ACTION OF THE TECTORIAL MEMBRANE 495 



end of each of the heavier wires was attached a piece of copper 

 wire of the same size as that interlooped with the platinum wire 

 above. Thus, a battery interposed between these two copper 

 wires would make possible an electric circuit which could be 

 made and broken at the contacts between the platinum wire 

 and the copper plate by vibrations of the artificial tectorial 

 membrane. Figure 5 shows a battery (B) interposed in the 

 circuit of the sixth interval, the circuit of the part of the model 

 representing the apical end of the cochlea. 



The object of the similar arrangements of the wires at the 6 

 intervals was for the experimental determination of the behavior 

 of the different regions of the tectorial membrane toward a given 

 form of vibratory activity imparted to the fluid in the model at 

 its basal end (BE). In addition to the necessary use of an 

 ordinary switch (S, fig. 5) in the electric circuit, a simple electric 

 signal-marker (SM, fig. 5) such as is used in physiological labora- 

 tories, and a telephone (TEL) were interpolated for use in observ- 

 ing results. A small piece of white paper was glued vertically 

 on the end of the vibrator of the signal-marker that vibrations 

 in it could be more easily seen. The noise of the horn (H) 

 usually obscured its clicking to the ear of the observer. The 

 telephone was found to be far more efficient than the signal- 

 marker used. It gave evidence of vibrations of all frequencies 

 whatever induced in the model with sufficient force and ampli- 

 tude to make and break the circuit, while the signal-marker was 

 found incapable of recording the higher vibration frequencies 

 of which the model was capable. In other words, with the 

 application of sounds of higher vibration frequencies, there could 

 be heard a continuous buzz in the telephone when the vibrator 

 of the signal-marker was practically motionless. An ordinary 

 telegraphic 'sounder' was tried in the earlier stages of the experi- 

 ments but had to be discarded because found capable of service 

 only with vibrations of lower frequencies. 



Before the use of the electric current was suggested, small 

 mirrors were tried with the hope that vibratory activities could 

 be read in the behavior of the small spots of light reflected by 

 them. Thin circular cover-glasses were silvered on one side 



