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, tough skin, but it is in reality so well 

 supplied 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 attract 

 it, it will fly round and round without ever 

 knocking against wall, cornice, or wardrobe, 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 mouse-like ears, 



