Handbook of diseases of the ear : for the use of students and practitioners / by Urban Pritchard.

  • Pritchard, Urban, 1845-1925.
Date:
1886
Catalogue details

Licence: Public Domain Mark

Credit: Handbook of diseases of the ear : for the use of students and practitioners / by Urban Pritchard. 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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    tion, its size, its constant presence even in early life, and its surgical and pathological importance it is better to consider it quite separately. Generally speaking it is roughly ovoid in shape, but it varies a good deal both in form and size. Its relations to the surrounding struc- tures are of no little importance. It is separated from the cranial cavity above by the extension of the thin bony plate (tegmen) covering the attic ; behind and be- low it usually communicates with the air cells of the mastoid process, when these exist; in front it is con- tinuous with the attic. It approaches nearest to the surface of the bone at a point immediately behind the opening of the osseous meatus, at which point a slight depression may be felt ; this is taken by the surgeon as a guide for the use of the chisel or drill. The bone in this region varies a good deal in thickness ; it may be that less than a quarter of an inch has to be cut through before the cavity is reached, but on the other hand, it may sometimes happen that over an inch has to be traversed The antrum is lined with closely adherent mucous membrane, but its walls, unlike those of the attic, are reticulated, and it has been suggested that it secretes and acts as a reservoir for the lubricating fluid of the tympanum.* Mastoid process.—The internal structure of the mastoid process is by no means constant. In the infant there are no air-cells, and they may even be entirely absent in the adult, or, if present, may vary much in size and number. We may in fact have four distinct types of mastoid formation, viz :— * An excellent description of the anatomy of the antrum will be found in Mr. Arthur Cheatle's paper, The Mastoid Antrum in Children, Lancet, vol. ii., p. 1264, 1892.