344 VOCAL APPARATUS. LiECT. XVIII. 



the voice, or, as it is generally called, the volume of the 

 voice, results, in part, from the force with which the air is 

 driven from the lungs, and from the size of the thoracic 

 cavity ; and in part, from the facility with which the vocal 

 cords and the other parts of the larynx are able to vibrate. 

 These modifications explain the difference which exists be- 

 tween the male and female voice. To the great resound- 

 ing cavities in the communication with the larynx, must be 

 attributed the faculty which several species of monkeys have 

 of giving vent to very shrill and deafening cries. 



Superiority of the Human Vocal Organ. In reflecting 

 upon all that we have said while studying the human voice, 

 we cannot withhold our feeling of admiration at the wonder- 

 ous skill displayed in the construction of the organ producing 

 it. No instrument which we possess approaches it in per- 

 fection. Some wind instruments can only run the octave, 

 and pass without gradation from one note to another ; while 

 in stringed instruments it is impossible to prolong the sound. 

 The organ with two registers, which is formed both with 

 reed-pipes, and mouth-pipes, gives sounds which resemble 

 somewhat those of the human voice ; but these advantages 

 are only obtained by means of a great number of tubes, and 

 much complication. In the vocal organ, on the contrary, this 

 infinite variety of sound is obtained by means of a very 

 simple apparatus. 



Artificial Larynx. I have seen in the museum of King's 

 College, London, a caoutchouc larynx, modelled from a 

 human larynx, to the different parts of which threads are 

 attached, in order to enable its walls to be stretched more 

 or less at pleasure, and to vary the capacity of the tube. By 

 means of a current of air, the force of which can be mo- 

 dified, a certain number of sounds are obtained which, for 

 their timbre and purity, closely resemble those of the hu- 

 man voice. 



