158 Irving Hardesty 



elements) of the organ of Corti resting upon the vibratory fibers should 

 be able to move up and down independently, but it is usually inferred 

 that both rods of the arch must rest upon the basilar membrane through- 

 out the extent of the cochlea. .In all of my vertical sections of the 

 cochlea of the pig, and Shambaugh notes the same in his preparations, 

 usually throughout the basal coil the feet of the inner rods of Corti do 

 not rest upon the supposedly vibrating basilar membrane, but reach over 

 to stand upon the thicker edge of the labium tympanicum. Ter Kuile, 

 '"00, recognized this, but made use of it to assume that contact of the 

 hairs of the hair cells against the tectorial membrane during stimulation 

 is not in a vertical direction, but occurs as a lateral, inward brushing 

 motion, the outer rods alone being moved by the vibrations of the 

 membrane while the inner rods merely act as fulcra in producing the 

 brushing motion. This assumption gains nothing but an increase in 

 the complexity of the resonance theory, since, above the basal coil, the feet 

 of both rods do rest upon the supposedly vibrating portion of the basilar 

 membrane. It is fairly well indicated from clinical evidence that the 

 nerve fibers from the basal coil mediate sensations of notes having the 

 higher pitch, and ter Kuile's assumption merely adds the anatomically 

 improbable condition that the neuro-epithelium is agitated by these 

 higher notes in a different way than it is by the lower notes supposedly 

 affecting the coils toward the apex. 



(7) To the anatomist, given structures in a given species of animal 

 are strikingly identical in character. For example, all cochleae of normal 

 individuals of a given species are strikingly alike in all details. 



The power of tone perception and tone distinction by different indi- 

 viduals is not as constant and uniform as would be expected with the 

 apparently constant anatomical mechanism for the mediation of sound. 

 Individuals without special training (habits) differ markedly, and it is 

 well knowTi that the "trained ear" in any special direction shows a far 

 greater power of analysis of sound and distinction of smaller differences 

 of tone than the untrained. Most of the investigators of the ph5'-siology 

 of hearing, including Helmholtz, recognize this and usually try to 

 obviate it by assuming modifications in the mechanism of the cochlea. 



More probably, as in all the other senses, the whole question of analysis 

 of stimuli and the power of finer perception, inherent or acquired by 

 education, must be transferred from the peripheral or receptive 

 mechanism to the central nervous organ. Just as in touch or smell 

 or sight, so in hearing, all being physiologically similar, the variety of 



