ACTION OF THE TECTORIAL MEMBEANE 475 



thrown into vibration by sound waves. (5) Sometimes in the 

 cochleae of the pig, and perhaps other mammals, a part of the 

 organ of Corti in the basal end may rest upon the bony spiral 

 lamina instead of the basilar membrane. 



The idea involved in the telephone theory was first suggested 

 by Rinne in 1865, or about thirty years before the elaboration 

 of the Helmholtz theory. It was more fully worked out by 

 Rutherford in 1886 and since modified by Waller in 1891, Meyer 

 in 1898, Ewald in 1899, Gray in 1900, and others. Originally 

 it assumed that the vibrations imparted effect the cochlea as a 

 whole. Rutherford at first suggested that all the hairs of the 

 hair cells are thrown into vibration by each note and the impulses 

 thus aroused in the cochlear nerve are merely similar in frequency, 

 intensity and quality to the vibration frequency, amplitude and 

 quality of the notes acting upon the apparatus. Therefore, the 

 analysis of sound would be wholly cerebral. This idea that the 

 impulses are aroused by the hairs being acted upon directly was 

 early abandoned by Rutherford and the telephone theory became 

 applied to the basilar membrane and all the later modifications 

 of it have applied it to this membrane. Waller and Meyer 

 assumed that the vibrations as transferred from the tympanic 

 membrane to the endolymph of the cochlea affect the basilar 

 membrane as a whole. Meyer supposed that the wave motion 

 produced by each note, as it passes in the scala vestibuli, affects 

 an extent of the basilar membrane just in the proportion that the 

 amplitude of the vibration is not decreased by the resistance to 

 be overcome in its passing toward the apex of the cochlea. Thus 

 certain wave motions will affect greater extents of the basilar 

 membrane than others and therefore will cause the hairs of a 

 greater number of hair cells to impinge against the tectorial 

 membrane. Waves of lesser amplitudes (intensity), in over- 

 coming the resistance met in passing from the basis of the stapes 

 toward the apex, earlier become too faint to sufficiently agitate 

 the basilar membrane, each note involving an extent of the 

 membrane according to its amplitude or intensity. In this idea 

 pitch depends upon the vibration frequency (the number of 

 stimulations of the hair cells per unit of time) and intensity is 



