THE BRAIN AND THE VOICE IN SPEECH AND SONG
BY
F.W. MOTT, F.R.S., M.D., F.R.C.P.
1910
PREFACE
The contents of this little book formed the subject of three lectures
delivered at the Royal Institution "On the Mechanism of the Human Voice"
and three London University lectures at King's College on "The Brain in
relation to Speech and Song." I have endeavoured to place this subject
before my readers in as simple language as scientific accuracy and
requirements permit. Where I have been obliged to use technical anatomical
and physiological terms I have either explained their meaning in the text,
aided by diagrams and figures, or I have given in brackets the English
equivalents of the terms used.
I trust my attempt to give a sketch of the mechanism of the human voice,
and how it is produced in speech and song, may prove of interest to the
general public, and I even hope that teachers of voice production may find
some of the pages dealing with the brain mechanism not unworthy of their
attention.
F.W. MOTT
LONDON
_July, 1910_
CONTENTS
THEORIES ON THE ORIGIN OF SPEECH
THE VOCAL INSTRUMENT: THREE QUALITIES OF MUSICAL SOUNDS, LOUDNESS, PITCH
AND TIMBRE
THE VOCAL INSTRUMENT AND ITS THREE PARTS
(1) THE BELLOWS AND ITS STRUCTURE: VOLUNTARY CONTROL OF BREATH
(2) THE REED CONTAINED IN THE VOICE-BOX OR LARYNX: ITS STRUCTURE AND ACTION
(3) THE RESONATOR AND ARTICULATOR, ITS STRUCTURE AND ACTION IN SONG AND
SPEECH
PATHOLOGICAL DEGENERATIVE CHANGES PRODUCING SPEECH DEFECTS AND WHAT THEY
TEACH
THE CEREBRAL MECHANISM OF SPEECH AND SONG
SPEECH AND RIGHT-HANDEDNESS
LOCALISATION OF SPEECH CENTRES IN THE BRAIN
THE PRIMARY SITE OF REVIVAL OF WORDS IN SILENT THOUGHT
CASE OF DEAFNESS ARISING FROM DESTRUCTION OF THE AUDITORY CENTRES IN THE
BRAIN CAUSING LOSS OF SPEECH
THE PRIMARY REVIVAL OF SOME SENSATIONS IN THE BRAIN
PSYCHIC MECHANISM OF THE VOICE
ILLUSTRATIONS
FIG.
1. The thoracic cage and its contents
2. The diaphragm and its attachments
3. Diagram illustrating changes of the chest and abdomen in breathing
4. Diagram of the cartilages of the voice-box or larynx with vocal cords
5. Front view of the larynx with muscles
6. Back view of the larynx with muscles
7. Diagram to illustrate movements of cartilages in breathing and phonation
8. Section through larynx and windpipe, showing muscles and vocal cords
9. The laryngoscope and its use
10. The glottis in breathing, whispering, and vocalisation
11. The vocal cords in singing, after French
12. Vertical section through the head and neck to show the larynx and
resonator
13. Diagram (after Aikin) of the resonator in the production of the vowel
sounds
14. König's flame manometer
15. Diagram of a neurone
16. Left hemisphere, showing cerebral localisation
17. Diagram to illustrate cerebral mechanism of speech, after Bastian
18. The course of innervation currents in phonation
THE BRAIN AND THE VOICE IN SPEECH AND SONG
In the following pages on the Relation of the Brain to the mechanism of the
Voice in Speech and Song, I intend, as far as possible, to explain the
mechanism of the instrument, and what I know regarding the cerebral
mechanism by which the instrument is played upon in the production of the
singing voice and articulate speech. Before, however, passing to consider
in detail the instrument, I will briefly direct your attention to some
facts and theories regarding the origin of speech.
THEORIES ON THE ORIGIN OF SPEECH
The evolutionary theory is thus propounded by Romanes in his "Mental
Evolution in Man," pp. 377-399: "Starting from the highly intelligent and
social species of anthropoid ape as pictured by Darwin, we can imagine that
this animal was accustomed to use its voice freely for the expression of
the emotions, uttering danger signals, and singing. Possibly it may also
have been sufficiently intelligent to use a few imitative sounds; and
certainly sooner or later the receptual life of this social animal must
have advanced far enough to have become comparable with that of an infant
of about two years of age. That is to say, this animal, although not yet
having begun to use articulate signs, must have advanced far enough in the
conventional use of natural signs (a sign with a natural origin in tone and
gesture, whether spontaneously or intentionally imitative) to have admitted
of a totally free exchange of receptual ideas, such as would be concerned
in animal wants and even, perhaps, in the simplest forms of co-operative
action. Next I think it probable that the advance of receptual intelligence
which would have been occasioned by this advance in sign-making would in
turn have led to a development of the latter--the two thus acting and
reacting on each other until the language of tone and gesture became
gradually raised to the level of imperfect pantomime, as in children before
they begin to use words. At this stage, however, or even before it, I think
very probably vowel sounds must have been employed in tone language, if not
also a few consonants. Eventually the action and reaction of receptual
intelligence and conventional sign-making must have ended in so far
developing the former as to have admitted of the breaking up (or
articulation) of vocal sounds, as the only direction in which any
improvement in vocal sign-making was possible." Romanes continues his
sketch by referring to the probability that this important stage in the
development of speech was greatly assisted by the already existing habit of
articulating musical notes, supposing our progenitors to have resembled the
gibbons or the chimpanzees in this respect. Darwin in his great work on the
"Expression of the Emotions" points to the fact that the gibbon, the most
erect and active of the anthropoid apes, is able to sing an octave in
half-tones, and it is interesting to note that Dubois considers his
Pithecanthropus Erectus is on the same stem as the gibbon. But it has
lately been shown that some animals much lower in the scale than monkeys,
namely, rodents, are able to produce correct musical tones. Therefore the
argument loses force that the progenitors of man probably uttered musical
sounds before they had acquired the power of articulate speech, and that
consequently, when the voice is used under any strong emotion, it tends to
assume through the principle of association a musical character. The work
of anthropologists and linguists, especially the former, supports the
progressive-evolution theory, which, briefly stated, is--that articulate
language is the result of an elaboration in the long procession of ages in
which there occurred three stages--the cry, vocalisation, and articulation.
