Now it is believed that it is somewhat after this fashion that the internal ear perceives sound. It has been noted (p. 468) that, in the internal ear, the organ of Corti contains a large number of cells with hairs projecting from them. It is supposed that each hair is sensi tive to a particular vibration. The vibrations of a sounding body are conducted to the internal ear in the manner already described, and agitate the fluid in the membranous canal of the cochlea. The waves produced will be complex waves, compounded, that is, of simple waves of different lengths, &c. Each hair, however, will vibrate in harmony with one particular simple wave, and if that one be contained in the complex one, it will pick it out and vibrate to it. Thus the complex wave of sound will be split up into simpler forms, each hair selecting and vibrating to its own, and a multitude of hairs will be set simultaneously vibrating by the mass of sound. The ear is thus an organ that analyses (splits up) sounds into their elements.
In support of this view it may be mentioned that hairs on the feelers of the Mysis, an animal belonging to the same general class as crabs and lobsters, have been seen to vibrate in harmony with particular notes and with these notes only.
Each hair cell is in communication with a nerve-fibre, and the vibration of each hair will thus cause an impression to be passed along a nerve. The various impressions will be passed along to the hearing centre in the brain, where they become fused, and the person is conscious of a sound of a particular kind. While the eat splits up complex sounds, and communicates to the brain the elements of which they consist, the brain reunites them. We are not conscious of the splitting-up process but only of the union.
The Range of the Ear for musical sounds has been determined to be from 32 to about 30,000 vibrations per second. That is to say, 32 vibrations per second produce the sensation of a low musical note, the lowest the human ear can appreciate, while vibrations occurring at the rate of about 30,000 per second produce the sensation of a very high pitch, the highest the human ear can appreciate. Vibrations more rapid cannot be taken knowledge of by the ear.
• The Sensation of Discord in music is due to the interference of two sounds which are nearly of the same pitch. As two waves in water way abolish one another if the crest of one meets the hollow of another, and may again add to one another's size by the two crests meeting, so two waves of sound differing slightly from one another may at one moment almost extin guish the sound by interference, and at the next produce increased loudness of the sound by being added to one another. The result is the production of what in music is called beats, characterized by a rising and falling of the sound. The effect on the ear is similar to the
effect of a flickering light on the eye. When the beats occur with sufficient rapidity they give a sensation of roughness to the sound, greatest when they number 33 in a second. When they reach the number of 132 in a second they are no longer perceived. Two notes that, when sounded together, produce beats are recog nized as discordant notes.
Judgments of the direction of sound are not actually performed by the ear ; they are the result of various other circumstances. Any one can prove this by shutting the eyes and trying to decide the direction from which a sound is coming. The distance from which a sound proceeds we judge of by its loudness or faintness. It is such facts as these that the ventriloquist takes advantage of to deceive people. He imitates the character of sound from a distance, or from some particular place, by giving it the required degree of loudness, and by directing the attention of the person to that quarter, &c., his own face at the same time giving no sign of movement.
"Educating the ear" is a phrase which de rives force by all that is known about the mode of action of the organ of hearing. We have seen that the ear actually analyses or splits up sounds into their simple elements, and that the brain fuses the elements together again. The habit is to pay attention only to the fused sen sation. But we all know that the trained musician detects the elements of a complex sound, while the person who has given no attention to his sensations knows only, per haps, that the sound is pleasant or the reverse. Just as surely as every ear performs the same process of analysis, so may every person, by careful training, become able to perceive some thing of the analysis, and to detect some of the varied elements of musical sounds that he listens to. The difference, indeed, between a "good ear" and a "bad ear" is to a large ex• tent the difference between careful training and bad training, or no training at all. Some thing, of course, must be admitted to natural aptitude ; but the excuse many people offer for their ignorance of music, that they have "no ear," is no excuse at all, in view of the facts that have been stated—is, indeed, but another way of implying carelessness and neglect. Just as the man, who is not blind, would be laughed at if he offered, as an excuse for being unable to read, that he had no eye, so ought a person, who is not deaf, to be laughed at if he offers, as an excuse for being unable to distinguish one note from another, or different notes in a chord, that he has no ear.