A treatise on the structure, economy, and diseases of the ear : being the essay for which the Fothergillian gold medal was awarded by the Medical society of London / By George Pilcher.

  • George Pilcher
Date:
1838
Catalogue details

Licence: Public Domain Mark

Credit: A treatise on the structure, economy, and diseases of the ear : being the essay for which the Fothergillian gold medal was awarded by the Medical society of London / By George Pilcher. 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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    rendering it probable that sound reaches the tym- panum through its channel: in the crocodile, the tube opens near the occipital condyle, and is thus protected by its valvular pharynx; in birds this canal]oms its fel- low, and thus they form a common opening in the me- dian line of the upper part of the pharynx, where it is deprived of cartilage. In the cetacea the tube is very large, and opens into the upper part of the blowing apparatus, where it is furnished with valves worked by muscles, by which contrivance the animal can prevent water from entering the tympanum ; whilst air is freely admitted. By this arrange- ment the passage seems to become an accessory external Ear, receiving and conveying those sounds most important to the animal when floating upon the ocean's surface, for the purpose of respiration. In this tribe a curious separation of the tympanum from the labyrinth exists, always in the early periods, and often throughout life; the tympanum being a bone rolled up upon itself; thus corresponding somewhat to the division of the petrous portion of the temporal bone in the human foetus (Plate 8). In mammalia the four ossicula auditus are com- pleted, or three, if the orbicular be considered an epiphysis of the incus ; the malleus is attached to the membrana tympani, the incus to the malleus and to the orbicular, as well as to the parietes of the cavity the orbicular intervenes between the incus and the stapes; which last extends inwards to the fenestra ovalis. These fanciful names were given to the bones partly from their supposed resemblance to the ham' mer, &c., and partly from their conceived function it benig imagined by the Antients that they actually