Voice and Speech.-The sound produced at the glottis is only an inarticulate sound, differing only in intensity, pitch, and tone; yet this glottid sound, by the re-enforcement of certain of its characteristics at the buccal and nasal cavities, and by the union with other sounds produced at these points, acquires special features constituting the voice and speech properly so-called (see Organs of the Senses (Hearing) for the explanation of the words intensity, pitch, tone, sounds, etc.).

The intensity of the sound produced in the glottis depends on the force with which the expiratory current of air strikes the edges of the glottis when so arranged as to emit any decided sound; this intensity depends essentially on the development and the elasticity of the lung, the breadth of the thoracic cage, and the force of the expiratory muscles.

The pitch of the sound produced by the vocal lips increases in proportion to their length and tension (or contraction); thus the human voice performs the gamut or scale in passing from the lower notes to the higher; it even forms two series of scales, the lower of which is generally designated under the name of chest register (chest voice), and the sharper and higher under that of head register (head voice). These expressions have no meaning in a physiological point of view, since the voice is formed in the glottis in both cases; but what has given rise to them (and, in a certain sense, justifies the use of them) is the sensations experienced during the emission of either the so-called head or chest voice, the accompanying vibrations being more strongly marked in the walls of the chest in the one instance, and in the supra-laryngeal cavities in the other. According to Mandl, the essential modification in the glottis which produces the emission of sounds in the two registers, consists in the fact that, in the case of the chest voice, the orifice of the glottis is open and vibrates throughout its whole extent, while in that of the head voice (or falsetto) the orifice is open and vibrates only in the interligamentous part; the entire intercartilaginous portion is then closed, while the superior vocal cords sink, and are adjusted to the inferior cords, covering a considerable part of them in such a manner as to diminish the extent of the vibrating part (an effect resembling that produced by the tongues employed in the pipes of an organ).1

The human voice has, therefore, generally a range of two

See also Ch. Bataille, "Nouvelles Recherches sur la Phonation." Paris, 1861.

octaves, and according to whether these two octaves belong to the upper or lower part of the scale of musical sounds, the human voice has been classified, beginning with the lowest, into the bass voice (from fa to re), the barytone (from la to fag), the tenor (from do, to lag), the contralto (from mi, to do), the mezzo-soprano (from sol, to mi̟4), and the soprano (from si, to sol), the three latter being women's voices. The differences between them are principally owing to variations in the length of the lips of the glottis; this length is represented in man by the number 25, in woman by 20, and by 15 in eunuchs, their voice being extremely high.

A child's voice is very high, the glottis being smaller than that of the adult. The change in the voice takes place at the age of puberty, the development of the larynx causing the voice to become an octave lower in the case of boys, and two notes only in that of girls. In old age, the ossification of the cartilages, and the atrophy of the muscular fibres (?) cause the voice to become still lower, while its intensity is also diminished; thus tenors become barytones (L. Mandl).

The tone of the voice is first produced by the lips of the glottis itself. Helmholtz has, we know, demonstrated that the tone (see Organs of the Senses, Hearing) is due to the fact that the sounds which appear to us so simple are really composed of a fundamental note, and several accessory netes, called harmonics (Sauveur). The varied combination of these harmonic notes, in different instruments, constitutes their special tone. The vocal lips, like the membranous pipes, beside the fundamental vibration of one sound, exhibit partial vibrations which give rise to various harmonics of this note: whence the different tones of the note produced by the glottis. What, however, especially marks the tone of the voice, is the manner in which these harmonic notes are reinforced in the cavities and vibrating edges above the glottis (the pharynx, mouth, nasal chambers, etc.), so as to impress their peculiar features upon the voice (see p. 357).

By studying these harmonic notes as being the means by which the tone of the voice is produced, Willis, Wheatstone, Donders, Du Bois-Reymond, and especially Helmholtz,1 have

See Helmholtz, "Théorie Physiologique de la Musique." Trad. fran par Guéroult, Paris, 1868.

Laugel, La Voix, l'Oreille, et la Musique." D'après les travaux de Helmholtz. In "Revue des Deux-Mondes.

Mai,

been enabled to discover the mechanism by which the vowels are produced. The vowels are essentially notes produced by the passage of the air through the pharyngeal and buccal cavities; these are arranged in a special manner, and, consequently, resound differently as each vowel is pronounced. When a vowel is pronounced in a whisper, the glottis takes no part in the process, the sound being produced simply by the passage of the air through the supra-glottidal cavities, which at that moment are so arranged as to give utterance to the vowel in question; when the same vowel is pronounced aloud, the supra-glottidal cavities, arranged as before, produce the effect of reinforcing those harmonics existing in the sound made in the glottis, which exactly correspond with those of the vowel to be pronounced. In other words, the buccal and pharyngeal cavities act as sounding boards, which may be variously harmonized.

