HANDBOOK OF ACOUSTICS - online book

A complete view of Acoustical Science & its bearings on music, for musicians & music students.

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ON THE EAR.
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for every wave that reaches it; that is, as we know from the pre­ceding chapter, it will perform one vibration for eveiy vibration of the sound-producing body.
Further, it follows from the arrangement of the Malleus, Incus, and Stapes, and the attachment of the first and last to the Tympanum and the Fenestra Ovalis respectively, that every movement of the Tympanum must cause a similar movement of the Fenestra Ovalis. We see, therefore, that this latter membrane faithfully repeats every vibration of the Tympanum, that is, every movement of the sound-originating body.
The Internal ear is of a much more complicated nature than the parts already described. It consists essentially of a closed membranous bag of a very irregular and intricate shape, which contains a liquid termed Endolymph, and which floats in another liquid called Perilymph. Both the Endolymph and the Perilymph are little else than water. This membranous bag may be divided, for the purpose of explanation, into two parts—the Membranous Labyrinth (M. L., fig. 16) and the Scala Media of the Cochlea (Sea. M., fig. 16).
The Membranous Labyrinth comprises the Utriculus (Ut., fig 17), the Sacculus, and the three Semi-circular Canals. All these parts
communicate with one another, forming one vessel; the two first lying one behind the other, and the three canals springing from the Utriculus. One end of each of the Semi-circular Canals is dilated at the point where it joins the Utriculus into a swelling called an Ampulla (A, fig. 17). Of the three canals two are placed vertically and the other horizontally ; hence their names—the Anterior Vertical Semi-circular Canal (Ant. V. S. O, fig. 17), the Posterior Vertical (Post. V. S. C, fig. 17) and the Horizontal (Hor. S. C, fig. 17). All these parts are contained in a bony casing, which follows