Chap. L] 
BATS. 
15 
which essentially distinguishes them from the feathery 
wings of a bird, and vindicates the appropriateness of 
the term Cheiro-ptera % or " winged hands/' by which 
the bats are designated. Over the entire surface of the 
thin membrane of which they are formed, sentient nerves 
of the utmost delicacy are distributed, by means of which 
the animal is enabled during the darkness to direct its 
motions with security, avoiding objects against contact 
with which at such times its eyes and other senses 
would be insufficient to protect it. 2 Spallanzani ascer- 
tained the perfection of this faculty by a series of cruel 
experiments, by which he demonstrated that bats, even 
after their eyes had been destroyed, and their external 
organs of smell and hearing obliterated, were still 
enabled to direct their flight with unhesitating con- 
fidence, avoiding even threads suspended to intercept 
them. But after ascertaining the fact, Spallanzani was 
slow to arrive at its origin ; and ascribed the surprising- 
power to the existence of some sixth supplementary 
sense, the enjoyment of which was withheld from other 
animals. Cuvier, however, dissipated the obscurity by 
showing the seat of this extraordinary endowment to 
be in the wings, the superficies of which retains the 
exquisite sensitiveness to touch that is inherent in 
the palms of the human hand and the extremities of the 
fingers, as well as in the feet of some of the mammalia. 3 
The face and head of the Pteropus are covered with 
brownish-grey hairs, the neck and chest are dark ferru- 
ginous grey, and the rest of the body brown, inclining 
to black. 
1 x 6 V> the "hand," and 7trephv, 3 See article on Cheiroptera, in 
a "wing." Todd's Cyclopaedia of Anatomy 
2 See Bell On the Hand, ch. iii. and Physiology, yol. i. p. 599. 
p. 70. 
