620 VOICE AND SPEECH. 



which of them can also be uttered in a modified character 

 conjoined with vocal 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 independently 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, however, 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 cor- 

 responding vowel when vocalized ; the only difference in 

 the two cases lies in the kind of sound emitted by 

 the larynx. Krantzenstein and Ivempelen have pointed 

 out that the conditions necessary for changing one and the 

 same sound into the different vowels, are differences in 

 the size of two parts the oral canal and the oral opening ; 

 and the same is the case with regard to the mute vowels. 

 By oral canal, Kempelen means here the space between 

 the tongue and palate : for the pronunciation of certain 

 vowels both the opening of the mouth and the space just 