The cry is the primordial, pure animal language; it is a simple vocal
aspiration without articulation; it is either a reflex expressing needs and
emotions, or at a higher stage intentional (to call, warn, menace, etc.).
Vocalisation (emission of vowels) is a natural production of the vocal
instrument, and does not in itself contain the essential elements of
speech. Many animals are capable of vocalisation, and in the child the
utterance of vowel sounds is the next stage after the cry.
The conditions necessary to the existence of speech arose with
articulation, and it is intelligence that has converted the vocal
instrument into the speaking instrument. For whereas correct intonation
depends upon the innate musical ear, which is able to control and regulate
the tensions of the minute muscles acting upon the vocal cords, it is
intelligence which alters and changes the form of the resonator by means of
movement of the lips, tongue, and jaw in the production of articulate
speech. The simple musical instrument in the production of phonation is
bilaterally represented in the brain, but as a speaking instrument it is
unilaterally represented in right-handed individuals in the left hemisphere
and in left-handed individuals in the right hemisphere. The reason for this
we shall consider later; but the fact supports Darwin's hypothesis.
Another hypothesis which was brought forward by Grieger and supported by
some authors is summarised by Ribot as follows: "Words are an imitation of
the movements of the mouth. The predominant sense in man is that of sight;
man is pre-eminently visual. Prior to the acquisition of speech he
communicated with his fellows by the aid of gestures and movement of the
mouth and face; he appealed to their eyes. Their facial 'grimaces,'
fulfilled and elucidated by gesture, became signs for others; they fixed
their attention upon them. When articulate sounds came into being, these
lent themselves to a more or less conventional language by reason of their
acquired importance." For support of this hypothesis the case of
non-educated deaf-mutes is cited. They invent articulate sounds which they
cannot hear and use them to designate certain things. Moreover, they employ
gesture language--a language which is universally understood.
Another theory of the origin of the speaking voice is that speech is an
instinct not evolved, but breaking forth spontaneously in man; but even if
this be so, it was originally so inadequate and weak that it required
support from the gesture language to become intelligible. This mixed
language still survives among some of the inferior races of men. Miss
Kingsley and Tylor have pointed out that tribes in Africa have to gather
round the camp fires at night in order to converse, because their
vocabulary is so incomplete that without being reinforced by gesture and
pantomime they would be unable to communicate with one another. Gesture is
indispensable for giving precision to vocal sounds in many languages, e.g.
those of the Tasmanians, Greenlanders, savage tribes of Brazil, and Grebos
of Western Africa. In other cases speech is associated with inarticulate
sounds. These sounds have been compared to clicking and clapping, and
according to Sayce, these clickings and clappings survive as though to show
us how man when deprived of speech can fix and transmit his thoughts by
certain sounds. These mixed states represent articulate speech in its
primordial state; they represent the stage of transition from pure
pantomime to articulate speech.
It seems, then, that originally man had two languages at his disposal which
he used simultaneously or interchangeably. They supported each other in the
intercommunication of ideas, but speech has triumphed because of its
greater practical utility. The language of gesture is disadvantageous for
the following reasons: (1) it monopolises the use of the hands; (2) it has
the disadvantage that it does not carry any distance; (3) it is useless in
the dark; (4) it is vague in character; (5) it is imitative in nature and
permits only of the intercommunication of ideas based upon concrete images.
