Page:Popular Science Monthly Volume 37.djvu/369

Rh opportunity of supplying himself pass. It is not for nothing that the fox watches night and day intent to take notice of the lightest movement in the air; or that the hare is a proverbially timid beast, for the existence of his species depends upon his being on the alert. We can thus understand to a certain extent why the rabbit has 7,800 auditory cells in his organ; a number that represents a wonderfully delicate refinement in his hearing, even if we do not suppose each of these 7,800 cells to correspond with a different tone, as, if we regard each cross-shaped group of four cells as representing a single tone, this would give an exceedingly large number—about two thousand—of tone-perceptions. We may realize how delicate must be the hearing that appreciates even a thousand tones when we recollect that our concert-piano scales give only eighty-seven tones. Even if we take a scale of greater compass, as of a hundred tones at intervals of a semitone, our rabbit will have capacity to distinguish nineteen intertones in each half-tone interval. We, ourselves, if we exercise our full power of hearing, could distinguish some thirty intertones between the tones A and Bb, of our scale—a few more than the difference in the number of vibrations corresponding with those notes (A=440, Bb=467·5).

To make this highly developed organization of the ear of real benefit to the animal, the parts of the brain corresponding with the auditory nerves must be constituted with like delicacy. So also must those parts which serve for the remembrance of sensations. For, without memory and the power to profit by the lessons of experience, those powers would be of little use to the animal.

It is only in a few instances that we can ascertain with any degree of sufficiency how far an animal is capable of really comprehending our music. The capacity often appears to be considerable; for it is well known that cavalry-horses frequently learn to recognize the signals given by the trumpeters as well as their riders do, and to make the motions answering to them before they are directed to do so. We have, furthermore, in many birds, which are far below the mammals we have named in mental capacity, good evidence that our music can be heard and comprehended by beings whose hearing apparatus has not been adapted to those ends. I refer especially to birds which have no or only very simple songs of their own, and are yet able to imitate both the more varied songs of other birds and human melodies. This is conspicuously the case with some of the parrots, which can learn to repeat short melodies well and distinctly. They also possess the proper organs for hearing music, although they do not themselves make it. Thus our proposition seems well founded that, as man possessed musical hearing organs before he made music, those