GENERAL AND PHYSIOLOGICAL CONSIDERATIONS.
The principle that knowledge consists in a perception of relations
will now be applied to the structure and functions or uses of the
different parts of the body.
The demonstration that all animals, even all living things, have
certain properties or functions in common is one of the great results
of modern science. Man no longer can be rightly viewed apart from
other animals. In many respects he is in no wise superior to them. The
most desirable course to pursue is to learn wherein animals resemble
and wherein they differ, without dwelling at great length on the
question of relative superiority or inferiority. It may be
unhesitatingly asserted that all animals live, move, and have their
being, in every essential respect, in the same way. Whether one
considers those creatures of microscopic size living in stagnant
ponds, or man himself, it is found that certain qualities characterize
them all. That minute mass of jelly-like substance known as
protoplasm, constituting the one-celled animal amoeba, may be
described as _ingestive_, _digestive_, _secretory_, _excretory_,
_assimilative_, _respiratory_, _irritable_, _contractile_, and
_reproductive_: that is to say, the amoeba must take in food;
must digest it, or change its form; must produce some fluid within
itself which acts on food; must cast out from itself what is no longer
of any use; must convert the digested material into its own
substance--perhaps the most wonderful property of living things; must
take up into its own substance oxygen, and expel carbonic acid gas
(carbon dioxide); and possess the power to respond to a stimulus, or
cause of change, the property of changing form, and, finally, the
ability to bring into being others like itself.
[Illustration: FIG. 1. Muscle-fibres from the heart, much magnified,
showing cross-stripings, nuclei, or the darkly stained central bodies
very important to the life of the cell, also the divisions and points
of union. (Schäfer's _Histology_.)]
[Illustration: FIG. 2. Appearance of a small portion of muscle under a
moderate magnification. Between the muscle-cells proper a form of
binding tissue may be seen.]
[Illustration: FIG. 3. Muscle-cells isolated from the muscular coats
of the intestine. Similar cells are found in some part of most of the
internal organs, including the bronchial tubes. These cells are less
ready in responding to a stimulus, contract more slowly, and tend to
remain longer contracted when they pass into this condition than
striped muscle cells. (Schäfer.)]
Before justifying these statements in detail it will be desirable to
say something of the anatomy or structure of a mammal, and we may
select man himself, though it is to be remembered that one might apply
exactly the same treatment to a dog, pig, mouse, or any other member
of this group of animals. The amoeba and creatures like it live
immersed in water; man, at the bottom of an ocean of air. Both move in
their own medium, the amoeba creeping with extreme slowness, man
moving with a speed incalculably greater. In each case the movements
are determined by some cause from without which is termed by
physiologists a _stimulus_. The slightest movement of the thin
cover-glass placed over the drop of water in which an amoeba is
immersed, on a microscopic slide, suffices to act as a stimulus, and
serves much the same purpose as an electric shock to the muscles of a
man. In man an elaborate apparatus exists for the process known as
respiration, but in this and in all other cases the mechanism is
composed of what is known technically as _cells_, the latter being the
units of structure, the individual bricks of the building, so to
speak; and just as any edifice is made up of individual pieces some of
which differ from one another while others do not to any appreciable
extent, so is it with the body. The individual cells of a muscle are
alike in structure and function, but they differ widely from those of
a gland or secreting organ, as the liver. But it is to be ever
remembered that the statements with which we set out hold: that is,
that however cells may differ, they have in all animals certain
properties in common. Of the muscle-cell, the liver-cell, and the
one-celled animal we may affirm the same properties, but the
difference is that while all are secretory the liver-cell is eminently
so, and produces bile, which other cells do not; that while it is but
feebly contractile, or susceptible of change of form, the muscle-cell
is characterized by this property above all others.
The lower we descend in the animal scale the more simple are the
mechanisms by which results are attained. The one-celled animal may be
said to breathe with its whole body, while the man employs a large
number of muscles, not to speak, at present, of other arrangements.
But when a muscle is examined under the microscope, it is found to
consist of cells, each one of which is physiologically in all
essentials like an amoeba, so that we may say that a muscle or other
tissue or organ is really a sort of colony of cells of similar
structure and function, all working in harmony like a happy family. We
actually do find colonies of unicellular animals much like amoeba,
so that the muscle-cells and all other cells of the body may be
compared to amoeba and other one-celled animals.