Speech, on the other hand, is transmitted in the dark and with objects
intervening; moreover, distance affects its transmission much less. The
images of auditory and visual symbols in the growth of speech replace in
our minds concrete images and they permit of abstract thought. It is
dependent primarily upon the ear, an organ of exquisite feeling, whose
sensations are infinite in number and in kind. This sensory receptor with
its cerebral perceptor has in the long process of time, aided by vision,
under the influence of natural laws of the survival of the fittest,
educated and developed an instrument of simple construction (primarily
adapted only for the vegetative functions of life and simple vocalisation)
into that wonderful instrument the human voice; but by that development,
borrowing the words of Huxley, "man has slowly accumulated and organised
the experience which is almost wholly lost with the cessation of every
individual life in other animals; so that now he stands raised as upon a
mountain-top, far above the level of his humble fellows, and transfigured
from his grosser nature by reflecting here and there a ray from the
infinite source of truth." Thought in all the higher mental processes could
not be carried on at all without the aid of language.
Written language probably originated in an analytical process analogous to
the language of gesture. Like that, it: (1) isolates terms; (2) arranges
them in a certain order; (3) translates thoughts in a crude and somewhat
vague form. A curious example of this may be found in Max Müller's "Chips
from a German Workshop," XIV.: "The aborigines of the Caroline Islands sent
a letter to a Spanish captain as follows: A man with extended arms, sign of
greeting; below to the left, the objects they have to barter--five big
shells, seven little ones, three others of different forms; to the right,
drawing of the objects they wanted in exchange--three large fish-hooks,
four small ones, two axes, two pieces of iron."
Language of graphic signs and spoken language have progressed together, and
simultaneously supported each other in the development of the higher mental
faculties that differentiate the savage from the brute and the civilised
human being from the savage. In spoken language, at any rate, it is not the
vocal instrument that has been changed, but the organ of mind with its
innate and invisible molecular potentialities, the result of racial and
ancestral experiences in past ages. Completely developed languages when
studied from the point of view of their evolution are stamped with the
print of an unconscious labour that has been fashioning them for centuries.
A little consideration and reflection upon words which have been coined in
our own time shows that language offers an abstract and brief chronicle of
social psychology.
Articulate language has converted the vocal instrument into the chief agent
of the will, but the brain in the process of time has developed by the
movements of the lips, tongue, jaw, and soft palate a kinæsthetic[A] sense
of articulate speech, which has been integrated and associated in the mind
with rhythmical modulated sounds conveyed to the brain by the auditory
nerves. There has thus been a reciprocal simultaneity in the development of
these two senses by which the mental ideas of spoken words are memorised
and recalled. Had man been limited to articulate speech he could not have
made the immense progress he has made in the development of complex mental
processes, for language, by using written verbal symbols, has allowed, not
merely the transmission of thought from one individual to another, but the
thoughts of the world, past and present, are in a certain measure at the
disposal of every individual. With this introduction to the subject I will
pass on to give a detailed description of the instrument of the voice.
[Footnote A: Sense of movement.]
THE VOCAL INSTRUMENT
A distinction is generally made in physics between sound and noise. Noise
affects our tympanic membrane as an irregular succession of shocks and we
are conscious of a jarring of the auditory apparatus; whereas a musical
sound is smooth and pleasant because the tympanic membrane is thrown into
successive periodic vibrations to which the auditory receptor (sense organ
of hearing) has been attuned. To produce musical sounds, a body must
vibrate with the regularity of a pendulum, but it must be capable of
imparting sharper or quicker shocks to the air than the pendulum. All
musical sounds, however they are produced and by whatever means they are
propagated, may be distinguished by three different qualities:
(1) Loudness, (2) Pitch, (3) Quality, timbre or klang, as the Germans call
it.
Loudness depends upon the amount of energy expended in producing the sound.
If I rub a tuning-fork with a well-rosined bow, I set it in vibration by
the resistance offered to the rosined hair; and if while it is vibrating I
again apply the bow, thus expending more energy, the note produced is
louder. Repeating the action several times, the width of excursion of the
prongs of the tuning-fork is increased. This I can demonstrate, not merely
by the loudness of the sound which can be heard, but by sight; for if a
small mirror be fixed on one of the prongs and a beam of light be cast upon
the mirror, the light being again reflected on to the screen, you will see
the spot of light dance up and down, and the more energetically the
tuning-fork is bowed the greater is the amplitude of the oscillation of the
spot of light. The duration of the time occupied is the same in traversing
a longer as in traversing a shorter space, as is the case of the swinging
pendulum. The vibrating prongs of the tuning-fork throw the air into
vibrations which are conveyed to the ear and produce the sensation of
sound. The duration of time occupied in the vibrations of the tuning-fork
is therefore independent of the space passed over. The greater or less
energy expended does not influence the duration of time occupied by the
vibration; it only influences the amplitude of the vibration.
The second quality of musical sounds is the pitch, and the pitch depends
upon the number of vibrations that a sounding body makes in each second of
time. The most unmusical ear can distinguish a high note from a low one,
even when the interval is not great. Low notes are characterised by a
relatively small number of vibrations, and as the pitch rises so the number
of vibrations increase. This can be proved in many ways. Take, for example,
two tuning-forks of different size: the shorter produces a considerably
higher pitched note than the longer one. If a mirror be attached to one of
the prongs of each fork, and a beam of light be cast upon each mirror
successively and then reflected in a revolving mirror, the oscillating spot
of light is converted into a series of waves; and if the waves obtained by
reflecting the light from the mirror of the smaller one be counted and
compared with those reflected from the mirror attached to the larger fork,
it will be found that the number of waves reflected from the smaller fork
is proportionally to the difference in the pitch more numerous than the
waves reflected from the larger. The air is thrown into corresponding
periodic vibrations according to the rate of vibration of the
sound-producing body.
