Sensory Discrimination : Hearing 119 



mean that the frog perceives such sounds as differing in pitch. 

 The absence of a cochlea throws doubt on such a supposition ; 

 the sensation differences are probably much cruder than 

 would be the case for a human being. 



39. Hearing in Higher Vertebrates 



The reptilian ear does not differ markedly from that of 

 amphibians. The writer knows of no experiments upon the 

 sense of hearing in reptiles. 



The cochlea is supposed to be the portion of the human 

 ear upon which the power to distinguish pitch differences 

 rests. Yet birds have no cochlea, though if we grant that 

 animals which produce sounds are those which are able to 

 hear them, some birds at least must be capable of pitch 

 discriminations of wide range and great acuteness. The 

 powers of imitation so often evidenced in bird song are 

 proof that this is the case. 1 The sense of hearing, so long 

 absent or problematical in the ascending scale of animal 

 forms, reaches great importance in the life of birds and 

 mammals. How far various mammals have the same 

 range of auditory qualities that a human being has, what 

 their capacity for pitch discrimination may be, has been 

 but little investigated. Raccoons have been taught to dis- 

 criminate between the note Aj on a harmonica and the 

 note A'", climbing on a box to be fed when the high 

 note was sounded and staying down when they heard the 

 low one (82). It is probable that the variety of auditory 

 qualities entering into the experience of the highest verte- 

 brates is large. 



1 Interesting evidence of this power in a bird which might not have been 

 supposed to possess it was obtained by Conradi, who found that English 

 sparrows reared by canaries acquired recognizable bits of the canary song 

 (83). 