We cannot carry this analysis any farther here; it belongs to the domain of pure physics, and we will only add that the form assumed by these cavities for the utterance of the different vowels, has been clearly ascertained, and that when the cavities are properly arranged, if the wind from a pair of bellows be made to pass before the mouth, even though the breath be held back, sounds are heard exactly resembling vowels pronounced in a whisper. In general it may be said that "the longitudinal diameter of the pharyngo-buccal cavity is reduced, and its transverse diameter increased by the vowel-sounds ah, a, and e (a, e, i); while in pronouncing the vowel-sounds o and u, the longitudinal diameter is increased and the transverse diameter diminished. The movements of the different parts of the cavity follow this general disposition. The lips make a horizontal movement, which is more and more decidedly antero-posterior in the case of the three first vowels, and anterior in that of the two latter. In pronouncing o and u, the tongue is drawn backward, while in a and e, it is more or less thrown forward. The movements of the cheeks, the velum of the palate, the uvula, and the pillars of the fauces, all unite in carrying out this general arrangement, etc. etc." (Mandl, op. cit.).

The consonants, which form the second element of articulate speech, are not sounds, like the vowels, but rather irregular vibrations, too confusedly mingled to be separately distinguished (see Hearing); they are sounds which cannot be distinctly heard by themselves, but differ by the manner in which they begin or finish the utterance of a vowel. The

consonants, therefore, can only be pronounced by being joined with a vowel, whence their name (cum sonare). When a vowel is uttered, the cavities of the mouth and pharynx are so arranged as to present certain obstructions to the air which produces the vowel, and the interruption to these latter causes the more or less loud sound of the consonants.

The consonants are labial, lingual, or guttural, according as the obstruction is found in the lips, the tongue, the velum of the palate, or the pharynx; and in accordance with the force employed to overcome the obstruction, whether by a sort of explosion, by vibratory friction, or by a trembling movement, we have explosive labials (b, p), resonant labials (f, v, m), and trembling labials (the lingual r); explosive gutturals (k, g), resonant gutturals (j and ch, especially in German), and trembling gutturals (the guttural r). In some languages, especially the Arabic, the gutturals are very marked, as, for instance, the sound which we designate as ha, and which appears to be produced by some obstacle situated as low down as the glottis. It was while seeking to discover the mechanism by which the really guttural sounds of the Arab tongue are produced that Czermak invented the laryngoscope which is now so universally employed for the exploration of the larynx.

The labial consonants, especially the explosive labials (b, p, m), are the most easy to pronounce, on account of the simplicity of the movements required: they are the first uttered by children (papa, mamma, etc.), and are those which are most easily taught to certain animals, and are naturally produced in bleating (L. Mandl).

This combination of phenomena, by means of which a sound is uttered by the glottis, modified by the pharyngeal and buccal cavities in such a manner as to represent a vowel, and joined to certain sounds, produced in the same cavities, and which form consonants, serves to constitute the articulate voice, while the intelligent combination of vowels and consonants in syllables, and of syllables in words, constitutes speech. In spoken words, the variations in pitch of the syllables are not strongly marked; in singing, on the contrary, the syllables, especially the vowels, which form their essential element, are produced with considerable and harmoniously arranged variations in pitch.

Innervation of the Laryngeal Organ. The organ of phonation of the larynx is dependent on the inferior laryngeal nerve, which appears to come from the pneumo-gastric,

but really represents the series of fibres which this great nerve trunk borrows from the accessory of Willis, or spinal nerve (internal branch of the spinal nerve). Section of the spinal nerve entirely destroys the voice: this might, therefore, be called the vocal nerve. It is remarkable that the other branches of the spinal nerve (the external branch) lead to two superficial and well-known muscles, the sternocleidomastoideus and the trapezius, both which muscles play an important part in expressions by signs, or what may be called the language of the neck and shoulders (shrugging the shoulders, making a sign of negation with the head, etc.). The spinal nerve thus appears to be the nerve of mimicry and phonation.

While serving for purposes of mimicry, the external branch of the spinal nerve takes an active though indirect part in phonation: this nerve innervates the sterno-mastoideus and trapezius muscles, when, during sonorous expiration, these muscles contract for the purpose of preventing the thoracic cage from sinking suddenly. This peculiarity is easily observed in singers, in whom it constitutes what Manal calls the vocal struggle; which consists in a struggle between the spinal nerve and the expiratory movement; Cl. Bernard has demonstrated, by numerous vivisections, that the spinal nerve plays the same part in animals during the utterance of a prolonged cry, and thus has proved that, in a physiological point of view, the spinal nerve is not the accessory, but rather the antagonist of the pneumo-gastric nerve, since it produces, both in the glottis (by its internal branch) and the walls of the thorax (by its external branch), movements which are opposed to those of respiration.

It is now proved that the nerve centre of phonation is situated in the spinal cord: it is plain that this centre is not found in the brain, for anencephalous patients have been known to scream under the influence of external excitation or internal pain. The centre of articulate speech, or rather, the centre of the memory of words, appears to reside in the brain; attempts have been made to fix its seat in the anterior lobes, but the observations made on this subject are, so far, contradictory. Both centres are independent of each other, for a cry may be easily uttered when articulation is very difficult. Amnesia, or the loss of memory of words, there

1 See Aug. Voisin, Art. "Amnésie," in "Nouveau Dict. de Méd. et de Chirur. Prat." Vol. II. p. 53.