MECHANICS OF THE INNER EAR 



23 



We have thus far taken into consideration only a single 

 movement of the stirrup, in either direction. We must now 

 study the result of a rhythmical movement 

 of the stirrup, back and forth, a number of 

 times during a certain length of time. In 

 order to have a definite case before our 

 mind we will suppose the stirrup to move 

 back and forth in such a way that it will 

 describe a sine curve on a board moving 

 parallel to the plane of the paper. In fig- 

 ure 8 is represented a single period of such a curve in a hor- 

 izontal position. It is not necessary, however, to imagine this 

 definite curve. What we shall have to say will apply equally 

 to any simple periodic movement, whether of the form of a 

 sinusoid or of a combination of straight lines or of any other 



Stimulations of 

 the brain resulting 

 from a given 

 rhythmical 

 movement of 

 the stirrup 



Fig. 8. A curve representing stirrup movement 



curve connecting each maximum with the preceding and the 

 following minimum. The question arises then by what means 

 — computation, simple description in words, or otherwise — ^we 

 can obtain a clear and sufficiently detailed view of the move- 

 ments of the partition. What we want to know is the form 

 of motion for each point of the partition, and the temporal 



