Physiology Of The Vocal Organs
The two principal cartilages, the cricoid and the thyroid, are connected with one another, as is seen in Fig. 67;
The ligament (1), crico-thyroid, connects the front sides of the two cartilages.
A muscle can be either elongated or shortened. The shortening, or contraction, of a muscle serves to bring the two parts to which it is attached toward each other, while an elongation would separate them. The elongation is brought away by a forcible outward pull, which stretches it beyond its natural length, thereby weakening the muscle. Only a natural contraction of a muscle is of any service to the body. Anything beyond that, or less than that, is useless or harmful.
The vocal chords, in contracting, pull the cricoid upward and the thyroid downward, but the cricoid cartilage is part of the trachea, thus forming with the other rings one solid air tube. The cricoid cartilage cannot be drawn upward; hence only the downward pulling force of the ligament is possible. This force is sufficient, however, to prevent the muscles which pull the thyroid cartilage upward (as will be later described) from pulling it out of place.
As this muscle connects only the frontal parts of the cartilage, and since the thyroid cartilage simply rests upon the back of the cricoid, other muscles are needed to prevent the rear part from leaving its position. These muscles are found to the left and the right sides of the ligament (2,3,4) in Fig. 67.
They are the crico-thyroid muscles.
Now, when all these muscles contract, the thyroid cartilage tilts downward in front and closes the hollow space or niche between it and the cricoid. Also, since the vocal chords are attached to the front of the thyroid cartilage, they are drawn somewhat down in front, and are thus stretched to some extent.
At the expense of seeming tedious, it must be stated that all these important actions could not take place if the cricoid cartilage were not firmly fixed as a part of the air tube. For, if the cricoid were movable, then the muscles which connect it with the thyroid could contract but very little. At least one of the two parts to which muscles are attached must be solid to afford the necessary resistance against which muscles can contract.
Take a friend’s hand and pull it toward you. If he does not resist, then you cannot exert yourself, but the more he resists, the stronger you can pull. Now, it is true that the entire air tube can be raised somewhat and that is what is done when the larynx is raised for high tones, as is often wrongly advised. But in so doing, it is made impossible for the muscles just described to contract sufficiently to stretch the vocal chords, because, if the air tube is raised, it loses its natural hold in the chest, and as a consequence, all the other forces are weakened. Similarly, if you lower the larynx for lower tones, you also lower the air tube and alter its natural position, weakening its action and that of all other parts with it. If you pull a finger out of a joint, it cannot move up or down, because it is dislocated. It is so throughout the human body; each member can do its best work only in its naturally appointed position and in no other.
Muscles Connecting The Cartilages Of The Larynx.
You are now requested to examine the position of the hyoid bone (9) in Fig. 67. Picture to yourself that the long horns reach far back on both sides of the throat and directly underneath the tongue, with which the hyoid bone is very closely connected. Just as the cricoid and thyroid cartilages are connected, so the thyroid and the hyoid bone are connected, first in front by a ligament (5), and then on both sides by muscles (6).
Now, rather close reasoning will be required of the reader to understand and digest the seemingly involved (but in reality, very simple) actions of all these muscles. The two cartilages, the cricoid and thyroid, and the hyoid bone, must be brought closely together to make a hollow tube. It was said that the cricoid, being a part of the air tube, affords a firm basis for the contraction of the muscles running to the thyroid, but if the latter cartilage were not itself provided with muscles to hold it, then it could not resist the cricoid muscles.
The two cartilages would merely lie one upon the other in a loose, flabby state, utterly useless for vocal purposes. Consequently, the thyro-hyoid muscles must be able to resist the muscles below them, but the hyoid bone, as illustrated, affords no hold to the muscles below it or to the thyroid. How, then, could all the described muscles contract? How could these three cartilages be brought into a firm, hollow tube? We must find some means whereby directly or indirectly a firm hold is provided for the hyoid bone. Otherwise the chain of resistance would be broken and musical tones would be impossible. The search for this support to the hyoid bone leads us again to the external voluntary muscles, and to the solution of the question of how voice can be developed.
