BATS 45 
bat?) We suppose that they are sense-organs, but 
all we know, or half know, about the matter is 
ancient history; it dates back to the eighteenth 
century, when Spallanzani, finding that bats were 
independent of sight when blinded and set flying 
in winding tunnels and other confined places, 
conjectured that they were endowed with a sixth 
sense. Cuvier’s explanation of these experiments 
was that the propinquity of solid bodies is per- 
ceived by the way in which the air, moved by the 
pulsations, reacts on the surface of the wings. 
Thus the sixth sense was a refinement, or extension, 
of the sense of touch—an excessive sensitiveness in 
the membrane. Blind men, we know, sometimes 
have a similar extreme sensibility of the skin of the 
face. I have known one who was accustomed to 
spend some hours walking every day in Kensington 
Gardens, taking short cuts in any direction among 
the trees and never touching one, and no person 
seeing him moving so freely about would have 
imagined that he was totally blind. 
My own experiments on bats in South America 
were inconclusive. I used to collect a dozen or 
twenty at a time, finding them sleeping by day 
on the trees in shady places, and after sealing up ° 
their eyes with adhesive gum, liberate them in a 
large room furnished with hanging ropes and 
objects of various sizes suspended from the rafters. 
The bats flew about without touching the walls, 
and deftly avoiding the numerous obstacles; but 
I soon discovered that they were able when flying 
