336 VOCAL APPARATUS. LECT. XVIII. 



ventricles are so close together that they form a kind of 

 second glottis, at from 15 to 18 millimetres above the 

 other one. 



Seat of the Voice. The air expelled from the lungs with- 

 out any extraordinary effort easily traverses the larynx 

 without producing sound. From the time of Galen, an 

 experiment has been known which shows, that to articulate 

 a sound, it is absolutely necessary to contract the muscles 

 of the larynx. This experiment consists in wounding the 

 laryngeal nerves, or in effecting their complete division on 

 both sides of the trachea: in this case, paralysis of the 

 larynx is complete, and the power of forming sounds is 

 entirely destroyed. By another experiment, we can ascer- 

 tain still more exactly the part of the organ which is the 

 most essential for the production of the voice. If we re- 

 move the superior ligaments of the glottis, the voice con- 

 tinues, though it becomes more feeble ; but if we divide 

 or injure the inferior ligaments, namely, the vocal cords, 

 the voice is completely destroyed. Muller ascertained that 

 it is easy to obtain sounds from the larynx of the dead human 

 subject, by forcing air through the trachea ; provided that 

 the inferior ligaments of the glottis be rendered in some de- 

 gree tense, and the aperture of the glottis narrowed. Ac- 

 cording to this learned physiologist, the experiment likewise 

 succeeds when all the parts above the glottis, such as the 

 epiglottis, the superior ligaments, and the ventricles of the 

 larynx, are removed. If the vocal cords alone remain, and 

 the chink between them be narrow, sound is always pro- 

 duced. Magendie laid bare the glottis in living animals, and 

 saw that the vocal cords were thrown into vibration, when 

 cries were uttered. I propose to show you one of Longet's 

 experiments, to prove the part which the vocal cords take 

 in the production of the voice. I have here a rabbit, whose 

 larynx has been laid bare ; and you observe that the animal 



