Читать книгу The Philosophy of Health (Vol. 1&2) - Thoman Southwood Smith - Страница 6

Table of Contents

Two distinct lives combined in the animal—Characters of the apparatus of the organic life—Characters of the apparatus of the animal life—Characteristic differences in the action of each—Progress of life—Progress of death.

Of the two sets of functions carried on by living beings, it has been shown, that the plant performs only one, while the animal exercises both. The two lives thus in continual play in the animal differ from each other as much as the process of vegetation differs from that of thought, yet they are united so closely, and act so harmoniously, that their existence as distinct states is not only not apparent to ordinary observation, but the very discovery of the fact is of recent date, and forms one among the splendid triumphs of modern physiology. Their action is perfect, yet their separate identity is so distinctly preserved, that each has its own apparatus and its own action, which are not only not the same, but, in many interesting circumstances, are in striking contrast to each other.

1. In general the organs that belong to the apparatus of the organic life are single, and not symmetrical; the organs that belong to the apparatus of the animal life are either double, or symmetrical, or both. As will be shown hereafter, the heart, the lungs, the stomach, the intestines, the liver, the pancreas, the spleen, the instruments by which the most important functions of the organic life are carried on, are single organs. (Chap. 5.) The figure of each is more or less irregular, so that if a line were carried through their centre, it would not divide them into two equal and precisely corresponding portions. On the contrary, the organs of the animal life are symmetrical. The brain and the spinal cord are divisible into two perfectly equal parts. (Chap. 5.) The nerves which go off from these organs for the most part go off in pairs equal in size and similar in distribution. (Ibid.) The trunk, so important an instrument of voluntary motion, when well formed, is divisible into two perfectly corresponding portions. (Ibid.) The muscular apparatus of one half of the body is the exact counterpart of that of the other; while the arms, the hands, and the lower extremities are not only double, but the organization of the one is precisely similar to that of its fellow.

2. In general, the apparatus of the organic life is placed in the interior of the body, while that of the animal life is placed on the external surface. The organic organs are the instruments by which life is maintained. There is no action of any one of them that can be suspended even for a short space of time without the inevitable extinction of life. But the animal organs are not so much instruments of life as means by which a certain relation is established between the living being and external objects. And this difference in their office is the reason of the difference in their position. Existence depending on the action of the organic organs, they are placed in the interior of the body; they are fixed firmly in their situation in order that they may not be disturbed by the movements of locomotion; they are enveloped in membranes, covered by muscles, placed under the shelter of bones, and every possible care is taken to secure them from accident and to shield them from violence. Existence not being immediately dependent on the action of the organs of the animal life, they do not need to be protected from the contact of external objects with extraordinary care, but it is necessary to the performance of their functions that they should be placed at the exterior of the body. And there they are placed, and so placed as to afford an effectual defence to the organic organs. Thus the groundwork of the animal is made the bulwark of the organic life. The muscles, the immediate agents by which voluntary motion is effected, and the bones, the fixed points and the levers by which that motion acquires the nicest precision and the most prodigious rapidity and power, are so disposed that, while the latter accomplish, in the most perfect manner, their primary and essential office in relation to the muscles, they serve a secondary but scarcely less important office in relation to the internal viscera. As we advance in our subject, we shall see that a beautiful illustration of this is afforded in the structure and action of the trunk; that the trunk is moveable; that it is composed of powerful muscles, and of firm and compact bones; and that while its movements are effected by the action of the muscles which are attached to the bones, these bones enclose a cavity, in which are placed the lungs, the heart, the great trunks of the venous system, the great trunks of the arterial system, and the main trunk of the thoracic duct, the vessel by which the digested aliment is carried into the blood. (Chap. 5.) Thus, by these strong and firm bones, together with the thick and powerful muscles that rest upon them, is formed a secure shelter for a main portion of the apparatus of the organic functions of respiration, circulation, and digestion. The bones and muscles of the thorax, themselves performing an important part in the function of respiration, afford to the lungs the chief organ of this function, composed of tender and delicate tissues, easily injured, and the slightest injury perilling life, a free and secure place to act in. The fragile part of the apparatus is defended by the osseous portion of it, the play of the latter being equally essential to the function as that of the former. In like manner the tender and delicate substance of the brain and spinal cord, the central seat of the animal life, with which all the senses are in intimate communion, is protected by bones and muscles which perform important voluntary movements while the organs of sense which put us in connexion with the external world, which render us susceptible of pleasure, and which give us notice of the approach of objects capable of exciting pain, are placed where external bodies may be brought most conveniently and completely into contact with them; and where alone they can be efficient as the sentinels of the system. For this reason, with the exception of the sense of touch, which, though placed especially at the extremities of the fingers, is also diffused over the whole external surface of the frame, all the senses have their several seats in the head, the most elevated part of the body, of an ovoid figure, capable of moving independently of the rest of the fabric, and which, being supported on a pivot, is enabled to describe at least two-thirds of a circle.

