70 THE AMERICAN BEAVER. 



numbers of tendons to the different bones and their 

 processes. 



INTERNAL ORGANS. 



The beaver presents many peculiarities of internal 

 structure; indeed, as a whole, it is a unique animal; 

 one that has hitherto baffled the skill of naturalists to 

 classify it. 



The cavity of the mouth is small, and destitute of 

 cheek pouches; the tongue is long and fleshy, and has 

 a pointed elevation between the molars. The palate 

 has a longitudinal ridge extending back from the in- 

 cisors to four transverse ridges. The epiglottis is 

 leaf-like and pointed, and the larynx is short. 



It is generally supposed that the rodent, in grind- 

 ing its food, is confined to the longitudinal motion of 

 the jaws. This is inferred from the form of the gle- 

 noid cavities, and the condyles; and the motion in 

 question has been adopted as a distinctive mark of 

 the rodent family. Waterhouse^ affirms that the ro- 

 dents possess "very little lateral motion to the jaw, 

 which, however, moves freely in the longitudinal di- 

 rection." At the same time he admits that the mo- 

 tion in the hares is chiefly lateral, inasmuch as the 

 crowns of their molars are never worn flat. 



That the articulation of the beaver jaw admits of 

 free lateral motion is easily demonstrated in the recent 

 subject. Neither the ligaments nor the bony struc- 

 tures afford any impediment, while the flattened 

 crowns of the molars, and the muscular provisions 



^ A Natural History of the Mammalia, by G. K. Waterhouse, 

 vol. ii. Rodeatia. London, 1848. 



