370 



itself, serve to express our passions, as well as our ideas, are supplemen- 

 tal to the language of convention, and often betray it, by saying the re- 

 verse of what it expresses. The study of gestures, of motions, and of 

 attitudes, considered as signs of ideas and passions, is the department of 

 metaphysicians, of painters, of sculptors, and physiognomists*. 



CHAPTER IX. 



OF VOICE AND SPEECH, 



CXCV. The voice-is an appreciable sound, resulting from the vibra- 

 tions which the air, expelled from the lungs, meets with, in passing 

 through the glottis. From this sound articulated by the motions of the 

 tongue, the lips, and other parts of the mouth, is produced speech, which 

 may be defined articulated voice. 



All animals furnished with a pulmonary organ have a voice 5 for it is 

 sufficient, to the production of this sound, that air, collected in any re- 

 ceiver, be driven out in a body, with a certain force, and that it meet, on 

 hs passage, with elastic and vibratory parts. Fish, that have only gills, 

 utter no sound ; but this defect, which is certainly an impediment to the 

 extent and facility of their relations, is in part made up by the extreme 

 velocity of their progressive motion. 



The instrument of voice is the larynx, a sort of cartilaginous box, 

 placed at the upper part of the trachea. The thin and elastic cartilages 

 which form its parietes are united by membranes, and moved on one an- 

 other by many little muscles, called laryngeal. Of these five cartilages, 

 three only are concerned in the production of voice, these are the aryte- 

 noid and the thyroid. The epiglottis is of no other use than to close, to 

 what we swallow, the entrance of the windpipe, whilst the cricoid, situa- 

 ted at the lower part of the organ, serves it for a base, on which the ary- 

 tenoid and the thyroid execute the motions, by which the opening of the 

 glottis is contracted or enlarged, for the formation of acute or grave 

 tones. 



This slit, from ten to eleven lines long in an adult, and from two to 

 three wide, where the width is greatest, is the most essential part of the 

 larynx. It is really tke organ of voice which is gone at once, when, by 

 opening the trachea or the larynx below it, the air is prevented from pass- 

 ing through it. Speech only is lost, when the wound is above the place 

 of the glottis; which shows that voice and speech are two distinct phe- 

 nomena, one taking place in the larynx, and the other resulting from the 

 action of divers parts of the mouth, and especially the lipsf. 



* See Condillac's Kssay on the Origin of Human Knowledge ; Button's Natural His- 

 tory of Man ; Winkelman's Treatise on Art ; Lavater's Essays on Physiognomy ; with 

 the impo.tant additions by M. Moreau (de la Sarthe) in the edition he has just pub- 

 lished. Jlutnor's Note. 



See APPENDIX, Note H H. 



