Deafness practically illustrated / [James Yearsley].

  • James Yearsley
Date:
[1849]
Catalogue details

Licence: Public Domain Mark

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

    24/200 page 12
    and inwards, till it terminates at the upper and lateral part of the throat in an oblique and elliptic orifice, sufficiently large to admit the insertion of a quill. The internal ear may well be named the “labyrinth,” for its complicated structure almost defies description. It consists of the vestibule or middle cavity, of the semicircular canals, and of the cochlea. In these cavities, the auditory nerve is delicately expanded, and » is surrounded by an aqueous fluid, termed the Liquor Cotunnii. The fenestra ovalis, over which the base of the stapes is placed, transmits the vibration it has received by the chain of bones in the tympanum, through the vestibule to the other parts of the laby- rinth. Sufficient of the physiology of the organ, for the comprehension of the subject, may be summed up in very few words. The vibrations of a sounding Hye act upon the air, and produce soniferous undulations. These enter the external auditory passage, and cause vibration of the membrana tympani. The vibratory motion is suc- cessively conveyed to the ossicula, to the fenestra ovalis, and thence to the labyrinthic fluid, which, being set in motion, acts by compression on the auditory nerve. The internal sensation is produced by the nerves conveying the impression to the brain; and it then remains for memory and association to complete the process, and to show the relation which exists be- tween the external agent and the internal impression. In enumerating the contents of the tympanum, I omitted to mention that which is the most important of all, as without its presence the function of hearing is lost—namely, atmospheric air. If the guttural ex-
    No text description is available for this image
    No text description is available for this image
    No text description is available for this image