A contribution to the pathology of congenital deafness / by Edward Cock.

  • Cock, Edward, 1805-1892.
Date:
[1838]
Catalogue details

Licence: Public Domain Mark

Credit: A contribution to the pathology of congenital deafness / by Edward Cock. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    18/28 (page 16)
    continuous canal, varying in its calibre at different parts, commencing at the fenestra ovalis, and terminating at the fenestra rotunda; and, that the sides of this canal are firm and solid, while its two extremities are shut in by yielding struc- tures, viz. the membranes occupying the two fenestraj. The construction of the labyrinth may be familiarly explained by comparing it to a long metallic tube filled with water, and secured at either end by bladder or caoutchouc. If an im- pulse be given to the yielding material at the one extremity of such a tube, the impression must necessarily be conveyed to the yielding material at the other extremity, and the whole column of ihtermediate water will be put in motion. It has been shewn in what manner vibrations are conveyed to the fenestra ovalis; and there can be little difficulty in conceiving how the impulse produced on the membrane occupying that opening must be propagated through the vestibule, through the scala vestibuli and scala tympani, until it is received on the membrane of the fenestra rotunda. The motion of the fluid causes a concussion on the nervous expan- sion lining the walls of the labyrinth; which concussion, being referred to the brain, we denominate * the sense of hearing.' In accordance with the physiological explanation just given, the organ of hearing may be said to consist of three parts or sets of structures:—1. The external ear and tjTnpanum, being the apparatus by which vibrations are communicated to the labyrinth, at the same time that they may be altered or modified in their intensity. 2. The water of the labyrinth, which is set in motion by the vibrations so communicated, to it. 3. The nervous expansion wliich surrounds the water, and, appreciating the motion of the fluid, produces the sense of hearing. It follows, that, for the due exercise of the sense, three con- ditions of the organ are required :—I. A capability to convey the vibratory oscillations from the sounding body to tlie labyrinth. 2. That the fluid should be susceptible of undu- lation. 3. That the nervous expansion should be in a state which enables it to appreciate the motion of the fluid, and transfer the impression to the sensorium. For the purpose of ascertaining liow far the malformations, and morbid altera-