Thirdly, the quality, timbre, or klang depends upon the overtones, in
respect to which I could cite many experiments to prove that whenever a
body vibrates, other bodies near it may be set in vibration, but only on
condition that such bodies shall be capable themselves of producing the
same note. A number of different forms of resonators can be used to
illustrate this law; a law indeed which is of the greatest importance in
connection with the mechanism of the human voice. Although notes are of the
same loudness and pitch when played on different instruments or spoken or
sung by different individuals, yet even a person with no ear for music can
easily detect a difference in the quality of the sound and is able to
recognise the nature of the instrument or the timbre of the voice. This
difference in the timbre is due to harmonics or overtones. Could we but see
the sonorous waves in the air during the transmission of the sound of a
voice, we should see stamped on it the conditions of motion upon which its
characteristic qualities depended; which is due to the fact that every
vocal sound whose vibrations have a complex form can be decomposed into a
series of simple notes all belonging to the harmonic series. These
harmonics or overtones will be considered later when dealing with the
timbre or quality of the human voice.
The vocal instrument is unlike any other musical instrument; it most nearly
approaches a reed instrument. The clarionet and the oboe are examples of
reed instruments, in which the reed does not alter but by means of stops
the length of the column of air in the resonating pipe varies and
determines the pitch of the fundamental note. The organ-pipe with the
vibrating tongue of metal serving as the reed is perhaps the nearest
approach to the vocal organ; but here again it is the length of the pipe
which determines the pitch of the note.
The vocal instrument may be said to consist of three parts: (1) the
bellows; (2) the membranous reed contained in the larynx, which by the
actions of groups of muscles can be altered in tension and thus variation
in pitch determined; (3) the resonator, which consists of the mouth, the
throat, the larynx, the nose, and air sinuses contained in the bones of the
skull, also the windpipe, the bronchial tubes, and the lungs. The main and
important part of the resonator, however, is situated above the glottis
(the opening between the vocal cords, _vide_ fig. 6), and it is capable of
only slight variations in length and of many and important variations in
form. In the production of musical sounds its chief influence is upon the
quality of the overtones and therefore upon the timbre of the voice;
moreover, the movable structures of the resonator, the lower jaw, the lips,
the tongue, the soft palate, can, by changing the form of the resonator,
not only impress upon the sound waves particular overtones as they issue
from the mouth, but simultaneously can effect the combination of vowels and
consonants with the formation of syllables, the combination of syllables
with the formation of words, and the combination of words with the
formation of articulate language. The reed portion of the instrument acting
alone can only express emotional feeling; the resonator, the effector of
articulate speech, is the instrument of intelligence, will, and feeling. It
must not, however, be thought that the vocal instrument consists of two
separately usable parts, for phonation (except in the whispered voice)
always accompanies articulation.
In speech, and more especially in singing, there is an art of breathing.
Ordinary inspiration and expiration necessary for the oxygenation of the
blood is performed automatically and unconsciously. But in singing the
respiratory apparatus is used like the bellows of a musical instrument, and
it is controlled and directed by the will; the art of breathing properly is
fundamental for the proper production of the singing voice and the speaking
voice of the orator. It is necessary always to maintain in the lungs, which
act as the bellows, a sufficient reserve of air to finish a phrase;
therefore when the opportunity arises it is desirable to take in as much
air as possible through the nostrils, and without any apparent effort; the
expenditure of the air in the lungs must be controlled and regulated by the
power of the will in such a manner as to produce efficiency in loudness
with economy of expenditure. It must be remembered, moreover, that mere
loudness of sound does not necessarily imply carrying power of the voice,
either when speaking or singing. Carrying power, as we shall see later,
depends as much upon the proper use of the resonator as upon the force of
expulsion of the air by the bellows. Again, a soft note, especially an
aspirate, owing to the vocal chink being widely opened, may be the cause of
an expenditure of a larger amount of air than a loud-sounding note.
Observations upon anencephalous monsters (infants born without the great
brain) show that breathing and crying can occur without the cerebral
hemispheres; moreover, Goltz's dog, in which all the brain had been removed
except the stem and base, was able to bark, growl, and snarl, indicating
that the primitive function of the vocal instrument can be performed by the
lower centres of the brain situated in the medulla oblongata. But the
animal growled and barked when the attendant, who fed it daily, approached
to give it food, which was a clear indication that the bark and growl had
lost both its affective and cognitive significance; it was, indeed, a
purely automatic reflex action. It was dependent upon a stimulus arousing
an excitation in an instinctive automatic nervous mechanism in the medulla
oblongata and spinal cord presiding over synergic groups of muscles
habitually brought into action for this simplest form of vocalisation,
connected with the primitive emotion of anger.
