THE LIFE OF MAMMALS 
equaled by human beings in a trance state, — they are sensitive to the 
slightest touch; merely blowing on the hair will induce an instantaneous 
response, although not in the least arousing the sleeper. 
The period of hibernation varies not only with different kinds of ani- 
mals, but with the same kinds under different or even the same circum- 
stances. One woodchuck experimented upon by Dr. Mills,'°* though kept 
(in Canada) under precisely the same conditions as others which slept 
profoundly, ‘‘did not hibernate for an hour the whole winter, though he 
drowsed and slept enough.” 
In spite of so much data we must confess that we are not yet 
certain what really causes this winter sleep; but that it is of a 
THE AMERICAN BEAVER. 
highly protective character cannot be doubted, since the true 
hibernaters are those whose food altogether fails in winter, and 
which is of such a nature that it could not be stored up, at least 
in sufficient quantity. Dr. A. S. Packard has discussed the 
whole subject ably in his article “Hibernation,” in the New 
International Encyclopedia. 
The beaver! How shall I tell of him and his works in the 
few pages at my command; and how keep you 
interested without repeating or even enlarging the 
marvelous tales upon which his reputation rests? 
In the first place, this big water squirrel — for so he is, just 
as the muskrat is a giant among the meadow mice —is not 
wholly American, but a native of the north of the Old World 
460 
Beaver. 
