354 THE POPULAR SCIENCE MONTHLY. 



the cat, and 7,800 in that of the rabbit. Hence man has a more 

 perfect hearing than those animals, although we are not able yet 

 to determine whether his superiority consists in finer delicacy or 

 greater compass; possibly in both. There are also differences, 

 but probably not of great extent, in the number of auditory cells 

 between men ; and we can explain by these differences why some 

 persons can hear more sharply, or lower tones or higher tones, 

 than others. I myself have a passably fine musical ear, but I can 

 not hear the high tones in which certain species of grasshoppers 

 make music, though hundreds of them may be "fiddling" at the 

 same time, and although other persons recognize them without 

 difficulty. 



The question now arises how, if only useful qualities become 

 established, this property of perceiving musical tones, possessed 

 by rabbits and cats in substantially nearly the same degree with 

 man, originated. It must be a matter of indifference to these ani- 

 mals, which do not make music, whether they have a musical 

 sense or not, and the development of their hearing apparatus 

 must have gone on with reference to other needs of theirs. What 

 were those needs ? In what respect is it useful to animals to have 

 the power of perceiving so great a number of distinct tones as are 

 provided for in their hearing apparatus ? The question has never 

 been discussed, and I confess that the answer is not easy, if a full 

 and detailed explanation is sought. But in a general sense the 

 reason seems easily comprehensible. Wild animals need a very 

 fine ear — beasts of prey, like cats, in order that they may hear and 

 distinguish all the tones that are emitted by their game. A con- 

 siderable scale is at once in demand for this ; one, for example, 

 which shall enable the wild cat to distinguish the cooing of the 

 dove, the call of the cuckoo through all its tones, and those of 

 the thrush, finch, linnet, pheasant, and the other birds and little 

 animals of the wood and field. The wild animal must also be 

 able to distinguish the sounds of his enemies — whether it be the 

 intended victim having to escape his pursuer, or the beast of prey 

 avoiding a rival; to the list of which, already large, has been 

 added man, who appeared after animals' organs of hearing were 

 fully developed. For this purpose the hearing of these animals 

 should be capable of perceiving low tones and high tones, and the 

 complete series of tones between. A feeling of wonder comes over 

 us when we see how highly developed the hearing of animals is, 

 and we can hardly comprehend it except we consider to what an 

 extent their existence in the wild condition depends upon an ex- 

 treme delicacy of the organ. There must be no uncertainty in 

 their minds as to the kind of source whence any sound comes. 

 A mistake may be a matter of life and death to them. The food 

 of a beast of prey is precarious, and he can not afford to let any 