I will now consider at greater length each part of the vocal instrument.
I. THE BELLOWS
[Illustration: Fig 1]
[Description: FIG. 1.--Front view of the thorax showing the breastbone, to
which on either side are attached the (shaded) rib cartilages. The
remainder of the thoracic cage is formed by the ribs attached behind to the
spine, which is only seen below. The lungs are represented filling the
chest cavity, except a little to the left of the breastbone, below where
the pericardium is shown (black). It can be seen that the ribs slope
forwards and downwards, and that they increase in length from above
downwards, so that if elevated by the muscles attached to them, they will
tend to push forward the elastic cartilages and breastbone and so increase
the antero-posterior diameter of the chest; moreover, the ribs being
elastic will tend to give a little at the angle, and so the lateral
diameter of the chest will be increased.]
The bellows consists of the lungs enclosed in the movable thorax. The
latter may be likened to a cage; it is formed by the spine behind and the
ribs, which are attached by cartilages to the breastbone (sternum) in front
(_vide_ fig. 1). The ribs and cartilages, as the diagram shows, form a
series of hoops which increase in length from above downwards; moreover,
they slope obliquely downwards and inwards (_vide_ fig. 2). The ribs are
jointed behind to the vertebrae in such a way that muscles attached to them
can, by shortening, elevate them; the effect is that the longer ribs are
raised, and pushing forward the breastbone and cartilages, the thoracic
cage enlarges from before back; but being elastic, the hoops will give a
little and cause some expansion from side to side; moreover, when the ribs
are raised, each one is rotated on its axis in such a way that the lower
border tends towards eversion; the total effect of this rotation is a
lateral expansion of the whole thorax. Between the ribs and the cartilages
the space is filled by the intercostal muscles (_vide_ fig. 2), the action
of which, in conjunction with other muscles, is to elevate the ribs. It is,
however, unnecessary to enter into anatomical details, and describe all
those muscles which elevate and rotate the ribs, and thereby cause
enlargement of the thorax in its antero-posterior and lateral diameters.
There is, however, one muscle which forms the floor of the thoracic cage
called the diaphragm that requires more than a passing notice (_vide_ fig.
2), inasmuch as it is the most effective agent in the expansion of the
chest. It consists of a central tendinous portion, above which lies the
heart, contained in its bag or pericardium; on either side attached to the
central tendon on the one hand and to the spine behind, to the last rib
laterally, and to the cartilages of the lowest six ribs anteriorly, is a
sheet of muscle fibres which form on either side of the chest a dome-like
partition between the lungs and the abdominal cavity (_vide_ fig. 2). The
phrenic nerve arises from the spinal cord in the upper cervical region and
descends through the neck and chest to the diaphragm; it is therefore a
special nerve of respiration. There are two--one on each side supplying the
two sheets of muscle fibres. When innervation currents flow down these
nerves the two muscular halves of the diaphragm contract, and the floor of
the chest on either side descends; thus the vertical diameter increases.
Now the elastic lungs are covered with a smooth pleura which is reflected
from them on to the inner side of the wall of the thorax, leaving no space
between; consequently when the chest expands in all three directions the
elastic lungs expand correspondingly. But when either voluntarily or
automatically the nerve currents that cause contraction of the muscles of
expansion cease, the elastic structures of the lungs and thorax, including
the muscles, recoil, the diaphragm ascends, and the ribs by the force of
gravity tend to fall into the position of rest. During expansion of the
chest a negative pressure is established in the air passages and air flows
into them from without. In contraction of the chest there is a positive
pressure in the air passages, and air is expelled; in normal quiet
breathing an ebb and flow of air takes place rhythmically and
subconsciously; thus in the ordinary speaking of conversation we do not
require to exercise any voluntary effort in controlling the breathing, but
the orator and more especially the singer uses his knowledge and experience
in the voluntary control of his breath, and he is thus enabled to use his
vocal instrument in the most effective manner.
[Illustration: FIG. 2
Adapted from Quain's "Anatomy" by permission of Messrs. Longmans, Green &
Co.]
[Description: FIG. 2.--Diagram modified from Quain's "Anatomy" to show the
attachment of the diaphragm by fleshy pillars to the spinal column, to the
rib cartilages, and lower end of the breastbone and last rib. The muscular
fibres, intercostals, and elevators of the ribs are seen, and it will be
observed that their action would be to rotate and elevate the ribs. The
dome-like shape of the diaphragm is seen, and it can be easily understood
that if the central tendon is fixed and the sheet of muscle fibres on
either side contracts, the floor of the chest on either side will flatten,
allowing the lungs to expand vertically. The joints of the ribs with the
spine can be seen, and the slope of the surface of the ribs is shown, so
that when elevation and rotation occur the chest will be increased in
diameter laterally.]