Such is the difference in the structure and position of the apparatus of the two lives, but the difference in their action is still more striking.

1. The action of the apparatus of the organic life when sound is without consciousness; the object of the action of the apparatus of the animal life is the production of consciousness. The final cause of the action of the apparatus of the organic life is the maintenance of existence; the final cause of the action of the apparatus of the animal life is the production of conscious existence. What purpose would be answered by connecting consciousness with the action of the organic organs? Were we sensible of the organic processes; did we know when the heart beats, and the lung plays, and the stomach digests, and the excretory organ excretes, the consciousness could not promote, but might disturb the due and orderly course of these processes. Moreover they would so occupy and engross our minds that we should have little inclination or time to attend to other objects. Beneficently therefore are they placed equally beyond our observation and control. Nevertheless, when our consciousness of these processes may be of service; when they are going wrong; when their too feeble or too intense action is in danger of destroying existence, the animal life is made sensible of what is passing in the organic, in order that the former may take beneficial cognizance of the latter, may do what experience may have taught to be conducive to the restoration of the diseased organ to a sound state, or avoid doing what may conduce to the increase or maintenance of its morbid condition.

But while the action of the organic organs is thus kept alike from our view and feeling, the sole object of the action of the animal organs is to produce and maintain a state of varied and extended consciousness. We do not know when the heart dilates to receive the vital current, nor when it contracts to propel it with renewed impetus through the system; nor when the blood rushes to the lung to give out its useless and noxious particles; nor when the air rushes to the blood to take up those particles, to replace them by others, and thus to purify and renovate the vital fluid. Many processes of this kind are continually going on within us during every moment of our existence, but we are no more conscious of them than we are of the motion of the fluids in the blade of grass on which we tread. On the contrary when an external object produces, in a sentient nerve, that change of state which we denote by the words "an impression;" when the sentient nerve transmits this impression to the brain; when the brain is thereby brought into the state of perception, the animal life is in active operation, and percipient or conscious existence takes place. Consciousness does not belong to the organic, it is the animal life.

2. The functions of the organic life are performed with uninterrupted continuity; to those of the animal life rest is indispensable. The action of the heart is unceasing; it takes not and needs not rest. On it goes, for the space of eighty or ninety years, at the rate of a hundred thousand strokes every twenty-four hours, having at every stroke a great resistance to overcome, yet it continues this action for this length of time without intermission. Alike incessant is the action of the lung, which is always receiving and always emitting air; and the action of the skin, which is always transpiring and always absorbing; and the action of the alimentary canal, which is always compensating the loss which the system is always sustaining.

But of this continuity of action the organs and functions of the animal life are incapable. No voluntary muscle can maintain its action beyond a given time; no effort of the will can keep it in a state of uninterrupted contraction; relaxation must alternate with contraction; and even this alternate action cannot go on long without rest. No organ of sense can continue to receive impression after impression without fatigue. By protracted exertion the ear loses its sensibility to sound, the eye to light, the tongue to savour, and the touch to the qualities of bodies about which it is conversant. The brain cannot carry on its intellectual operations with vigour beyond a certain period; the trains of ideas with which it works become, after a time, indistinct and confused; nor is it capable of reacting with energy until it has remained in a state of rest proportioned to the duration of its preceding activity.

And this rest is sleep. Sleep is the repose of the senses, the rest of the muscles, their support and sustenance. What food is to the organic, sleep is to the animal life. Nutrition can no more go on without aliment, than sensation, thought, and motion without sleep.

But it is the animal life only that sleeps: death would be the consequence of the momentary slumber of the organic. If, when the brain betook itself to repose, the engine that moves the blood ceased to supply it with its vital fluid, never again would it awake. The animal life is active only during a portion of its existence; the activity of the organic life is never for a moment suspended; and in order to endow its organs with the power of continuing this uninterrupted action, they are rendered incapable of fatigue: fatigue, on the contrary, is inseparable from the action of the organs of the animal life; fatigue imposes the necessity of rest, rest is sleep, and sleep is renovation.

