344 Voice ** B *r<ts. [Book IX. 



and piercing note, are found to be poffefled of a nar- 

 row larynx ; animals, which are hoarfe or mute, of a, 

 wide one. The fame fact is proved in ourfelves. We 

 may perceive, by applying the finger to the throat, 

 when we endeavour to produce a fhrill tone, that the 

 larynx is contracted, rendered tenfe, and elevated; 

 when we produce a grave found, it is enlarged, re- 

 laxed, and deprefied j by endeavouring to produce a 

 graver tone than we are capable of, the larynx is too 

 much relaxed to perform its office, and the air pafles 

 through it without producing any found whatever. 



Bonnet obferves, that birds are furnifhed with what 

 may be called two larynxes, the one at the fuperior ex- 

 tremity of the windpipe, as in men and quadrupeds j 

 the other (which is the principal organ of found with 

 them) at the inferior extremity, and clofe to the bron- 

 chia?. The chief inftrument for the modulation of 

 the voice in this lower larynx is a membrane fituated 

 tranfyerfely between the two bronchia?, communicating 

 with other membranes, refembling the reed of a haut- 

 boy. On the greater or lefs elafticity of thefe mem- 

 branes depends the tone of the voice, in the fame 

 manner as in other animals it depends on the tenfion 

 or relaxation of -the cords of the glottis *. 



It has been much debated, whether the larynx, iq 

 producing the voice, acts as a wind or a ftringed inftru- 

 ment ; bat there can be little doubt, from the ftruc- 

 ture and motions of the larynx, that it poflefles the 

 advantages of both. 



Singing is a modulation of the voice, through va- 

 rious degrees of acutenefs and gravity, and is per- 

 formed almoft folely by the larynx, though the nofe 

 and mouth are in fome degree concerned in improving 

 and foftening the tones. During fpeech, the larynx 



is 

 * Bon, Cent, p. 7, 



