326 TEANSACTIONS LIVEEPOOL BIOLOGICAL SOCIETY. 



1. The changes produced within the cochlea by one 



inward movement of the stapes followed by its 

 immediate return to its position of rest. 



2. The changes produced by two such double move- 



ments. 



3. The changes produced by a long series of such 



movements at equal intervals of time — as by the 

 impact of the sound-waves due to the sounding 

 of a constant pure tone. 



4. The changes produced by the simultaneous action 



of two such series of waves due to sounding two 

 notes in harmony. 



5. The corresponding problem in the case of discordant 



tones. 



Problem I. Changes produced within the cochlea by 

 one double movement of the stapes {in, then out). 



The stapes, and of course the fenestra ovalis in which 

 it is embedded, moving inwards, the rotunda must on the 

 foregoing assumptions move outwards simultaneously. 

 This involves movement of the fluids between. This 

 movement is interfered with by the membranes lying 

 between the two scalae, upper and lower {i.e., scalae 

 vestibuli et tympani), of the walls of which they form 

 parts, and the displacement of these membranes together 

 with the subsequent effects of those displacements presents 

 the fundamental and most important problem we shall 

 have to consider. 



For convenience the cochlea will be regarded as a spiral 

 with its axis vertical and the apex at the top : the basal 

 region is then the region where the fenestra are placed : 

 the three scalae, tympani, media and vestibuli become 

 the lower, middle and upper canals and the basilar and 

 Keissnerian membranes become the lower and upper 

 membranes respectively. Movement along a canal will 



