riiE MOUSE 431 



been imported to Americu about 1544. It has existed from 

 time immemorial in Europe ; it has a mild disposition, and 

 from it the white rats we keeji as pets have been derived. 



The brown, or Norway, rat has been the latest importation. 

 The histor}' of its migrations has been written. Probal)ly 

 originating in central Asia, it crossed the Volga in great troops 

 in 1727, occupied Russia in 1730, France in 1750, and Deirmark 

 about 1810. Before the advance of this powerful and aggres- 

 sive foe, the black rat of Europe gave way and ))ecame well- 

 nigh exterminated, although of late it is said to be reasserting 

 itself in Germany. The brown rat was introduced into Amer- 

 ica in 1775, has spread over the whole countr}', reaching the 

 Pacific coast at)out 1855 and, as in Europe, has nearly exter- 

 minated the black rat except in inland towns remote from rail- 

 roads. 



The habits of rats and mice are well known. The}"" inhal^it 

 our buildings, gnaw our doors and furniture, destroy our pro- 

 visions, kill poultry, and aid in spreading disease. They shun 

 the light, living in holes during the day, run with great agility, 

 and are capable of making long leaps. Owing to their instinct 

 to go into holes, they are easily trapped by a funnel-shaped 

 opening leading into a closed box. Despite the ease of trapping 

 and their destruction by cats, thej^ maintain themselves by 

 virtue of a great fecundit}', for, if no deaths occur, more than 

 a hundred yoimg may, in one year, descend from a single pair. 



The food of mice is very varied. They naturally thrive 

 best on a vegetable diet ; oats especially are recommended for 

 tame mice, and hard-shelled nuts are useful because the mice 

 keep their teeth sharp by gnawing the shells. If the teeth 

 are not kept worn off, they soon become inconveniently long, 

 owing to the fact that they grow continuously throughout 



