f^62 THE HUMAN VOiCfl. 



LESSON 119. ''-WK' 



The Human Voice. 



£piglot'tis, a small and thin piece of cartilage, placed at the back 

 of the tongue, and having the office of closing the glottis, when 

 the food is passing. 



The parts employed in the production of the voice are 

 three in number, the trachea, or wind-pipe, by which the 

 air passes to and from the lungs ; the larynx, Which is a 

 short cylindrical canal at the head of the trachea ; and the 

 glottis, which is a small oval opening between two semicir- 

 cular membranes. The glottis being very narrow compared 

 with the size of the trachea, the air can never pass through 

 it without acquiring a considerable degree of velocity ; so 

 that the air thus compressed and forced on communicates, as 

 it passes, a vibratory motion to the particles of the two lips 

 of the glottis, which produces the sound. The sound thus 

 produced is reverberated through the different parts of the 

 mouth ; and it is the mixture of different reverberations, 

 well proportioned to one another, which produces in the 

 human voice a harmony, whicli no instrument can equal. 



The most wonderful part of the mechanism of the voice 

 is the contraction and dilatation of the glottis. It is these 

 changes which produce all the variety of tone. The diame- 

 ter of the glottis never exceeds one tenth of an inch : now 

 suppose a person capable of sounding twelve notes — to which 

 the voice easily reaches, — there must be the difference of 

 the hundred and twentieth part of an inch for each note. 

 But if we consider the subdivision of notes of which the 

 voice is capable, the motion of the sides of the glottis ap- 

 pears still more minute. Suppose that a voice can divide a 

 note into one hundred parts ; it will follow that the different 

 openings of the glottis will be twelve hundred in one tenth 

 of an inch, and it is known that each of these will produce 

 sounds perceptibly different to a good ear. But the move- 

 ment of each side of the glottis being equal, it is necessary 

 to double this number, and the side of the glottis, therefore, 

 actually divides the tenth of an inch into twenty-four hun- 

 dred equal parts. 



Speech is articulated voice, that is, voice modified by the 

 action of the palate, teeth, tongue, and lips. All animals 



