Popular Science Monthly/Volume 21/August 1882/The Physiology of Exercise II
|THE PHYSIOLOGY OF EXERCISE.|
By EMIL DU BOIS-REYMOND.
BETWEEN the external sensation and the internal perception stands the time-sense, adapted to the distinction and estimation of the succession; it is really a grosser hearing and sight, for the cochlea and retina do nothing more than distinguish the more or less rapid succession of impressions. The time-sense is susceptible of a high degree of training, as may be learned from intercourse with astronomers and watch-makers. The later chronoscopy has warranted the possibility of determining the educability of the nervous system to a punctual obedience. In the experiments which Herr Donders first made tentatively, the mean of the time which the same observer required to execute a determined movement in accordance with some signal which he saw, heard, or perceived, sunk from day to day to a limit which was soon reached. The result was the same in a small degree which the drill-master enjoys in a large degree, when to his command a single sound responds, hardly longer protracted than to twice the difference in the time required for the sound-wave to pass from him to the nearest and to the farthest man.
Finally, the internal sense also, which has already entered into our considerations, is susceptible of exercise. Before all, the memory is strengthened by practice to a certain degree, and according to its employment in different directions. It may be recorded here that, as I have heard Schleiden relate, Robert Brown was able to distinguish twenty-five thousand species, Kunth only twenty thousand species of plants; and, if Kunth undertook to impress more than that number upon his mind, others passed out. The morphologist remembers forms, the mathematician formulas, though he may prefer to work them out anew; the philologist speech-forms and citations, the chess-player games. Personages whose high positions in life require them to recognize many faces have wonderful accomplishments in that faculty. I have myself learned from my own experience that the same person by changing his employment may, if we may use such an expression, change the direction of his memory. I have also observed upon myself the influence of exercise upon the memory. Faraday was, it is well known, accustomed to lament the weakness of his memory. And when I (if I may compare small things with great) was engaged continuously for ten years, as he was during his whole life, with qualitative experiments, I remarked that my former good memory declined, undoubtedly because I needed each day, to continue my work, only the steps of the experiments of the day before. My memory began to improve again when I began to give lectures. Like the memory, the power of the most various mental activities increases with exercise and diminishes with neglect. We hear a great deal said in teachers' associations about how school-youth should not only appropriate what is taught them, but should also learn to exercise their sensations and perceptions, and make their mental powers facile. General and diplomatist, jurist and physician, mathematician and descriptive naturalist, chess-player and mechanician all are practiced in their peculiar methods of thought. The effects of exercise extend into the emotional life: who would doubt that a Heine exercised himself in giving free course to the flow of his conceptions, in allowing them to strengthen themselves, as it were, in order to draw half deliberately out of the fountain the immortal complaint of self-created sorrow?
There are in psychology few darker points than the doubling of our I in this mental exercise. A final incomprehensible something in us oppose as subject another equally Incomprehensible as object, which is ourselves, yet also really is not, and forces it to a painful exertion, as at another time it compels its bodily substratum to practice itself in a composite movement, with aching muscles and other pains. Whoever comprehends the fundamental fact of metaphysics, that no arrangement and movement of matter can afford an explanation of consciousness even in its simplest form, will never think ultimately of conceiving these processes as mechanical ones.
This confessedly does not exclude our at least ideally, looking through to the play of the ultimate atoms of our present elements, somewhat as Herr Clausius, before our mental eyes, causes the molecules in a gasometer to perform their crossings and reboundings; and we may even confidently anticipate an important result, just the already declared fundamental distinction between exercise of the central nerve-system and exercise of the muscles, connective substances, etc. While in these tissues we deal with nutritive and formative stimulation, by exercise of the central nerve-system is signified, in the first place, the making fluent certain molecular movements, partly through regulation and suitable re-enforcement of the impulses producing them, partly by the elimination of the obstacles originally opposing them. It must not, however, be said with this, that the highly vascular gray substance is not also nutritively stimulated by the activity incumbent upon it. Every thing indicates that, without a proper degree of activity, gray substance wears away as muscle does. But every increase in the fluency of definite forms of motion with a definitely enduring course is a newly acceding moment, indicative of exercise of the central nerve-system.