[Illustration: FIG 3]
[Description: FIG 3.--Diagram after Barth to illustrate the changes in the
diaphragm, the chest, and abdomen in ordinary inspiration _b-b_', and
expiration _a-a_', and in voluntary inspiration _d-d_' and expiration
_c-c_', for vocalisation In normal breathing the position of the chest and
abdomen in inspiration and expiration is represented respectively by the
lines _b_ and _a_; the position of the diaphragm is represented by _b_' and
_a_'. In breathing for vocalisation the position of the chest and abdomen
is represented by the lines _d_ and _e_, and the diaphragm by _d_' and
_c_'; it will be observed that in voluntary costal breathing _d-d_ the
expansion of the chest is much greater and also the diaphragm _d_' sinks
deeper, but by the contraction of the abdominal muscles the protrusion of
the belly wall _d_ is much less than in normal breathing _b_.]
A glance at the diagram (fig. 3) shows the changes in the shape of the
thorax in normal subconscious automatic breathing, and the changes in the
voluntary conscious breathing of vocalisation. It will be observed that
there are marked differences: when voluntary control is exercised, the
expansion of the chest is greater in all directions; moreover, by voluntary
conscious effort the contraction of the chest is much greater in all
directions; the result is that a larger amount of air can be taken into the
bellows and a larger amount expelled. The mind can therefore bring into
play at will more muscular forces, and so control and regulate those forces
as to produce infinite variations in the pressure of the air in the
sound-pipe of the vocal instrument. But the forces which tend to contract
the chest and drive the air out of the lungs would be ineffective if there
were not simultaneously the power of closing the sound-pipe; this we shall
see is accomplished by the synergic action of the muscles which make tense
and approximate the vocal cords. Although the elastic recoil of the lungs
and the structure of the expanded thorax is the main force employed in
normal breathing and to some extent in vocalisation (for it keeps up a
constant steady pressure), the mind, by exercising control over the
continuance of elevation of the ribs and contraction of the abdominal
muscles, regulates the force of the expiratory blast of air so as to employ
the bellows most efficiently in vocalisation. Not only does the contraction
of the abdominal muscles permit of control over the expulsion of the air,
but by fixing the cartilages of the lowest six ribs it prevents the
diaphragm drawing them upwards and _inwards_ (_vide_ fig. 2). The greatest
expansion is just above the waistband (_vide_ fig. 3). We are not conscious
of the contraction of the diaphragm; we are conscious of the position of
the walls of the chest and abdomen; the messages the mind receives relating
to the amount of air in the bellows at our disposal come from sensations
derived from the structures forming the wall of the chest and abdomen, viz.
the position of the ribs, their degree of elevation and forward protrusion
combined with the feeling that the ribs are falling back into the position
of rest; besides there is the feeling that the abdominal muscles can
contract no more--a feeling which should never be allowed to arise before
we become conscious of the necessity of replenishing the supply of air.
This should be effected by quickly drawing in air through the nostrils
without apparent effort and to as full extent as opportunity offers between
the phrases. By intelligence and perseverance the guiding sense which
informs the singer of the amount of air at his disposal, and when and how
it should be replenished and voluntarily used, is of fundamental importance
to good vocalisation. Collar-bone breathing is deprecated by some
authorities, but I see no reason why the apices of the lungs should not be
expanded, and seeing the frequency with which tubercle occurs in this
region, it might by improving the circulation and nutrition be even
beneficial. The proper mode of breathing comes almost natural to some
individuals; to others it requires patient cultivation under a teacher who
understands the art of singing and the importance of the correct methods of
breathing.
The more powerfully the abdominal muscles contract the laxer must become
the diaphragm muscle; and by the law of the reciprocal innervation of
antagonistic muscles it is probable that with the augmented innervation
currents to the expiratory centre of the medulla there is a corresponding
inhibition of the innervation currents to the inspiratory centre (_vide_
fig. 18, page 101). These centres in the medulla preside over the centres
in the spinal cord which are in direct relation to the inspiratory and
expiratory muscles. It is, however, probable that there is a direct
relation between the brain and the spinal nerve centres which control the
costal and abdominal muscles independently of the respiratory centres of
the medulla oblongata (_vide_ fig. 18). The best method of breathing is
that which is most natural; there should not be a protruded abdomen on the
one hand, nor an unduly inflated chest on the other hand; the maximum
expansion should involve the lower part of the chest and the uppermost part
of the abdomen on a level of an inch or more below the tip of the
breastbone; the expansion of the ribs should be maintained as long as
possible. In short phrases the movement may be limited to an ascent of the
diaphragm, over which we have not the same control as we have of the
elevation of the ribs; but it is better to reserve the costal air, over
which we have more voluntary control, for maintaining a continuous pressure
and for varying the pressure.
II. THE REED
I will now pass on to the consideration of the voice-box, or larynx,
containing the reed portion of the vocal instrument.
[Illustration: FIG. 4 From Behnke's "Mechanism of the Human Voice"]
[Description: FIG. 4.--The cartilages of the larynx or voice-box. A large
portion of the shield cartilage on the right side has been cut away, in
order to show the two pyramid cartilages; these are seen jointed by their
bases with the ring cartilage; anteriorly are seen the two vocal processes
which give attachment to the two vocal cords (white ligaments), which
extend across the voice-box to be inserted in front in the angle of the
shield cartilage. Groups of muscles pull upon these cartilages in such a
manner as to increase, or diminish, the chink between the vocal cord in
ordinary inspiration and expiration; in phonation a group of muscles
approximate the cords, while another muscle makes them tense.]
