VARIETIES OF VOCAL TONES. 487 



characterized by the prevalence in them of certain classes of 

 these sounds, while others are less frequent or altogether ab- 

 sent. 



The sounds produced in speech, or articulate sounds, are com- 

 monly divided into vowels and consonants ; the distinction be- 

 tween which is, that the sounds for the former are generated 

 by the larynx, while those for the latter are produced by 

 interruption of the current of air in some part of the air-pas- 

 sages above the larynx. The term consonant has been given 

 to these because several of them are not properly sounded, 

 except consonantly with a vowel. Thus, if it be attempted to 

 pronounce aloud the consonants b, d, and g, or their modifica- 

 tions, p, t, k, the intonation only follows them in their combi- 

 nation with a vowel. 



To recognize the essential properties of the articulate sounds, 

 we must, according to Muller, first examine them as they are 

 produced in whispering, and then investigate which of them 

 can also be uttered in a modified character conjoined with 

 local tone. By this procedure we find two series of sounds : 

 in one the sounds are mute, and cannot be uttered with a 

 vocal tone ; the sounds of the other series can be formed inde- 

 pendently of voice, but are also capable of being uttered in 

 conjunction with it. 



All the vowels can be expressed in a whisper without vocal 

 tone, that is, mutely. These mute vowel-sounds differ, how- 

 ever, in some measure, as to their mode of production, from 

 the consonants. All the mute consonants are formed in the 

 vocal-tube above the glottis, or in the cavity of the mouth or 

 nose, by the mere rushing of the air between the surfaces 

 differently modified in disposition. But the sound of the 

 vowels, even when mute, has its source in the glottis though 

 its vocal cords are not thrown into the vibrations necessary 

 for the production of voice ; and the sound seems to be 

 produced by the passage of the current of air between the 

 relaxed vocal cords. The same vowel-sound can be produced 

 in the larynx when the mouth is closed, the nostrils being 

 open, and the utterance of all vocal tone avoided. This 

 sound, when the mouth is open, is so modified by varied forms 

 of the oral cavity, as to assume the characters of the vowels 

 a, i, o, u, in all their modifications. 



The cavity of the mouth assumes the same form for the 

 articulation of each of the mute vowels as for the correspond- 

 ing vowel when vocalized ; the only difference in the two cases 

 lies in the kind of sound emitted by the larynx. Krantzen- 

 stein and Kempelen have pointed out that the conditions 

 necessary for changing one and the same sound into the differ- 



