Deafness practically illustrated / [James Yearsley].

  • James Yearsley
Date:
[1849]
Catalogue details

Licence: Public Domain Mark

Credit: Deafness practically illustrated / [James Yearsley]. Source: Wellcome Collection.

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    that of connecting the tympanic cavity with the ex- ternal air, it may be stated,* that a tuning-fork will give a much louder and clearer sound, when it has a side tube affixed to it after the manner of the canal leading to the tympanum, than when devoid of such an aperture. So likewise, in actual experiment and diseases of the ear, it can be proved, that in temporary imperforation of the Eustachian tube itself, dulness of hearing ensues as a necessary consequence. With regard to the second direct office of this canal, that of maintaining a tubular communication between the cavity of the tympanum and the cavities of the nose and forehead, it is believed that considerable resonance and increase of force are given to the sounds in their transit through the ear by means of the cavernous passages mentioned. Dr. Henle believes this to occur in a mode analogous to the reinforcement afforded by the belly of a violin to the musical sounds emitted from the strings of the instrument, the openings in the sounding board being compared by him to the Eusta- chian canals. But it is the indirect utility of the Eustachian tubes which gives them their great and acknowledged im- portance, both in the consideration of deafness, and the physiology and pathology of the ear. Without them, the cavity of the tympanum would become completely isolated from the external air; there being in the normal state no communication by means of the mem- brana tympani through the external passage. When such perforations do exist, they are strictly malforma- tions, congenital or otherwise. It is necessary to the
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