380 



VEKTEBRATA. 



beaver. — (^See p. 33S.) 



not seem to have been greatly prized — and knowing this fact, were accustomed to bite oft" the 

 part that yielded it ! 



This animal is furnished with two incisors and eight molars in each jaw, twenty in all; and is 

 particularly distinguished from all the rest of the rodentia by a broad horizontally-flattened tail, 

 which is nearly oval and covered with scales. There are five toes on each of the feet, but tl 

 of the hinder ones — somewhat resembling those of a goose — only are webbed, the webs extending 

 beyond the roots of the nails. The second toe of these last is furnished with a double nail, or 

 rather two, one like those of the other toes, and another beneath it, situated obliquely, with a 

 sharp edge directed downward. There is also a less perfect double nail on the inner toe of the 

 hind-feet. 



The incisor teeth of the beaver are broad, flattened, and, as in most of the order, protected an- 

 teriorly by a coat of very hard orange-colored enamel, the rest of the tooth being of a compara- 

 tively -"ft substance, whereby a cutting, chisel-like edge is obtained; and, indeed, no edge-i 

 with all its combinations of hard and soft metal, could answer the purpose better. In fact, the 

 iver'a incisor tooth is fashioned much upon the same principle as that followed by the tool- 

 maker, who forms a cutting instrument by a skillful adaptation of hard and soft materials till be 



produces a g 1 edge. But the natural instrument has one great advantage over the artificial 



tool; \<>r the former is so organized that as fast as it is worn away by use, a reproduction and pro- 

 ion from the base takes place, and thus the two pairs of chisel-teeth working opposite to cadi 

 other are always kept in good repair, with their edges at the proper cutting angle. When in- 

 jury or dis( troyg one of these, incisors, its opposite, meeting with no check to resist tb< 

 protrusion from behind, is pushed forward into a monstrous elongation. So hard is the enamel, 

 and s. . good a cutting instrument is the incisor tooth of the heaver, that, when fixed in a woodert 1 

 handle, it was used by the Northern Indians to cut hone, and fashion their horn-tipped spears, 

 iV-e., till it was superseded by the introduction of iron, when the beaver-tooth was supplanted by 

 the English file. 



The power of these natural tools is such, that a beaver will bite off a sapling of the size of ;' 