3. Between all the functions of the organic life there is a close relation and dependence. Without the circulation there can be no secretion; without secretion, no digestion; without digestion, no nutrition; without nutrition, no new supply of circulating matter, and so through the entire circle. But the functions of the animal life are not thus dependent on each other. One of the circle may be disordered without much disturbance of the rest; and one may cease altogether, while another continues in vigorous action. Sensation may be lost, while motion continues; and the muscle may contract though it cannot feel. One organ of sense may sleep while the rest are awake. One intellectual faculty may be in operation while others slumber. The muscle of volition may act, while there is no consciousness of will. Even the organs of the voice and of progression may perform their office while the sensorium is deeply locked in sleep.

4. The two lives are born at different periods, and the one is in active operation before the other is even in existence. The first action observable in the embryo is a minute pulsating point. It is the young heart propelling its infant stream. Before brain, or nerve, or muscle can be distinguished, the heart is in existence and in action; that is, the apparatus of the organic function of the circulation is built up and is in operation before there is any trace of an animal organ. Arteries and veins circulate blood, capillary vessels receive the vital fluid, and out of it form brain and muscle, the organs of the animal, no less than the various substances that compose the organs of the organic life. The organic is not only anterior to the animal life, but it is by the action of the organic that existence is given to the animal life. The organic life is born at the first moment of existence; the animal life not until a period comparatively distant; the epoch emphatically called the period of birth, namely, the period when the new being is detached from its mother; when it first comes into contact with external objects; when it carries on all the functions of its economy by its own organs, and consequently enjoys independent existence.

5. The functions of the organic life are perfect at once. The heart contracts as well, the arteries secrete as well, the respiratory organs work as well the first moment they begin to act as at any subsequent period. They require no teaching from experience, and they profit nothing from its lessons. On the contrary, the operations of the brain, and the actions of the voluntary muscles, feeble and uncertain at first, acquire strength by slow degrees, and attain their ultimate perfection only at the adult age. How indistinct and confused the first sensations of the infant! Before it acquire accuracy, precision, and truth, how immense the labour spent upon perception! Sensations are succeeded by ideas; sensations and ideas coalesce with sensations and ideas; combinations thus formed suggest other combinations previously formed, and these a third, and the third a fourth, and so is constituted a continuous train of thought. But the infantile associations between sensation and sensation, between idea and idea, and between sensations and ideas, are, to a certain extent, incorrect, and to a still greater extent inadequate; and the misconception necessarily resulting from this early imperfection in the intellectual operations is capable of correction only by subsequent and more extended impressions. During its making hours, a large portion of the time of the infant is spent in receiving impressions which come to it every instant from all directions, and which it stores up in its little treasury; but a large portion is also consumed in the far more serious and difficult business of discrimination and correction. Could any man, after having attained the age of manhood, reverse the order of the course through which he has passed; could he, with the power of observation, together with the experience that belong to manhood, retrace with perfect exactness every step of his sentient existence, from the age of forty to the moment that the air first came into contact with his body at the moment of his leaving his maternal dwelling, among the truths he would learn, the most interesting, if not the most surprising, would be those which relate to the manner in which he dealt with his earliest impressions; with the mode in which he combined them, recalled them, laid them by for future use; made his first general deduction; observed what subsequent experience taught to be conformable, and what not conformable, to this general inference; his emotions on detecting his first errors, and his contrasted feelings on discovering those comprehensive truths, the certainty of which became confirmed by every subsequent impression. Thus to live backwards would be, in fact, to go through the analysis of the intellectual combinations, and, consequently, to obtain a perfect insight into the constitution of the mind; and among the curious results which would then become manifest, perhaps few would appear more surprising than the true action of the senses. The eye, when first impressed by light, does not perceive the objects that reflect it; the ear, when first impressed by sound, does not distinguish the sonorous body. When the operation for cataract has been successfully performed in a person born blind, the eye immediately becomes sensible to light, but the impression of light does not immediately give information relative to the properties of bodies. It is gradually, not instantaneously; it is even by slow degrees that luminous objects are discerned with distinctness and accuracy. To see, to hear, to smell, to taste, to touch, are processes which appear to be performed instantaneously, and which actually are performed with astonishing rapidity in a person who observes them in himself; but they were not always performed thus rapidly: they are processes acquired, businesses learnt; processes and businesses acquired and learnt, not without the cost of many efforts and much labour. But the senses afford merely the materials for the intellectual operations of memory, combination, comparison, discrimination, induction, operations the progress of which is so slow, that they acquire precision, energy, and comprehensiveness only after the culture of years.

