MOVEMENTS OF THE VOCAL CORDS 551 



first, and apparently at the posterior part, the base of the tongue^ immediately 

 below which is the accurate outline of the epiglottis, with its cushion or tubercle, 

 figure 348. Then are seen in the central line the true vocal cords, white and 

 shining in their normal condition. In the inverted image the cords are closer 

 together posteriorly. Between them is left an open slit, narrow while a high 

 note is being sounded, wide during a deep inspiration. On each side of the 

 true vocal cords, and on a higher level, are the false vocal cords. Still more 

 externally than the false vocal cords is the aryteno-epiglottidean fold, in which 

 are situated upon each side three small elevations ; of these the most external 

 is the cartilage of Wrisberg, the intermediate is the cartilage of Santorini, while 

 in front and somewhat below the preceding is the summit of the arytenoid 

 cartilage seen only during deep inspiration. 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 occasionally seen. 



Movements of the Vocal Cords. The position of the vocal cords in ordi- 

 nary tranquil breathing is so adapted by the muscles that the opening of the 

 glottis is wide and triangular, figure .348, B, becoming a little wider at each 

 inspiration, and a little narrower at each expiration. On making a rapid 

 and deep inspiration the opening of the glottis is widely dilated, figure 348, C, 

 and somewhat lozenge-shaped. 



In Vocalization. At the moment of the emission of a note the opening 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 that their tension is much increased. The higher the note produced, the 

 tenser do the cords become, figure 348, A; and the range of a voice depends, 

 of course, in the main, on the extent to which the degree 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 utterance of low tones, on the other hand, the 

 epiglottis is depressed and brought over the vocal cords, figure 349. 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, just as covering the end of a short tube placed in front of 

 caoutchouc tongues lowers the tone. In no other respect does the epiglottis 

 appear to have any effect in modifying the vocal sounds. 



The degree of approximation of the vocal cords also usually corresponds 

 with the height of the note produced; but probably not always, for 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, the part of the aperture which is formed by the space between 

 the arytenoid cartilages. For if the arytenoid cartilages be approximated in 

 such a manner that their anterior processes touch each other, but yet leave an 



