The Mechanism of the Human Voice Part 2

10. RING-s.h.i.+ELD (CRICO-THYROID) APERTURE COVERED BY MEMBRANE.

11. LID (EPIGLOTTIS).

12. WINDPIPE (TRACHEA).

[Ill.u.s.tration: PLATE VI.

FRONT VIEW OF THE VOICEBOX, OR LARYNX.

1, 2. UPPER HORNS OF THE s.h.i.+ELD.

3. TONGUE (HYOID) BONE.

4, 5. HORNS OF THE TONGUE-BONE.

6, 7. BANDS UNITING THE s.h.i.+ELD WITH THE TONGUE-BONE.

8, 9. LID.

10, 11. PLATES OF THE s.h.i.+ELD.

12. RING.

13. ELASTIC BAND UNITING THE s.h.i.+ELD WITH THE RING.

14. WINDPIPE.

This is a very particular point, and I beg the reader particularly to notice that if the s.h.i.+eld cartilage (pl. V, 5) were gradually drawn downwards and forwards, the s.p.a.ce which we now see between the s.h.i.+eld and the ring (pl. V, 10) would get smaller and smaller, until at last it quite disappeared; and the distance between the front of the s.h.i.+eld (pl.

V, 1) and the highest part of the back of the ring (pl. V, 4) would be increased.

I may observe here that authorities differ as to whether the s.h.i.+eld moves upon the ring, or the ring upon the s.h.i.+eld, and that some maintain the one is drawn down while the other is tipped upward. It is sufficient for our purpose, however, that a movement as upon a hinge takes place, whereby, as explained just now, the distance between the front of the s.h.i.+eld and the highest part of the back of the ring is increased.

3rd. =The Lid= (pl. V, 11) is an elastic cartilage which serves to close the voicebox in the act of swallowing, in order to protect it against any intruding foreign substances. The food we take has to pa.s.s over it, and it sometimes happens, when the lid has not been pulled down tight enough, that a particle of food enters the voicebox, in which case we say it has "gone the wrong way," and there is then no peace until the intruder has been got rid of, generally by a violent fit of coughing.

The lid, it is true, is not the only means of protection which the voicebox possesses. Professor C. J. Eberth, for instance, mentions (Archiv fur pathol: Anatomie, vol. lxiii., p. 135, Berlin, 1868) the case of a woman who, upon dissection, was found to be entirely without the free upper part of the lid, which could alone cover the voicebox. She had never experienced any difficulty in swallowing, and it is therefore clear that with her the closing of some of the parts immediately below was sufficient to prevent the food from getting into the voicebox. But "the exception proves the rule," and in spite of this and other similar cases, the fact remains that the lid is obviously the first and most natural protector of the voicebox.

4th and 5th. We have thus far become acquainted with three cartilages out of the five. Let us now remove one plate of the s.h.i.+eld, as though cutting it off with a knife (pl. VII, 1 and 2), in order that we may look inside and see the remaining two cartilages which have hitherto been hidden by it. These are--

=The Pyramids= (pl. VII, 1 and 2), so called because of their shape. Their bases are triangular and hollowed out; their sides taper upwards and terminate in points which are bent slightly backwards, and they have each two projections, one pointing forwards (pl. VII, 3) and the other outwards and backwards (pl. VII, 4). It will be convenient to have a special name for the projections pointing outwards and backwards, which we will therefore call the Levers.

The Pyramids are attached with their hollow bases to the borders of the ring (pl. VII, 5), and they are capable of executing rotary movements with surprising freedom and rapidity. Their inner sides may be made to run parallel or to diverge. In addition to this they can be drawn towards each other, or away from each other, so that their summits may either be widely separated or brought close together.

=The Vocal Ligaments= are two ledges of elastic tissue covered with a very delicate membrane. Each one of them is connected along its whole length, on one side, with the s.h.i.+eld cartilage. The vocal ligaments are attached by their hinder ends to those little projections of the pyramids which point forwards (pl. VII, 3, 3), and by their front ends to the centre of the s.h.i.+eld (pl. VII, 6), where the two plates meet under a more or less acute angle.

[Ill.u.s.tration: PLATE VII.

SIDE VIEW OF THE VOICEBOX, OR LARYNX, SHOWING THE INTERIOR OF IT, THE RIGHT PLATE BEING REMOVED.

1, 2. PYRAMIDS (ARYTENOID CARTILAGES).

3, 3. FRONT PROJECTIONS OF THE PYRAMIDS.

4. LEVER OF THE RIGHT PYRAMID.

5. UPPER BORDER OF THE RING.

6, 3, 3. VOCAL LIGAMENTS.

7. LID.

8. s.h.i.+ELD.

9. LEFT UPPER HORN OF THE s.h.i.+ELD.

10. RING.

11. WINDPIPE.

These vocal ligaments are generally called the vocal cords, but this term is misleading, as it implies strings like those, for instance, of the violin, which are attached only at either end and are free at every other point. This, however, as we have just seen, is not the case, the "Cords" being free only along their inner edges. The name "Vocal Bands," which German physiologists have subst.i.tuted for "Vocal Cords," does not mend the matter, as it is open to exactly the same objections. The term "Vocal Lips," also used by some writers, is, in my judgment, the most unfortunate of all, because it conveys a totally wrong idea of these parts, as will be seen from a description in another chapter of their movements in the act of singing. I have, therefore, sought for a word which, as a proper description of the thing it is to designate, shall always call a correct image to the reader's mind, and as I cannot find a better one than "Ligament," I have adopted it. I shall consequently in these pages always speak of the tone-producing element as the "Vocal Ligaments."

