838 SPECIAL SENSES. 



and it remains for us now to determine how far these laws are applicable to the physi- 

 ology of the vibrations of the membrana tyinpani and the action of these vibrations in 

 the accurate perception of musical sounds. 



There are certain phenomena of vibration of the membrana tympani that must occur, 

 as a physical necessity, under favorable conditions, which it is important to note in this 

 connection ; and these have hardly attracted sufficient attention at the hands of physio- 

 logical writers. In the first place, this membrane must obey the laws of vibration by 

 influence. It is undoubtedly thrown into vibration by irregular waves of noise, as contra- 

 distinguished from musical tones ; but, when a tone is sounded in unison with its funda- 

 mental tone, or when the tone sounded is one of the octaves of its fundamental, it must 

 undergo a vibration by influence, like an artificial membrane. If we suppose the mem- 

 brane to be tuned in unison with a certain note, it will not only return this note by influ- 

 ence, but it will repeat its quality. Not only this, when a combination of harmonious 

 tones is sounded, the combined sound will be returned, with all the shades in quality 

 which the combined tones produce. On account of its small size, the sound produced by 

 the exposed membrane itself cannot be heard ; but that the membrane does vibrate by 

 influence, has been proven by experiments with small particles of sand on its surface. 



We are certainly justified in supposing that vibrations of the membrana tympani, too 

 delicate to be revealed to the eye or the ear in objective experiments, may be appreciated 

 by the auditory nerves as a subjective phenomenon. In other words, we can probably ap- 

 preciate vibrations in our own tympanic membrane, when these would be too delicate to 

 be observed by the eye or ear, in a membrane exposed and subjected to similar influences. 

 This point must be accepted as probable ; and it cannot be proven by direct experiment. 

 If this be true, the most complex combinations of sound produced by an orchestra might 

 be actually reproduced by the tympanic membrane, if this membrane were accurately 

 tuned to the fundamental tone. 



The arrangement of the muscles and bones of the middle ear admits of the possibility 

 of tuning the membrana tympani with exquisite nicety. These muscles are sometimes so 

 far under the control of the will that we can tighten the membrane to its limit by a vol- 

 untary effort ; the muscles are of the striated variety, and are capable of rapid action ; 

 they are supplied with motor filaments from the cerebro-spinal system ; the ear is fatigued 

 by long attention to particular tones ; persons not endowed with what is termed a musical 

 ear cannot appreciate slight distinctions between different tones ; the ear is capable of 

 education in the appreciation of pitch and in following rapid successions of tones; and, in 

 short, there are many points in the mechanism of the transmission of musical sounds in 

 the ear that seem to involve muscular action. In the larynx, we nre conscious of differ- 

 ences in the tension of the vocal chords only from differences in the character and pitch 

 of the sounds produced ; in the eye, we are conscious of the contraction of 'the muscle of 

 accommodation from the fact that an effort enables us to see objects distinctly at differ- 

 ent distances; and it is not impossible that, under ordinary conditions, the consciousness 

 of contractions of the muscles of the middle ear may be revealed only by the fact of the 

 correct appreciation of certain musical tones. Some persons can educate the ear so as to 

 acquire what is called the faculty of absolute pitch; that is, without the aid of a tuning- 

 fork or any musical instrument, they can give the exact musical value of any given tone. 

 A possible explanation of this is that such persons may have educated the muscles of the 

 ear so as to put the tympanic membrane in such a condition of tension as to respond to 

 a given note and to recognize the position of this note in the musical scale. Finally, an 

 accomplished musician, in conducting an orchestra, can, by a voluntary effort, direct his 

 attention to certain instruments, and hear their notes distinctly, separating them, as it 

 were, from the general mass of sound, can distinguish the faintest discords, and immedi- 

 ately designate a single instrument making a false note. 



The fact that rapid successions of notes are readily appreciated does not of necessity 

 argue against the possibility of following these notes with the muscles of the ear ; for the 



