340 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



and the top of the organ of Corti. These hairs are stiff 

 and the ultimate fibrils of the auditory nerve terminate at 

 their bases. This means that at the particular point in 

 the length of the organ of Corti where the two waves pass 

 in corresponding phases the ends of the stiff hairs of 

 the hair-cells of the organ of Corti are suddenly thrust 

 down upon the nerve-ends of the auditory nerve-fibres. 

 Physiologists will understand what result will follow. 



Taking a general review of this second problem, the 

 result may be stated thus : When two sound waves im- 

 pinge upon the tympanic membrane at a suitable interval 

 of time, one definite region of the organ of Corti will be 

 stimulated by the thrusting of the hairs of its hair-cells 

 upon the nerve-ends ; and the region to be so stimulated, 

 will be determined wholly by the interval of time between 

 the two sound waves, that is, upon the pitch of the note 

 sounded. 



Problem III. The changes produced within the cochlea 

 by a long series of in and outward movements of the stapes, 

 such as would be brought about by the impact upon the 

 tympanic membrane of the sound leaves produced by the 

 sounding of a constant pure tone. 



If the interval between successive vibrations be of such 

 length that two and only two cochlear waves were passing 

 along the membranes of the cochlea at any one moment, 

 the problem is identical with the previous one. When the 

 intervals are much shorter the problem becomes more 

 complex ; and certain details have to be considered which 

 were for the sake of simplicity omitted from consideration 

 in the previous problem. In the first place there will no 

 longer be one place and only one where the cochlear 

 waves on the two membranes will pass each other in 

 corresponding phases. They will pass at many such places 