And the same is true of the muscles of volition. How many efforts are made before the power of distinct articulation is acquired! how many before the infant can stand! how many before the child can walk! The organic life is born perfect; the animal life becomes perfect only by servitude, and the aptitude which service gives.

6. The organic life may exist after the animal life has perished. The animal life is extinguished when sensation is abolished, and voluntary motion can be performed no more. But disease may abolish sensation and destroy the power of voluntary motion, while circulation, respiration, secretion, excretion, in a word, the entire circle of the organic functions continues to be performed. In a single instant apoplexy may reduce to drivelling fatuity the most exalted intellect, and render powerless and motionless muscles of gigantic strength; while the action of the heart and the involuntary contractions of the muscles may not only not be weakened, but may act with preternatural energy. In a single instant, apoplexy may even completely extinguish the animal life, and yet the organic may go on for hours, days, and even weeks; while catalepsy, perhaps the most singular disease to which the human frame is subject, may wholly abolish sensation and volition, while it may impart to the voluntary muscles the power of contracting with such unnatural energy and continuity, that the head, the trunk, the limbs may become immoveably fixed in whatever attitude they happen to be at the moment the paroxysm comes on. In this extraordinary condition of the nervous system, however long the paroxysm last, and however complete the abolition of consciousness, the heart continues to beat, and the pulse to throb, and the lungs to respire, and all the organic organs to perform their ordinary functions. Dr. Jebb gives the following description of the condition of a young lady who was the subject of this curious malady.

"My patient was seized with an attack just as I was announced. At that moment she was employed in netting; she was in the act of passing the needle through the mesh; in that position she became immoveably rigid, exhibiting, in a pleasing form, a figure of death-like sleep, beyond the power of art to imitate, or the imagination to conceive. Her forehead was serene, her features perfectly composed. The paleness of her colour, and her breathing, which at a distance was scarcely perceptible, operated in rendering the similitude to marble more exact and striking. The position of her fingers, hands, and arms was altered with difficulty, but preserved every form of flexure they acquired: nor were the muscles of the neck exempted from this law, her head maintaining every situation in which the hand could place it, as firmly as her limbs."

In this condition of the system the senses were in a state of profound sleep; the voluntary muscles, on the contrary, were in a state of violent action; but this action not being excited by volition, nor under its control, the patient remained as motionless as she was insensible. The brain was in a state of temporary death; the muscle in a state of intense life. And the converse may happen: the muscle may die, while the brain lives; contractility may be destroyed, while sensibility is perfect; the power of motion may be lost, while that of sensation may remain unaffected. A case is on record, which affords an illustration of this condition of the system. A woman had been for some time confined to her bed, labouring under severe indisposition. On a sudden she was deprived of the power of moving a single muscle of the body; she attempted to speak, but she had no power to articulate; she endeavoured to stretch out her hand, but her muscles refused to obey the commands of her will, yet her consciousness was perfect, and she retained the complete possession of her intellectual faculties. She perceived that her attendants thought her dead, and was conscious of the performance upon her own person of the services usually paid to the dead; she was laid out, her toes were bound together, her chin was tied up; she heard the arrangements for her funeral discussed, and yet she was unable to make the slightest sign that she was still in the possession of sense, feeling, and life.

In one form of disease, then, the animal life, both the sensitive and the motive portions of it, may perish; and in another form of disease, either the one or the other part of it may be suspended, while the organic life continues in full operation: it follows that the two lives, blended as they are, are distinct, since the one is capable of perishing without immediately and inevitably involving the destruction of the other.

7. And, finally, as the organic life is the first born, so it is the last to die; while the animal life, as it is the latest born, and the last to attain its full development, so it is the earliest to decline and the first to perish. In the process of natural death, the extinction of the animal is always anterior to that of the organic life. Real death is a later, and sometimes a much later event than apparent death. An animal appears to be dead when, together with the abolition of sensation and the loss of voluntary motion, respiration, circulation, and the rest of the organic functions can no longer be distinguished; but these functions go on some time after they have ceased to afford external indications of their action. In man, and the warmblooded animals in general, suspension or submersion extinguishes the animal life, at the latest, within the space of four minutes from the time that the atmospheric air is completely excluded from the lung; but did the organic functions also cease at the same period, it would be impossible to restore an animal to life after apparent death from drowning and the like. But however complete and protracted the abolition of the animal functions, re-animation is always possible as long as the organic organs are capable of being restored to their usual vigour. The cessation of the animal life is but the first stage of death, from which recovery is possible; death is complete only when the organic together with the animal functions have wholly ceased, and are incapable of being re-established.

