of the Membrana Tympani. 363 



the a'r in the meatus being compreffed upon the membrana 

 tympani. In tbe cafe here defcribed, no fuch fenfation was 

 produced : for, in Mr. P.'s ear, the air, meeting with no 

 impediment, could fuller no compreffion ; fince it found a 

 patfage, through the open membrane, to the mouth, by 

 means of the Euftachian tube. 



Mr. P. was liable to the fenfation commonly called the 

 teeth being en edge, in the fame degree as it exiits in others; 

 and it was produced by fimilar acute founds, as by the filing 

 of a faw, the rubbing of filk, &c. Its occurring in him 

 feems to difprove the idea which has been entertained of its 

 caufe; for it has been thought, that the clofe connection of 

 the nerve called the corda tympani with the membrana tym- 

 pani, expofed it to be affected by the motions of the malleus ; 

 and that, as it pafles to nerves connected with the teeth, 

 they would fufler from the vibratorv ftate of the nerve, pro- 

 duced by the agitations of the membrane. But, in this cafe, 

 as the membrane was entirely deftroved on that fide on w :h 

 the fenfation was produced, fome other explanation muft be 

 reforted to; and I fee no reafon why this efti -el fliould not 

 be referred to that part of the auditory nerve which lines the 

 labyrinth of the ear, which, being imprefled by acute and 

 difagreeable founds, would convey the impreflion to tlie 

 portio dura of the fame nerve, and to the teeth with which 

 that nerve is connected. 



The external car, though two diftincl: mufcles are inferted 

 into it, is capable, in its natural ftate, of little motion: how- 

 ever, when an organ becomes imperfect, every agent which 

 can be employed to increafe its powers is called into action ; 

 and, in the cafe here defcribed, the external ear had acquired 

 a diftincl motion upward and backward, which was ohferv-. 

 able whenever Mr. P. liftencd to anything which he did not 

 diftinctlv hear. This power over the mufcles was fo great, 

 that when defired to raife the ear, or to draw it backwards, 

 he was capable of moving it in either direction. 



This cafe is not the only one of this defcription which has 

 come under my obfervation ; tor another gentleman, Mr. A., 

 applied to me under a fimilar complaint, (but in one ear 

 only.) proceeding from fuppuratioff, aud producing the lame 



effects, 



