326 THE VOICE. [BOOK in. 



\vc find, as we have already ( 655 659) seen, an area in the motor 

 ivgion of the cerebral cortex devoted to phonation. This in the 

 monkey (Fig. 126) lies at the lowest part of the ascending frontal 

 convolution wedged in between the sylvian fissure and the lower 

 end of the precentral fissure; in man as we have seen (Fig. 131) 

 the more highly developed area for 'speech' is situate at the 

 posterior end of the third frontal convolution, having as we have 

 also seen an importance on the left side of the brain which it 

 does not possess on the right. 



Stimulation of the area in question in the monkey or of the 

 corresponding area in the dog leads to adduction of the cords and 

 closure of the glottis, the resulting movement being bilateral. As 

 in the case of other areas, the effect is more pure, the laryngeal 

 movement is less mixed with other movements, when the stimula- 

 tion is strictly limited to a certain part of the whole area, in this 

 case to the lower part. So far adduction only has been the 

 experimental result of stimulation of the cortex in the monkey 

 and the dog, an area for abduction having been found in the cat 

 alone ; and as we have said adduction is the salient movement in 

 phonation. But stimulation of the cortex near the pure centre 

 for phonation leads to an acceleration in the rhythm of and 

 exaggeration of the laryngeal respiratory movements, as indeed of 

 the respiratory movemertts as a whole ; though the respiratory 

 laryngeal movements are in the main worked by a bulbar mecha- 

 nism, they can be influenced by cortical changes. 



As in the case of the other cortical motor areas, the path from 

 the cortical area for phonation to the muscles whose actions it 

 governs runs in the pyramidal tract through the internal capsule. 

 Moreover in the bulb there appears to be a subordinate nervous 

 mechanism, with which the impulses or influences descending the 

 pyramidal tract make connection before they issue as coordinate 

 motor impulses along the laryngeal nerves; and indeed by local 

 electrical stimulation of the bulb, in the floor of the fourth ven- 

 tricle, adduction or abduction of the cords may be brought about. 

 The bulbar mechanism for abduction is placed higher up than 

 that for adduction, and stimulation of either side produces in 

 both cases bilateral movements. 



911. So far we have mainly spoken of the voice as the 

 result of two gross acts, the narrowing of the glottis and the 

 tightening of the cords. We must now say a few words on some 

 other changes in the larynx, especially in reference to the various 

 qualities and kinds of voice. Many of the features of the voice 

 are conferred upon it by means of the parts of the respiratory 

 passage above or below the vocal cords, by what we have spoken 

 of as the resonance chamber or tube ; these we shall deal with in 

 treating of ' speech,' and may here confine ourselves, in the main, 

 to changes in the larynx itself. It should be noted however that 

 whenever voice is uttered the larynx is more or less firmly fixed 



