MAMMALIA. 



425 



is this effected — what is the mechanism by which the power 

 of flight is given to the Bat? It is furnished with wings. 

 Do tliey resemble those of the bird? They are altogether 

 unlike, differing not only in the absence of feathers, but in 

 their entire structure. lu birds the feathers are principally 

 attached to bones which correspond with those of our arm. 

 But to compare the bones of the Bat's wing with those of Uie 

 human frame, let us suppose the skeleton of a man with the 

 fore-arm gently prolonged, and the fingers about ayai'd and 

 a-half in length. The bones would then form a framework 

 analogous to that of an umbrella, and capable like it of being 

 shut up or expanded. Let us suppose this bony framework 

 covered with some light and pliant material, which is con- 

 tinued between the legs and down to the ankles, and we 

 would then have a figure resembling in the organs of flight 

 that which is in reality possessed by the Bat, and which is 

 represented in the accompanying figure {Fir/. 334). The 

 bones of the fingers constitute the framework of the wing, 

 and hence the term Cheiroptera,* or " hand-winged," is that 

 by which the order is designated. The thumb does not 

 partake of this extraordinaiy development; it remains free, 

 and is furnished with a hooked nail. 



If a Bat be placed on the smooth surface of a table, its 

 awkward attempts at walking (Fig. 335), give an idea of 

 helplessness akin to that which was suggested to naturalists 

 when the Sloth was seen upon the ground. Yet compassion 

 in both cases would be alike misplaced. Each animal is gifted 

 with powers of locomotion adapted to its wants. The Bat can 

 climb with ease the rugged and pei-pendicular surface of a 

 tree, or can wheel its flight in the air, though burthened with 

 one or two young adhering to its teats. 



The use of the wings 

 does not seem to be 

 limited to that of flight. 

 They appear to be endued 

 with a most delicate sense 

 of touch, a sense so ex- 

 quisitely fine as to be af- 

 fected by the slightest dif- 

 feren9e in the vibrations 

 of the air. Bv the cruel fik- 335.-Bai WAtKiNo, 



* From tlie Greek words meanins "a baud" and "a wing." 



