68 Mammals of Eastern Asia 
permanently rotated so that the knee points outward and back- 
ward. Since the foot, too, points backward, the long, hook-like 
claws must to some extent hinder attempts to crawl. However, 
Bats on the ground do scramble along with some degree of 
agility, although they lack the speed and assurance of movement 
of most ground-living mammals. 
"Blind as a bat" is an expression representing yet another 
human misconception. Bats see well, some of them very well. 
The giant Fruit Bats of the tropics of the Old World have large 
eyes that glow at night in the beam of a flashlight like those of 
dogs and horses. In many of the little Bats found here in the 
north, the eyes are proportionately small and partly concealed 
by hair. Such Bats, hiding in a cave, may be dazzled when a 
light is thrown upon them, though scarcely more than we our- 
selves would be. 
The senses of touch and hearing in the Bats have become 
extremely acute. In many kinds there are special leaf-like folds 
of skin about the muzzle, which are believed to play a part in 
helping their sense of touch. The inner parts of the ears, where 
the actual hearing takes place, are tuned up for the perception 
of the shrill chirps of other Bats, which are sometimes above the 
range of human hearing. In this connection it is now known 
that some Bats can hear "supersonic sounds" — vibrations far 
more rapid than anything we can appreciate, sounds which can 
be produced in our laboratories mechanically. The ability of 
some Bats to avoid obstacles in the dark may be connected with 
the detection of echoes from those obstacles. 
The geological age of Bats, counted in years, is scarcely 
imaginable even by a public accustomed to modern financial 
statistics. When the little five-toed horse and the tapir-like ele- 
phant still roamed this earth, Bats were already Bats. One of 
the oldest American fossil Bats, from the rocks of the Middle 
Eocene, is much like a modern insect-eating Bat. 
Even in the reproduction of their kind, Bats have done un- 
