MECHANICS OF THE INNER EAR 87 



The second of our provisional assumptions is that the 

 partition is perfectly inelastic, that is, not offering any re- 

 sistance to a displacement until either of 

 The second ^^^ limits is reached, and then offering ab- 



provisional solute resistance. Now, does our anatom- 



assumption ical knowledge warrant such an assump- 



recalled tion ? The most striking fact derived from 



an anatomical study of the organ is the 

 absence of any solid body which might serve to interfere sud- 

 denly, abruptly, with a yielding movement of the partition in 

 either direction. Even the analogy with the leather seat 

 of a chair is hardly admissible if we mean thereby a flabby, 

 wrinkled piece of leather. The analogy probably holds good 

 only if we imagine the leather in such a condition as we find 

 it in a new, unused chair, occupying a perfect plane, being 

 practically free, however, from any stresses as long as no weight 

 is resting upon it, yielding to a certain extent if a certain weight 

 is placed upon it, but not yielding in proportion to the weight 

 if the weight is increased. It is probably in a similar manner 

 that the partition resists pressure. What determines the 

 limit of yielding must be the partition's own elasticity. But 

 let us always remember that there is no elastic force — no 

 stress — in the partition while in its normal position, that its 

 elastic force is the result of a displacement in either direction, 

 that this elastic force increases much more rapidly than the 

 displacement, and that therefore a constant increase of press- 

 ure on any point of the partition does not cause a constant 

 movement of this point, but a movement first rapid, then 

 quickly decreasing in velocity. Figure 27 is a graphic repre- 

 sentation of such a function under the arbitrary assumption — 

 which, perhaps, may be regarded as a rough approximation 

 to the actual conditions — that the elastic force of the partition 

 increases proportionally to the tangent of its displacement. The 

 abscissae represent the increasing pressure, the ordinates 