The circle is again completed. It does not matter from what point of the vocal organ one starts, one always arrives at the muscles from the hyoid bone to the tongue, as the keystone or mainspring upon which all other parts of the vocal organ depend.
If you hold a rubber band between your hands, you must pull equally strongly in opposite directions to stretch it. If the rubber band is doubled or quadrupled in size, considerable strength is required to stretch it. Now, with the vocal chords there is this additional difficulty, that they cannot be stretched lengthwise, like the rubber band, which you elongate in tensing and stretching. The main part of the stretching the vocal chords is accomplished by “bending” them downward. This bending downward can only be accomplished by muscles which act upon the thyroid cartilage in such a way that it is tilted forward and downward; this is done by the muscles which are attached to the larynx in front and in the rear. The front muscles rise out of the breast and collar bones and pull the thyroid downward.
The rear muscles spring from the soft palate above, and are attached to the rear horns of the thyroid cartilage. The thyroid cartilage, remember, is astraddle upon the cricoid cartilage below it, as a man rides a horse. The legs of the man correspond to the shorter horns of the thyroid, the riser’s arms correspond to the long horns of the thyroid cartilage. The rider can bend forward or backward and that is exactly what the thyroid does also. Every bend, of course, carries the vocal chords with it. In reference to a horse and its rider, the horse holds the bit firmly in its mouth, thus supporting the reins in front. The rider supports the rear ends of the reins (which are the vocal chords).
Now, if the horse moves its head forward and the rider leans at the same time backward, the reins (the vocal chords) are taunt or stretched very much indeed.
But, if the horse moves its head backward, or the rider bends forward, the reins are relaxed.
By bending forward, the vocal chords are stretched; by bending backward they are relaxed.
Now, if you can think mechanically, that is, if you can follow a mechanism in its logical construction, you would naturally ask yourself this question: What is it that holds the larynx so firm and stead that the muscles can contract powerfully and bend the vocal chords inside the larynx?
Here we arrive at the wonderful provision in nature which has escaped the observation of many physiologists and practically all teachers of voice.
Directly, or indirectly, all muscles of the vocal organ (and as we shall see in the lessons on breathing), even those which have to do with breathing, are dependent upon the tongue, as the central organ. The muscles starting from the breast and collar bone, and those starting from the chin, the hard palate and the skull, have at their one end a firm, solid structure or bone; at their other end, they are fastened, some directly (other indirectly by other muscles), into the tongue.
Now the tongue in its natural state is a most flexible organ, of very little strength. In that natural relaxed state it could give no hold, no firm support to the muscles with center into it. Think of the wonderful thing that Nature has done for the tongue:
The tongue has a shoe; it is given a firm, bony structure, just as a horse’s foot is shod to give it a support against the hard ground or paved streets.
All you have to do is to keep this shoe firmly connected with the tongue. From a purely vocal point of view, this is the chief necessity and the greatest work to be accomplished. Thy hyo-glossus muscle, as has been fully described, connects the hyoid bone or horseshoe to the under part of the tongue, its rear part. In this manner that part of the tongue becomes solid and firm, giving the muscles which depend upon it a strong foundation and resistance against which all muscles attached to the tongue can contract with their full power.
This leaves the front of the tongue free. The rear part can adjust itself to the different changes of positions needed for articulation, for extremes in range, power, and for all the variations of tone color, from the softest whisper to the strongest and loudest tone.
The hyo-glossus muscle needs to be very strong indeed to afford the other muscles attached to it the resistance and hold which they must have, in order to bend and stretch the vocal chords. Every means must be employed to strengthen the hyo-glossus muscle and the student must never relax in the effort to accomplish this purpose.
