caverns and other places
where, so far as our judgment goes, no light can possibly penetrate.
Hence it was long since suspected that some other sense than that of
sight must come to their aid when they plunge into such outer darkness
as prevails in some places through which they fly with the greatest
freedom, and more than a century ago numerous experiment were made by
a distinguished Italian naturalist, the Abbe Spallanzani, in order to
discover, if possible, what might be the secret of these curious
phenomena.

He set free, in a long passage which was bent at a right angle about
the middle of its length, a blinded Bat, which flew through the whole
of this passage, turning the corner correctly, without anywhere
touching the walls; while flying, too, it in some mysterious manner
detected a hole in the roof at a distance of eighteen inches, and
proceeded at once to ensconce itself in this shelter. In another
experiment the Abbe took two Bats, one blinded, the other not, and
placed them in a space shut off from a garden and roofed in with nets,
and with sixteen strings suspended from the top in different parts.
Both Bats flew about briskly and avoided the hanging strings equally
well, until at length the _blinded_ Bat discovered that the meshes of
the net were large enough for him to get through, when he at once made
his escape, and after flying about for a short time, went off directly
to the only roof in the vicinity, under which he disappeared. In
short, from these experiments it became perfectly clear that under
these circumstances the sense of sight was not of primary importance
in guiding the course of the Bat. Similar trials with the organs of
smell and hearing showed that they had nothing to do with it, and the
only other sense that could be appealed to was the general sense of
touch. Baron Cuvier, the great French comparative anatomist, was the
first to suggest, from the consideration of the results obtained by
the Abbe Spallanzani and others, especially by M. de Jurine, of
Geneva, that the peculiar phenomena in question might be accounted for
by the existence, especially in the great membranous expansions of the
wings, of a most delicate sensibility; and subsequent investigations
of the structure of those organs has tended to confirm this view, so
that it is now the one generally accepted. It is found that these
great membranes are traversed in all parts by numerous nerves, the
delicate terminations of which f