the ileo-caecal valve along the colon, one on each side of the inner surface of the mesenteric longitudinal band, which is the compound one formed by one division of the bifurcate caecal longitudinal band and the other caecal band. These ridges diverge at first and are afterwards separated by an interval of two thirds cf an inch. For the proximal diverging 2 inches they are simple ; but after that they are puckered regularly in exactly the same way as M . A. Milne-Edwards has figured the gastric cardio-pyloric ridges in Lophiomys, which they also resemble in general direction and arrangement. These puckered ridges, after diverging, again approach till within one fourth of an inch of one another, after which they continue parallel for a little more than 2 feet, where, just after the sharp colic bend, they suddenly cease, joining one another just before doino* so. The puckering, however, does not continue the whole way, |