BATS OR HAND-WINGED ANIMALS 
2 55 
their way through the air. So we find that it also is furnished with 
organs of flight, and those of so useful a character that the animal is 
really able to fly as well as many birds. 
A peculiarity in the bat's structure is that the fore limbs take the 
form of wings, and are connected with the body by means of a delicate 
skin-like membrane. This membrane, indeed, is nothing more than 
the skin of the flanks, which is greatly widened, and is stretched 
between the bones of the hand, running along the body as far as the 
tail. Like the body itself, it has its upper and lower surfaces, which, 
with a little care, may be separated from one another, even though in 
some parts of the wing the membrane is so extremely thin that, with 
the aid of a good microscope, the blood may be clearly seen as it courses 
rapidly through the threadlike vessels which run to all parts of the 
organ. 
Now, this membrane, to be of service, must, of course, be 
stretched upon a framework, and this framework is supplied by the 
bones of the hand and arm. The entire wing, indeed, is very much 
like a boy's kite, if we imagine the shape to be a little altered, for 
the wooden cross pieces are represented by the bones of the arm and 
fingers, and the linen or paper which is stretchd across, by the skin¬ 
like membrane. 
If you were to take a dead bat and to carefully strip the skin 
from the wing you would find that the bones are most curiously altered 
in form, being not only extremely light and slender, but also of really 
wonderful length. The middle finger alone, for instance, is fully as 
long as the entire body. 
Nature has taken away the second bone of the lower arm of the 
bat, or, to speak more strictly, has left it in a small and imperfect form, 
so that the limb cannot revolve from side to side. The stroke of the 
wing, therefore, is firm and regular, and flight is rendered quite easy 
so that the bat can remain for hours in the air without feeling the 
least signs of fatigue. 
The fingers, again, which are not intended to be used for grasp¬ 
ing purposes, are perfectly rigid, and cannot be bent downwards 
toward the palm of the hand. Their only motion, indeed, is a side 
one, so that the wings, when not in use, can be closed just like a lady's 
fan, and folded neatly away by the sides of the body. 
