ON THE PHONOGRAPH. 781 



Assuming that the number of auditory filaments is the same for each of the eleven octaves, which 

 is unlikely, the probability being that there will be fewer for the range below 64 and 

 above 4096. 



1273 x 6 = 7638 for the six octaves under consideration. 



1273 



""To - = 106 fibres for each semitone. 



106 



-~j- = Less than 2 fibres for each fa of a semitone. 



2. Fibres in Membrana basilaris, 24,000. 



24,000 

 — j5 — = 2182 fibres for each octave. 



2182 x 6 = 13,092 for the six octaves under consideration. 

 2182 



12 



= 180 fibres for each semitone. 



180 



-p~r = Less than 3 fibres for each fa of a semitone. 



3. Hair Cells: Inner, 3487; Outer, 11,750 = 15,237. 



15 237 



— j^j — = 1385 cells for each octave. 



1385 x 6 = 8310 hair cells for the six octaves under consideration. 



-y~- = 115 cells for each semitone. 



-ttj- = Less than 2 for each fa semitone. 



4. Corti's Bods : Inner, 5590 ; Outer, 3848 = 9438. 



9438 nM . . 

 ,, =858 rods for each octave. 



858 x 6 = 5148 rods for six octaves under consideration. 



-j= =71 for each semitone. 



71 



^r = at least one rod for each fa semitone. 



As there is a high probability that there are fewer nerve fibres for the five octaves left out of con- 

 sideration, and consequently more in the six octaves tised in music, it folloios that we have in 

 the cochlea a sufficient number of possibly vibratile masses to satisfy the demands of theory. 



29. The view that the cochlea is a differential apparatus is also supported by the 

 fact that careful measurements made of the same parts of the organ in man, the cat, 

 and rabbit show considerable variations, variations that correspond also with all we know 

 of the auditory powers of these examples. These measurements also help to give one a 

 conception of the relative dimensions of different parts of the organ, and, to make this more 

 obvious, I have given a column in which the measurement has been multiplied by one 

 hundred. These measurements have been collected chiefly from the works of Eetzius : — 



a. Lengths of Cochlear portion of Internal Ear in Man, Cat, and Rabbit. 







Membrana basilaris and papilla 

 basilaris. 





Ductus cochlearis. 







mm. inch. 100 times. 



mm. 



inch. 



100 times 



Man, 





35-5 1-42 142 



36 



1-44 



144 



Cat, . 





23-5 0-94 94 



25 



100 



100 



Eabbit, 





15-0 060 60 



16 



•64 



64 



VOL. XXXVIII. PART 



IV 



. (NO. 22). 









5 Q 



