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 animals, 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 considerable 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 extreme 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
