ON THE MEMBRANA TYMPaNI OF THE EAR. 105 



operation, Mr. Cooper had the pleafure to receive an a'flur- 

 ance from him, that he had fufTered no relapfe, nor any in- 

 convenience from the openings which had been made, and 

 that his hearing continued perfect. 



The operation confifts in palling into the ear a canula, of Mode of per- 

 the fize of a common probe, in which a trocar is concealed : 2^ C 

 the canula is to reft upon the membrana tympani, and the 

 trocar is then to be thruft through the membrane. The trocar 

 fliould be fo adjufted, as not to pafs more than one-eighth of 

 an inch beyond the canula, to prevent its reaching the oppo- 

 site fide of the cavity of the tympanum. Should it however 

 touch the periofteum of the- tympanum, it can be productive 

 of no ferious harm. The aperture fliould be made in the 

 anterior and inferior part of the membrane, under the handle 

 of the malleus, which muft not be injured in the operation; 

 and it is therefore neceflfary, that the operator be acquainted 

 with the exact fituation of this bone. Though the membrana 

 tympani is vafcular, the veffels are fo fmall, that they bleed 

 but litde ; and therefore, if much blood be difcharged, the 

 operation cannot have been properly performed. In an ear 

 othervvife healthy, the operation is attended with fo flight a 

 degree of pain, that, when it has been performed in one ear, 

 the patient exprefles no unwillingnefs to fubmit in the other. 

 The fenfation it occafions is momentary ; and no fubfequent 

 jnconvenience of any kind arifes : though if the ear have been 

 previoufly irritated by ftimulating applications, the operation 

 will be painful, and ihould be deferred, till the inflammation 

 has fubfided. 



As this operation affords relief only in cafes of clofure of Cafes in which. 

 Jhe Euflachian tube, attention fliould be paid to the following k affords . relie *- 

 jcriteria of this defect. 



If a perfon, on blowing fhe nofe violently, feel, a fwelling Criteria for 

 in the ear, from the membrana tympani being forced outward, d » ftin § u iflf' n S 

 the Euflachian tube is open. Though the tube be .doled, if 

 the beating of a watch placed between the teeth, or prefled 

 againft the fide of the head, cannot be heard, the operation 

 cannot relieve, as the power of the auditory nerve muft have 

 jbeen deftroyed. In a doled Euftachian tube there is no noile 

 in the head, like that accompanying nervous deaf hefs. Laftly, 

 jt is right to inquire, whether the deafnefs were immediately 

 preceded by any complaint in the throat. 

 * The 



