BRANCH CHORD AT A: CLASS MAMMALIA 379 



its original habitat. The mouse came to this country in 

 the vessels of early explorers. Similarly the brown and 

 black rats, now so abundant all over North America, and 

 members of the same genus as the mouse, were intro- 

 duced from Europe. Accompanying man in his travels 

 the mouse has spread from Asia until it is now to be 

 found over the whole world. 



The habits of mice are welt known ; their fondness for 

 living in our homes and outbuildings makes them familiar 

 acquaintances. Their food is varied ; they seem to thrive 

 best, however, on a vegetable diet. Grains and nuts are 

 favorite foods. The house-cat is their greatest enemy, 

 but man takes advantage of their instinct to go into holes 

 by constructing traps with funnel or tunnel entrances 

 which, baited with cheese or other favorite food, are 

 fatally attractive. In climbing, mice are aided by the 

 tail. Their strong hind legs enable them to stand erect, 

 and even to take several steps in this posture. They can 

 swim readily, although naturally they rarely take to 

 water. Their special senses are keen, the senses of hear- 

 ing and taste being unusually well developed. Their 

 " singing," which has been the subject of much discussion, 

 seems to be actually a voluntary and normal performance 

 which, however, hardly deserves to be called singing, but 

 rather a slightly varied peeping or whistling. 



The mouse is a prolific mammal, producing from four 

 to six times a year broods of from four to eight young. 

 The mouse makes a cosy nest of straw, bits of paper, 

 feathers, wool or other soft materials, and in this the 

 young are born. The newly born mice are very small 

 and are blind and helpless. They are odd little creatures, 

 being naked and almost transparent. They grow rapidly, 

 being covered with hair in a week, although not opening 

 their eyes for about two weeks. A day or two after their 

 eyes are open they begin to leave the nest, and hunt for 

 food for themselves. 



