550 



VOICE AND SPEECH. 



properties of the brain that enable him to acquire the series of movements that constitute 

 articulate language ; and this faculty is nearly always impaired paripassu 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 afterward, the manner in which the voice is 

 modified in the production of articulate sounds. 



The voice in the human subject, presenting, as it does, a variety of characters as 

 regards intensity, pitch, and quality, and being susceptible of great modifications by habit 

 and cultivation, affords a very extended field for physiological study. Of late years, this 

 has been the subject of careful investigation by the most eminent pbysicists and physiolo- 

 gists of the day ; but to follow it out to its extreme 

 limits requires a knowledge of the physics of sound 

 and the theory of music, a full consideration of which 

 would be inconsistent with the scope and objects of 

 this work. We shall content ourselves, therefore, with 

 a sketch of the physiological anatomy of the parts con- 

 cerned in the formation of the voice, and the mechanism 

 by which sounds are produced in the larynx, without 

 treating fully of their varied modifications in quality. 

 It will not be necessary to treat of the different the- 

 ories of the voice that have been presented from time 

 to time, except in so far as they have been confirmed 

 by recent and complete observations, particularly 

 those in which the vocal organs have been studied in 

 action by means of the laryngoscope. 



/Sketch of the Physiological Anatomy of the Vocal 

 Organs. The principal organ concerned in the pro- 

 duction of the voice is the larynx. The accessory or- 

 gans are the lungs, trachea, and expiratory muscles, 

 and the mouth and resonant cavities about the face. 

 The lungs furnish the air by which the vocal chords 

 are thrown into vibration, and the mechanism of this 

 action is merely a modification of the process of expira- 

 tion. By the action of the expiratory muscles the 

 intensity of vocal sounds is regulated. The trachea 

 not only conducts the air to the larynx, but, by cer- 

 tain variations in its length and caliber, it may assist 

 in modifying the pitch of the voice. Most of the varia- 

 tions in the tone and quality, however, are effected by 

 the action of the larynx itself and of the parts situated 

 above it. 



It is impossible to give a complete account of the 

 structure of the larynx, without going more fully than 



FIG. 170. Longitudinal section of the hu- 

 man larynx, showing the vocal chords. 

 (Sappey.) 



1, ventricle of the larynx ; 2, superior vocal 

 chord ; 3, inferior vocal chord ; 4, aryte- 

 noid cartilape ; 5, section of the arytenoid 

 muscle: 6. 6, inferior portion of the cav- 

 ity of the larynx ; 7, section of the pos- 

 terior portion of the cricoid cartilage ; 8, 

 section of the anterior portion of the cri- 

 coid cartilage ; 9, superior border of the 

 cricoid cartilape ; 10, section of the thy- 



roid cartilage ; it. ii, superior portion of 



' desirable into purely anatomical details. Some an- 

 i9 S8 i9 ; 2o 8 trache!i 0n f the hyOid bone ' atomical points have already been referred to under 



the head of respiration, in connection with the respi- 



ratory movements of the glottis ; and we propose here only to refer to the situation of 

 the vocal chords, and to indicate the modifications that they can be made to undergo in 

 their relations and tension by the action of certain muscles. 



The vocal chords are stretched across the superior opening of the larynx from before 