But while in such unicellular creatures all functions are properties
of the individual cell, among higher forms _systems_ take the place of
the protoplasm of the single cell. There is a circulatory system, a
respiratory system, etc.; but we must once more point out that such
systems are made up of cells, so that every function of the highest
animal may be finally reduced to what takes place in the unicellular
animal. A circulatory system consists of a heart and blood-vessels,
all filled with blood, which latter is "the life," as was known from
the earliest times; yet this same blood is of no more use for the
nourishment of the body while it is contained in those tubes which
constitute the blood-vessels than is bread locked up in a pantry to a
hungry boy. That which really provides the nutriment for the body is a
fluid derived from the blood, a something like the liquid part of
blood and known as _lymph_. This latter is to the cells of any tissue,
as a muscle, as is the water filled with the food on which an amoeba
lives. In like manner, in spite of the complicated apparatus which
supplies oxygen and removes carbon dioxide, the respiratory system,
respiration is finally the work of the cell, as in amoeba; a
muscle-cell respires exactly as does the one-celled animal.
When we consider the marvellous complexity of structure of one of the
higher animals, and the amazing variety of its functions, the question
naturally arises as to how all this is brought about without any sort
of clashing of the interests of one part with those of another. Why is
it that the stomach has enough and not too much blood? By what means
has Nature solved the problem of supplying more oxygen to parts in
action than to those at rest? How is it that one set of muscles acts
with instead of antagonizing another set, as in any complicated series
of movements, such as walking?
To bring about this harmonization, or _co-ordination_, the nervous
system has been provided. As the nervous and muscular systems are of
preëminent importance in voice-production, they will now be considered
with more detail than it is necessary to give to other systems.
Complicated as is the nervous system, modern advances in the sciences
of anatomy and physiology have made the comprehension of the subject
easier. It is now known that the nervous system, in spite of its wide
ramifications, is also made up of cells which are structurally and
functionally related to each other, and make connection with every
part of the whole community, the body. A nerve-cell, or _neurone_, may
be very complicated in its structure because of its many branches
or extensions from the main body of the cell.
[Illustration: FIG. 4. Body of a nerve-cell of the spinal cord,
specially stained so as to show the minute structure. (Schäfer's
_Histology_.)]
[Illustration: FIG. 5. A large nerve-cell from the spinal cord of the
ox, magnified 175 diameters. (Schäfer.)]
[Illustration: FIG. 6. A cell of another form, from the superficial or
outer part of the greater brain (cortex cerebri). The great amount of
branching is suggestive of the power to receive and to transmit
nervous influences (impulses) from various other cells; in other
words, complexity of structure suggests a corresponding complexity of
function.]
[Illustration: FIG. 7. Representation of the manner in which a nerve
is seen to terminate in a muscle, such ending being one form of
"nerve-ending" termed a "muscle plate." It tends to emphasize the
close relationship existing between muscle and nerve, and to justify
the expression "neuro-muscular mechanism," the nervous system being as
important for movements as the muscles. (Schäfer's _Histology_.)]
[Illustration: FIG. 8. Three muscle-fibres lying beside each other,
with the small blood-vessels (capillaries) around and between them.
Such are the appearances presented under the microscope by skeletal or
striped muscles such as those of the larynx. (Schäfer.)]
It may be said, in general terms, that the nervous _centres_, the
brain and the spinal cord, which are parts of one anatomical whole,
are characterized by the presence of the cell-bodies as well as their
extensions, while nerves consist only of the extensions or arms of the
cell-bodies. The nerve-cell whose body is in the top of the brain may
have an extension or arm which may reach practically to the end of the
spinal cord, and there make communication with another cell whose arm,
in turn, may reach as far as the toe. Such nerve arms or extensions
constitute the _nerve-fibres_, and bundles of these _nerves_, or
_nerve-trunks_.
