794 



MAMMALIA. 



the Porcupine (Hyst-rix), and the Hyrax are amongst the most striking 

 examples. 



(2307.) The compound stomach is that possessed by the RUMINANTIA, 

 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 

 (fig. 402, d) is called the paunch (rumen), and is of very great size, 

 occupying a considerable portion of the abdominal cavity, and forming 

 the great receptacle 



into which the crude Fig. 402. 



vegetable aliment is 

 received when first 

 swallowed : this cham- 

 ber is lined with shaggy 

 villi. The second cavity 

 (reticulum) (c) is much 

 smaller, and its walls 

 are covered with nu- 

 merous polygonal cells, 

 from whence it derives 

 the name it bears. The 

 third chamber (e), call- 

 ed the psalterium, has 

 its lining membrane 

 disposed so as to form 

 deep lamellae, arranged 

 longitudinally in alter- stomach of the Sheep, 



nating large and small 



layers, and thus presenting a most extensive surface. The fourth sto- 

 mach (abomasus) (/) 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 

 ordinary gastric secretions, and appears to be more especially the di- 

 gestive stomach. 



(2308.) The passage of the food through these different chambers 

 will be easily understood on referring to the preceding figure, in which 

 the course of the aliment before and after rumination is indicated by 

 the direction of the probes a, b. The oesophagus, it will be observed, 

 communicates on the one hand with the paunch (d), and on the other 

 with the cavities c, e, f', and, moreover, by means of a muscular fold 

 formed by the walls of the second cavity, a passage may be formed 

 leading directly into the third stomach (<?) without communicating with 



