218 GNAWING ANIMALS 



they work. Then, with their huge, chisel-like incisors they 

 cut out chips, circling round the trunk all the while, until 

 only the heart of the trunk remains, and the tree falls. 



THE FAMILY OF MICE AND RATS 



Muridae 



When their groups and relationships are fairly under- 

 stood, the wild mice and rats will be found quite interesting. 

 They are so widely distributed it is very desirable that coun- 

 try dwellers should know something about them, and appre- 

 ciate their good points as well as their bad ones. A moder- 

 ate effort, properly aided and encouraged, will give any one 

 a fair conception of the grand divisions of this great group; 

 and there the general student can stop, if he so elects. 



In approaching this assemblage of North American mam- 

 mals, the first thought is that its members are difficult to 

 deal with. In some respects they are, but they are by no 

 means as difficult as might be supposed. Like many other 

 new subjects, they yield to a little old-fashioned study. It 

 is not necessary for the general reader to enter into the 

 study of a large number of species. Lay the foundation first 

 by becoming acquainted with each genus, and one typical 

 species. Observe the following injunctions: 



1. Treat this bit of study with serious attention. 



2. Learn first the names of the Families and the approxi- 

 mate size of each Family. 



3. Next learn by rote, in regular order, the common names 

 of the typical examples given. 



