A manual of aural surgery for the use of students and practitioners of medicine / by James Keene.

  • Keene, James.
Date:
1873
Catalogue details

Licence: Public Domain Mark

Credit: A manual of aural surgery for the use of students and practitioners of medicine / by James Keene. Source: Wellcome Collection.

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

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    voice. Instances are on record in wHcb. deaf persons could only liear conversation in the midst of the noise of a mill, while leather was being pounded on the lapstone, or while travelling over a rough road, which we must endeavour to explain in a more physiological manner. Wilde states that this symptom occurs in cases of relaxation of the membrana tympani; and there is no doubt it does so, but we sometimes meet with the same symptom when the membrana tympani is deficient, and we must therefore seek an explanation which will meet both these circumstances; the one given by Dr. Allen is perhaps the best. The muscles which are connected with the function of hearing are two in number ; the tensor tympani, supplied with innervation from the otic ganglion, is an involuntary muscle, whilst the stapedius, deriving its supply from the facial, is a voluntary one. We have already seen that some patients can only hear when they listen attentively, and that they are almost deaf to conversation unless they do so; these exert their hearing power by a voluntary effort, which can only be made by 'the stapedius muscle, but in cases where its move- ments are impeded from any cause, or where its action alone is insufficient to produce the effect desired, further assistance is called for which must be obtained from the tensor tympani. Now we have seen that this muscle is not influenced by the will, and can only be brought into action by some other stimulus which is afforded by noise, in the same manner that light will contract the iris quite