“The meeting of the lips of the glottis, naturally proceeding from the front towards the back, if this movement is well managed, will allow, between the apophyses, _of the formation of a triangular space or inter-cartilaginous glottis_, but one which, however, is closed as soon as the sounds are produced.
“After some essays we perceive that this internal disposition of the larynx is only visible when the epiglottis remains raised. But neither all the registers of the voice, nor all the degrees of intensity, are equally fitted for its taking this position. We soon discover that the brilliant and powerful sounds of the chest register contract the cavity of the larynx, and close still more its orifice; and, on the contrary, that veiled notes, and notes of moderate power, open both, so as to render any observation easy. The falsetto register especially possesses this prerogative, as well as the first notes of the head voice. So as to render these facts more precise, we will study in the voice of the tenor the ascending progression of the chest register, and in the soprano that of the falsetto and head registers.
“If we emit veiled and feeble sounds, the larynx opens at the notes do re me (c d e), and we see the glottis agitated by large and loose vibrations throughout its entire extent. Its lips comprehend in their length the anterior apophyses of the arytenoid cartilages and the vocal chords; but, I repeat it, there remains no triangular space.
“As the sounds ascend, the apophyses, which are slightly rounded on their internal side, by a gradual apposition commencing at the back encroach on the length of the glottis, and as soon as we reach the sounds si do (b c¹) they finish by touching each other throughout their whole extent; but their summits are only solidly fixed one against the other at the notes do re (c♯¹ d¹). In some organs these summits are a little vacillating when they form the posterior end of the glottis, and two or three half-tones which are formed show a certain want of purity and strength, which is very well known to singers. From do re (c♯¹ d¹) the vibrations, having become rounder and purer, are accomplished by _the vocal ligaments alone_, up to the end of the register.
