12 
ANIMALS OF NORTH AMERICA. 
membrane which forms the wings, only a little hook, called 
the thumb-nail, is left free. With this the animal suspends 
itself on any rough or uneven surface where it happens to 
alight ; while the hind feet are also provided with claws, by 
which it hangs head downwards on the sides of chimneys, 
hollow trees, and roofs of caverns, a favorite resort, still and 
silent, sleeping, or perhaps nursing its young by day, till the 
approach of evening, when it begins its excursions in search 
of food. 
Having neither the disposition nor the power to exercise 
themselves by day, bats are strictly nocturnal animals, com- 
mencing their search after insects soon after the swallow has 
quitted his operations for the day. Its motions, as it flits 
about in the dim twilight, seldom moving more than a few 
yards in a straight line, darting up or down, this way or that, 
instead of being for its mere pleasure, as many would 
suppose, are really its only- means of procuring its living, 
since at every turn it seizes, or attempts to seize, some one of 
the insect tribe, which swarm under cover of darkness in the 
air. While on the wing it continually utters a low shrill cry, 
not unlike the squeaking of a mouse. 
Naturalists have long since discovered by experiments, 
that bats deprived of sight, still avoided obstacles as perfectly 
as those with their sight entire, flying through small aper- 
tures only just large enough to admit them without touching ; 
numerous small threads also were drawn across the room 
where the experiment was made at different angles, and still 
the blind bat would fly about in every possible direction without 
ever touching them. The vibration of the air striking against 
the impediment, was supposed to return a sound by which 
the animal was warned of its direction. But it has since 
been found that the destruction of hearing as well, made no 
difference in the fact, and the only theory that has been pro- 
posed to account for this curious circumstance is, that some 
peculiar sense is lodged in the expanded nerves of the nose. 
