XII. Hypo-glossal,—motor of the tongue. It communicates with the
pneumogastric and sympathetic nerves.
[Illustration: =DIAGRAM OF THE FIRST SIX CRANIAL NERVES, WITH THEIR
CHIEF BRANCHES OF DISTRIBUTION.=]
[Illustration: =DIAGRAM OF THE LAST SIX CRANIAL NERVES, WITH THEIR CHIEF
BRANCHES OF DISTRIBUTION.=]
* * * * *
My principal object in writing of the relation of the voice to the
nervous system is to show anatomical and physiological reasons for
denominating the voice the reporter of the states of mind.
We have before us the names of the nerves which connect the organs of
speech with the organ of thought. Through some of the cranial nerves the
mind immediately discharges its impulses upon certain organs, both
consciously and subconsciously. This is illustrated by the motor occuli,
patheticus, and abducens, which move the eye sometimes consciously and
sometimes subconsciously. This shows that these nerves may, and often
do, act upon the eye, without any conscious plan or purpose on the part
of the individual.
The mind often manifests, through the cranial nerves, states of mind of
which the person is unconscious. While consciousness is the power by
which one knows his own states of mind, there is no proof that
consciousness takes note of all one’s states of mind. The proof that it
does not is found in the fact that people, through involuntary acts,
often manifest mental activities of which they are unconscious.
Spontaneous expression is truest.
The facial nerve causes the muscles of the face to portray the thoughts
and feelings of the soul more truthfully than any artist could delineate
them with pencil and brush. Before we can properly teach vocal culture
and oratorical expression we must understand the principle of
spontaneous manifestation by means of cranial nerves as distinct from
purposeful forms of expression. The facial nerve not only acts as a
motor of expression through the face, causing it to reveal thought and
emotion, but acts in the same manner upon the tongue, causing it to form
and modulate tones in song and speech.
Again note the nature of the hypo-glossal cranial nerve, which is not
only a motor of the tongue, causing it to act spontaneously, but is
distributed also to the muscles of the neck which are concerned in the
movements of the larynx. The purpose of this distribution is probably to
associate the action of the tongue with that of the larynx which is
necessary for articulate speech. All the motions of the tongue are
performed through the medium of these nerves.
[Illustration: The drawing exhibits the cerebral connection of all the
cerebral nerves except the first. It is from a sketch taken from two
dissections of this part. D. Posterior optic tubercle. The generative
bodies of the thalamus are just above it. E. Cerebellum. H. Spinal cord.
I. Tuber cinereum. K. Optic thalamus divided perpendicularly. W. Corpus
restiforme. X. Pons Varolii. _b b._ Optic nerves: this nerve is traced
on the left side back beneath the optic thalamus and round the crus
cerebri. It divides into four roots; the first (_g g_) plunges into the
substance of the thalamus, the next runs over the external geniculate
body and surface of the thalamus, the third goes to the anterior optic
tubercle, the fourth runs to D, the testis or posterior optic tubercle.
C. Third pair common oculo-muscular, arising by two roots like the
spinal roots of the spinal nerves, the upper from the gray neurine of
the locus niger, the lower from the continuation of the pyramidal
columns in the crus cerebri and Pons Varolii, _p t_. _d_, Fourth pair,
apparently arising from the inter-cerebral commissure (I _c_), but
really plunging down to the olivary tract (_o t_) as it ascends to the
optic tubercles. _e m._ Motor or non-ganglionic root of the fifth pair,
arising from the posterior edge of the olivary tract. _e._ Sensory root
of the fifth pair running down between the olivary tract and restiform
body to the sensory tract. _f._ Sixth pair, or abducens, arising from
the pyramidal tract. _g._ Seventh pair, facial nerve, or portio dura,
arising by an anterior portion from the olivary tract and by a posterior
portion from the cerebellic fibers of the anterior columns as they
ascend on the corpus restiforme, W. _h._ Eighth pair, portio mollis, or
auditory nerve, with its two roots embracing the restiform body. _i._
Ninth pair, or glosso-pharyngeal; and _j._ Tenth pair, or par vagum,
plunging into the restiform ganglion. J J. Fibers of the optic nerve
plunging into the thalamus; immediately below these letters is the
corpus geniculatum externum. _k._ Eleventh pair, or lingual nerve; the
olivary body has been nearly sliced off and turned out of its natural
position; some of the filaments of the lingual nerve are traced into the
deeper portion of the ganglion, which is left in its situation; others
which are the highest are evidently connected with the pyramidal tract.]
