418 



ANATOMY OF VERTEBRATES. 



phagana l 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. tuyuanoides 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 Phalano-ers the duodenum winds round the root 



^3 



of the mesentery, descending pretty low down on the right side, 

 and becoming a loose intestine or jejunum on the left side. The 

 long cajcum 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 mesenterv. 



/ 



In the Koala the caecum and large intestines arrive at their 



O 



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 



O 



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 valvulre 

 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 



o o 



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

 but is disposed in long convolutions through its whole course, 



316 



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



