288 AYERS. [Vol. VI. 



most intense, penetrating, or irritating) on the nervous system, 

 we recognize that the old idea of a gradual ascent from the 

 lower to the higher notes, or vice versa, as the case might be, 

 is probably incorrect, for it would give as much prominence to 

 the low notes as to the high ; in fact, the relation of the differ- 

 ent tone-perceptive structures was supposed to be very like the 

 relation of the keys of a piano. If, however, the length of the 

 auditory hair determines the selection of the stimulus to be 

 transmitted, then, as it is certainly an anatomical fact that the 

 length of the hairs of the organ of Corti vary from the middle 

 towards both ends, — growing shorter each way, — it follows 

 that it must be a physiological fact that the waves productive 

 of the lowest audible sound affect the hairs of the centre of the 

 organ, while those affecting the hairs of the two ends of 

 the organ of Corti as surely are the highest audible tones, 

 the intermediate portions of the organ being affected by the 

 audible intermediate tones. Thus we find an explanation in 

 the anatomy of the ear for the long-known but never explained 

 or understood fact that the lower end of the tone series 

 falls off very rapidly in the distinctness and separateness of 

 its audible tones (because it has only one-half as many per- 

 ceptive structures for its lowest tones), while the higher end 

 of the tone series disappears much more slowly for a similar 

 reason. 



The vibrations are taken up from the fluid by the free ends of 

 the auditory hairs, and transmitted in the form of undulations 

 to the basal plate of the hair cells ; but since I have shown the 

 basal plate to be not a homogeneous structure, but merely a 

 perforated cell end wall, there is no break in the continuity of 

 the undulatory motion, but only a transformation of the form 

 of the wave, i.e. b. reduction in the extent of the excursion, with 

 the consequent result of an increase in the energy of the undu- 

 lations transmitted through the perforations of the end plate and 

 the cell protoplasm, to the, and perhaps through the, nucleus, to 

 the nerve ends at the base of the cell. It is not likely that the 

 hair fibrilli are changed in their progress through the nucleus. 

 The undulations are passed down the hairs in several ways, the 

 most common and perhaps powerful being as waves, causing the 

 hairs to bend in a plane perpendicular to the surface of the organ 

 of Corti, at the point of insertion of the hair cells. There are 



