7° 



PHYSIOLOGICAL TRIGGERS 



too extreme or prolonged, is consistent with the hypothesis that the cochlear 

 microphonic depends upon the endolymphatic potential. (We here neglect a 

 small residual anaerobic cochlear microphonic that persists after death and 

 which is evidently generated by some other mechanism.) Our present hypothe- 

 sis specifically attributes the changes in potential, i.e. the cochlear microphonic, 

 to changes in current flow through the hair cells as a result of passive changes in 



MODEL OF 

 COCHLEAR EXCITATION 



"POLARIZED RELAY 

 OR OTHER DETECTOR 

 THAT TRIGGERS THE 

 NERVE IMPULSE 



Fig. 9. The 'resistance microphone' theory of the origin of the cochlear microphonic. In 

 this diagram the 'battery' is hypothetically located in the stria vascularis, as originally pro- 

 posed (6, 7). 



electrical resistance. The observed changes in potential are supposed to be due 

 to changes in the 'IR drop' across the upper ends of the hair cells (7). 



The source of the endolymphatic potential has not been identified. In the 

 first formulation of the present hypothesis, the writer located it tentatively in 

 the stria vascularis, which forms part of the external wall of the scala media, as 

 shown in figure 9. The chief reason for this guess was that here is the richest 

 blood supply, and the endolymphatic potential is very closely dependent on 

 oxidative metabolism. Other evidence, not yet conclusive, seems to point to the 

 hair cells themselves as the source of the endolymphatic potential. If this proves 



