(Lettered to compare with bird’s skeleton, p. 126). _fa_, fore arm; _w_, wrist; _t_, thumb; _ha_, hand; _h_, heel; _f_, foot.] Now this creature is no longer like the flying squirrels or the colugo, which can only take floating leaps; for though like them it has only a membrane stretching out from its body, yet this has become a long flexible wing, formed on a widely outstretched arm and abnormally long hand, and moved by powerful muscles like the wings of birds or insects. It is essentially fitted for flitting through the air in search of prey, while it makes but little use of the running power which it possesses in common with all other insect-eaters. If you see a bat moving along the ground, you will acknowledge at once that it is a true quadruped, yet, by its awkward gait as it shuffles along on its clawed thumb and toes, you will judge that it is not an earth-loving animal. Watch it at night on the wing and it is quite another creature; then it will flit about in and out of cracks and crevices, under the eaves, round the haystacks, or among the trees, and never once strike its wings against anything, though it has been proved that it does not trust chiefly to its bead-like eyes to guide it. Bats have been blinded, their ears stopped with wool, and their noses with sponge dipped in camphor; and yet, without sight, hearing, or smell, they steered quite successfully between outstretched threads or tree-branches, or found their way into a hole in the roof. In truth, as they have become fitted to navigate the air, they seem also to have become sensitive to its currents. Their wings are abundantly supplied with nerves and blood-vessels, and have little rough points all over the surface; their ears have generally a second ear-lobe or leaf within the outer one, and those which have not this have leaves of skin or membrane round their nose. With all these they seem to feel the slightest difference in the air, so as to detect at once whether they are in the open, or whether any resisting object is near them. [Illustration: Fig. 62. A Bat walking.]