SPEECH 



315 



has come to the conclusion that the mouth does not act as a mere 

 resonator, but that for each vowel, in addition to the fundamental 

 note due to the vibration of the vocal cords, the pitch of which is, of 

 course, variable, one or, it may be, two other notes (formants, as he 

 calls them), not necessarily harmonics of the laryngeal note, but separ- 

 ated from it by a constant or nearly constant musical interval, are 

 directly produced by the passage of the regularly interrupted expiratory 

 blast through the mouth, the air contained in that cavity being for 

 an instant set into vibration at each interruption. On this view it 

 is the musical effect produced by the oscillation or continual recurrence, 

 in short series, of these vibrations which gives the vowels their quality. 

 The fact that it is by no means difficult to sing (with the larynx) and 

 whistle (with the mouth) at the same time, shows the possibility of 

 Hermann's view, that a fixed tone can be generated in the mouth by 

 the intermittent stream of air issuing from between the vibrating vocal 

 cords, just as a tone is generated in a pipe by blowing into or over it, 

 and his records do show continually recurring groups of vibrations as 

 his theory requires. McKendrick takes up a middle position, believing 

 that both theories are partially true, and this seems to be the best 

 conclusion which can at present be arrived at. It seems clear, at any 

 rate, that more than one factor is concerned in the timbre of the vowel 

 sounds. 



When the vowels are being uttered, the soft palate closes the 

 entrance to the nasal chambers completely, as may be shown by 

 holding a candle in front of the nose, or trying to inject water 

 through the nares. If the cavities of the nose are not completely 

 blocked off, the voice assumes a nasal character in pronouncing 

 certain of the vowels; and in some languages this is the ordinary 

 and correct pronunciation. 



Many animals have the power of emitting articulated sounds; a 

 few have risen, like man, to the dignity of sentences, but these only 

 by imitation of the human voice. Both vowels and consonants can 

 be distinguished in the notes of birds, the vocal powers of which 

 are in general higher than those of mammalian animals. The latter, 

 as a rule, produce only vowels, though some are able to form con- 

 sonants too. 



The nervous mechanism of voice and speech will have to be 

 again considered when we come to study the physiology of the brain 

 and spinal cord. But the curious physiological antithesis between 

 the functions of abduction and of adduction of the vocal cords may 

 be mentioned here. The abductor muscles are not employed in the 

 production of voice; they are associated with the less specialized, 

 the less skilled and purposive function of respiration. The adductor 

 muscles are not brought into action in respiration; they are asso- 

 ciated with the highly specialized function of speech. Correspond- 

 ing to this difference of function, we find that adduction is pre- 

 ponderatingly represented in the cortex of the brain, abduction in 

 the medulla oblongata. Stimulation of an area in the lower part 

 of the ascending frontal convolution, near the fissure of Rolando, in 

 the macaque monkey, causes adduction of the vocal cords, never 



