NATURAL HISTORY. 103 



Order IV. ... GLIRJES.(Lat. Gils, a Dormouse.) 



Family I Muridse. (Gr. Mflf, a Mouse. Mouse kind.) 



Sub-family a. Murina. 



Decmnanus (Lat. tenth or large), the Rat. 



WE now arrive at the Rodentia, or gnawing animals, so 

 called from their habit of gnawing through, or paring away, 

 the substances on which they feed. For this purpose their 

 teeth are admirably formed, and by these teeth it is always 

 easy to ascertain a member of the Rodents. They have none 

 of those sharp teeth called canine, such as are seen in the lions 

 and in those animals which seize and destroy living animals, 

 but in the front of each jaw there are two long flat teeth, 

 slightly curved, and having a kind of chisel edge for rasping 

 away wood, or other articles. The constant labour which 

 these teeth (called incisors, from the Latin v/ord, incido, 

 I cut) undergo, would rapidly w r ear them away. To coun- 

 teract this loss, the teeth are constantly growing, and being 

 pushed forward, so that as fast as the upper part is worn 

 away, the tooth is replenished from below. So constant is this 

 increase, that when an unfortunate rabbit, or rather rodent, 

 has lost one of its incisors, the opposite one, meeting nothing to 

 stop its progress, continually grows, until sometimes the tooth 

 curls upwards over the lips, and prevents the wretched animal 

 from eating. An example of this preternatural growth may 

 be seen in the vignette under the article Rabbit. The sketch 

 was drawn from a specimen in the Anatomical Museum at 

 Oxford. 



The Rodentia include the mice, beavers, rabbits, squirrels, 

 and porcupines. 



