314 BACKBONED ANIMALS. 
Hedgehog (Zrinaceidz).* We now come to the 
true hedgehogs (Fig. 339), that are not found in the 
western hemisphere, and are characterized by a thick 
Fic. 339.—A group of insect-eaters: i, common shrew; 2, hedgehog; 
3, mole ; 4, bat. 
growth of sharp, spinous bristles upon the back, that, 
when the animal rolls itself into a ball, form a perfect 
protection. 
VALUE.—Skin and spines. 
* The nest is generally underground, and carefully made, and 
here the adults, as a rule, pass the cold months in a state of hiber- 
nation—a sleep so deep that no outward sign of breathing can be de- 
tected. In Dr. Hall’s experiments with a hibernating animal suddenly 
decapitated, the heart continued to beat for a long time, as if possessed 
with an independent life. In another, where the brain and entire 
spinal cord were removed, the heart continued to beat for two hours, 
as if nothing had happened, and twelve hours after would contract 
when touched. 
