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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    The external auditory passage forms the second portion of the external ear. This passage is partly cartilaginous, and partly bony, varying considerably in length as well as in diameter. In some individuals it will be found only three quarters of an inch in length, whilst in others it will reach to an inch and a half. Its diameter is no less variable, and differs in different parts of its course, being generally . narrower in the middle than at the extremities, and larger at its external than at its internal extremity. Its perpendicular will exceed its transverse diameter, and owing to the oblique position of the membrana tympani, at which the passage terminates, its lower boundary will be found longer than the upper. Its general direction is first forwards, upwards, and in- wards, and then downwards and inwards. It is, there- fore, always more or less incurvated. It is lined by a thin cuticle, beneath which are deposited the cerumi- nous glands, and from its surface towards the external extremity, frequently project many small hairs. The external auditory passage is terminated and closed by a thin semi-transparent membrane, named the membrana tympani. In the natural state, it is wholly closed by it, and not partially so, as is supposed by many who can make the smoke of tobacco pass through their ears by stopping the nose and mouth, and’ forcing their breath into the upper part of the fauces. Such a feat only proves the imperfection of the mem- brana tympani. The middle ear comprises the tympanum or drum of the ear and its contents. : The tympanum is a bony cavity of so irregular a figure as to admit of no exact description.
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