ALIMENTARY CANAL OF MAESUPIALIA. 415 



Brush-tailed or Rock Kangaroo (Macropus penicillatus) the car- 

 diac extremity terminates in a single subclavate cul-de-sac : the 

 oesophagus opens into the middle division of the stomach, close 

 to the produced crescentic fold which separates it from the cardiac 

 compartment. In the great Kangaroo a second slighter fold is 

 continued from the right side of the cardiac orifice parallel with 

 the preceding, and forming with it a canal, somewhat analogous 

 to that in the true ruminating stomachs, and along which fluids, 

 or solid food not requiring previous preparation in the cardiac 

 cavity, might be conducted into the middle compartment. 



I have more than once observed the act of rumination in the 

 Kangaroos kept in the vivarium of the Zoological Society. It 

 does not take place while they are recumbent, but when the 

 animal is erect upon the tripod of the hind legs and tail. The 

 abdominal muscles are in violent action for a few seconds, the 

 head is then a little depressed, and the cud is masticated by a 

 rapid rotatory motion of the jaws. This act is by no means re- 

 peated in the Kangaroos with the same frequency or regularity 

 as in the true Ruminants. A fact may, however, be noticed as an 

 additional analogy between them ; balls of hair, cemented by 

 mucus, adpressed and arranged in the same direction, are occa- 

 sionally formed in the stomach, of which I have met with two, 

 of an oval shape, in the Macropus parryi. 



In the genus Hypsiprymnus the stomach is as singularly com- 

 plicated as in the Kangaroos, and the complication is essentially 

 the same in both ; arising from the sacculation of the parietes of 

 a very long canal by a partial disposition of shorter bands of 

 longitudinal fibres ; but in the Potoroos this sacculation is con- 



o ' 



fined to that part of the stomach which lies to the left of the 

 oesophagus, while the right division of the cavity has the ordinary 

 form and structure of the pyloric moiety of a simple stomach. 

 The left or cardiac division is enormously developed ; in relative 

 proportion, indeed, it is surpassed only by the true ruminant 

 stomachs, in which both the rumen and reticulum are expansions 

 of the corresponding or cardiac moiety of the stomach. The re- 

 lation of the stomach of a Potoroo to that of a Kangaroo may be 

 concisely expressed by stating that the termination of the oeso- 

 phagus in the former is removed from the commencement, or left, 

 of the middle sacculated compartment to its termination. 



When fluid is injected into the stomach of a dead Potoroo, it 

 distends first the pyloric division ; it is probably by a kind of 

 antiperistaltic action that the aliment is propelled into the long 

 sacculated cascum to the left of the oesophagus. 



Having seen that, with the exception of the Potoroos and Kan- 



