The Voice in Singing

by Emma Seiler

To the cartilages of the larynx must be further added the Epiglottis, with the little cartilage at the centre of its inner side.

1. The thyroid cartilage is the largest cartilage of the larynx, and consists of two four-cornered cartilaginous plates held together in front and diverging behind; the anterior borders are convex, and consequently where the two plates meet in front they form an upper and a lower notch or slit. The posterior angles of this cartilage extend into the so-called horns of the thyroid cartilage. At the upper horns are ligaments attached, which form the connection between the hyoid bone and the larynx, while the lower horns serve to join the thyroid to the cricoid cartilage. In females and boys the angle formed by the two plates of the thyroid cartilage is obtuse. In the male sex at a certain period the larynx changes its shape, and the plates of the thyroid cartilage then form an acute angle, which is visible on the outside of the throat, and is popularly known as the Adam’s apple. At this time the diameter of the male larynx becomes a third larger than that of the female larynx, and in consequence the voice is lower, and its different registers are more enlarged in compass.

2. The cricoid cartilage resembles in shape a seal ring; its broader side is situated posteriorly between the lower horns of the thyroid cartilage, and it is connected by its lower edges immediately with the upper edge of the first ring of the trachea. From its side at the back part project two rounded surfaces, which give attachment to the arytenoid cartilages.

3. The arytenoid cartilages are two small but very mobile bodies in the form of three-cornered pyramids. The base of the pyramid rests upon the before-mentioned rounded surface at the back of the upper border of the cricoid cartilage; one of its sides turns to the front, the two others to the back and outwards. The surfaces between the anterior and postero-interior corners are accordingly turned towards one another. The surface posteriorly is concave, and affords space for a part of the arytenoid muscle; the inner surface is smooth, and forms, during quiet breathing, a part of the lateral wall of the larynx; the anterior surface is rough and irregular, and to it adhere the vocal chords, the thyro-arytenoid muscle, the lateral and posterior crico-arytenoid muscles, and upon these the bases of the cuneiform cartilages. The arytenoid cartilages are lengthened at their summits by two little pear-shaped elevations, the cartilages of Santorini (called apophyses in Garcia’s observations), which are connected with them by ligamentous fibres, and extend with them some distance into the larynx.

4. The cartilages of Wrisberg are described by Hyrtl as slight elevations upon the front or anterior edge of the arytenoid cartilages, inclining towards the interior, and, like all parts of the larynx, covered by the mucous membrane.

5. The cuneiform cartilages (as Wilson names them) are two long, slender cartilaginous laminæ which become somewhat broader at both ends. These cartilages, with their base, rest in the middle of the anterior surface of the arytenoid cartilages, and reach to the middle of the vocal chords, by which they are enveloped. The action of these cartilages renders possible the production of the head tones, but they are not found in every larynx. The fact that they are oftener found in the female larynx than in that of the male, and that the male larynx is mostly used in scientific investigations, as it is larger and more easily dissected, may be the reason why up to the present time no mention is made of them either in German or French manuals. They are sometimes referred to as cuneiform cartilages, or confounded with the cartilages of Wrisberg, probably because it seemed unaccountable that these important bodies should so long have escaped the attention of anatomists.

From the anterior surface of the arytenoid cartilages, extending towards the centre of the inner wall of the thyroid cartilage, running diagonally through the cavity of the larynx, are stretched the two pairs of chords already more than once mentioned—the vocal chords, consisting of folds of the mucous membrane which envelopes the whole larynx. The two lower of these chords, the vocal chords strictly so called, into which the cuneiform cartilages project and through which the interior thyro-arytenoid muscles run, have their points of attachment at the arytenoid cartilages, somewhat lower than the upper pair. Each of these parallel pairs of chords form between their lips a slit running antero-posteriorly. The slit of the upper pair is opened in the shape of an ellipse; that of the lower pair, the glottis, is very narrow. As the upper chords have their point of attachment posteriorly and higher, they form with the lower chords two lateral cavities, the ventricles.

The two pairs of chords, therefore, are the free interior edges of the membrane, covering the whole larynx and extending into it to the right and the left. Only the lower vocal chords serve directly for the generation of tones. More or less stretched and presenting resistance to the air forcibly expired from the lungs through the trachea, they are thus made to vibrate. The upper or false vocal chords do not co-operate with them to generate tone, but like all the remaining parts of the mouth and throat belong to the resonance apparatus of the voice, to which also appertains the back part of the mouth, the pharynx, over the œsophagus, the throat, or gullet. This is separated from the anterior cavity of the mouth by the palate, which is a curtain formed by the mucous membranes of the cavity of the mouth, and the centre of which forms the pendent uvula.

Above the œsophagus, immediately over the palate, lie close together, and separated only by a very thin osseous partition, the two posterior nasal orifices. These serve as passages for the air during inspiration and expiration; they are likewise considered as belonging to the resonance apparatus.

Upon both sides of the cavity of the mouth, between the two wings of the palate, lie the tonsils, two glandular bodies, which separate the sides of the cavity of the mouth from the pharynx. The anterior cavity of the mouth, which is separated from the nasal cavities by the palate, requires no description, as every one can acquaint himself with its structure in his own person and in others. Upon its formation, as well as upon the position of its different parts and upon the character of those parts of the larynx and of the cavity of the mouth which have been described as the resonance apparatus, the difference in the fulness and timbre of tones depends.