In man, the process of death is seldom altogether natural. It is generally rendered premature by the operation of circumstances which destroy life otherwise than by that progressive and slow decay which is the inevitable result of the action of organized structure. Death, when natural, is the last event of an extended series, of which the first that is appreciable is a change in the animal life and in the noblest portion of that life. The higher faculties fail in the reverse order of their development; the retrogression is the inverse of the progression, and the noblest creature, in returning to the state of non-existence, retraces step by step each successive stage by which it reached the summit of life.

In the advancing series, the animal is superadded to the organic life; sensation, the lowest faculty of the animal life, precedes ratiocination, the highest. The senses called into play at the moment of birth soon acquire the utmost perfection of which they are capable; but the intellectual faculties, later developed, are still later perfected, and the highest the latest.

In the descending series, the animal life fails before the organic, and its nobler powers decay sooner and more rapidly than the subordinate. First of all, the impressions which the organs of sense convey to the brain become less numerous and distinct, and consequently the material on which the mind operates is less abundant and perfect; but at the same time, the power of working vigorously with the material it possesses more than proportionally diminishes. Memory fails; analogous phenomena are less readily and less completely recalled by the presence of those which should suggest the entire train; the connecting links are dimly seen or wholly lost; the train itself is less vivid and less coherent; train succeeds train with preternatural slowness, and the consequence of these growing imperfections is that, at last, induction becomes unsound just as it was in early youth; and for the same reason, namely, because there is not in the mental view an adequate range of individual phenomena; the only difference being that the range comprehended in the view of the old man is too narrow, because that which he had learnt he has forgotten; while in the youth it is too narrow, because that which it is necessary to learn has not been acquired.

And with the diminution of intellectual power the senses continue progressively to fail: the eye grows more dim, the ear more dull, the sense of smell less delicate, the sense of touch less acute, while the sense of taste immediately subservient to the organic function of nutrition is the last to diminish in intensity and correctness, and wholly fails but with the extinction of the life it serves.

But the senses are not the only servants of the brain; the voluntary muscles are so equally; but these ministers to the master-power, no longer kept in active service, the former no longer employed to convey new, varied, and vivid impressions, the latter no longer employed to execute the commands of new, varied, and intense desires, become successively feebler, slower, and more uncertain in their action. The hand trembles, the step totters, and every movement is tardy and unsteady. And thus, by the loss of one intellectual faculty after another, by the obliteration of sense after sense, by the progressive failure of the power of voluntary motion; in a word, by the declining energy and the ultimate extinction of the animal life, man, from the state of maturity, passes a second time through the stage of childhood back to that of infancy; lapses even into the condition of the embryo: what the fœtus was, the man of extreme old age is: when he began to exist, he possessed only organic life; and before he is ripe for the tomb, he returns to the condition of the plant.

And even this merely organic existence cannot be long maintained. Slow may be the waste of the organic organs; but they do waste, and that waste is not repaired, and consequently their functions languish, and no amount of stimulus is capable of invigorating their failing action. The arteries are rigid and cannot nourish; the veins are relaxed and cannot carry on the mass of blood that oppresses them; the lungs, partly choked up by the deposition of adventitious matter, and partly incapable of expanding and collapsing by reason of the feeble action of the respiratory apparatus, imperfectly aërate the small quantity of blood that flows through them; the heart, deprived of its wonted nutriment and stimulus, is unable to contract with the energy requisite to propel the vital current; the various organs, no longer supplied with the quantity and quality of material necessary for carrying on their respective processes, cease to act; the machinery stops, and this is death.

And now the processes of life at an end, the body falls within the dominion of the powers which preside universally over matter; the tie that linked all its parts together, holding them in union and keeping them in action, in direct opposition to those powers dissolved, it feels and obeys the new attractions to which it has become subject; particle after particle that stood in beautiful order fall from their place; the wonderful structures they composed melt away; the very substances of which those structures were built up are resolved into their primitive elements; these elements, set at liberty, enter into new combinations, and become constituent parts of new beings; those new beings in their turn perish; from their death springs life, and so the changes go on in an everlasting circle.

As far as relates to the organized structures in which life has its seat, and to the operations of life dependent on those structures, such is its history; a history not merely curious, but abounding with practical suggestions of the last importance. The usefulness of a familiar acquaintance with the phenomena which have now been elucidated will be apparent at every step as we proceed.