150 ZOOLOGY. 



musical instruments is known to vary much, according as 

 they are constructed of wood, metal, or of other substances ; 

 and certain modifications of the voice seem to be referable to 

 a hardening of the tissues composing the larynx, and espe- 

 cially the cartilages. In women and children these cartilages 

 are soft and flexible ; whilst in men, and in women with a 

 masculine voice, these cartilages have become ossified. 



The form and direction of the passages through which the 

 air passes after having escaped beyond the rima glottidis, 

 affect also the character of the voice. Thus, in passing 

 strongly through the nostrils it becomes nasal and unplea- 

 sant ; the form of the mouth, palate, and velum palati affect, 

 no doubt, the quality of the voice. 



303. In birds, as will be afterwards more fully explained, 

 the voice is formed in a supplementary larynx formed much 

 lower down or in the trachea; in singing birds this organ is 

 very complex. 



304. Modification of the Voice. The sounds produced 

 by the vocal apparatus may be divided into the cry, the song, 

 and the ordinary or acquired voice. 



The cry is the only sound which most animals can pro- 

 duce. It is not modulated, and is generally sharp and dis- 

 agreeable. The cry of man is instinctive, and not generally a 

 voluntary act. It is quite peculiar when it expresses agony 

 or distress. The child can only cry, and it is by imitation of 

 his fellows as he grows up that he learns the art of modu- 

 lating his voice so as to produce articulate sounds. This 

 acquired voice differs from the instinctive cry, but is essen- 

 tially formed in the same way, that is, by sounds whose 

 intervals and harmonic relations are imperceptible to the ear, 

 at least, clearly and distinctly. Singing, on the contrary, is 

 composed of appreciable or musical sounds, of which the 

 oscillations are regular, and may, as it were, be reckoned by 

 the ear. 



305. Man also possesses the remarkable power of articu- 

 lating the sounds of his voice, and this act is called pro- 

 nunciation. 



The organs of pronunciation are the pharynx, the nasal 

 fossae, and the various parts of the mouth. But man is not the 

 only animal which has this power, although he is the only one 

 who knows how to attach meaning to the words he pro- 

 nounces, and to the arrangement he gives them ; he alone is 

 gifted with the power of speech. 



