734 VOICE AND SPEECH. [CH. LIV. 



The rings of the trachea, and even the bifurcation of the trachea itself, if the 

 patient be directed to draw a deep breath, may be seen in the interval 

 between the true vocal cords. 



Movements of the Vocal Cords. 



In Respiration. The position of the vocal cords in ordinary 

 tranquil breathing is so adapted by the muscles, that the opening 

 of the glottis is wide and triangular (fig. 556, B) . For all practical 

 purposes, the glottis remains unaltered during ordinary quiet 

 breathing, though in a small proportion of people it becomes a 

 little wider at each inspiration, and a little narrower at each 

 expiration. In the cadaveric position the glottis has about half 

 the width it has during ordinary breathing; during life, there- 

 fore, except during vocalisation, the abductors of the vocal cords 

 (posterior crico-arytenoids) are in constant action. (F. Semon.) 

 On making a rapid and deep inspiration the opening of the 

 glottis is widely dilated (fig. 556, c), and somewhat lozenge- 

 shaped. 



In Vocalisation. At the moment of the emission of a note, 

 the chink is narrowed, the margins of the arytenoid cartilages 

 being brought into contact and the edges of the vocal cords 

 approximated and made parallel ; at the same time their tension 

 is much increased. The higher the note produced, the tenser do 

 the cords become (fig. 556, A) ; and the range of a voice depends, 

 in the main, on the extent to which the degre.6 of tension of the 

 vocal cords can be thus altered. In the production of a high 

 note the vocal cords are brought well within sight, so as to be 

 plainly visible with the help of the laryngoscope. In the utter- 

 ance of low-pitched tones, on the other hand, the epiglottis is 

 depressed and brought over them, and the arytenoid cartilages 

 look as if they were trying to hide themselves under it (fig. 557). 

 The epiglottis, by being somewhat pressed down so as to cover 

 the superior cavity of the larynx, serves to render the notes 

 deeper in tone and at the same time somewhat duller. 



The degree of approximation of the vocal cords also usually 

 corresponds with the height of the note produced; but the width 

 of the aperture has no essential influence on the pitch of the 

 note, as long as the vocal cords have the same tension: only 

 with a wide aperture the tone is more difficult to produce and 

 is less perfect, the rushing of the air through the aperture being 

 heard at the same time. 



No true vocal sound is produced at the posterior part of the 

 aperture of the glottis, that, viz., which is formed by the space 

 between the arytenoid cartilages. 



