THE SENSE OF HEARING 



re transmitted to it. This it does by vibrating in unison with them. The 

 ibrations which the membrane exhibits correspond in amplitude, in fre- 

 lency and in form to those of the atmosphere. That this membrane 

 rtuallv reproduces all vibrations within the range of audibility has been 

 xperimentally demonstrated. The membrane, not being fixed as far as it 

 ension is concerned, does not possess a fixed fundamental note like a station- 

 "ry fixed membrane, and is, therefore, just as well adapted for the reception of 

 tee set of vibrations as another. This is made possible by variations in Us 

 ension in accordance with the pitch or frequency of the atmospheric vibra- 

 ions In the absence of vibration the membrane is in a condition of : 



xat'ion- with the advent of sound-waves possessing a gradual increase of 

 as in the ascent of the music scale, the tension of the membrane m- 

 - eases until its maximum is reached at the upper limit of the range of 

 audibility. By this change" in tension certain tones become perceptible and 

 iistinct while others become imperceptible and indistinct 



The Function of the Tensor Tympani Muscle. -The function of this 



.. ...responding , .n mc,,. 



bones is to transmit the effects 01 me atmo P fa d becomes evident 



labyrinth. The manner t uch h hjgjj one another and to the 



and to the fluid of the labyrinth on 



the other. surface of the tympanic membrane 



When P'"^.^ ^^ 1 ^^ handle of the malleus, the 

 it is at once pushed "f^J^mrf around an axis corresponding to its 

 head at the same :t,me rot ^ emove s inward a small ledge of bone 



and hence pushes mwa - 



