From above downward one feels in the middle line the parts in the order previously mentioned, beginning with the hyoid bone. One may learn that the larynx is movable and yielding, a hard structure covered with softer tissues, but what these are, and much more, can only be learned by examination of the larynx after it has been removed from some animal. Every butcher can provide the material for getting a sound, practical knowledge of the respiratory apparatus. He may be asked to supply the following:
1. A pig's "pluck"—i.e., the "lights," or lungs, with the windpipe attached. The liver, heart, etc., are not required, though to observe the relations of the circulatory system—i.e., the heart and large blood-vessels—to the respiratory system will be time well spent. Unless special instructions are given, the larynx, which the butcher may term the "weezend," may be lacking or mutilated. It should be explained that this organ, with a part of the windpipe and the extreme back part of the tongue, and all below it, are required. For one sitting this single "pluck" will suffice, as it will serve for a general examination. The lungs may be dilated by inserting a tube into the windpipe, tying it in position, and blowing into it with greater or less force. It should be especially observed how suddenly the lungs collapse when the breath force is removed, as this illustrates well their elasticity. By cutting through the windpipe lengthwise and following it downward one learns how numerous are the branches of the bronchial tree, etc.
For a second sitting one should secure at least two specimens of the larynx of the pig or sheep, though the former is more like the human, and so the better on the whole. A case of dissecting instruments is not essential; a sharp pocket-knife will serve the purpose. In order that the student may have a clear idea of the cartilages, all the soft tissues must be cut or scraped away. It is necessary to exercise great care, or the membranes connecting the cartilages together will be cut through; and on the other hand, unless the work in the neighborhood of the arytenoids be cautiously done, these cartilages may be injured, and it is most important that their swivel-like action and their relations to the true vocal bands be observed. The glottic chink can be seen from above or below, and should be observed from both view-points. Its margins are formed by the true vocal bands.
Then, with the figures before him, the student should endeavor to isolate each of the muscles described. The muscles can always be recognized by their red color, but it is to be remembered that those on the inner surface of the larynx, such as the crico-arytenoid, are covered with mucous membrane, which after death is very pale. This can by careful dissection be removed, and if in doing this a small pair of forceps be employed, the work will be greatly facilitated. One must be very skilful indeed if he would get all the muscles "out," or well exposed to view as individuals, on a single specimen. Likely several will be required before entirely satisfactory results are reached, but these are well worth all the time and labor required. The action of the muscles can in some measure be demonstrated by pulling on them in the direction of their loosest attachment, though it must be confessed this is much more difficult in the case of most of the muscles of the larynx than in those of other parts of the body.
Should the specimens be very successfully dissected, it may be worth while to keep them for future observation, in rather weak alcohol (40 per cent.), in, say, a preserve jar.
All examinations of the vocal bands may leave the observer disappointed; he may fail to realize, most likely, how such wonderful results can be accomplished by structures so simple as those he sees before him. But when the laryngoscope is brought into use, then comes a revelation. This instrument will be described in the next chapter.
HYGIENE.
Some of the hygienic principles involved have already been referred to and illustrated, and others follow from the facts already set forth. It is very important for the voice-user to bear in mind that his larynx is a part of the respiratory tract, and that the whole of this region and the entire digestive tract, part of which is common to both, are lined with mucous membrane. If the nose be affected with catarrh, the throat does not usually long escape; and if the back of the mouth cavity (pharynx) be disordered, the vocal bands and other parts of the larynx are almost sure to be involved more or less.
The condition of the stomach is reflexly, if not by direct continuity through the mucous membrane, expressed in the throat generally; hence as experience shows, the voice-user cannot exercise too great care as to what and how much he eats, especially before a public appearance. He must know himself what best suits him, in this regard, to a degree that is necessary for few others.
When singing, more blood is sent to the organs used, hence the great danger of that excess of blood being retained in the parts too long, as might easily happen from pressure about the neck, etc. It is scarcely necessary to point out that draughts, cold rooms, etc., will also determine the blood from the skin inward, and set up that complicated condition of multiform evils known as "a cold." The obvious principle of prevention lies in keeping the body, and especially the neck, shoulders, and chest, warm after using the vocal organs in any way in public. To hand the singer a wrap after leaving the platform is always wise, and the judicious friend will see that conversation is not allowed, much less forced on the possibly breathless and wearied voice-user—a precaution that is probably more honored in the breach than in the observance, for in this as in other cases one's friends are sometimes his worst enemies.