The more easy unfolding of a frequently repeated molecular movement in the ganglion-cells may be represented under the figure of a water-channel or a stone-slide, in which the path originally built roughly is so worked out and polished by the continuous passage of water, snow, and stones through it, that thenceforth water, snow, and stones reach the bottom surely and quickly, almost as soon as they begin to fall upon the ways converging toward it. All machines are improved with time through the wearing away of little roughnesses, so that their course becomes a more or less evenly or periodically varying one. Since they afterward become shackling through usage, they have, it seems, an age of development, one of bloom, and one of decay; and Tiede speaks of his chronometer as of a living being with a definite period of life. In order to bring nearer to comprehension the facilitating of the molecular movements in the ganglion cells, it will be well to remember that the tone of a violin becomes softened by long use, as inversely India-rubber, that is not stretched at intervals, becomes brittle. The instructiveness of this comparison lies in its poverty. It shows us the utterly hopeless insufficiency of our knowledge in the face of such mysteries.
Herr Fechner has mentioned a particularly curious case of exercise of the central nerve-system, which sets anew in a clear light the comparatively slight importance of exercise of the muscles. In the Andoyer method of teaching to write, the pupil writes over with a pen for twenty times in succession the identical letters that have been previously written with a pencil, and the hand returns with a swing from the end of the line to its beginning, in order to write it over again without a pause. Ernst Heinrich Weber has observed in the case of his children that the left hand learned to write some at the same time with the right, but it wrote as in a looking-glass. We do not understand how the right side of the brain gained by exercise without the left hand moving during the exercise.
But equally whether we understand it or not, man is adapted to self-improvement by means of exercise. It makes his muscles stronger and more enduring; his skin becomes fortified against all injury; through exercise his limbs become more flexible, his glands more productive. It fits his central nerve-system for the most complicated functions; it sharpens his senses, and by it his mind, reacting upon itself, is enabled to augment its own elasticity and versatility. Returning to our starting-point, we ask, Is not this one of the means, perhaps the principal one, by which the collectivity of living existence becomes a self-improving machine? As to the crystal, the parts of like structure and properties composing it; as to the whole organism, the elementary organisms whose life makes up its life, so are related to the whole of organic nature the single living existences, that is, the properties and functions of the whole are the sum of the functions and properties of the individuals; and if the individual living being is improved by exercise, does not this also sufficiently explain the progress of the aggregate? Lucid as the supposition appears, on a nearer trial it encounters serious difficulties.
First, only the most highly organized animals are amenable to exercise, or, what means the same thing, trainable. After the generally distributed companions of man, the horse and the dog, the most teachable animal is the elephant. Chamisso found intercourse with the apes on board the Rurik uncommonly instructive, "for," as Calderon says of the ass, "they are almost men," and he made the profound remark that they might be able to bring themselves up to the mark if they did not lack the property which Newton held to be one with genius, steadfastness. Carnivores, with the exception of the cheetah (Felis jubata), ruminants, and rodents, exhibit only moderate teachability; yet Herr Fritsch considered the draft-oxen at the Cape of Good Hope wiser than the horse, and in Brazil and Thibet sheep are trained to carry loads. Among the birds, the higher ones are the parrots, starlings, bullfinches, and canary-birds; the falcon ranks with the cheetah in teachableness. Chameleons, snakes, and carp are only moderately teachable. The training of fleas is only apparent; they always perform their tricks under a kind of compulsion. The immense host of other creatures all around us show no more aptitude for training than they do, for the reason that every animal within its own circle has no need of instruction; what we call instinct affords to animals, without effort of the individual, more than any exercise can. What practice could teach birds to build warmer nests, to find the way south more certainly,-or bees to solve their geometrical, spiders their mechanical problems? Instinct and perfectibility complement each other as it were in the ascending series of animals to a growing sum, so that, the more instinct retreats before perfectibility, by so much does the living being stand at a higher stage. Secondly, although the animals we have named, and many others besides, are susceptible to exercise and trainable, animals still do not of themselves exercise and perfect themselves, but do so only when man takes them to school. Therefore, the animals around him appear less susceptible to training, the lower the stage at which he himself remains. Higher races of men would certainly have tamed the beautiful zebra and quagga; the elephant, brought by Hannibal over the Alps, fell back with Northern Africa into wildness. Only nutritive and formative augmentation of advantages which an animal may have acquired in the wild state could come into consideration here, and these would have to be hereditary to lead to perfection in a course of generations.
