324 TRANSACTIONS LIVEEPOOL BIOLOGICAL SOCIETY. 



enormously long period and enormously great amplitude : 

 the wave length being enormously great as compared with 

 the length of the wire. It is only necessary therefore to 

 point out here that the movements of the base of the 

 stapes follow those of the tympanic membrane but lag 

 slightly behind them : how much they lag probably 

 depends on the wave-length and on the intensity of the 

 sound : the lag is probably less with intense sounds than 

 with fainter ones. It probably amounts to less than a 

 wave-period with low tones and to more than a wave- 

 period with high tones. With very violent waves of long 

 period the elasticity of the displaced membrane, the 

 inertia of the ossicles, and the tension of the muscles and 

 ligaments attached to the ossicles as well as the nature of 

 the joint (saddle-shaped) between the malleus and incus will 

 come into play and reduce the amplitude of displacement 

 to a very small fraction of what it would otherwise be. 

 The scale of relative amplitudes of displacements of the 

 fenestra ovalis will therefore be very much smaller than that 

 of the displacements of the tympanic membrane. Yery faint 

 sounds, in other words, will produce a relatively far 

 greater effect on the ovalis than very loud ones : nearly 

 the whole energy of high tones and of faint sounds will 

 be transmitted to the ovalis, but only a very small fraction 

 of the energy of more violent waves and especially of waves 

 of great amplitude in the absolute sense (e.g. explosion- 

 waves) . This is a highly important protective arrangement 

 and is analogous to the protective action of the iris in 

 the eye. 



The Changes in the Inner Ear. 



The whole inner ear may be rightly regarded as a rigid 

 box with only two yielding areas in its walls and filled 

 with an incompressible fluid. The two yielding areas are 

 the fenestrae rotunda et ovalis, 



