416 



ANATOMY OF VERTEBRATES. 



garoos, the stomach is simple in the Marsupialia, presenting only 

 some additional mucous glands in the Koala and Wombat, it is 

 to the succeeding parts of the alimentary canal that we have to 

 look for those modifications which should correspond with a vege- 

 table, a mixed, or an animal diet ; and never perhaps was a 

 physiological problem more clearly illustrated by comparative 

 anatomy than is the use of the caecum coli by the varying con- 

 ditions which it presents in the present group of Mammalia. 



In the most purely carnivorous group of the Marsupial order 

 the stomach presents in the magnitude of the left cul-de-sac a 

 structure better adapted for the retention of food than we find in 

 the stomachs of the corresponding group in the placental series. 

 In the most strictly carnivorous Ferce, as the cat-tribe, there is a 

 caecum, though it is simple and short ; but in the Marsupial 

 Sarcophaga 1 this part is entirely wanting, and the intestinal canal, 

 short and wide, is continued, like the intestine of a reptile, along 

 the margin of a single and simple mesentery from the pylorus to 

 the rectum. The jejunum, in the Thylacine, has a diameter of 

 two inches and a half. 



In the entomophagous 1 Marsupials, some of which are suspected 

 with reason to have a mixed diet, the intestinal canal is relatively 

 longer ; the distinction of small and large intestine is established ; 

 and the latter division commences with a simple, moderate-sized, 

 subclavate caecum, fig. 312. 



In the carpophagous 1 Phalangers, whose stomach resembles that 

 of the predatory Dasyure, the compensation is made by a longer 

 intestine, but principally by the extraordinary length of the 

 caecum, which in some species is twice that of the body itself. 



312 313 314 



CEecum of the Opossum. 



Lastly, in the Koala, 

 which is, perhaps, a more 

 strictly vegetable feeder 

 than the Petaurists or 

 Phalangers, the caecum, 

 fig. 313, is more than Cxcum of the Ka0,a - Ca3Cum of the Kan * aro °- 



three times the length of the animal, and its essential part, 



1 lxxiv' and lxxx', p. 330. 



