MECHANICS OF THE INNER EAR 43 



thirteen, and eleven, according to the number of sections which 

 receive the greater or smaller number of shocks. 



Let us now apply the second graphic method to another 



given movement of the stirrup, which will make clear to us 



another interesting property of the ear with 



_..„ r respect to the manner in which this or- 



Difterence of *^ . n^, 



phase Charac- S^^ analyzes an objective sound. The curve 

 teristic curves of the stirrup (Fig. 14) is made up of 



of a tone combi- two component curves, very similar to the 

 nation curves composing the last curve discussed. 



That is, each of the two components is ap- 

 proximately a sinusoid, one of a period equal to two thirds of the 

 other's period, both of approximately the same amplitude. The 

 resultant curve is constructed here as before by measuring 

 and adding together the ordinate values of the components 

 in the drawing. The difference between the present case and 

 the last case discussed is a difference of phase. If the reader 

 should not know what this means, it can be easily understood 

 by the aid of figure 14. We find there two sinusoids, one with 

 two and one with three maxima within the same period, which 

 accordingly may be called curve two and curve three. Now 

 imagine curve two moved slightly to the right until the 

 minima at the extreme right and also the mimma at the ex- 

 treme left coincide. We then have exactly the case discussed 

 above; that is, the addition of the two curves would result 

 in a compound curve as represented by figure 11. The curves 

 of figure I'l and of figure 14 may be called the characteristic 

 curves of the ratio 2 : 3, because they are the two extreme forms 

 between which the compound curve changes as the result of 

 a change of phase, that is, of a lateral movement of curve two, 

 while curve three remains stationary. Let us convince our- 

 selves here that there are no more than two characteristic 

 compound curves. If we move curve two again slightly to the 

 right, the same distance as before, that is, one twelfth of the 



