THE TEETH OF RODENTIA. 365 



relieve from direct pressure their growing pulps, which 

 come to be situated far back in the jaw, the open end of the 

 lower incisor, for example, being in many species actually 

 behind the last of the molar teeth. The nerve going to 

 supply the persistent pulps is of very large size, and, owing 

 to the open end of the tooth having formerly occupied a 

 more anterior position in the jaw, runs forward beneath the 



FIG. 157 - 



tooth, and then bends abruptly backwards to reach the 

 tooth-pulp. In many Rodents the enamel of the front of 

 the large incisors is stained of a deep orange colour ; this 

 colour is situated in the substance of the enamel itself. 



The scalpriform incisors terminate by cutting edges, the 

 sharpness of which is constantly maintained by the peculiar 

 disposition of the tissues of the tooth. 



The investment of enamel, instead of being continued 

 round the whole circumference of the tooth, is confined to 

 its anterior and lateral surfaces, on the former of which it is 

 thickest. 



It is said by HilgeudorfF (Berlin Akad. d. Wiss. Monats- 

 bericht, 1865), that the incisors of Hares differ from those of 



*) Side view of skull of a Rodent, giving a general idea of the denti- 

 tion of the order. 



