ACTION OF THE TECTORIAL MEMBRANE 501 



(1) A structure imitating the tectorial membrane in shape, 

 proportions and environment can be thrown into vibrations by 

 sound waves so appHed that their energy is transferred to the 

 fluid in which the structure lies and in a way similar to that 

 employed in the actual ear. 



(2) With sounds of low vibration frequency, at least, the 

 tectorial membrane is thrown into vibrations of the same fre- 

 quency as those of the sound giving rise to them. This fact 

 was determined by allowing the vibrator of the signal-marker 

 to write upon the drum of a kymograph, on which drum had 

 been already traced the vibrations of a standard tuning fork. 

 With the sound waves of higher vibration frequencies by which 

 the model was capable of being acted upon, the signal marker 

 either did not vibrate at all or acted irregularly. 



(3) With the distance between the copper plates and ends of 

 the platinum wires adjusted, a heavy step on the floor of the room, 

 a slight blow upon the table or a hand laid upon the apparatus 

 would produce vibrations of the artificial tectorial membrane 

 sufficient to cause a series of makes and breaks of the current. 

 This may be advanced as illustrating the possibility by which 

 sensations of sound are aroused by way of other parts of the 

 body than the tympanic membrane, stimuli explained as con- 

 veyed to the bony labyrinth, and thus to the structures within 

 it, directly by way of the skull bones, teeth, etc. Sensations 

 received in this way are among those of lower pitch. 



(4) The model showed slightly less sensitiveness to vibrations 

 imparted to the membrane covering the fenestra cochleae 

 (rodunda) than to the same vibrations applied at the fenestra 

 vestibuli. This slight difference is explained as due to damping 

 out effects or absorbtion of the vibrations by the fluid in the 

 scala tympani before they pass directly into the scala vestibuli 

 by way of the helicotrema at the apex of the cochlea. 



(5) Jarring of the model and notes of low vibration frequency 

 applied to the tympanic membrane by way of the horn, were 

 found to throw the entire tectorial membrane into vibration. 

 This was determined by interposing battery, signal-marker and 

 telephone at each of the regions of the membrane from 1 to 6, 



