Arris and Gale lecture on the physiology of the human labyrinth : delivered before the Royal College of Surgeons of England on March 18th, 1910 / by Sydney Scott.

  • Scott, Sydney Richard, 1875-1966.
Date:
1910
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Licence: In copyright

Credit: Arris and Gale lecture on the physiology of the human labyrinth : delivered before the Royal College of Surgeons of England on March 18th, 1910 / by Sydney Scott. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    of the cochlea, and we must seek the most acceptable work- ing hypothesis as a basis for further investigations. The problem is reduced to the stage when we wish to ascertain whether sound waves produce a movement of the hairs in the organ of Corti, and if so what is the character of the move- ment of these hairs and by what direct means is such movement accomplished. It is thought possible that the motion produced by sound waves on the labyrinth reaches the cells through the fluid of the labyrinth, either through motions in the basilar mem- brane, or by motion of the membrana tectoria, which impinges upon the free ends of the cilia of the hair-cells. By means of the mechanism of the stapedial foot-plate and the formation of the membrana secundaria which closes the fenestra rotunda, it will be understood that any to-and-fro movement of the stapes, due to compression and rarefaction waves of sound, will cause synchronous movements of the membrana secundaria through the intervention of the perilymph. Those who have studied the cochlea from the physical aspect conclude that the motion in the perilymph can be no other than mass motion.40 Such mass movement of peri- lymph must affect the pressure in the endolymph, possibly in the form of compression and rarefaction waves ; other- wise we cannot possibly explain the mechanism of the sound stimulus. We cannot imagine an effectual resistance to changes in pressure in the perilymph from the membrane of Eeissner, and although it is by no means clear in what form sound waves traverse the cochlea we must admit a mechanical motion of some kind is produced. But we cannot ignore the fact that sound-waves fall upon the membrana secundaria synchronously with those which reach the stapes—e.g., after removal of the tympanic membrane. It is assumed that either the basilar or tectorial membrane vibrates ; which should be regarded as the essential vibrator is a matter of controversy. If these membranes vibrate, do they do so in part, or throughout their whole length, and to all sounds, or only to some ? Or do they only vibrate in a particular part for a particular sound? Von Helmholtz propounded and elaborated the theory that each portion of the basilar membrane was set into reciprocal vibration by tones of one and only one pitch. Normally, the human subject is capable of hearing about 11£ octaves—i.e., tones of from 16 double vibrations per second up to tones of nearly 50,000 vibrations per second. Von Helmholtz showed how it might be possible for high tones to cause sympathetic vibration of the basilar membrane at its basal extremity, where the membrane is narrowest 40 Weber. Von Helmholtz, p. 106. Cf. Sir Thomas Wrightson : On the Impulses of Compound Sound Waves and their Mechanical Trans- mission through the Ear, 1907.
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