A NEW THEOEY OF HEAKING. 345 



being overpowered by the primary stimulation, until the 

 first region is deprived of its sensitiveness by fatigue. It 

 is theoretically possible to fatigue even the second point 

 and then hear a spurious tone whose wave-length is three- 

 times that of the actual note sounded. Experimentally I 

 have failed to produce this effect and this is probably due 

 to the enormous damping effect of the mechanism of the 

 middle ear upon sounds of such deafening intensity. 



Problem IV. Effects within the cochlea dice to simul- 

 taneous sounding of two continuous mutually harmonious 

 pure tones. 



The effects arising in various parts of the cochlea when 

 two series of periodic movements of the tympanic mem- 

 brane occur simultaneously will differ widely in the cases 

 when the "period" of one series bears different relations 

 to the period of the other. We will consider first the 

 case of two series the periods of which bear a simple 

 relation one to the other. 



We have already seen that a tone due to a vibrations 

 per second may produce a stimulation in the organ of 

 Corti at points a, J a, J a, etc., but that the primary 

 stimulus at a will be by far the most intense. If while 

 this tone is being sounded, the tone | or | be also sounded, 

 even though so faintly as to be in itself inaudible, its cochlear 

 waves may, so far as they happen to coincide with certain 

 waves of the series a so increase the disturbance at 

 | or | (as the case may be) as to render this tone distinctly 

 audible. Similarly if the tone a {i.e., a vibrations per 

 second) be sounded too faintly to be audible, and the tone 

 2a simultaneously sounded so faintly that it would be 

 inaudible if sounded alone, each tone may so cooperate 

 with the other as to render both audible, but not quite in 

 the same way in the case of the two, 