_The Larynx_.--The larynx is situated at the top of the sound-pipe (trachea
or windpipe), and consists of a framework of cartilages articulated or
jointed with one another so as to permit of movement (_vide_ fig. 4). The
cartilages are called by names which indicate their form and shape: (1)
shield or thyroid, (2) the ring or cricoid, and (3) a pair of pyramidal or
arytenoid cartilages. Besides these there is the epiglottis, which from its
situation above the glottis acts more or less as a lid. The shield
cartilage is attached by ligaments and muscles to the bone (hyoid) in the
root of the tongue, a pair of muscles also connect this cartilage with the
sternum or breastbone. The ring cartilage is attached to the windpipe by
its lower border; by its upper border in front it is connected with the
inner surface of the shield cartilage by a ligament; it is also jointed on
either side with the shield cartilage. The posterior part of the ring
cartilage is much wider than the anterior portion, and seated upon its
upper and posterior rim and articulated with it by separate joints are the
two pyramidal cartilages (_vide_ fig. 4). The two vocal cords as shown in
the diagram are attached to the shield cartilage in front, their
attachments being close together; posteriorly they are attached to the
pyramidal cartilages. It is necessary, however, to describe a little more
fully these attachments. Extending forwards from the base of the pyramids
are processes termed the "vocal processes," and these processes give
attachment to the elastic fibres of which the vocal cords mainly consist.
There are certain groups of muscles which by their attachment to the
cartilages of the larynx and their action on the joints are able to
separate the vocal cords or approximate them; these are termed respectively
abductor and adductor muscles (figs. 5 and 6). In normal respiration the
posterior ring-pyramidal muscles contract synergically with the muscles of
inspiration and by separating the vocal cords open wide the glottis,
whereby there is a free entrance of air to the windpipe; during expiration
this muscle ceases to contract and the aperture of the glottis becomes
narrower (_vide_ fig. 10). But when the pressure is required to be raised
in the air passages, as in the simple reflex act of coughing or in
vocalisation, the glottis must be closed by approximation of the vocal
cords, and this is effected by a group of muscles termed the adductors,
which pull on the pyramid cartilages in such a way that the vocal processes
are drawn towards one another in the manner shown in fig. 7. Besides the
abductor and adductor groups of muscles, there is a muscle which acts in
conjunction with the adductor group, and by its attachments to the shield
cartilage above and the ring cartilage below makes tense the vocal cords
(_vide_ fig. 5); it is of interest to note that this muscle has a separate
nerve supply to that of the abductor and adductor muscles.
[Illustration: FIG. 5
Diagram after Testut (modified), showing the larynx from the front.]
[Illustration: FIG. 6
Diagram after Testut (modified), showing the posterior view of the larynx
with the muscles.]
On the top of the pyramid cartilages, in the folds of mucous membrane which
cover the whole inside of the larynx are two little pieces of yellow
elastic cartilage; and in the folds of mucous membrane uniting these
cartilages with the leaf-like lid cartilage (epiglottis) is a thin sheet of
muscle fibres which acts in conjunction with the fibres between the two
pyramid cartilages (_vide_ fig. 8). I must also direct especial attention
to a muscle belonging to the adductor group, which has another important
function especially related to vocalisation: it is sometimes called the
vocal muscle; it runs from the pyramid cartilage to the shield cartilage;
it apparently consists of two portions, an external, which acts with the
lateral ring-shield muscle and helps to approximate the vocal cords; and
another portion situated within the vocal cord itself, which by contracting
shortens the vocal cord and probably allows only the free edge to vibrate;
moreover, when not contracting, by virtue of the perfect elasticity of
muscle the whole thickness of the cord, including this vocal muscle, can be
stretched and thrown into vibration (_vide_ fig. 8). In the production of
chest notes the whole vocal cord is vibrating, the difference in the pitch
depending upon the tension produced by the contraction of the tensor
(ring-shield) muscle. When, however, the change from the lower to the upper
register occurs, as the photographs taken by Dr. French and reproduced in a
lecture at the Royal Institution by Sir Felix Semon show, the vocal cords
become shorter, thicker, and rounder; and this can be explained by
supposing that the inner portion of the vocal muscle contracts at the break
from the lower to the upper register (_vide_ fig. 11); and that as a result
only the free edges of the cords vibrate, causing a change in the quality
of the tone. As the scale is ascended the photographs show that the cords
become longer and tenser, which we may presume is due to the continued
action of the tensor muscle. Another explanation is possible, viz. that in
the lower register the two edges of the vocal cords are comparatively thick
strings. When the break occurs, owing to the contraction of the inner
portion of the vocal muscle, we have a transformation into thin strings, at
first short, but as the pitch of the note rises, the thin string formed by
the edge of the vocal cord is stretched and made longer by the tensor. It
should be mentioned that Aikin and many other good authorities do not hold
this view.