When the hyo-glossus muscle is weak, the hyoid bone will not be held firmly enough to the tongue to give the necessary support. In this case all other muscles relax their effort correspondingly. Of course the vocal chords also relax and the tone becomes inferior. This fault, of a too weak hyo-glossus muscle, is almost universal. Out of it arise not only inferior voices generally, but imperfect voices, stammering, stuttering, huskiness, loss of breath, constant coughing and similar troubles. The tongue’s shoe not only has to fit, but it must be held firmly fixed to the under part of the tongue, and as it were, automatically, without any effort. This is only possible when the hyo-glossus muscle is very strong.
The Laryngeal Tube
The tube or space of the hollow throat, within which the larynx is situated, can be compared somewhat to an hour-glass. The lower and upper parts are wide, but the middle part, through which sand runs in an hour-glass, is narrow.
The upper division of the laryngeal tube consists of the epiglottis, which is the flexible gristle that we touch when a finger is passed down the throat. The epiglottis forms a cover to the air tube, so that the food cannot enter the air tube when swallowed. The epiglottis is the front wall of the upper section. The rear wall is formed by the upper parts of the cricoid and arytaenoid cartilages.
The middle part consists of the vocal muscles, which again are divided into false and true vocal chords. The false or spurious vocal chords are above the true vocal chords. They are much farther apart than the true vocal chords; hence they cannot be brought close enough together to make a sound. The true vocal chords form a sharp corner, which is set into vibration by the breath. As the sharp corners are only the outward edge of all the vocal muscles, it follows that not only the edges are made to vibrate and produce sound, but the entire mass of muscles back of them.
Between the false and the true vocal chords is the ventricle or space which permits a free vibration of the vocal chords.
The lower section of the laryngeal tube is merely the continuation of the trachea or air tube, only much wider. It narrows gradually toward the root of the vocal mechanism.
Position Of The Larynx
The larynx is situated in front of the spinal column and opposite the “4-6” vertebrae. Between the larynx and the spinal column is the food pipe or esophagus, so that food passes between the larynx and the spine. The larynx is of a larger size in a man than in a woman.
Fig. 70. The larynx, when viewed from above, discloses the vocal chords, epiglottis, ventricle, etc.
These are seen much better when breathing silently and when light is reflected down the throat. The false chords are the dark mass of muscles above and the light lines of the true vocal chords are seen below. Notice that the false vocal chords are much further apart than the true vocal chords.
Because the larynx lies so near the spine two special advantages are gained. One of these is that since the omohyoid muscle, running from the hyoid bone to the rear part of the collar bone, runs in an oblique direction, it must and does, when contracted, press the lower part of the larynx, the cricoid or ring cartilage, firmly against the spine. The spine therefore acts as a fulcrum for the cricoid, so that all the muscles of the larynx can exert their full power when contracting and stretching the vocal chords. The second advantage of this firmly fixed position of the larynx against the spine, is the gain in additional resonance of tone. As the vocal chords, and with them the larynx, vibrate, the spine will also vibrate, enlarging and beautifying the tone.
When you strike a tuning fork and merely hold it in your hand, the tone will be comparatively small, but when you rest the fork against the broad surface of the table, the tone will be greatly augmented. In a similar way, the spine augments the vocal tone.
The great importance of the spine is that it is one of the agents which assist the external laryngeal muscles in their effort to stretch the vocal chords. Another discovery is that the spine actually does add to the volume and quality of the voice; that, in short, the spine is a true resonator.
In the next lesson it will be necessary to consider, and to briefly describe, the blood vessels and nerve supply of the vocal organ. Then, again, we shall obtain additional proof of the importance of the tongue and especially the hyo-glossi muscles, as the central organ or keystone of the entire vocal organ.
The reason that illustrations of the vocal chords and the entire vocal organ in such detail is to prove to you just why the exercises given you are such as they have so far been and will be as we advance. You should be convinced that these exercises are right and that no other exercises could, by any possibility, do for you that which these exercises are sure to do. When you see for yourself that these things taught are exact and logical, you will make them your own, and you will be content to work, knowing and feeling that the results will justify your efforts and expectations.