the Mode in which it administers to the Perception of Sound. 375 



tympanal membrane. If this assumption were true, therefore, 

 Valsalva's experiment would occasion deafness rather than re- 

 move it. 



V. As a particular instance under the last head, we may take 

 the case where the tympanal membrane is relaxed. 



The deafness hence arising is known to be temporarily relieved 

 by Valsalva's experiment ; and that it is so may be explained 

 in this way : — When a rarefied wave is incident, its effect will be 

 immediately to move the tympanal membrane outwards ; but, on 

 account of the relaxed state of the membrane, the effect will not 

 be immediately to move out the stapes, the moving oat of which 

 is essential to produce the sensation of sound. Before this latter 

 effect can be produced the membrane must be moved outwards 

 until it becomes tightly stretched ; and when it is so stretched, 

 and not till then, the stapes will begin to move outwards. We 

 may thus see how relaxation of the membrane diminishes the 

 hearing-power. 



VI. In contrast with the foregoing may be taken the following 

 case related by Meniere*: — "An old judge had been accus- 

 tomed for at least sixteen years, by pressure of a blunt gold 

 needle against the membrana tympani, to make himself, for an 

 hour or so, a tolerably good hearing-power. Meniere examined 

 the ear during this state of things, found the membrana tympani 

 uninjured, and that the pressure was made upon the handle of 

 the malleus, which was pressed somewhat inwards. He speaks of 

 having seen several similar cases, and considers them cases of ner- 

 vous deafness, which were improved to a certain degree by pressure 

 upon the ossicula auditus, and through them on the labyrinth." 



I think there can be no doubt that the explanation here sug- 

 gested (if it can be called such) is erroneous. In elucidation of 

 the case before us, I give the following passage from Dr. Bren- 

 nan's article on Elasticity, in the Cyclopaedia of Anatomy and 

 Surgery f:— 



" When the disturbing force .... is slowly applied, there ap- 

 pears to exist some degree of elasticity, even in fibrous mem- 

 branes ; thus in hydrops articuli the structures about the joint 

 are frequently much distended by the accumulation of fluid 

 within, upon the absorption of which they slowly resume their 

 proper condition." 



The true explanation of the case in Meniere I take to be, that 

 in the undisturbed state of the patient's ear, before the applica- 

 tion of the needle, the tympanal membrane was unnaturally tight- 



* The citation which follows in the text is taken from an American 

 translation of Von Troltsch's Lectures, Philadelphia, 1864. 



t The passage here cited immediately follows the statement as to the in- 

 elastic character of fibrous membrane quoted in my former paper. 



