MECHANICS OF THE INNER EAR 19 



There is only one way of deciding for our present pur- 

 pose the question as to the elasticity of the basilar mem- 

 brane. We must recall our knowledge 

 Is the basilar °f tne elastic properties of similar mem- 



membrane elastic? branous tissues which are found in divers 

 parts of the human body and elsewhere 

 in the organic world. Now, we know that there are plenty 

 of membranes in the body which, when stretched within 

 certain limits, show a tendency to return to the original 

 shape. But they never remain in a stretched condition, that 

 is, under tension, for any length of time. Indeed, they would 

 become permanently lengthened if they remained thus. This 

 is the consequence of a universal biological law. We may, 

 for instance, bend a sapling and expect it to straighten itself 

 as soon as we let it go, because of the elasticity of the 

 stretched tissues of the convex side and the compressed tis- 

 sues of the concave side. Btit if we tie it in this bent po- 

 sition to another tree and return after a year and cut 

 the tie, we find that it has adjusted itself to the position 

 we gave it. This biological fact does away at once with cer- 

 tain theories found quite frequently in physical and other 

 textbooks, \vhich speak of the basilar membrane as con- 

 sisting of a great number of stretched strings, comparable 

 to the strings in a piano. These theories assert, after having 

 introduced, in opposition to the laws of biologv, the idea 

 of a permanent, constant tension of the basilar membrane, 

 that these different strings — as in a piano — are under different 

 tension and differently weighted and that they serve accord- 

 ingly as resonators, responding sympathetically to the va- 

 rious sounds of the external world. However prettv this 

 theory of "the piano in the ear" may appear, authors who 

 expect their readers to accept it as the truth should first of all 

 try to convince them of the possibility of living animal tissues 

 retaining their tension for anv length of time instead of ad- 



