CHAPTER XX 



THE MOUSE AND ITS ALLIES 



THE mouse belongs to the class Mammalia, 1 character- 

 ized by having milk glands whose secretion is used to 

 nourish the young, and hair, which may be nearly or 

 quite absent as in the case of porpoises or whales. 2 



The distribution of the house mouse, from which the 

 different kinds of fancy mice have been derived, is now co- 

 incident with that of civilized man ; but in early times it 

 was limited to Asia. From Asia it made its way to Europe, 

 and thence by vessels to other continents. It was imported 

 to America (which has no indigenous members of the genus 

 Mus) by the early explorers. There have also been im- 

 ported to this country three other species of this genus, of 

 such size that they are commonly called rats. Of these, 

 the roof rat seems to have been imported by the early 

 Spanish discoverers to the Southern States, where it still 

 persists. It originated in Egypt. The second was the 

 black rat, believed to have been imported to America about 

 1544. It has existed from time immemorial in Europe : it 

 has a mild disposition, and from it the white rats we keep 

 as pets have been derived. The brown, or Norway rat, 

 has been the latest importation. The history of its migra- 

 tions has been written. Probably originating in central 



belonging to the breast. 



- A key to the orders of Mammalia will be found in the Appendix to 



this Chapter, page 331. 



318 



