C. GENERAL PHYSICS. 193 



ilar membrane, the only cords in the ductus which enter 

 into vibration are those in tune with the elementary vibra- 

 tions existing in the membrane. Also, it is to be observed 

 that as the loaded string makes only one vibration to two of 

 the membrane, so the cord in the ear makes only one vibra- 

 tion to two of the basilar membrane, or of the membrane of 

 the drum of the ear. 



Reaching this curious inference, Professor Mayer, in order 

 to bring his supposition to a rigid experimental test, reasoned 

 in the following manner : If it be true that when simple vi- 

 brations impinge on the ear the tympanic and basilar mem- 

 branes vibrate twice while the stretched cord in the ear vi- 

 brates only once, then it follows that if we hold a vibrating 

 tuning-fork near the ear, and clearly apprehend the charac- 

 ter of its sound, we will have a sensation which corresponds 

 to that usually designated as the pitch of this fork; and this 

 sensation does not contain in it a sound corresponding to 

 the higher octave of the' fork. In this experiment, accord- 

 ing to Professor Mayer, the auditory nerve fibrils made half 

 as many vibrations per second as did the prong of the fork 

 and the tympanic membrane. But if the vibrations of this 

 fork be sent directly into the inner ear through the bony 

 parts of the temporal bone, by placing the foot of the fork on 

 the zygomatic process, close to the ear, or on the mastoid 

 bone behind the ear, we will, according to his hypothesis, vi- 

 brate the auditory nerve fibrils as often as the fork vibrates, 

 and therefore, in this second experiment, the sound of the 

 fork should rise one octave in pitch above what was perceived 

 when the fork vibrated the air outside of the head. This ex- 

 periment has been repeatedly tried by many persons, and it 

 always gives the result predicted by Professor Mayer, as a 

 necessary consequence of his reasoning on the mode of audi- 

 tion. Among others who have confirmed this remarkable 

 deduction, is Madame Seiler (whose educated musical ear as- 

 sisted Helmholtz in his delicate researches in physiological 

 acoustics), who bears testimony to the above fact, first dis- 

 covered by Professor Mayer. 



Professor Mayer ends his paper on this subject as follows : 

 "The fact that sound pulses sent into the inner ear through 

 the head give the sensation corresponding to the higher oc- 

 tave of that perceived when the fork vibrates the air outside 



I 



