THE RODENTS OR "GNAWING" ANIMALS 29 



and chisel-like ; and this because the front surface of the tooth 

 is coated with an exceedingly hard layer of " enamel," while 

 the tissue of the tooth behind this layer is softer and more easily 

 worn by the grinding action of the jaws and the consequent 

 chafing of the opposed teeth. Thus provided these animals 

 are enabled, by that curious biting movement known as " gnaw- 

 ing," to attack and demolish hard-coated seeds or nuts of various 

 kinds, as well as the bark of trees and other vegetable matter. 

 Immediately behind the " incisors " there is a big, toothless gap, 

 beyond which come the cheek teeth or grinders, whose surfaces 

 are thrown into a series of ridges admirably adapted for the 

 reduction of the long " shavings " of food passed into the mouth 

 by the actions of these incisors. But the rabbit and hare, it 

 is to be noticed, are peculiar among the rodents, in that, behind 

 the large pair of incisors common to all the tribe, they have a 

 pair of very small teeth, the use of which is problematical. 



The power of continuous growth possessed by these teeth is not 

 altogether an unmixed blessing, for should either or both of the 

 teeth of the upper or lower jaw happen to become displaced, 

 as by biting on a stone, whereby the edges no longer oppose 

 those of the opposite series, they go on growing till eventually 

 they form a circle, and re-entering the skull cause death where 

 this does not occur earlier from starvation. 



The mouse and the rabbit differ again in some other striking 

 particulars. Thus in the mouse the feet are bare, in the rabbit 

 they are thickly covered in hair, even the soles being thus clad. 

 The mouse has short ears and a long scaly tail, the rabbit long 

 ears and a short bushy tail. The tail of the rabbit, moreover, 

 like that of the hare, is white beneath, and this it is supposed 

 for a very useful purpose. Briefly, it is used as a danger signal, 

 for, as we have already remarked, the rabbit is very largely 

 a night feeding animal, and in a wild state, lives in companies, 

 in " warrens." On the least alarm a mad rush is made for the 

 burrows, and each, bounding along, cocks up the tail over the 

 back, exposing to the full the white surface. This, showing 

 conspicuously in the gloaming, serves as a guide to those behind ; 

 thus each helps the other towards safety. 



The hare, to which reference has been made, differs, it should 



