II | Physiological View Formation of Sound by the Organ of the Human Voice
The great physiologist, Johannes Müller, fastened a larynx, which he had cut out with the whole trachea belonging to it, to a board, and, stretching the vocal chords by a weight that could be increased or diminished at pleasure, caused vibrations in it by blowing through the trachea with a pair of bellows, or through a tube with his own breath. In this way he succeeded in producing almost all the tones of the human voice, and even some which are beyond the compass of this organ.
He distinguished two different kinds of tones, to which he gave the names of the chest register and the falsetto register. The chest tones were produced when the vocal ligaments, slackly stretched, were made to vibrate easily in their whole breadth; the falsetto tones came merely through the vibration of the fine inner edges of the vocal chords when they were more tightly stretched. At a moderate stretching of the vocal chords, it depended upon the manner of blowing whether a sound corresponding to the chest voice or to the falsetto were produced, or whether it were higher or lower for several tones, often for a whole octave. A series of tones of more than two octaves could thus be produced in the same larynx, with, however, gaps and places at which the vocal chords, instead of being stretched gradually, have to be stretched at once very strongly, in order that the succeeding higher half tone may be reached. Such a place Müller indicates from c2 to c♯2, or d2 to d♯2, with the remark that it differs in different larynxes, being in some higher and in some lower. But in order to render practicable the proper stretching of the exsected larynx, muscles and membranes have to be cut, which sufficiently proves that the functions of the organ of singing in the living must be differently carried on.
Dr. Merkel, in Leipzig, has continued these experiments, and by means of a peculiar contrivance has succeeded in producing all the tones in the exsected larynx, without mutilating it. But these investigations, interesting as they are, throw no certain light upon the formation of sound by the vocal organ in the living.
The celebrated singing master, Manuel Garcia, now living in London, was the first to adopt the right mode of scientific inquiry in this department, with favorable results. He undertook to apply the laryngoscope (previously invented by the Englishman, Liston) to the larynx in the act of singing. The interesting results of these observations were published by him in the Philosophical Mag. and Journal of Science, vol. x. p. 218. While men of science immediately repeated Garcia’s experiments and applied them with the greatest advantage to pathological purposes, they were received with distrust, scarcely noticed, and in many instances entirely rejected, by teachers of vocal music. The few who attempted to follow the path thus opened soon gave it up, because they lacked either patience or the anatomical knowledge necessary to such investigations.
The laryngoscope is well known among medical men. It is a small plane mirror of glass or metal, having a long handle. Before it is introduced into the throat, it is first warmed, to prevent its becoming dimmed. The reflecting surface of this instrument is directed downwards and forwards, so that it receives the reflection caught from a concave mirror, and presents to the eye of the observer a picture of the illuminated larynx. In using it upon oneself, there is need of a second mirror, which must be so held that the image may be seen in the laryngoscope.
The use of the laryngoscope requires in the observer a certain adroitness and long-continued practice—almost more in the observer than in the subject of observation. In self-observation one must first learn to overcome the irritation always caused at the first by the contact of the mirror with the back of the throat. Once accustomed to the contact, one soon succeeds in obtaining a sight of the larynx, sufficient for the most part for pathological purposes. But it requires long practice before one can control those organs, usually not immediately submissive to the will, and raise the epiglottis, so as to be able to see into the whole larynx. But this is absolutely indispensable, in the observation of the formation of sound, to the attainment of any substantial results. Garcia says himself that one-third of the glottis was always hidden from him by the epiglottis, and to this circumstance is the unsatisfactory character of his observations to be ascribed. But even when, after long practice, one is able at last to bring the whole glottis into view, this is not by any means enough. Not until observation has been so long continued that all the movements of the vocal organ are normal, notwithstanding the unnatural drawing back of the epiglottis, and not until the process that goes on is found again and again to be always the same, can it be recognized as fact.
As Garcia is the most eminent of singing masters now living, and as he has sought, solely in the interest of vocal music, to ascertain the mechanism by which sound is formed, and as his observations have been confirmed by men of science, I give them here in his own words.
In order that what follows may be better understood by those unacquainted with anatomy, a brief anatomical description of the vocal organ will be found in an Appendix to the present work.