256 AVERS. [Vol. VI. 



Our author further says (p. 151) : "If we maintain that every 

 nervous fibre hears in its own special pitch, we should have to 

 conclude that the vibrating parts of the ear, which convey these 

 sensations of the highest tones to the ear, are much less sharply 

 defined in their capabilities of resonance than those for deeper 

 tones. 



" This means that they lose any motion excited in them com- 

 paratively soon, and are also comparatively more easily brought 

 into a state of motion necessary for sensation. This last as- 

 sumption must be made, because for parts which are so strongly 

 damped the possibility of adding together many separate im- 

 pulses is very limited, and the construction of the auditory cilia 

 in the little bags of otoliths seems to me to be more suited for 

 this purpose than that of the shortest fibres of the basilar 

 membrane. If this hypothesis is confirmed, we should have to 

 regard the auditory ciha as the bearers of squeaking, hissing, 

 chirping, crackling sensations of sound, and to consider their 

 reaction as differing only in degree from that of the cochlear 

 fibres." 



The vibrations of the membrana basilaris cochleae Helmholtz 

 describes in the following manner : — 



"The mechanical problem here attempted is to examine 

 whether a connected membrane with properties similar to those 

 of the membrana basilaris in the cochlea could vibrate as Herr 

 Hensen has supposed this particular membrane to do ; that is, 

 in such a way that every bundle of nerves in the membrane 

 could vibrate sympathetically with a tone corresponding to its 

 length and tension, without, being sensibly set in motion by the 

 adjacent fibres. For this investigation we may disregard the 

 spiral expansion of the basilar membrane and assume it to be 

 stretched between the legs of an angle of the magnitude of 277." 



Here follows an extended mathematical computation of the 

 amount of vibration of such a membrane, for which the reader 

 is referred to Helmholtz's treatise. 



The membrane assumed is perfectly uniform in structure in 

 all its parts, is tensely stretched in one direction, its transverse, 

 but not so in its longitudinal direction. Under the conditions 

 of the calculations (which Helmholtz assumes may be those 

 conditioning the cochlear organ), each simple tone sets in vibra- 

 tion only some narrow strips of the membrane in the direction 



