CHAPTER XVII. 



VOICE AND SPEECH. 



Sketch of the physiological anatomy of the vocal organs Vocal chords Mus- 

 cles of the larynx Crico-thyroid muscles Arytenoid muscle Lateral 

 crico-arytenoid muscles Thyro-arytenoid muscles Mechanism of the pro- 

 duction of the voice Appearance of the glottis during ordinary respira- 

 tion Movements of the glottis during phonation Variations in the quality 

 of the voice, depending upon differences in the size and form of the larynx 

 and the vocal chords Action of the intrinsic muscles of the larynx in 

 phonation Action of the accessory vocal organs Mechanism of the dif- 

 ferent vocal registers Mechanism of speech. 



THERE are few subjects connected with human physiology 

 of greater interest than the mechanism of voice and speech. 

 In common with most of the higher classes of animals, man 

 is endowed with voice ; but, in addition, he is able to express, 

 by speech, the ideas that are the result of the working of the 

 brain. In this regard there is a difference between man 

 and all other animals. It is the remarkable development 

 and the peculiar properties of the brain that enable him 

 to acquire the series of movements that constitute articulate 

 language ; and this faculty is always impaired pari passu 

 with deficiency in the intellectual endowment. Language 

 is one of the chief expressions of intelligence ; and its study, 

 in itself, constitutes almost a distinct science, inseparably 

 connected with psychology. In connection with the study 

 of movements, therefore, it is not necessary to discuss the 

 origin and construction of language, but simply to indicate 

 the mechanism, first, of the formation of the voice, and 



