VOICES OF EXPERIENCE 



their wings, tliey prefer darkness, are quite at home in 

 the blackest caves and generally encountered only as 

 unwanted invaders of attic or summer cottage. At first 

 glance nothing would seem to be more remote from any 

 humanitarian contribution to the biophysics of orienta- 

 tion of blind human beings. 



It is the startling strangeness of bats, plus the folklore 

 that couples them with demons and the nether regions, 

 which makes it so hard to think of them with anything 

 other than repugnance. But they are experts in the use 

 of echoes, and if we wish to find out what can be learned 

 about objects from echoes, we must be prepared to ac- 

 cept important evidence regardless of our feelings about 

 its source. It would be a real oversight to ignore the skills 

 attained by bats in guiding their rapid flight by means 

 of echoes. 



Our knowledge of bat navigation really started in 

 1793 when the brilliant Italian scientist Lazzaro Spal- 

 lanzani became interested in how various animals found 

 their way about in darkness. Owls and other nocturnal 

 creatures, he found, were relying on their large eyes, and 

 they became helpless in complete darkness. But when 

 he experimented with bats, he was puzzled to discover 

 that they continued to fly almost perfectly when they 

 could not possibly see a thing. Not content with experi- 

 ments in which they flitted unconcernedly through the 

 darkest chambers he could find, he finally resorted to 

 blinding several bats. Even then they flew as well as 

 ever. He released a number of blinded bats out of doors 

 and looked for them four days later in the beU tower of 

 the cathedral at Pavia, where he had caught them for his 

 experiments in the first place. Wishing to know whether 

 they had been able to continue their ordinary activities 

 without their eyes, he climbed up to the bell tower early 

 in the morning just after the bats' usual time for retum- 



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