1:48 THE VITAL FUNCTIONS. 



afford them a broad basis of attachment. The 

 surfaces of the molar teeth are flattened and of 

 great extent, and they are at the same time kept 

 rough, hke those of mill-stones, their office 

 being in fact very similar to that performed by 

 these implements for grinding. All these cir- 

 cumstances of difference are exemplified in the 

 most marked manner, in comparing together the 

 skulls of the larger beasts of prey, as the tiger, 

 the wolf, or the bear, with riiose of the antelope, 

 the horse, or the ox. 



The Rodent ia, or gnawing quadrupeds, which 

 I have already had occasion to notice, compose 

 a well-marked family of Mammalia. These 

 animals are formed for subsisting on dry and 

 tough materials, from which but little nutriment 

 can be extracted ; such as the bark, and roots, 

 and even the woody fibres of trees, and the 

 harder animal textures, which would appear to 

 be most difficult of digestion. They are all 

 animals of diminutive stature, whose teeth are 



expressly formed for 

 gnawing, nibbling, 

 and wearing away by 

 continued attrition, 

 the harder textures 

 of organized bodies. 

 The i2«^, whose skull 

 is delineated in Fig. 276, belongs to this tribe. 

 They are all furnished with two incisor teeth in 