[Illustration: The course and distribution of the Hypoglossal or Ninth
pair of nerves; the deep-seated nerves of the neck are also seen: 1, the
hypoglossal nerve; 2, branches communicating with the gustatory nerve;
3, a branch to the origin of the hyoid muscles; 4, the descendens noni
nerve; 5, the loop formed with the branch from the cervical nerves; 6,
muscular branches to the depressor muscles of the larynx; 7, a filament
from the second cervical nerve, and 8, a filament from the third
cervical, uniting to form the communicating branch with the loop from
the descendens noni; 9, the auricular nerve; 10, the inferior dental
nerve; 11, its mylohyoidean branch; 12, the gustatory nerve; 13, the
chorda tympani passing to the gustatory nerve; 14, the chorda tympani
leaving the gustatory nerve to join the submaxillary ganglion; 15, the
submaxillary ganglion; 16, filaments of communication with the lingual
nerve; 17, the glosso-pharyngeal nerve; 18, the pneumogastric or par
vagum nerve; 19, the three upper cervical nerves; 20, the four inferior
cervical nerves; 21, the first dorsal nerve; 22, 23, the brachial
plexus; 24, 25, the phrenic nerve; 26, the carotid artery; 27, the
internal jugular vein.]
The study of the functions of the cranial nerves convinces me that the
state of mind which conceives a tone acts upon the organs of speech
through the cranial nerves in a way to give vocal expression. In perfect
expression the conception and the expression are absolutely synchronous.
=_RELATION OF PITCH TO RESONANCE._=
In the production of a good tone there is an exact relation between
pitch and resonance. This relation is provided for in nature and a
disobedience to it brings an unpleasant quality into the voice. This is
true in both speech and song, for the speaking and singing voices rest
upon the same fundamental principles. Speech is one application or use
of the voice, song is another. The voice of true speech is as melodic as
the voice of song. There are, however, many persons who use their voices
better when they sing than when they speak, while others use their
voices better in speaking than in singing.
There is a difference between tone and noise. Voice is produced by a
succession of vibrating waves of air. In a musical tone the waves are
regular in their succession; in noise they are irregular.
Resonance, or echo, is produced by the universal law of reflex action
which manifests itself in light, sound, etc. How interesting and
delightful is the echo! It makes the mountains, like the morning stars,
sing together for joy. Listen to a thunder storm among the mountains.
There is a sudden explosion, then a silence, as the vibrating waves of
mighty amplitude pass over the valley to wake the voice of the mountain
beyond, which, standing like a sentinel on guard, speaks in thunder
tones to the next, and that repeats the sublime echo until all the
mountains join in the chorus, answering back to the heavens. This law of
sympathy, undulating from mountain to mountain, so inspired the Greeks
that they said the gods spoke to each other from mountain peak to
mountain peak.
Every pitch in the human voice has its corresponding chamber of
resonance, formed by the nares, by the trachea, by the pharynx, or by
the mouth, and sometimes by more than one of these. The transient
resonant chambers are formed by the adjustment of the lips, and by the
relation of the tongue to the upper gum, the hard palate, the soft
palate, and the pharynx. With the exception of the pharynx, these and
the nasal forms constitute the resonant chambers which produce the
different elements of speech in our language. The tone, though smooth
when it leaves the vocal cords, may be made harsh by the transient
resonant chambers. The nares resound different intervals of the scale in
different portions of their length, never resounding two intervals in
the same portion.
The cultivation of the voice is produced, first, through perfecting the
forms of the transient chambers of resonance; second, through
establishing perfect freedom and regularity in the action of the vocal
cords; third, through developing the rhythmic impulses of the tone. No
person ever speaks continuously in a perfect monotone; the pitch is
constantly changing with the varying thoughts; as the pitch changes, the
resonant chambers change the quality. Nature, unhindered, never reports
the same quality on two different degrees of pitch. It is not that the
individual, while speaking, intends to change the quality; but nature
has so arranged the vocal organs and so determined the laws of
acoustics, that unless the voice be interfered with by wrong mental
determination, she herself changes the quality as the voice rises or
falls.
It is a law of acoustics that a low pitch is resounded in a
comparatively large resonant chamber; a high pitch in a comparatively
small one. A simple and instructive experiment in illustration of this
principle is this: Take a large bottle, strike a C tuning fork, hold it
over the empty bottle, and no sound will be heard. The bottle does not
respond, because the cavity is too large for the pitch of the fork. If
water is poured into the bottle, the air column inside thereby being
shortened until the proper sized chamber is formed, by then holding the
high-pitched tuning fork over it, the sound of the fork will be
resounded by the resonant chamber and the tone will burst forth quite
loudly. Use any number of tuning forks, each on a different key, and a
resonant chamber can thus be made which will resound each fork.
I once tried an experiment with two tuning forks which were fastened to
sounding boxes and which had been tuned to exactly the same pitch. I
struck one fork and stopping its vibration, the sound of the other,
vibrating responsively, was distinctly heard. The same result was
achieved when one of the tuning forks was placed in a remote part of the
room. I also placed the fork upon the piano, struck it, and the string
of the same pitch, in connection with its overtones, responded. In order
that any resonant cavity may resound, the pitch that belongs to that
cavity must be struck. Every room in a house, in consequence of its
size, its form, and the material of which it is constructed, resounds to
a certain pitch. Sometimes in the course of conversation the globe of a
chandelier in the room resounds. This is because the pitch which is
agreeable to its size, form, and substance is struck.