678 



MAMMALIA. 



sen ting any difference of organization, such as in the present state 

 of physiological knowledge would lead us to suppose them to pos- 

 sess different functions: neither are we at all able to find any con- 

 nection between such an arrangement and the nature of the sub- 

 stances used as food. The Kangaroo (Macropus major), the 

 Kangaroo Rat (Hypsiprymnus), the Porcupine (Hystrix), and 

 the Hi/rax, are amongst the most striking examples. 



(763.) The compound stomach is that possessed by the Ru- 

 MINANTIA, or animals that chew the cud ; and consists of four 

 distinct cavities, differing very materially both in their size and 

 in the arrangement of their lining membranes. The first and by 

 far the largest cavity (Jig. 316, d) is called the paunch (rwwiew), 

 and is of very great 

 size, occupying a 

 considerable portion 

 of the abdominal 

 cavity, and forming 

 the great receptacle 

 into which the crude 

 vegetable aliment 

 is received when 

 first swallowed : this 

 chamber is lined with 

 shaggy villi. The 

 second cavity (reti- 

 culum) (c) is much 

 smaller, and its walls 

 are covered with 

 numerous polygonal 

 cells, from whence 



it derives the name it bears. The third chamber (e), called 

 the psalterium^ has its lining membrane disposed so as to form 

 deep lamellse, arranged longitudinally in alternating large and 

 small layers, and thus presenting a most extensive surface. The 

 fourth stomach (abomasus) (f) also exhibits very numerous 

 folds of mucous membrane : it is of a pyriform shape, and by 

 its smaller end terminates at the pylorus (g). The three first 

 stomachs are lined internally with a thin cuticular investment ; 

 but the last, apparently the representative of the single stomach 

 of those quadrupeds that have but one stomachal cavity, is 

 coated with a soft membrane that furnishes abundantly the ordi- 



