450 Prof. A. M. Mayers Researches in Acoustics. 



function ; for while in man they are arranged alternately in five 

 rows and number 18,000, in other Mammalia there are only 

 two or three rows*. These hair-cell cords are more perpen- 

 dicular to the basilar membrane than the Corti rods, and are 

 also different in their forms, having swellings in the middle of 

 their lengths. These swellings must cause them to act like 

 loaded strings ; and hence each hair-cell cord is peculiarly well 

 adapted to covibrate with only one special sound. Also these 

 hair-cell cords are placed in reference to the sound-pulses 

 striking them somewhat in the relation which the antennal 

 fibrils of the mosquito bear to a wave-surface to which their 

 lengths are perpendicular. The hair-ceil cords, therefore, will 

 not be set in vibration by the action of the feeble pulses which 

 may reach them directly through the meoibrana Reissneri from 

 the scala vestibuli ; and, furthermore, the shielding influence of 

 the membrana tectoria tends to prevent this direct action on the 

 cords. 



If my view be correct, that these cords receive their vibra- 

 tions from the basilar membrane, and not directly from the im- 

 pulses sent into the ductus, it necessarily follows that these cords 

 hear, to the membrane to which they are attached, the same re- 

 lation as stretched strings bear to the vibrating tuning-forks in 

 Melde's experiments; and therefore a cord in the ductus will 

 vibrate only half as often in a second as the basilar membrane to 

 which it is fastened. Experiments similar to those described in 

 section 1 of this paper illustrate very well our hypothesis of 

 audition. Thus the membrane placed near the sounding-reed 

 stands for the basilar membrane; strings of various lengths 

 and diameters and loaded at their centres are fastened to the 

 membrane, and represent the hair-cell cords. On sounding the 

 reed-pipe, only those strings in tune with the harmonics exist- 

 ing in the composite sound of the reed will enter into vibration, 

 just as, when the same sound- vibrations enter the ear and vibrate 

 the basilar membrane, the only hair-cell cords which enter into 

 vibration are those in tune with the elementary vibrations exist- 

 ing in the membrane. Also it is to be observed that as the 

 loaded string makes one vibration to two of the membrane, so 

 the hair-cell cord makes only one vibration to two of the basilar 

 membrane. 



* It is to be regretted that no accurate measures of the length and dia- 

 meters of the rods and cords of the organ of Corti have been secured. The 

 outer pillars of the arch of Corti certainly double their length in going 

 from the base to the top of the ductus ; but does this fact point them out 

 as bodies suitably proportioned to covibrate to sounds extending through 

 at least eight octaves ? I know of no measures on the hair- cell cords. 

 When their dimensions are determined, physiologists will be able to give 

 more precision to their hypotheses. - „ .. — - - 





