Deafness practically illustrated / [James Yearsley].

  • James Yearsley
Date:
[1849]
Catalogue details

Licence: Public Domain Mark

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

    40/200 page 28
    Before passing to a consideration of the diseases of the Eustachian tubes, and the deafness thereby occa- sioned, it will be useful to glance briefly at the physio- logical action of these tubes, both for the purpose of elucidating the nature of the consequent loss of hearing, and the utility of the treatment recommended. The Eustachian tube is lined throughout by a deli- cate prolongation of the mucous membrane covering the pharynx, which connects the cavity of the tympa- num with the throat and passages of the nose. A chief characteristic of mucous membranes, and from which they derive their name, is the secretion of a mucous fluid which lubricates their surfaces, and preserves them in a healthy condition. As this secretion, under ordinary circumstances, always proceeds without inter- mission, it is necessary for the preservation of the normal condition of the membrane, that the super- abundant mucus should be continually removed; other- wise, it would become viscid, and constitute a departure from the state of health. This removal of the super- fluous mucus is effected in different modes, in different parts of the mucous system. Sometimes by a proper muscular tunic, which occasions movements of the membrane itself in a certain direction; in other organs, by the transit of large quantities of fluid over the secreting surface; or, by alternate contractions and dila- tations of the mucous tubes, by the ingress and egress of air in respiration. Of these different kinds of motion, only the latter is possessed by the Eustachian canal; and this but in a very limited degree. The contraction and dilatation of the tube in respiration, however slight, is of course favourable to the escape of mucous fluid from the tympanic cavity and Eusta-
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