Deafness practically illustrated / [James Yearsley].

  • James Yearsley
Date:
[1849]
Catalogue details

Licence: Public Domain Mark

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

    23/200 page 11
    Towards the external auditory passage is a con- siderable deficiency in the structure of this bony cavity, and it is across this large circular opening that the membrana tympani is extended. On the internal side may be observed a tubercular eminence termed the promontory, with the fenestra ovalis and the fenestra rotunda, the former communicating with the vestibule or central cavity of the labyrinth, the latter with the scala of the cochlea. Both the fenestra are closed by membranes not dissimilar in structure to the membrana tympani. The tympanum, then, may be said to be bounded externally by the membrana tympani, and internally by the labyrinth. Posteriorly by a short canal, which leads to the mastoid cells; and, anteriorly, by the opening of the Eustachian tube, which connects us ear with the throat. Within the tympanum is seen a chain of four small bones, the malleus, incus, os orbiculare, and the stapes. They are thus named from their shape. The malleus, for instance, from its supposed resemblance to a ham- mer or mallet; the imcus, from its resemblance to the blacksmith’s anvil; and the stapes, from being shaped like a stirrup. It must be allowed that no bones of the skeleton are more appropriately or descriptively named. Ligamentous attachments connect them together so as to form an uninterrupted chain between the membrana tympani and the membrane of the fenestra ovalis, by means of which the impressions of sound are strength- ened and conveyed from the former to the internal ear. The Eustachian tube, so called after its discoverer Eustachio, commences at the anterior and lower part of the tympanum, and proceeds forwards, downwards,
    No text description is available for this image
    No text description is available for this image
    No text description is available for this image