240 CONFORMATION OF WINGS. 



conformation of the fore-limbs, however, and especially to that of 

 the bones of the fingers, upon which the wing-membrane is 

 stretched, that the Bat is enabled to make its way through the air 

 by means of this singular structure. These bones are all greatly 

 elongated ; those of the fingers having much the appearance of 

 the ribs of an umbrella, and, like them, serve to expand or fold 

 \\p the covering to which they are attached. The thumb is the 

 only part of the hand which does not partake of the general en- 

 largement. This member remains undeveloped, and is furnished 

 with a powerful hooked claw, by means of which the Bat is 

 enabled to drag itself forward on flat surfaces, and climb about 

 in the dark retreats to which it retires by day. The hind legs, 

 although connected with the wings, and serving in part to 

 support them, exhibit no marked peculiarity of form. The feet 

 have five toes, armed with strong claws, by which the animal 

 usually suspends itself in its seasons of repose, hanging with its 

 head downwards. The entire power of the Bat seems con- 

 centrated upon the fore part of its body and the organs of flight. 

 The principal bones of the wing are all possessed of great 

 strength, and the sternum or breast-bone has the same keel-like 

 projection for the attachment of the muscles which move the 

 wing as is observable in birds. 



Thus expressly organized for an aerial existence, it is not to 

 be wondered at that the Bat is incapable of any but the most 

 awkward and grotesque movements on the ground. In this 

 position, indeed, with its wings folded, and shuffling or jerking 

 itself along, it would scarcely be recognized as the same being 

 which a few minutes before, it may be, was skimming the air 

 with easy graceful movements, wheeling, doubling, and again 

 darting forward with the greatest rapidity. The Bat is greatly 

 aided in these abrupt evolutions by the tail, which acts as a sort 

 of rudder, enabling the animal to regulate and change the 

 direction of its flight, whatever its speed, with the utmost 

 facility. 



The membrane of which the wing is composed is usually 

 entirely naked, both above and below, and endowed with the 

 most exquisite sensibility. It was long since proved by 

 Spallanzaui, indeed, that it is chiefly owing to the extreme 

 delicacy of perception in this membrane that the Bat is enabled 

 to avoid coming into collision with obstacles in its path when 



