ECHOES OF BATS AND MEN 



summer insect hunting, then their agility and finesse at 

 flying through comphcated pathways are truly amazing. 

 Flitting between the rungs of a chair is easy for an ani- 

 mal which naturally flies between the smaller branches 

 of pine trees on the darkest nights. 



After considering these two expert practitioners of 

 echolocation and before moving ahead, let us put our- 

 selves back into the frame of mind in which Spallanzani 

 must have viewed these phenomena. From curiosity 

 about the vision of nocturnal animals he had been led 

 to perform a long series of careful and critical experi- 

 ments with bats. While he could hear no sound as they 

 flew about, he had convinced himself, despite his strong 

 initial skepticism, that the ears and not the eyes were the 

 sense organs that informed bats about such small objects 

 as threads strung across the rooms in which he made 

 them fly. He could make no more sense out of this con- 

 clusion than could his critics. But he trusted experimen- 

 tally demonstrated facts sufficiently to be convinced of 

 the correctness of his findings, even though he could not 

 fit them into a satisfactory logical framework. This sit- 

 uation may arise from time to time in any branch of 

 science, and often it means that some important new 

 principle is just beyond our grasp. When facts fail to 

 fit into our theories, there is usually a need to modify the 

 theories. 



Is there any reason to suppose that scientific history 

 has just recently come to an end? Almost certainly not, 

 and this inevitably means that new and totally unex- 

 pected discoveries are going to be made in the future. 

 The example of Spallanzani and the acoustic orientation 

 of bats can remind us of several important points. First, 

 the most rewarding discoveries may be awaiting us in 

 what seem at first sight the most unlikely places. Second, 

 accepted theories explaining a phenomenon have often 



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