304 SIR CHARLES BELL ON THE ORGANS OF THE HUMAN VOICE. 
incorrect. Ferrein described the edge of the glottis as being like the strings 
of the violin, and the air brushing over it like the bow. But even in that 
supposition, though the vibration of the string of the violin is necessary to the 
production of sound, yet that sound receives modification through the form 
and condition of the instrument. As the same chord, vibrating in the same 
time, will produce a sound the quality of which varies in different instruments, 
so will the sound of the chordae vocales be influenced in the pharynx. As a 
tuning-fork, or a moveable musical instrument, will have the quality and 
power of the tone changed by its position and the material with which it is 
in contact, so will the vibrations of the human glottis be affected by the parts 
above and against which the sound is directed. 
The breath, which plays inaudibly in respiration, becomes vocalized when the 
ligaments of the glottis, or chordae vocales, are braced so as to cause the edges 
of the glottis to vibrate in the stream of air. In a wind instrument the air 
must be impelled with a force to make the sides of the tube vibrate ; so, in the 
production of sound from the human organs, there must be a certain pressure 
of the column of air. But in the organs of the voice there is this superiority, 
that there are not only the means of regulating the pressure of the column of 
air, but of adjusting the vocal chords, feo as to suit them to the most delicate 
issue of the breath. The metal tongue in the organ-pipe is, by lengthening or 
shortening it, accommodated so as to vibrate in time with the air contained 
in the tube. So is the edge of the glottis regulated ; but with an apparatus 
for adjustment the most perfect. 
Besides the adjustment of the vocal chords, there is a very superior provision 
in the motions of the chest which supply the air, to that of any musical instru¬ 
ment. Although the organ has allotted to each note a separate pipe, whose 
relative dimensions are proportioned with mathematical precision, yet the air 
propelled through the pipes can never be so regulated as it is by the combina¬ 
tion which exists betwixt the motions of the chest and the glottis. The church 
organ could not be made to approach the precision of adjustment in the human 
organs, were there as many pairs of bellows as there are pipes, and each ad¬ 
justed by a weight or spring, to accommodate the pressure of air to the dimen¬ 
sions of the pipes *. 
Referring to the Plates for the anatomy^, I may continue my comment on 
* Which is attempted in some automata. t See Plate IX. ; and Plate X. fig. 2. 
