AUDITORY SENSATIONS 519 



that represented by the organ of Corti would be sufficient, if no analysis of the stimulus 

 took place in the peripheral organ. 



When a bow is drawn against the edge of a plate the vibrations affect different 

 parts of the plate unequally, so that lycopodium powder sprinkled on such a plate 

 assumes a complicated pattern. Waller suggests that the basilar membrane vibrates 

 as a whole to every tone, but that it presents nodal and internodal points, like the 

 vibrating plate. Since the hair-cells move with the basilar membrane they produce 

 what may be called ' pressure patterns ' against the membrana tectoria, so that different 

 combinations of nerve fibres are stimulated according to the pattern, i.e. according 

 to the shape of the compound wave. A somewhat similar hypothesis has been put 

 forward by Ewald, but neither of these theories presents any advantages over the 

 resonator theory of Helmholtz, nor does it account satisfactorily, as the Helmholtz 

 theory does, for the remarkable powers we possess of analysing all kinds of complex 

 sounds. The cochlea becomes more elaborate in structure as we ascend the animal 

 scale, and there is no doubt that this elaboration attains its greatest height in man, 

 who possesses greater powers of analysing sounds than are possessed by any other 

 animal. 