[Illustration: FIG. 7 A-A', Ring cartilage. B, Shield cartilage. 1, Pyramid
cartilage. 2, Vocal process, with 2', its position after contraction of
muscle. 3, Postero-external base of pyramid, giving attachment to abductor
and adductor muscles at rest, with 3', its new position after contraction
of the muscles. 4, Centre of movement of the pyramid cartilage. 5, The
vocal cords at rest. 5', Their new position after contraction of the
abductor and adductor muscles, respectively seen in I and II. 6, The
interligamentous, with 7, the intercartilaginous chink of the glottis. 8,
The arrow indicating respectively in I and II the action of the abductor
and adductor in opening and closing the glottis.]
[Description: FIG. 7.--Diagram after Testut (modified), showing: (i.) the
action of the abductor muscle upon the pyramid cartilages in separating the
vocal cords; (ii.) the action of the adductor muscles in approximating the
vocal cords.]
[Illustration: FIG. 8]
[Description: FIG. 8.--Diagram after Testut (modified) with hinder portion
of larynx and windpipe cut away, showing the conical cavity of the
sound-pipe below the vocal cords. The ventricle above the vocal cords is
seen with the surface sloping upwards towards the mid line.]
A diagram showing a vertical section through the middle of the larynx at
right angles to the vocal cords shows some important facts in connection
with the mechanism of this portion of the vocal instrument (_vide_ fig. 8).
It will be observed that the sound-pipe just beneath the membranous reed
assumes the form of a cone, thus the expired air is driven like a wedge
against the closed glottis. Another fact of importance may be observed,
that above the vocal cords on either side is a pouch called a ventricle,
and the upper surfaces of the vocal cords slope somewhat upwards from
without inwards, so that the pressure of the air from above tends to press
the edges together. The force of the expiratory blast of air from below
overcomes the forces which approximate the edges of the cords and throws
them into vibration. With each vibration of the membranous reeds the valve
is opened, and as in the case of the siren a little puff of air escapes;
thus successive rhythmical undulations of the air are produced,
constituting the sound waves. The pitch of the note depends upon the number
of waves per second, and the _register_ of the voice therefore depends upon
two factors: (1) the size of the voice-box, or larynx, and the length of
the cords, and (2) the action of the neuro-muscular mechanism whereby the
length, approximation, and tension of the vocal cords can be modified when
singing from the lowest note to the highest note of the register.
Thus the compass of the--
Bass voice is D to f 75- 354 vibs. per sec.
Tenor " c " c'' 133- 562 " "
Contralto " e " g'' 167- 795 " "
Soprano " b " f''' 239-1417 " "
The complete compass of the human voice therefore ranges from about D 75 to
f''' 1417 vibrations per second, but the quality of the same notes varies
in different individuals.
[Illustration: Fig. 9]
[Description: Fig. 9.--_Description of the laryngoscope and its mode of
use_.--The laryngoscope consists of a concave mirror which is fixed on the
forehead with a band in such a way that the right eye looks through the
hole in the middle. This mirror reflects the light from a lamp placed
behind the right side of the patient, who is told to open the mouth and put
out the tongue. The observer holds the tongue out gently with a napkin and
reflects the light from the mirror on his forehead on to the back of the
throat. The small mirror, set at an angle of 45° with the shaft, is of
varying size, from half an inch to one inch in diameter, and may be fixed
in a handle according to the size required. The mirror is warmed to prevent
the moisture of the breath obscuring the image, and it is introduced into
the back of the throat in such a manner that the glottis appears reflected
in it. The light from the lamp is reflected by the concave mirror on to the
small mirror, which, owing to its angle of 45°, illuminates the glottis and
reflects the image of the glottis with the vocal cords.]
The discovery of the laryngoscope by Garcia enabled him by its means to see
the vocal cords in action and how the reed portion of the vocal instrument
works (_vide_ fig. 9 and description). The chink of the glottis or the
opening between the vocal cords as seen in the mirror of the laryngoscope
varies in size. The vocal cords or ligaments appear dead white and contrast
with the surrounding pink mucous membrane covering the remaining structures
of the larynx. Fig. 10 shows the appearance of the glottis in respiration
and vocalisation. The vocal cords of a man are about seven-twelfths of an
inch in length, and those of a boy (before the voice breaks) or of a woman
are about five-twelfths of an inch; and there is a corresponding difference
in size of the voice-box or larynx. This difference in length of the vocal
cords accounts for the difference in the pitch of the speaking voice and
the register of the singing voice of the two sexes. We should also expect a
constant difference in the length of the cords of a tenor and a bass in the
male, and of the contralto and soprano in the female, but such is not the
case. It is not possible to determine by laryngoscopic examination what is
the natural register of an individual's voice. The vocal cords may be as
long in the tenor as in the bass; this shows what an important part the
resonator plays in the timbre or quality of the voice. Still, it is
generally speaking true, that a small larynx is more often associated with
a higher pitch of voice than a large larynx.
[Illustration: Fig. 10]