A clinical manual of the diseases of the ear / by Laurence Turnbull.

  • Turnbull, Laurence, 1821-1900.
Date:
1872
Catalogue details

Licence: Public Domain Mark

Credit: A clinical manual of the diseases of the ear / by Laurence Turnbull. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    The exact dimensions of each section of such instruments, therefore, becomes a matter of importance. Tubes of wood, metal, glass, etc. are not merely con- ductors of sound, by preventing the rays from diverging and increasing their power by reflection, but the molecules com- prising the instrument themselves vibrate. These vibrations are in harmony with the sound intro- duced, but varying in their perfection. It is evident, therefore, that if tubes prevent sounds from being lost in the air by expansion, they must conduct it to an almost indefinite distance; hence the great utility of hear- ing- and speaking-trumpets. INSTRUMENTS TO ASSIST HEARING. Ear-trumpets are to the ears what spectacles are to the eyes, but the aid which they render is neither as perfect nor as complete. Yet with all their defects they could not be dispensed with, as they are the only means by which deaf persons have intercourse with their friends, or are enabled to listen to a lecture or sermon; each individual generally has his or her favorite instrument, and would not part with it on any consideration. Ear-trumpets are bent so as to cause the sound to be de- flected from a straight line in passing into the ear; and by making the portion which receives the sound like a funnel, a much larger volume is received for the impression on the impaired auditory nerve. The simplest form is seen at Fig. 12. Fig. 12.—Simple Ear-Trumpet. Those who are very deaf require a tube from fifteen to eighteen inches in length; those moderately deaf, one not so long. In treating many deaf persons we must have a variety of 4