Page:EB1911 - Volume 28.djvu/191

Rh the perception of musical tone begins, and that from this note to the upper note of Lucrezia Ajugari there is a range of nearly six octaves, whilst the extreme range of ordinary voices, from the lowest bass to the highest soprano, is a little over three octaves. It is also interesting to observe that the range of the human ear for the perception of musical tone is from do−1 to do10, or from about 32 to 32,768 vibrations per second—eleven octaves.

3. The Voice Registers.—The voice has been divided by writers into three registers—the lower or chest, the middle and the small or head register. In singing, the voice changes in volume and in quality in passing from one register into another. There is remarkable diversity of opinion as to what happens in the larynx in passing through the various registers. There has also been much discussion as to the production of falsetto tones. Lehfeldt and Johannes Müller held that a weak blast of air caused only a portion of the cords, as regards length, to vibrate; M. J. Ortel noticed that when a falsetto tone is produced nodal lines are formed in the cords parallel to their edges, an observation supporting the first contention; M. Garcia was of opinion that as the voice rose in pitch into falsetto only the ligamentous edges of the cords vibrated; and W. R. E. Hodgkinson showed, by dusting finely powdered indigo into the larynx and observing the blue specks with the laryngoscope, that “in the deeper note of the lower register the vibrating margin extended from the thyroid cartilage in front to a point behind the junction of the ligamentous and cartilaginous portions of the cord.” In singing falsetto tones these additional parts are not thrown into action. Some remarkable and instructive photographs obtained by French show that in proceeding from the lowest to the highest notes of the lower register the cords became lengthened by one-eighth of an inch in a contralto singer's larynx; the same singer, in passing into the middle register, showed a shortening of the cords by one-sixteenth of an inch, and another increase in length when the upper part of the middle register was reached.

4. Condition of the Larynx in the Various Registers.—In singing, one can readily observe that the tone may appear to come chiefly from the chest, from the throat or from the head, or it may show the peculiar quality of tone termed falsetto. Authorities differ much in the nomenclature applied to these varieties of the voice. Thus the old Italian music masters spoke of the voce di petto, voce di gola and voce di testa. Madame Seller describes five conditions, viz. the first series of tones of the chest register, the second series of tones of the chest register, the first series of tones of the falsetto register, the second series of tones of the falsetto register, and the head register. French writers usually refer to two registers only, the chest and the head; whilst Behnke gives three registers for male voices (lower thick, upper thick and upper thin) and five for the voices of women and children (lower thick, upper thick, lower thin, upper thin and small). These distinctions are of more importance practically than as implying any marked physiological differences in the mechanism of the larynx during the production of the tones in the different registers. By means of the laryngoscope it is possible to see the condition of the rima glottidis and the cords in passing through all the range of the voice.

In 1807 Bozzini first showed that it was possible to see into the dark cavities of the body by illumining them with a mirror, and in 1829 W. Babington first saw the glottis in this way. In 1854 Garcia investigated his own larynx and that of other singers, and three years later Türck, and especially J. N. Czermak, perfected the construction of the laryngoscope. In 1883 Lennox Browne and Emil Behnke obtained photographs of the glottis in the living man. The laryngoscope is a small mirror, about the diameter of a shilling, fixed to the end of a long handle at an angle of 125° to 130°. This mirror is gently pushed towards the back of the throat, and if sufficient light be thrown into the mouth from a lamp, and if the eye of the observer be in the proper position, by angling the small mirror it is not difficult to get a view of the glottis. The light from the lamp is reflected by the mirror down on the glottis; from this it is reflected back to the mirror, and then by the mirror it is finally reflected to the eye of the observer. Usually the observer has in front of his eye a mirror by which a powerful beam of light

can be thrown from a lamp into the mouth and throat. In the centre of the mirror there is a small hole through which the eye of the observer sees the image in the small mirror at the back of the throat. By placing a second plane mirror in front of the face, an observer can easily study the mechanism of his own larynx.

Suppose the picture of the larynx to be examined in the small mirror at the back of the throat, an image will be seen as in fig. 4. During calm breathing, the glottis is lance-shaped, between the yellowish white cords. A deep inspiration causes the glottis to open widely, and in favourable circumstances one may look into the trachea. When a sound is to be made, the vocal cords are brought close together, either along their whole length, as in fig. 7, or only along the ligamentous portion, the space between the arytenoids being still open, as in fig. 8. Then when the sound begins the glottis opens (fig. 4), the form of the opening influencing the kind of voice, whilst the degree of tension of the cords will determine the pitch.

During inspiration the edges of the true vocal cords may occasionally be close together, as in sobbing, and during inspiration the false cords are easily separated, even when they touch, and during expiration, owing to dilatation of the ventricles, they come together and may readily close. Thus, from the plane of the cords, the true cords are most easily closed during inspiration and the false cords during expiration. J. Wyllie clearly showed in 1865 that the false vocal cords play the chief part in closure of the glottis during expiration. Lauder Brunton and Cash have confirmed J. Wyllie's results, and have shown further that the function of the false cords is to close the glottis and thus fix the thorax for muscular effort.

During the production of the chest voice, the space between the arytenoid cartilages is open, and between the vocal cords there is an ellipsoidal opening which gradually closes as the pitch of the sound rises (see figs. 9, 10, 11). During head voice, the opening between the arytenoids is completely closed; the portion between the vocal cords is open, but in place of being almost a narrow straight slit as in chest voice, it is wide open so as to allow an escape of more air (see fig. 12). Paralysis of the motor fibres causes aphonia, or loss of voice. If one cord is paralysed the voice may be lost or become falsetto in tone. Sometimes the cords may move in breathing or during coughing, but be motionless during an attempt at the production of voice. Rarely, incomplete unilateral paralysis of the recurrent nerve, or the existence of a tumour on each cord, thus making them unequal in length, may cause a double tone, or diphthongia. Hoarseness is caused by roughness or swelling of the cords.

5. The quality of the human voice depends on the same laws that determine the quality, clang-tint or timbre of the tones produced by any musical instrument. Musical tones are formed by the vibrations of the true vocal cords. These tones may be either pure or mixed, and in both cases they are