THE VIBRATORY SENSE 



is in keeping with the needs of a completely aquatic 

 life, with branchial respiration. It is absent in Ceta- 

 ceans, which have lungs and perfected hearing organs. 

 When it does exist, it adds its field of action to that of 

 the little auditory organ proper, and provides a measure 

 of wealth to what, without it, would be poverty or 

 destitution. 



Its field of action, partaking at once of touch and 

 hearing, is considerable. It includes the vast register 

 of ultra-sounds, of the vibrations imparted to the 

 water by the passage of a resistant body even some 

 distance away, or by the movements of objects close 

 at hand, by shocks transmitted from afar, or even by 

 currents from time to time. Water being incapable 

 of compression, these various forms of concussion are 

 easily transmitted. The listening apparatus used by 

 sailors and hydrographers enables its users to hear 

 the propeller of a ship several miles away. The organ 

 of the lateral line is, after its own fashion, a listening 

 apparatus with several tiny receivers; thanks to its 

 structure and its position it is able to receive and 

 perceive sensations which would escape the ordinary 

 auditory apparatus, the ear itself. It has its own 

 register, concerned with deep tonalities, multiple and 

 varied. 



The fishes do not hear exactly as we do, but none 

 the less they hear. If they are deaf to the majority 

 of the sound vibrations which we distinguish and 

 which the air transmits to the water ; if they feel them 

 only slightly, and often not at all, they are, on the 

 other hand, sensitive to vibratory shocks which we 

 do not perceive at all, or which we do not receive in 

 their way, for, according to circumstances, we should 

 transform them either into a rough touch or a confused 

 hearing. Thanks to their organs, these sensations in 

 fishes are more intense and precise. Through them 

 fishes acquire a knowledge of what is going on in 

 the water around them. At every moment they control 

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