Imágenes de páginas
PDF
EPUB

THE ORGANS OF VOICE.1

AN exact anatomical knowledge of the vocal organs is not essential to our purpose. All that is aimed at, in the following observations, is to impart such an idea of organic structure and action as is indispensable to an intelligent, voluntary use of the vocal organs.

We commence our investigation with the primary action of inspiration, or inhaling breath. A person in good health draws in breath by an exertion, partly involuntary, partly voluntary, of those muscles which, by a combined act, expand, and at the same time raise the chest, and consequently enlarge the cavity called the thorax, the region between the neck and the stomach. The degree of freedom and energy, in this muscular action, decides of course the extent to which the thoracic cavity is enlarged, and the volume of air which is inhaled: it decides, also, as a natural consequence, the capacity of resonance in the chest, and the fulness of the supply of breath, the material of sound.

These preliminary facts teach us the first practical lesson in the cultivation of the voice, the necessity of maintaining an erect, free, expansive, unembarrassed posture of the chest, as an indispensable condition of full, clear, distinct, effective, and appropriate utterance.

The next practical lesson here taught is that utterance demands a free expulsion, not less than a deep inhalation of breath; that there must be a vigorous consentaneous action of the will, along with the silent involuntary process of nature.

1 For further study the student is referred to Dr. Ghislani Durant's admirable work on the Hygiene of the Voice.

The full function of expiration, when carried to the extent of vocalized exclamation, implies an energetic use of the lower muscles of the trunk, those which are termed the abdominal,1 to impart, by upward and inward impulse, a powerful percussion to the diaphragm, by which the breath contained in the air-cells of the lungs is forced through the bronchial tubes and the trachea, towards the glottis and the larynx, where it is converted into sound, and thence into and through the mouth, and the cavity of the head, where it is modified into speech by the action of the nasal passage, the tongue, the palate, the teeth, and the lips, in the various functions of articulate utterance.

The engraved figures will serve to impart a clearer idea than can be conveyed by words of the place and form of the vocal organs, together with their action in the production of sound.

Figure 1 represents the principal abdominal muscle by which the first expulsory movement terminating in sound is produced. The action of this muscle, in energetic and abrupt forms of utterance, is nearly the same in kind, though not in degree, with that which takes place in the sudden shrinking from a blow aimed at or below the stomach. In vigorous utterance of a steady and sustained character, or in the energetic singing of long notes, a powerful and continued upward and inward pressure of the abdominal muscles takes place, as in the attitude observed in swift riding on horseback.

2. The diaphragm, which by an upward impulse, consentaneous with that of the abdominal muscles, and imparted to the pleura or enveloping membrane of the lungs, forces the breath from the air cells into the bronchi, and thence into the trachea and the larynx. .

3. The thorax, the great cavity of the chest. By the ex

1 In shouting and calling, and other violent exertions of voice, the dorsal - those of the lower part of the back - partake in the expulsory

muscles

effort.

[ocr errors]

pansion and compression of this capacious organ, the process of breathing is conducted; and by its resonance the voice receives depth and volume.

4. The intercostal muscles at the lower, and

5. The thoracic and pectoral muscles, at the upper part of the chest, serve to dilate and compress it, in the acts of breathing and of utterance.

6. The pleura, a membrane which envelops the lungs, and propagates to their cells the impulse by which these are emptied of their successive supplies of air inhaled at the intervals of speaking or singing.

7. The lungs, a spongy body in the form of lobes, into the cells or little cavities of which the air inhaled in breathing is drawn, and from which it is expelled by the impulse communicated, as mentioned before, by the pleura, and derived from the diaphragm and the abdominal muscles.

8. The bronchi, or two main branches of the trachea or wind-pipe. These two tubes are themselves subdivided into many subordinate and minute ramifications, which serve to distribute to the air-cells of the lungs. in which they terminate the breath inhaled through the trachea, and to convey that which is expelled from the lungs by the impulsive action of the diaphragm into the trachea, the larynx, and the mouth. One important office of the bronchial ramifications is to vibrate, and thereby aid in rendering vocal the column of air which is emitted from the cells of the lungs.

9. The trachea or wind-pipe, a series of connected cartilaginous or gristly rings, forming the great air-tube, which receives and conducts the breath to and from the lungs, in the acts of inspiration and expiration, and in the function of utterance.

10. The larynx, a cartilaginous box on the top of the trachea, the exterior projection of which is familiarly called the Adam's apple, in allusion to the fabled origin of this part, which was anciently said to have owed its existence

to Adam's fatal offence in swallowing the forbidden fruit. The whole larynx is the immediate seat and general instrument of vocal sound. The portions of this organ which are immediately concerned in the production of sound are, 11. The cricoid cartilage, situated immediately over the uppermost ring of the trachea, resembling in form a sealring, from which it takes its name, but having the broad part at the back, and the narrow in front. The form and position of this portion of the larynx admit of the elevation and depression of its parts, one step in the process by which tone is rendered grave or acute.

12. The arytenoid cartilages so called from their fancied resemblance in shape to a ladle, funnel, or pitcher. These fill up the space at the back of the thyroid and cricoïd cartilages, and are connected with both; while they serve also as points of support and of tension for the vocal ligaments.

13. The thyroid cartilage, which has its name from its partial resemblance to the form of a buckler or shield, but much bent. Its two main plates form the walls or sides of the larynx; and their size usually determines the capacity of the voice, as we observe, in their comparative smallness in females and children, and their great expansion and projection in men.

The comparative solidity of texture, in all these component portions of the larynx, and in the gristly rings of which the trachea is itself composed, give them the power of rendering the voice compact and sonorous.

14. The vocal ligaments extend across the upper part of the larynx, and form the lips of the glottis, and by their vibration, together with the action of the current of air expelled through the trachea and larynx, produce the phenomena of vocal sound or voice, and, by their tension or remission, the effect of high or low pitch.

15. The glottis, so denominated from the partial resemblance of its shape to that of the tongue, is a small chink, or opening, which forms the mouth of the larynx. The

opening and the contraction of this portion of the vocal apparatus decide, in part, the gravity or the shrillness of

tone.

All the parts of the larynx are interconnected by ligaments, and by muscles which move in concerted action, so as to expand or contract, raise or lower the whole larynx, and thus enlarge or diminish its capacity, and elevate or depress the pitch of the voice, and increase or diminish its force. The whole interior of the larynx is lined with a continuation of the mucous membrane of the mouth, which imparts to it a vivid sensibility and a unity of action. Hoarseness is the result of the embarrassment or obstruction of this membrane, by the mucous accumulations arising from colds or catarrh, or the injudicious habit of using cold water too freely during the exercise of speaking.

16. The epiglottis, the valve or lid, which, when the larynx is elevated, as in the act of swallowing, covers the glottis or orifice of the windpipe and prevents strangulation. Its usual erect position allows free ingress and egress to the breath. But in some instances of intensely impassioned utterance its pressure against the glottis becomes an additional preparative for the ultimate explosive eruption of voice.

17. At the root of the tongue lies a small crescentshaped or horseshoe-formed bone, called, from its resemblance to the Greek v, the hyoïd, or u-like bone. This member serves, by its firm texture, as a gateway from the trachea and larynx to the mouth, or from the latter to the former. It forms a point of tension for the muscles which connect the larynx with the mouth. Its hard texture enables it to perform this office effectually, and thus to aid in giving pitch in vocal sounds.

18. The thyro-hyoïdean membrane connects the thyroïd cartilage with the instrument just described, and facilitates the functions of both in elevating or depressing the pitch of the voice.

17

« AnteriorContinuar »