508 Professor Arthur Keith [March 14, 



WEEKLY EVENING MEETING, 

 Friday, March 14, 1919. 



Sir James Crichtox-Browne, J.P. M.D. LL.D. D.Sc. F.R.S., 



Treasurer and Vice-President, in the Chair. 



Professor Arthur Keith, M.D. LL.D. F.R.S. F.R.O.S. M.R.I., 



Fullerian Professor of Physiology. 



The Organ of Hearing from a New Point of View. 



According to the theory put forward by von Helmholtz in 1863, 

 the internal ear may be regarded as a microscopic piano, furnished 

 with resonating strings, almost ultra-microscopic in size, and some 

 1 6,000 in number. Each string or set of strings is supposed to pass 

 into a state of vibration when its sympathetic note enters the ear. 

 Each string or set of strings is supposed to have a corresponding 

 nerve-fibre, which is stimulated by the vibrations and carries them 

 towards the brain as nerve messages. We must also suppose that 

 these nerve-fibres lead ultimately to a central nerve-cell siation or 

 exchange, where 16,000 nerve-cells receive messages from their 

 corresponding ear strings. The sorting out and recognition of the 

 messages streaming on from the various strings must fall, even if 

 Ilelmholtz's theory is accepted, on central nerve exchanges. However 

 satisfactory from the point of view of the pure physicist, Helmholtz's 

 theory of the ear from the point of view of the psycliologist, physio- 

 logist, or the anatomist, is an impossibility. The strings are present 

 in the internal ear, but they are so placed and so conditioned that the 

 one thing they cannot do is to vibrate ; Nature has taken the utmost 

 care to render individual vibration an impossibility. In a theory first 

 put forward by Sir Thomas Wrightson in 1876, and recently 

 elaborated in his treatise on the " Mechanism of the Internal Ear " 

 (1918), the cochlea is supposed to act as a single machine ; he has 

 shown it to be the most minute and most delicately adjusted spring 

 balance ever evolved or invented— one designed not only to weigh 

 the simplest and sUghtest sound w^ave but also the most complex 

 and voluminous. The ear not only weighs every fluctuation in 

 pressure but automatically registers and records the minutest variation, 

 and through the hair-cells or semaphores w^hich form an intrinsic 

 part of the machine the system of messages or semaphoric signals 

 transmitted from the ear may be compared to the dot-and-dash 

 system of the Morse code. The whole of the organ of Corti is 

 involved in the production of this code of signals ; all the fibres of 



