132 UNIVERSITY OF MISSOURI STUDIES 



the other, and every movement of the head would greatly alter 

 these conditions ; while the resulting consciousness would be, 

 of course, the sum total of the tones heard by each ear. It 

 is unnecessary to point out in further detail how this fact of 

 hearing with two ears complicates the comparison of experi- 

 mental results with the theoretical deductions of the present 

 study, which refer only to one stirrup and one inner ear, and 

 to an unalterable form of the components of stirrup movement 

 in a given case. 



The fact that we have two ears would be irrelevant only 

 with exceedingly high tones, whose wave lengths in air would 

 be so small as to be negligible quantities in comparison with 

 the distance between our ears, as the wave lengths of light 

 are negligible quantities in comparison with the distance be- 

 tween our eyes and even with the sensory elements of each 

 eye. 



Every one is familiar with the comparative clearness with. 

 which the ticking of a watch or the sound of a tuning fork 

 is perceived if the vibrating body is firmly 

 Hearing without pressed on the head or against the teeth, 

 the ear drum Some believe that the physiological func- 



tion of the ear in such a case is not essen- 

 tially different from hearing under ordinary conditions ; that the 

 sound waves, the rhythmic changes of molecular density, which 

 pass through the head, naturally pass also through the cavities 

 of the head, of which one, the middle ear, particularly concerns 

 us here. As soon as rhythmic changes of density occur in 

 the air of the middle ear, the tympanum adjusts itself to them 

 by rhythmically moving back and forth. The stirrup cannot 

 help following the tympanum, and so on. The only difference 

 between this case and a case of ordinary hearing consists 

 in the fact that the changes of density of the air affecting 

 the tympanum originate on the inside of the tympanum in- 



