Chapter II

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.

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.

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.