NATURAL H I S T O 11 Y 



361 



- bing of silk, &c. Its occurring in 

 Mm seems to disprove the idea 

 which has been entertained of its 

 cause; for it has been tliought, that 

 the close connection of the nerve 

 called the corda ti/mpani with the 

 membrana fi/7npani, exposed it to be 

 affected by the motions of the mal- 

 leus; and that, as it passed to nerves 

 connected with the teeth, they suf- 

 fered from the vibratory state of the 

 nerve, produced by the agitations 

 of the membrane. But, in this case, 



■ as the membrane was entirely de- 

 stroyed on that side on which the 

 sensation was produced, some other 

 explanation must be resorted to; 

 and I see no reason why this effect 

 should not be referred to that part 

 of the auditory nerve which lines 

 the labyrinth of the ear, which, be- 

 ing impressed by acute and disagree- 

 able sounds, would convey the im- 

 pression to the portlo diwa of the 

 same nerve, and to the teeth with 

 which that nerve is connected. 



The external ear, though two 

 distinct muscles are inserted into it, 

 is capable, in its natural state, of 

 little motion ; however, when an 

 organ becomes imperfect, every 

 agent which can be employed to 

 increase its powers is called into ac- 

 tion; and, in the case here de- 

 scribed, the external ear Iiad ac- 

 quired a distinct motion upward 

 and backward, which was observa- 

 ble whenever Mr. P. — listened to 

 any thing which he did not dis- 

 tinctly hear. This power over the 

 muscles was so great, that when de- 

 sired to raise the ear, or to draw it 

 backwards, he was capable of mo- 

 ving it in either direction. 



This case is not the only one of 

 this description which lias come 

 under my observation ; for another 

 gentleman, Mr. A — , applied to 



This gentleman has 

 forcing air 



me under a similar complaint (but 

 in one ear only), proceeding I'rom 

 suppuration, and producingj the 

 same effects, 

 the same power of 

 through the imperfect ear ; suffers 

 equally from bathing, \i xhe meatus 

 auditorius be unprotected; and 

 feels, even from exposure to a 

 stream of cold air, very considera- 

 ble pain. The only difference I 

 could observe was, that in Mr. A's 

 case, the defect of hearing in the 

 diseased organ was somewhatgreater 

 than in the former; for though, 

 when his sound ear was closed, he 

 could hear what was said in a com- 

 mon tone of voice, yet he could not 

 distinguish the notes of a pianoforte 

 at the same distance : a difference 

 which might have in part arisen 

 from the confused noise which is 

 always produced by closing the 

 sound ear ; or because, as he heard 

 well on one side, the imperfect ear 

 had remained unemployed, and 

 consequently had been enfeebled 

 by disuse. 



From these observations it seems 

 evidently to follow, that the loss of 

 the membrana lympani in both ears, 

 far from producing total deafness, 

 occasions only a slight diminution 

 of the powers of hearing. 



Anatomists, who have destroyed 

 this membrane in dogs, have as- 

 serted, that at first the effect on the 

 sense of liearing was trivial ; but 

 that, after the lapse of a few 

 months, a total deafness ensued. — 

 Baron Haller also has said, that if 

 the membrane of the tympanum be 

 broken, the person becomes at first 

 hard of hearing, and afterwards 

 perfectly deaf. But, in these in- 

 stances, the destruction must have 

 extended farther than the membrajia 

 tjmpani; and the labyrintli must 



