MECHANISM OF VOICE. 235 



necessary for voice ; the superior vocal cords should be con- 

 sidered simply as a means of perfection in regard to the 

 variation and modulation of sounds. 



Haller thought the epiglottis had no influence on voice, 

 but that it permitted the swelling of the sounds into grave or 

 acute without changing the tone, as did also Magendie and 

 Biot. Longet thinks that it assists in the expulsion of the 

 air by the nasal fossae in the production of very acute 

 sounds, and that it may contribute to the timbre of the voice. 



The part of the pharyngeal, buccal, and nasal cavities in 

 the production and modification of sound is differently stated 

 by different authors. Savart thought that they regulated the 

 height of vocal sounds ; they have been considered as sup- 

 plementary apparatus, and that it is to their peculiar reson- 

 ance that the quality of the voice is due. 



The invention of the laryngoscope, by enabling us to see 

 the interior of the larynx, has given us exact notions of its 

 function. It enables us to verify the changes of form, the 

 appearance of the glottis at different ages, and during the 

 emission of the voice. This method of studying the larynx 

 has resulted in late years in works of the greatest interest. 



M. Fournie considers the larynx as a membranous reed- 

 instrument, and the mechanism of the voice, according to 

 this learned observer, is as follows: The vocal cords pro- 

 duce the sound by their vibration, but do not vibrate in their 

 totality. Fixed in front and at the back, at the level of their 

 free border, they may be separated by the air, but not caused 

 to vibrate in their entire thickness, while the mucous mem- 

 brane which covers their free border, and which adheres only 

 very slightly, detaches itself under the influence of the passing 

 air, and thus forms the free vibrating portion of the reed. 

 On this part only of the larynx the epithelium of the mucous 

 membrane is of the same nature as that of the membranes 

 in the other parts of the organism which are subjected to 

 constant friction, as those of the articulations for example, 

 and this gives it the power of resisting the friction of the air 

 and of the vibrations which it causes. In the emission of 

 the voice the vocal cords are stretched lengthwise and 

 breadthwise. By producing mechanically this double tension 



