In the Wombat the ccecum is extremely short, but wide ; it is remarkable for being provided with a vermiform appendage.
In this animal, however, the colon is relatively longer, larger, and it is puckered up into sacculi by two broad longitudinal bands.
In the specimen dissected by me, one of these sacculi was so much longer than the rest as to 4 almost merit special notice as a second ccecum.
The most interesting peculiarity which the Zoophagous Marsupials exhibit in the disposition of their simple intestinal canal, consists in its being suspended from the very , commencement of the duodenum on a simple and continuous me sentery, like the intestine of a carnivorous reptile. The duodenum makes the ordi nary fold on the right side, but it is not tied to the spine at its termination ; the com mencement of the jejunum may, however, be distin guished by a slight twist of the mesentery, and a fold of peritoneum is continued from the lowest curve of the loop of the duodenum to the right iliac region, as in the Kangaroos. The intestine is a little narrower at its middle part than at its two extremes ; the tunics in crease in thickness towards the rectum. There is a zone of glands at the commencement of the duodenum.
In the Entomophaga the duodenum is tightly connected to the spine, where it crosses to be continued into the jejunum : from this part the mesentery is continued uninterruptedly along the small intestines and colon to the rectum ; so that although the ccecum is gene rally found on the right side, its connections are sufficiently loose to admit of a change of position.
In the Petaurus pygmtrus the duodenum is attached to the spine as in the ()possums, but it is not tied down to the right iliac region by a fold of peritoneum continued from the con vexity of its depending curve. I found the ccecum in this species disposed in a spiral curve in the left lumbar region; the colon ascended a little way in front of the stomach, receiving a branch of the superior mesenteric artery, and was then continued straight down to the anus; thus we are again reminded of the oviparous character by the shortness of the large intestine.
In the Pet. taguanoides the duodenum is tied down to the iliac region, as in the Da syure ; the ccecum is four inches long, and the colon is relatively longer than in the Acro bates ; it makes the tour of the abdomen much as in man, but is continued into the rectum without forming a sigmoid flexure.
In the Plialangers the duodenum winds round the root of the mesentery, descending pretty low down on the right side, and becoming a loose intestine or jejunum on the left side. The long ccecum is suspended by a broad du plicature of peritoneum continued from the mesocolon; and the colon is closely attached at its transverse arch to the duodenum and root of the mesentery.
In the Koala the ccecum and large intestines arrive at their maximum of development. The duodenum commences with a small pyriform sacculus nearly an inch in breadth, and soon contracts to a diameter of five lines, which is the general calibre of the small intestines. The large intestines, where the ilium terminates, have a diameter of two inches. The end of the ileum (a, fig. 129) protrudes for the extent of a quarter of an inch within the ccecum, forming a very effectual valve : near this part there are two wide and deep glandular the longitudinal valvulre conniventes of the large intestines have already been noticed.
In the Potoroos the small intestines are dis posed nearly as in the Phalangers: the short and wide ccecum lies in the right hypogastrium: the colon makes the usual tour of the abdomen, but is disposed in long convolutions through its whole course, being suspended on a broad mesocolon. The diameter of both small and large intestines is nearly the same : in Hyps. setosus I found this to be half-an-inch.
In the great Kangaroo the descending por tion of the duodenum is attached posteriorly, by means of a thin peritoneal duplicature, to the spine, and anteriorly to the co lon : it makes an abrupt turn upon itself, and a fold of peritoneum is continued from the con vexity of the curve to the right iliac region. The small intestines are short folds on a rather narrow mesentery. ccecum is in part suspended from the same mesenteric fold. The colon, besides its posterior con nexions with a mesocolon, is attached, as be fore observed, to the duodenum ; and also, by means of the great omentum, pretty closely to the stomach, whence it passes down, forming many large and loose convolutions to the rec tum, being attached by a broad mesocolon to the left hypochondriac region.