OJJ THE MEMBRANA TYMPANI OF THE EAR. ' 103 



m extracting which confiderable lacerations have been macfe 

 in the membrana tympani. Fig. 5 fhews one torn in at- 

 tempting to remove a pin. . ' 



The membrana tympani may be eafily feen in fome perfontf, How the mem- 

 by directing the rays of the fun, or a condenfed light from a J rane ™ z ? 

 common lamp, into the ear : bnt this is not the cafe in all ; 

 for the meatus differs confiderably in different perfons, both 

 in its depth and diameter. If the ear be clear of wax, the its appearance, 

 membrane has a bright tendinous appearance ; and an aper- Means of dlf- 

 ture in it appears as a dark fpot, which, by the filvery J^ 1 ^™ apcr " 

 furface of the membrane furrounding it, is rendered diftin&ly 

 perceptible. If there be an aperture, air alfo, upon blowing 

 the nofe with violence, will be forced with a whittling noife 

 through the ear ; the fmoke of tobacco may be driven from 

 the mouth through the ear ; or water may be injecled from 

 the ear into the throat. 



If the whole of the membrane be deftroyed, and three out Effects of the 

 of four of the fmatf bones of the tympanum be removed, an ^frnfmblane. 

 almoft total deafnefs enfues ; but the ear, after a time, begins 

 to recover its powers, and, in the end, regains them, with 

 that ^degree of imperfection only, which was defcribed in 



the cafe of Mr. P ', in Mr. Cooper's former paper. 



When the membrane of one ear only is deftroyed, a greater 

 degree of deafnefs takes place in that ear, than would happen 

 in either, were the membrane deftroyed in both. This pro- 

 bably arifes from the difufe, into which the imperfect ear falls. 



Thus Mr. G , at an early period of life, loft a great por- Fig. 3. 



tion of the membrana tympani of the left ear ; and as he heard 

 fomewhat better with his right ear, he was little in the habit df 

 employing the left, till at length he eonfidered himfelf almoft 

 totally deaf in it. Becoming deaf in the right ear, however, 

 and confequently obliged to employ the left, he found it by 

 no means deprived of its powers. 



Thefe obfervations have induced Mr. Cooper to fry the Cu J* e of a fpecies 

 effea of an operation, which has proved fuccefsful in feverai of deafnefs - 

 infiances of one fpecies of deafnefs, — that which arifes from 

 ob'ftruction of the Euftachian tube. Of this obftru&ion there The Euftachlan 

 arc feverai caufes. A common cold, affecting the parts corij- fh-u^^from 1 '" 

 tiguous to the orifice of the tube, may prevent the free feverai caufes* 

 patlage of the air into the tympanum. The deafnefs thus 6c- ■ 

 Caiioncd is in general temporary ; but ft 'may b#cOtri*e p^- 



manent, 



