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38 capable of striking the air with sufficient force and rapidity to produce a true flight, easy, swift, and continued. The sternum, or breast-bone, has a ridge as in birds; and the muscles which are attached to it, and which move the arm, are thick and powerful.

The volar membrane, though so thin as to be nearly transparent, is exceedingly sensible; it is seen, on being held up to the light, to be studded with innumerable little white papillæ, which run in irregular lines, and which, consisting probably of nervous matter, may be conjectured to be the seat of the extraordinary delicacy of touch with which this membrane is endowed; a delicacy so great as to enable the animal after its ears and eyes have been cruelly destroyed, to avoid threads stretched in various directions across its flight, and to pass through the narrowest passages without touching the sides.

It has been ascertained that the interfemoral part of the membrane has another interesting use. By the curving upward of the tail, the hind feet being extended, the membrane forms a hollow cradle, into which the newborn young is received.

The Bats are exclusively nocturnal animals. During the day they congregate in hollow trees, in caverns, or in unfrequented buildings, where they suspend themselves, with the head downwards, by means of the strong and curved claws of the hinder feet. In the same gloomy recesses, the species which inhabit the temperate zone pass the winter in a state of torpidity.

The species of this Order are very numerous, and are scattered over all parts of the world, with