336 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Problem II. Changes produced within the cochlea by 

 two double movements of the stapes {in then out.) 



If the first wave has already traversed the whole length 

 of the basilar first and then of the Eeissnerian, and finally 

 died out before the second wave is started, the second 

 will obviously pursue the same course as the first and 

 produce only the same effects. This consideration enables 

 us to roughly estimate the average velocity of the waves 

 along the membranes ; for if the time-interval between 

 the two waves be progressively diminished in successive 

 experiments, a minimum period of no physiological effect 

 will ultimately be reached, and as soon as this is passed a 

 sensation of sound is produced. That minimum time- 

 interval of no physiological effect thus corresponds to the 

 time occupied by a single wave in completing its whole 

 course up the basilar and down the Eeissnerian mem- 

 branes. This time-interval differs with different persons, 

 normally ranging between Jth and T yth of a second. 



When the time-interval is less than this the second 

 wave will be started on its journey up the basilar mem- 

 brane while the first wave is still somewhere on one or 

 other of the membranes ; and before the second reaches 

 the helicotrema it must of necessity pass some point on 

 the basilar membrane at the same moment as the first 

 wave passes a point opposite to this on the Eeissnerian. 

 Two points have to be considered in connection with this 

 passing of the waves ; (1) the point at which the passing 

 will occur, and (2) the effects within the organ of Corti 

 which will be produced thereby. 



(1) The velocity of transmission of a wave at any given 

 point of either membrane being constant (as it must be 

 very nearly if the waves are similar to each other), it 

 follows that the distance from the position of the second 

 wave measured along the basilar through the helicotrema 



