330 TRANSACTIONS LIVEBPOOL BIOLOGICAL SOCIETY. 



occur in the opposite direction. The upper and lower 

 canals communicate freely at the apex of the spiral and if 

 the displacement of the stapes were infinitely slow the 

 flow would be a steady one alike in all parts of each 

 canal, i.e., during advance of the stapes it would now 

 forwards (i.e., towards the apex) in the upper and back- 

 wards in the lower canal. Or if the basilar membrane 

 were perfectly rigid the same result would follow. 



With a rapid movement of the stapes and with a 

 yielding though highly elastic basilar membrane the case 

 is very different : the inertia of the whole column of fluids 

 in both canals prevents their sudden movement and only 

 the basal portion is moved first, the rest being only 

 subsequently set in movement by the elasticity of the 

 membrane called into action by its displacement. 



The figures 1 and 2 and the constant reference to the 

 elasticity of the displaced membrane are liable to suggest 

 a longitudinal tension comparable with that of a vibrating 

 string. There is, however, practically no such longitudinal 

 tension. The stretched fibres lie transversely in the 

 membrane, and each stretched portion of the membrane 

 acts on adjoining parts of the membrane only through the 

 intermediation of the incompressible fluids in which the 

 whole membrane is immersed, fluids which are prevented 

 from moving transversely by the rigid walls of the canals. 

 We have here the conditions necessary for transmission 

 of a wave-like disturbance : we have indeed conditions 

 which render such a transmission inevitable. The con- 

 ditions at C for instance are precisely those which at an 

 earlier moment obtained at B and will in a moment later 

 hold at D. The whole of the conditions are such as must 

 give rise to like conditions in an adjoining portion of the 

 membrane further forwards. That is the disturbance will 

 of necessity give rise to a like disturbance in every 



