SENSE AND SPEECH IN MAN. 249 



precisely right and left to its fellow, or to the axis. The little 

 shelves in the ampullar dilatations at the ends of these canals 

 lie in three rectangular planes to each other. The antero- 

 posterior canal has its shelf horizontal. The posterior has its 

 shelf facing forwards and backwards. The shelf of the ex- 

 ternal or horizontal canal faces right and left. 



h, The horizontal position, which appears essential to the 

 efficiency of the semicircular canals, and is a marked feature 

 in man, is provided for in the head of the animal by the same 

 chances which render its visual axis horizontal. 



*e>" 



4 — Voice. 



a. The human larynx is characteristically simple and com- 

 plete in its arrangements. Its special characters are the 

 mobility of the arytenoid cartilages, the complex curvatures 

 of the crico-arytenoid articulations, and the total absence of 

 any superadded acoustic arrangement. The perfection of its 

 structure is evinced in the purity of its tones, and the extent 

 of its intonation. The erect attitude in man, by which the 

 lungs are brought beneath, and the air sinuses of the head 

 above the larynx, and, in addition, the vertical position of the 

 organ itself, all conduce to the perfection of the mechanism of 

 the human larynx. 



b. The cochlea is apparently the structure which controls 

 the action of the larynx. Loth structures are co-ordinated in 

 the most remarkable manner with the aesthetic phases of the 

 human conscious principle. They appear ;ilso to be intimately 

 associated, through connections of the ear and the brain, with 

 the higher forms of associated muscular action. In playing 

 mi musical instruments, the wonderful power of manipulation 

 which can be attained is nol ;i mere habit. It is due to ;i 

 positive nervous mechanism connected indirectly with tin' 

 organ <>l hearing. 



