GENERAL STRUCTURE. 
249 
the usual manner; and this peculiar arrangement renders a bat’s movement on 
the ground an awkward kind of shuffle. 
In order to afford space for the attachment of the powerful muscles necessary 
to move the wings, the chest of hats, like that of birds, is remarkably large. But 
as these animals are poor walkers, the haunch-bones are relatively small and weak. 
The great majority of bats feed solely on insects, and have their 
Teeth. J J 
cheek-teeth furnished with a number of sharp cusps, admirably 
adapted for holding and piercing the tough integuments of beetles and many other 
insects. A few bats, however, are blood-suckers, and these have the front teeth 
specially modified for piercing the skin of the animals they select as their victims. 
Others, and among them the largest representatives of the order, are fruit-eaters; 
and these accordingly have a quite different kind of cheek-teeth, in which the 
crowns are nearly smooth, and without cusps. 
The number of the different teeth in different bats is variable, and is of great 
importance in distinguishing the different genera; but as some of these teeth may 
be exceedingly minute, their enumeration requires great care. No bat, it may be 
observed, has more than two pairs of incisor teeth in the upper jaw; neither are 
there ever more than three premolars on each side of the upper and lower jaws, so 
that the number of teeth behind the tusks, or canines, never exceeds six. 
So thoroughly are bats adapted for a life in the air, that most of them but 
seldom resort to the ground, and even when they do so they generally endeavour 
to leave it as soon as possible by ascending a tree, rock, or wall, whence they either 
again take flight, or settle themselves into their favourite position of repose, 
suspended head downwards by the feet. Not only do most bats feed and drink 
while on the wing, but the females even carry their young tightly clinging to their 
bodies. 
Sense of touch. 
In their active life bats being mostly crepuscular or nocturnal, 
while their eyes are relatively small, it is obvious that they must 
be provided with some special means of avoiding contact with objects during 
flight. This appears to be effected by the extreme development of a sense more or 
less akin to our sense of touch, by which the neighbourhood of objects is per¬ 
ceived without actual contact; and it was demonstrated as long ago as 1793, by 
the cruel experiment of depriving bats of sight and then allowing them to fly 
in a room across which silken threads were stretched in such a manner as to leave 
just sufficient space for them to pass between with outstretched wings. The unfor¬ 
tunate bats not only succeeded in passing between these threads without contact, 
and likewise avoided the walls and ceiling of the room, but, when the threads were 
placed still nearer together, they contracted their wings in order to be able to 
pass without contact. In the same manner they flew between branches and 
twigs of trees placed in their course, and suspended themselves when tired of 
flight on the walls of the room, just as easily as when they enjoyed the use of 
their eyes. In the great majority of bats it appears that this sense of touch is 
situated in the wing-membranes, and in the delicate and frequently enormously 
elongated ears, which are often provided with a kind of secondary inner ear, known 
as the tragus. There are, moreover, certain bats provided with an additional organ 
of perception, which takes the form of expansions of skin from the nose and 
