314 PHYSIOLOGY. 



syllable, not even in a whisper, until the wind-pipe healed 

 up ; his voice was then restored to its former condition. 



8. Volition is necessary to the production of voice. If 

 the nerves going to the larynx are cut^ the voice will be 

 lost.A Palsy of the muscles of the larynx, also causes dumb- 

 ness ; and fear effects the voice by paralyzing muscular ef- 

 fort. The epiglottis is found not to be concerned in the pro- 

 duction of the voice, as it may be removed without affecting 

 it ; its sole office being to guard the wind-pipe against the in- 

 troduction of foreign substances. 



9. It has been proved by experiments, that mearly all the 

 larynx except the chorda vocales, or vocal chords, may be 

 removed without destroying the voice.} These are the small 

 ligaments that pass from the arytenoid cartilages to the thy- 

 roid cartilages, and are usually called the inferior ligaments, 

 or the lower vocal chords. 



10. \It is now ascertained that these chords perform the 

 principal part in the production of the voice.^ In what way 

 this is done, is not precisely known ; but, we may suppose 

 that the air in passing from the lungs in expiration, is forced 

 out of small cavities, as the air-cells and minute branches of 

 the wind-pipe, into the main channel ; it it is thence sent 

 through a narrow passage, on each side of which is a vibra- 

 tory chord ; the vibrations of which, by the action of the air 

 produces voice or sound. 



11. It has been said that if this theory of the voice be cor- 

 rect, there ought to be sound produced by forcing air through 

 the wind-pipe of a dead animal. But this takes for granted 

 what is not true, namely, that the voice is the result of a 

 purely mechanical process ; instead of which, it is a vital 

 function, performed by living agents, and therefore under 

 the control of voluntary action. 



12. In producing sound, there can be no doubt that nume- 

 rous Toluntary muscles are put in action, bringing the ary- 

 tenoid cartilages in contact with each other, thus putting 

 upon the stretch the lower vocal chords which are attached 



