CHAP, xxxi.] PRODUCTION OF VOCAL SOUNDS, 



441 



sides and apex in front ; in the latter, it becomes a simple slit, or 

 nearly so, with parallel sides. In the human larynx, the thyro- 

 arytenoid muscles, lying on the outside of each of the vocal chords, 

 exercise a principal influence in determining their relative position, 

 and in adapting them for vocalization. 



3rd. If a tube be adapted to the membranous tongues, in such a 

 manner that the air may play upon them through it, and may pass 

 through another tube after it has acted upon them, an influence is 

 exercised not only on the timbre of the sounds produced, but also 

 upon the pitch, which varies with the length of either and of both. 

 In the human organ of voice, the larynx and bronchi represent a 

 tube prefixed to the membranous tongues and chordae vocales ; and 

 the cavity in front of the inferior ligaments of the larynx, a tube 

 placed below the tongues.* 



The vocal sounds may be produced by blowing air from the 

 trachea through the aperture of the glottis in a larynx removed 

 from the dead body ; and by adopting means to vary the tension 

 and the relative position of the vocal chords, the phenomena of the 

 voice may be very closely 

 imitated. When air is thus 

 blown through the glottis, 

 the vocal chords being ap- 

 proximated, clear and full 

 tones are generated. They 

 are produced most readily 

 and certainly when the pos- 

 terior part of the glottis, 

 situated between the aryte- 

 noid cartilages, is closed. A 

 certain constriction of the 

 glottis appears necessary, as, 

 when it is too open, an in- 

 distinct noise'is merely pro- 

 duced. The pitch of the note 

 is determined by the tension 

 of the vocal chords, that of 

 both being equal; it is not in- 

 fluenced by Changes in the 



width of the aperture of the 



* The reader is referred for the detail of Miiller's experiments to p. 988 et 

 seqq. of Dr. Baly'.s Translation, vol. ii., and to Miiller's separate work, Ueber 

 Compensation der phys. Krafte am menschlich. Organ. Berlin, 1839. 



VOL. IT. G G 



Diagram to show parts concerned in vocalization, and 



shape ' 



