420 THE BODY AT WORK 



a correspondingly limited number of elementary sensations. 

 The ideal of those who take this view is an octave of qualities 

 and of elementary sensations sounded in the middle of the 

 scale when x nerve-endings are stimulated, as the octave above 



/y 



when 2x nerves respond, the octave below with -. Such a 



conception seems to guide thought round insurmountable 

 barriers. There is, however, a risk of making too much of the 

 periodic intervals, because they take so important a place in 

 music. At one side of the gap which sound bridges between 

 the individual and his environment is an elastic body shaking 

 at any possible rate within the range of hearing. At the other 

 side of the gap is the ear. If, having arranged several thou- 

 sands of stones along the side of the road in order of size, I 

 were to state, picking up No. 512, " This is the fundamental 

 of which No. 1,024 is the octave," answer would be made to 

 me : " It may be that the larger could be broken into halves, 

 each as heavy as the smaller stone ; but I recognize no differ- 

 ence between the stones in shape, colour, or hardness." A 

 vibrating string divides into equal segments, each of which 

 vibrates within the vibrations of the whole string, sounding the 

 octave. We recognize a similarity in quality between tones 

 and their octaves because we are accustomed to hear the 

 octave, the most prominent of overtones, in all musical sounds. 

 Hence, from association, it has become more difficult to dis- 

 tinguish a note from its octave than it is to distinguish it from 

 its fifth ; but it does not follow that the effect of 1,024 vibrations 

 upon the sensory cells more nearly resembles the effect of 512 

 than does that of 768. But at this point we are compelled to 

 construct some hypothesis as to the way in which the vibra- 

 tions affect the sensory cells. The protoplasm of the cells 

 is not directly sensitive to them. We can account for the 

 generation of impulses in the nerve connected with a par- 

 ticular cell, or group of cells, only on the supposition that a 

 resonating mechanism which responds to vibrations of a certain 

 frequency shakes the cell! Even then it seems necessary to 

 suppose that there is an accessory mechanism which disturbs 

 the cell protoplasm sufficiently to render the shake effective, 

 probably the hairs rubbing against the tectorial membrane. 

 Anatomical study gives us no confidence in the theory of the 



