THE MASTERY OF THE AIR 253 



stretches along the upper margin of the arm 

 to the hand. The thumb, which is small and 

 clawed, is left free, but the membrane stretches 

 across all five palm-bones and to the very tips 

 of the four very long outspread fingers, and 

 from them to the legs. The knees are turned 

 outwards and backwards like our elbows, to 

 meet the membrane, which reaches down to 

 the ankles, leaving the feet free, but filling the 

 space between the hind-legs, and including all 

 the tail except its tip. The span of the out- 

 stretched wings varies from 2 inches to 5 feet. 

 This wing membrane is a very wonderful 

 thing. On a dead bat it looks like a piece of 

 dry y tough skin, but it is in reality so well sup- 

 plied with nerves and blood-vessels that it is 

 exquisitely sensitive. The bat is, in the most 

 literal sense, alive to its finger-tips, for the 

 sense of touch in the whole of its wing is 

 extraordinarily delicate. When it gets into a 

 room, as it often does, for light seems to at- 

 tract it, it will fly round and round without 

 ever knocking against wall, cornice, or ward- 

 robe, and out of doors will pass in and out 

 among the branches of a tree without coming 

 in contact with them, because of its power of 

 feeling things before it touches them. Its 



