NATURAL HISTORY OF SOUTH AFRICA 



to do so. In some mysterious way, probably by 

 vibrations set up in the atmosphere, they are aware 

 of the proximity of objects. This was proven many 

 years ago by what would seem a rather cruel experi- 

 ment, but which was undertaken in the interests of 

 science. Bats were deprived of their sight and then 

 allowed to fly in a room, across which silk threads 

 were stretched at a distance apart — just sufficient to 

 enable the bats to pass through with outstretched 

 wings. The bats not only successfully avoided- 

 striking the ceiling or walls, but not in a single in- 

 stance did they come in contact with the threads. 

 More threads were then stretched across the room, 

 so close together that the bats, to avoid touching 

 them, were obliged to considerably contract their 

 wings. This they accomplished satisfactorily. 

 Branches were then placed in their way, and they 

 flew in and out between the twigs and leaves, and 

 even suspended themselves by their legs, just as 

 efficiently as if they possessed sight. 



In most of the bats this acute sense is situated in 

 the wing membranes, and in the delicate and often 

 large ears. However, many species of bats have 

 curious expansions of skin on the face, usually called 

 the " Nose leaf." In some this facial membrane is 

 small, but in others it is both large and complicated. 

 These nose leaves are always fringed round with 

 delicate hairs, attached to the roots of which are 

 exceedingly sensitive nerves. 



The Fruit Bats do not possess this facial mem- 

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