A guide to the study of ear disease / by P. Mcbride.

  • McBride, P. (Peter), 1854-1946.
Date:
[1884]
Catalogue details

Licence: Public Domain Mark

Credit: A guide to the study of ear disease / by P. Mcbride. Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

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    pocket. A similar reflection anteriorly is sometimes spoken of as the anterior pocket. The outer surface of the membrane receives its blood supply from the deep auricular branch of the internal maxillary artery, a twig from which runs just behind and parallel to the manubrium mallei. If the drumhead be slightly hypersemic, this vessel can be well seen in the living subject. The internal or mucous layer is supplied with a fine network from the tympanic vessels. The nerve supply of the outer or dermoid layer is furnished by a branch of the fifth nerve which runs with the artery, while the mucous membrane is supplied from the tympanic plexus. The tympanum is a six-sided cavity. In height1 and width it measures about half an inch, while its dej)th from within outwards varies from one to two lines. The roof is formed by a thin plate of bone which is occasionally defective, leaving a foramen, in which case the lining membrane is directly in contact with the dura mater. The outer wall consists to a great extent of the tympanic membrane, but a ring of bone also enters into its formation, from which it follows that even in cases where the entire membrane has been destroyed, many parts of the cavity cannot be inspected (Plate I. C). The inner wall is of great importance to aural sur- geons, and presents for examination the following points :—(1) The fenestra ovalis; (2) the fenestra rotunda; (3) the promontory; (4) the ridge of the aqueductus Fallopii; (5) the pyramid (Plate I. D). The fenestra ovalis is a reniform opening lying at the upper and posterior part of the inner wall. Its long axis is almost horizontal, or slightly inclined from behind 1 Burnett, he. cit. p. 79.