The vocal ligaments, having met, are struck by the air blown against them from below, and being elastic they yield, allowing themselves to be forced upwards. A little air is thereby set free, and the pressure from below diminished, in consequence of which the vocal ligaments resume their former position, and even move a little more downwards. The renewed pressure of the air once more overcomes the resistance of the vocal ligaments, which again recede as soon as another escape of air has taken place, and this process is repeated in rapid and regular succession. In this manner, and in this manner alone, is vocal tone produced, whether it be called chest, falsetto, head, or by any other name.

There are still some writers who teach a different doctrine. For instance, Miss Sabilla Novello, in her "Voice and Vocal Art,"

embodied in the "Collegiate Vocal Tutor," published by Novello, Ewer, and Co., says on p. 9, that "The head voice results from the upper [_i.e._, the false] vocal cords" (these we shall see presently), and on page 13, that the falsetto tones "are created princ.i.p.ally by the action of the trachea [windpipe] and not by that of the vocal ligaments." Another writer, Mr. Rumney Illingworth, in a paper "On the Larynx and its Physiology," read before the Royal Medical Society of Edinburgh, on March 3rd, 1879, and communicated to "The Students' Journal and Hospital Gazette" (Vol. IV., No. 91, p. 151), says that "The falsetto voice is produced by the laryngeal sacculi [the pockets of the voicebox, which will be described further on] acting in the same way as a hazel-nut can be made to act as a whistle, when the kernel has been extracted through a small hole in the sh.e.l.l; or as part of the cavity of the mouth acts in whistling." I shall refer to these theories again as the opportunity for their proper discussion arises; for the present I will quote a few authorities on the subject.

Dr. CARPENTER, in his "Human Physiology," eighth edition, page 914, says, "The true theory of the voice may now be considered as well established in regard to this essential particular that the sound is the result of the vibrations of the vocal cords," &c.

Professor MARSHALL, in his "Outlines of Physiology," page 255, says: "Experiments on living animals show that the vocal cords are alone the essential organs for the production of voice, for so long as these remain untouched, although all the other parts in the interior of the larynx be destroyed, the animal is able to emit vocal sounds.... The existence of an opening in the larynx of a living animal, or of man, _above_ the glottis [glottis means the vibrating element of the voicebox] in no way prevents the formation of vocal sound; such an opening if situated in the trachea [windpipe] causes total loss of voice, but by simply closing it, vocal sounds can again be produced. Such openings, in man, are met with, either as the results of accidents, of suicidal attempts, or of operations performed on the larynx or trachea for the relief of disease."

Dr. TOBOLD, Professor in the University of Berlin, in his "Laryngoscopie and Kehlkopf Krankheiten" (Laryngoscopy and Diseases of the Larynx), p. 131, says, "Soft palate, lid, pockets, and pocket-bands are not directly active in the production of either chest or falsetto tones; they only modify the tone produced in the glottis."

Dr. LUSCHKA, Professor in the University of Tubingen, in his great work "Der Kehlkopf des Menschen" (The Human Larynx), says in the introduction: "Only the vocal cords, with the slit they form, have specifically functional signification, in a narrower sense, of a voice apparatus, as the parts of the larynx which lie under and over them have no material and deciding influence on the production of sound."

I will bring my quotations to a close with the following, which seeks to prove the contrary. Dr. C. B. GARRETT ("The Human Voice,"

J. and J. Churchill, London, 1875, p. 17) says, "It is recorded that the larynx of a blackbird was removed by severing the windpipe just below it; that the poor 'thing continued to _sing_, though in a feebler tone.' This proves that notes can be formed _behind the instrument_ and before the air reaches it." This argument, however, is of no value, because it so happens that birds have two larynges, one at the bottom and the other at the top of the windpipe. Dr.

Garrett seems not to have been aware of this fact.

The vocal ligaments in the adult male are, in a state of rest, about three-quarters of an inch long, and in the female about half an inch. I pointed out before that the vocal ligaments are attached in front to the s.h.i.+eld (pl. VII, 6) and behind to the pyramids (pl. VII, 3, 3). Let it now be borne in mind--1st, That the pyramids, in their turn, are fastened to the upper border of the ring cartilage; and 2nd, That by drawing the s.h.i.+eld downwards and forwards upon the ring, the distance between the upper border of the ring (pl. VII, 5) and the front of the s.h.i.+eld (pl. VII, 6) is increased, and it will be easily seen that this movement must of necessity have the effect of stretching the vocal ligaments.

This drawing of the s.h.i.+eld downwards and forwards upon the ring is brought about by a pair of muscles ascending on either side, in the shape of a fan, from the ring to the s.h.i.+eld cartilage (pl. VIII, 1, 2).

These muscles we name the "Ring-s.h.i.+eld Muscles." In opposition to them there is another pair inside the s.h.i.+eld, running parallel with the vocal ligaments (pl. IX, 1, 2, 3). They are attached (like the vocal ligaments) in front to the s.h.i.+eld cartilage and behind to the pyramids.

These muscles we will call the "s.h.i.+eld-Pyramid Muscles." They counteract the ring-s.h.i.+eld muscles, and having overcome their resistance, pull the s.h.i.+eld cartilage up again, thereby, of course, relaxing the vocal ligaments. The ring-s.h.i.+eld muscles, therefore, _stretch_ the vocal ligaments and the s.h.i.+eld-pyramid muscles _relax_ them. The s.h.i.+eld-pyramid muscles have an additional function--that of pressing together the vocal ligaments, under certain circ.u.mstances, thereby narrowing the opening between them. They have therefore been, in these later days, called the Sphincter[G] muscle of the glottis. They have also been called the Vocal Muscles, since they play so important a part in the formation of all vocal tone that a paralysis of them causes total loss of voice.