HANDBOOK OF ACOUSTICS - online book

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

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26
HAND-BOOK OF ACOUSTICS.
their outline pretty closely, so that there is a bony labyrinth, bony semi-circular canals, and so on. There is however a space between the bony casing and the membranous parts, which is filled by the Perilymph referred to above.
Every part of the Membranous Labyrinth is lined by an exceed­ingly delicate coat—the Epithelium—the cells of which, at certain parts, are prolonged into very minute hairs, which thus project into the Endolymph. In close communication with these cells are the ultimate fibres of one branch of the Auditory Nerve, which, ramifying in the wall of the Membranous Labyrinth, pierces its bony casing and proceeds to the brain. Floating in the Endolymph, there are also minute hard solid particles called Otoliths.
The remaining part of the Internal ear is more difficult to describe. It consists essentially of a long tube of bone closed at one end, of which fig. 18 is a diagrammatic section. A thin bony partition—
the Lamina Spiralis, L. S.—projecting more than half way into the interior, runs along the tube from the bottom, nearly but not quite to the top, so that the two chambers—Sc. V. and Sc. T—communi­cate at the closed end of the tube. These two chambers—the Scala Vestibuli and the Scala Tympani—are filled with Perilymph. Diverging from the interior edge of the Lamina Spiralis and ter­minating in the bony wall of the tube, are two membranous partitions, the Membrane of Eeissner — m.r. — and the Basilar Membrane—h. m. The chamber between these two membranes which is termed the Scala Media—Sc. M.—is filled with Endolymph. So far the tube has been described for simplicity as if it were straight. Now, we must imagine it forming a close coil of two and a half turns round a central axis of bone—the Modiolus; the Scala Media being outwards and the Lamina Spiralis springing from the axis. The whole arrangement is not unlike a small snail's shell,