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 sup- 
pled 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 
