OF THE HUMAN VOICE. 
563 
during the elevation of the larynx, when the trachea is found to ascend out of the 
chest, and afterwards to return to its former position ; a movement in which the 
lungs and bronchi participate. The alteration of the tube in diameter may also be 
perceived by grasping the trachea with the finger and thumb during the elevation 
and depression of the larynx*. These movements are so striking as to lead irre- 
sistibly to the conclusion, that there exists a constant adaptation between the tension 
and the vibrating lengt h of the thyro-arytenoid ligaments and the walls of the vocal 
tube, in the production of tones of the ordinary register ; for we have seen that the 
variations of the vocal cords, at least so far as relates to the modulation of sound, 
are perfectly independent of the length of the vocal tube, and consequently the 
changes in its length which we have just described are not at all necessary for that 
purpose. Again, the vocal tube is so short, that, as has been ascertained by Weber 
and others, it could not, were it rigid, affect the pitch of the note produced by the 
glottis. As however this tube is composed of flexible materials, its effects are similar 
to those observed in M. Savart’s experiments ; that is, the relaxed state of the 
parietes compensates for its want of length, and enables it to vibrate synchronously, 
and therefore to give forth sounds equally grave with those of the glottis, thereby 
reinforcing the tone which would indeed be produced, though with much less inten- 
sity, without this aid. 
The falsetto, or voce di testa , has always been considered a most embarrassing 
subject of research, and its peculiar quality has excited the attention both of the phy- 
siologist and of the musician. Its most remarkable characteristic consists in its being 
less reedy in tone, and partaking nearly of the quality of the harmonic sounds of 
stringed and wind instruments. The change produced in the voice when passing from 
the falsetto into the common tone, or the reverse, is in some persons very sensible to 
the ear, whilst in others it is almost imperceptible. Some individuals, moreover, have 
the faculty of producing in the same pitch as many as eight or ten tones, possessing 
either the falsetto or the common character. The falsetto has been generally ascribed 
to some particular adaptation of the upper ligaments of the larynx. Dodart'|~ has 
attempted to prove that it is a supra-laryngeal function, and that the nose becomes 
the principal tube of sound instead of the cavity of the mouth. Bennati^ also con- 
sidered these tones to be modulated by the supra-laryngeal cavity alone. This hypo- 
thesis however is untenable, since it supposes the column of air not to be influenced 
by the trachea, which is contrary to experience. In order to detect some of the 
movements of the larynx while the voice is passing from the first to the second, or 
falsetto register, it is only necessary to place the point of the finger in the crico-thyroid 
chink, when it is found that at the moment the transition from the primary to the 
secondary register takes place, this chink, which was closed during the production 
* Essays by the author in the London and Edinburgh Philosophical Magazine, for September, October and 
November, 1836. 
t Mem. de l’Acad. 1707. { Recherches sur le Mechanisme de la voix humaine. 
4 d 2 
