11J19] on The Organ of Hearing from a New Point of View 511 



is decreasing. Each phase of a sound wave produces a definite action 

 on the hairlets or levers, and thus gives rise to a separate signal or 

 nerve message. 



Sir Thomas Wrightson's original discovery, announced in 1876, 

 was the recognition of the fact that, if it could be supposed that each 

 phase of a sound wave did give rise to an effective stimulus in the 

 ear, then the brain was supphed, through the ear, with a sufficiency 

 of data to give a complete analysis of the most complex sound, 

 lielmholtz had supposed that such an analysis could be accom- 

 phshed only on the principle of resonance ; Sir Thomas AVrightsou 

 sliowed that there was an alternative method, one in which the 

 cochlea acts as a whole, weighing and registering the pressures 

 produced by sound waves. 



That each phase of a sound wave is effective in producing a 

 distinctive movement of the auditory hairlets was a later discovery, 

 but forms a very . essential part of Sir Thomas Wrightson's theory. 

 It was a sequel "^to a neglected discovery of Sir William Bowman's, 

 made somewhere about the year 1846, that the basilar membrane is 

 composed of two parts — a striate zone and a hyaline zone ; the hyaline 

 zone resembles the capsule of the lens in structure and in staining 

 reaction, and must be regarded as elastic in nature. Sir Thomas 

 Wrightson has demonstrated that the displacements which sound 

 ^\aves set up in the fluids w^ithin the ear act against the elastic 

 resistance of the basilar membrane, and that thus each of the four 

 phases of a sound wave, which he had originally postulated on 

 theoretical grounds, do thereby become effective in producing a 

 separate and distinctive movement of the hairlets. In Prof. Keith's 

 opinion the various parts of the cochlea, of the organ of Corti and the 

 conformation of the various hquid passages of the ear, which were 

 left unaccounted for on Helmholtz's theory, now receive a satisfactory 

 explanation. He was also convinced that when physiologists, 

 psychologists, and aural surgeons have mastered the details of the 

 neV theory they will find themselves provided with clues to phenomena 

 whicli were formerlv inexplicable. 



[A. K.] 



