418 



ANATOMY OF VERTEBRATES. 



phagans ' the pygmy Petaurist {Acrobates) shows the duodenum 

 attached to the spine as in the opossums, but it is not tied 

 down to the right iliac region by a fold of peritoneum continued 

 from the convexity of its depending curve. The caecum is dis- 

 posed in a spiral curve in the left lumbar region ; the colon 

 ascends a little way in front of the stomach, receiving a branch 

 of the superior mesenteric artery, and is then continued straight 

 down to the anus ; again exemplifying 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 Dasyure ; 

 the caecum is four inches long, and the colon is relatively longer 

 than in Acrobates ; it makes the tour of the abdomen much as in 

 Man, but is continued into the rectum without forming a sigmoid 

 flexure. In the Phalangers 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 caecum is suspended by a broad duplicature 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 caecum 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 

 ileum terminates, have a 

 diameter of two inches. 

 The end of the ileum, fig. 

 316, «, protrudes for the 

 extent of a quarter of an 

 inch within the caecum, 

 forming a very effectual 

 valve : near this part there 

 are two wide and deep glandular fossae : the longitudinal valvulae 

 conniventes of the large intestines have already been noticed. 



In the Potoroos the small intestines are disposed nearly as in 

 the Phalangers: the short and wide caecum lies in the right 

 hypogastrium : the colon makes the usual tour of the abdomen, 

 but is disposed in long convolutions through its whole course, 



1 rxxiv'. 



310 



Ileo-caecal valve, Koala. Half its natural size. 



