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XXIII. Farther Observations on the Effects which take Place from 
the Destruction of the Membrana Tympani of the Ear ; with an 
Account of an Operation for the Removal of a particular Species 
of Deafness. By Mr. Astley Cooper. Communicated by 
Everard Home, Esq . F. R. S . 
Read June 25, 1801. 
In the Paper which I had last year the honour of presenting to 
the Royal Society, I endeavoured to point out the effects which 
are produced upon the organ of hearing, by a partial loss, or 
entire destruction, of the membrana tympani. 
From the facts therein detailed it appears, that an aperture in 
the membrana tympani does not diminish the power of the ear, 
and that even a complete destruction of the membrane is not 
followed by a total deprivation of the sense of hearing ; a sup- 
position which medical men have adopted, and common opinion 
has generally sanctioned. 
Convinced of the importance of the subject, and desirous, as 
far as my other avocations would allow, of pursuing my inqui- 
ries, I have, since the publication of that Paper, examined more 
than twenty cases of a similar defect in the membrana tympani ; 
and these instances have uniformly tended to confirm me in my 
former opinion, as to the use of the membrane, and the effects 
which follow from its loss. 
Injury may arise to the membrana tympani, or its destruction 
take place, from various causes, of which the most common is, 
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