Bats are supposed to perceive external objects without coming actually in contact with them, because in their rapid and irregular flight, amidst various surrounding bodies, they never fly against them; yet, to some naturalists, it does not appear that the senses of hearing, seeing, or smelling serve them on these occasions, for they avoid any obstacles with equal certainty when the eye, ear, and nose are closed: hence has been ascribed a _sixth sense_ to these animals. The nerves of the wing are large and numerous, and distributed in a minute network between the integuments. The impulse of the air against this part may possibly be so modified by the objects near which the animal passes as to indicate their situation and nature. The Bat tribe fly by means of the fingers of the fore feet, the thumb excepted, being, in these animals, longer than the whole body; and between them is stretched a thin membrane, or web, for flying. It is probable that, in the action of flight, the air, when struck by this wing, or very sensitive hand, impresses a sensation of heat, cold, mobility, and resistance on that organ, which indicates to the animal the existence or absence of obstacles which would interrupt its progress. In this manner blind men discover by their hands, and even by the skin of their faces, the proximity of a wall, door of a house, or side of a street, even without the assistance of touch, and merely by the sensation which the difference in the resistance of the air occasions. Hence they are as little capable of walking on the ground as apes with their hands, or sloths with their hooked claws, which are calculated for climbing. In a certain kind of Bat, the _Nycteris_, there exists a power of inflation to such a degree that, when inflated, the animal looks, according to Geoffroy St. Hilaire, like a _little balloon_ fitted with wings, a head, and feet. It is filled with air through the cheek-pouches, which are perforated at the bottom, so as to communicate with the spaces of the skin to be filled. When the Bat wishes to inflate, it draws in its breath, closes its nostrils, and transmits the air through the perforations of the cheek-pouches to the spaces; and the air is prevented from returning by the action of a muscle which closes those openings, and by valves of considerable size on the neck and back. There was formerly a vulgar opinion that Bats, when down on a flat surface, could not get on the wing again, by rising with great ease from the floor; but White saw a Bat run, with more dispatch than he was aware of, though in a most ridiculous and grotesque manner. The adroitness with which this Bat sheared off the wings of flies, which were always rejected, was very amusing. He did not refuse raw flesh when offered; so that the notion that Bats go down chimneys, and gnaw men's bacon, seems no improbable story.