Usually nerve-fibres make connection with the cells of an organ by a
special modification of structure known as a _nerve-ending_. A nervous
message or influence (_nerve-impulse_) may pass either to the
centre--_i.e._, toward a cell-body--or from it; in other words, a
nervous impulse may originate in the centre or in some organ more or
less distant from it; a nervous impulse may be _central_ or
_peripheral_. Nearly all central impulses, we now know, arise because
of the peripheral ones. One may illustrate this important relation by
a telegraph system. The message a railroad operator sends out--_e.g._,
that which determines whether a train is to be held at a certain
station or sent on--might depend wholly on information received from
another office. The extra flow of blood to the stomach when food
enters it is owing to such a relation of things. The food acts as a
stimulus to the ends of the nerve-fibres, and, in consequence, there
is an ingoing (_afferent_) message or impulse, and, by reason of this,
an outgoing (_efferent_) one to the muscle-cells of the small
blood-vessels, owing to which they contract less strongly and the
calibre of these vessels is increased; hence more blood reaches the
smallest vessels of all (_capillaries_.) Such a physiological relation
of things is termed _reflex action_. For such reflex action there are
required structurally at least two neurones or nerve-cells, and
functionally a stimulus of a certain strength and quality. Of course,
if more blood passes to the stomach there must be less somewhere else,
as the total volume of the blood is limited. The value of the
knowledge of such a fact is obvious. It must be unwise to exercise
vigorously immediately after meals, for this determines blood to the
muscles which would serve a better purpose in the digestive organs.
For a like reason the singer who would do his best before the public
will refrain from taking a large meal before appearing.
As this subject of reflex action is of the highest importance, the
reader is advised to make himself thoroughly familiar with the
principles involved before perusing the future chapters of this work.
Fig. 16 shows the structural relations for reflex action. It also
indicates how such nervous relations may be complicated by other
connections of the nerve-cells involved in the reflex action. It will
be seen that they make many upward connections with the brain, in
consequence of which consciousness may be involved. Ordinarily one is
more or less conscious of reflex action, though the will is not
involved; in fact, a willed or voluntary action is usually considered
the reverse of a reflex or involuntary action. But for a reflex action
the brain is not essential. As is well known, a snake's hinder part
will move in response to a touch when completely severed from the head
end; and movements of considerable complexity can be evoked in a
headless frog.
Herein, then, lies the solution of the problem. This is Nature's way
of bringing one part into harmonious relations with another. As by a
telegraphic system the most distant parts of a vast railway system may
be brought into harmonious working, so is it with the body by means of
the nervous system. The nerve-centres correspond to the heads of the
railway system, or, perhaps more correctly, to the various officials
resident in some large city who from this centre regulate the affairs
of the whole line.
The muscular system is made up of cells of two kinds, those
characteristic of the muscles used in ordinary movements, and those
employed for the movements of the internal organs. The muscles of the
limbs are made up of striped muscle-cells; those of the stomach, etc.,
of unstriped cells. These latter are slower to act when stimulated,
contract more slowly, and cease to function more tardily when the
stimulus is withdrawn.
The muscular mechanisms used by the singer and speaker are of the
skeletal variety.
If it be true that the welfare of one part of the body is bound up
with that of every other, as are the interests of one member of a firm
with those of another, in a great business, it will at once appear
that the most perfect results can follow for the voice-user only under
certain conditions. However perfect by nature the vocal mechanism, the
result in any case must be largely determined by the character of the
body as a whole. The man of fine physique generally has naturally more
to hope for than one with an ill-developed body.
In the natural working of the body the stimulus to a muscle is
nervous; hence we may appropriately, and often to advantage, speak of
_neuro-muscular_ mechanism, the nervous element being as important as
the muscular.
In a later chapter it will be shown that the work of the singer and
speaker when most successfully carried out must be largely reflex in
nature--a fact on which hang weighty considerations with regard to
many questions, among them methods of practice, the influence of
example, etc.--be he ever so much the natural artist. It will be the
writer's aim, however, to give such warnings and advice as may assist
each reader in his own best development. Many who began with a
comparatively poor physical stock in trade have surpassed the
self-satisfied ones who trusted too much to what nature gave them.
Singers as well as others would do well to believe that _Labor omnia
vincit_.
SUMMARY.
The same fundamental physiological principles apply to the lowest and
to the highest animals. To all belong certain properties or qualities.
As structure is differentiated, or as one animal differs from another
owing to greater or less complexity of form, there is a corresponding
differentiation of function, none, however, ever losing the
fundamental properties of protoplasm. Each organ comes to perform some
one function better than all others. This is specialization, and
implies advance among animals as it does in civilization.
The neuro-muscular system is of great moment to the voice-user. He is
a specialist as regards the neuro-muscular systems of the vocal
mechanism. But the same laws apply to it as to other neuro-muscular
mechanisms. It is of great theoretical and practical importance to
recognize this, and that one part of the body is related to every
other, which relationship is maintained chiefly by the nervous system,
and largely through reflex action.