Deafness practically illustrated / [James Yearsley].

  • James Yearsley
Date:
[1849]
Catalogue details

Licence: Public Domain Mark

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

    148/200 page 136
    as of the Eustachian tubes, is of great importance to the acuteness and preservation of the hearing. It is generally acknowledged that the presence of air is necessary in the tympanum, and also that the air should not differ greatly in temperature from the air on the external surface of the membrane of the drum. The means by which these requirements are provided for, are well known to be the Eustachian tube; but I believe, in addition to this, a free state of the nasal pas- sage is a necessary auxiliary, and that without it the function of the Eustachian canal cannot be properly performed. This view is supported by the anatomical position of the mouth of the Eustachian tube, which points towards the external nasal aperture, and is directly in the line of the passage of air through the nose both in inspira- tion and expiration; further, the trumpet-shaped ex- tremity of the tube, and its direction, obliquely back- wards to reach the middle ear, favours, and appears to provide for, the entrance of air to the tympanum in inspiration rather than in expiration. It is not that simple stoppage of the nasal passages can cause deafness, because the nose may be closed without producing the slightest immediate effect on the hearing; but I consider that when it is permanently obstructed, the want of a free circulation of air in the tympanum lessens the sensibility and acuteness of the auditory organ, or favours the accumulation of mucus in the middle ear. By examining my own sensations in ordinary expiration, I believe that air does not enter the tympanum during this act, but passes out from the ear with the expiratory stream of air escaping from the nostrils.
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