This seems, thirdly, not to come to pass. No matter for how many generations man cuts off the tail and ears of dogs, tail and ears return with each new brood. The mutilation which the Semitic races have performed on their children for hundreds of ages, and which Islam has imposed upon a great part of the population of the Old World, is not yet chronicled in nature. If, now, artificial defects are not hereditary, how may we venture to suppose that those artificially acquired changes which appear as favorable results of exercise are conveyed through egg and seed to posterity?
To this argument the following considerations are opposed: Although deformities produced by exterior force are not inheritable, we nevertheless see that incontestably internally acquired changes are only too surely transmitted. Of this, the host of hereditary diseases affords an example. Since cellular pathology has shown that the most various heritable diseases of the tissues, the most malignant as well as the most harmless forms, move within the limits of the once given type, the difference appears exposed to light which separates an artificial deformity from a retrogression caused by disease; and it becomes comprehensible why in tame rabbits, the tips of the ears of which may have been idle for many generations, the ear-muscles disappear, and the ears hang down limp; and why the eye and visory substance of subterranean and cave-inhabiting animals waste away. But, even if a deterioration within the type of the species by lack of exercise becomes hereditary, formations dependent on nutritive and formative stimulation, which also remain necessarily within the type of the species, may likewise be transmitted. This appears even to be the case with the inworking of the central nerve-system in certain forms of emotion, of which the growing wild of the at first confiding bird on a formerly uninhabited island furnishes a classical example. Certainly animals in freedom do not, like those under human training, become habituated to definite, frequently repeated functions, yet hunger and love, hatred, cold, thirst, etc., drive them likewise to the frequent performance of certain acts. So? finally, might the innate superiority called instinct (Kunsttrieb) have been gradually developed through practice, and the more easily, as a certain degree of pleasure is connected with the execution of series of movements that have become familiar. If, then, instinct does all that is necessary for the maintenance of the species, there is no more room for further improvement or for development in new directions, and the species remains at the stage it has reached as bees and spiders have done ever since man has known them. We may confidently assert that at the farthest no other actions of the ganglion-cells in the nervous system of these animals are possible than those which serve their particular, instinctive actions. As the artisans from Newcastle-on-Tyne, at the Bureau of Emigration of New York, replied to the question what kind of work they understood, "Packing files," so animals with a perfected instinct purchase their superiority with a one-sidedness which, because they can learn no more, makes them appear as if they had never learned.
Susceptibility to exercise first enters into the animal world when the maintenance of the individual and the species has been so assured, through outer and inner circumstances, that the creature does not need a further particularly one-sided development. We are, then, free to conceive, with an appearance of justification, that the strength of the muscles employed in flight and digging, the thickened epidermis on the palms of the hands and the soles of the feet, the callus on the prehensile tail and the buttocks of apes, the bone-prominences at the attachments of the muscles, and many other similar things, depend on the inherited consequences of nutritive and formative stimulation, while the most diversified kinds of skill may be traced back to inherited concatenations of actions of the ganglion-cells; and this, whether we consider the waves which flow along apparently in a purely mechanical manner in the gymnotus-fin, or in the thousand feet of the woodlouse; or the intelligent posture of the French pointer, which, untaught, and without ever having seen one before, points at the lizard in the sub-tropical shrubbery as his ancestors pointed at the partridge on the plain of St. Denis. With Mr. Herbert Spencer meeting me in the same thought, which I believe, however, I have more sharply grasped, I deduced on a former occasion how, in such transmissibility of educationally derived aptitudes, possibly lies the reconciliation of the great antitheses of the theory of knowledge—of the empirical and the innate views.
Besides improvement by exercise, improvement by natural selection should not be left out of the account, if we would understand the adaptability of organic nature, for a threefold reason: First, there are numerous adaptations—I mean only the so-called sympathetic colorings—for which natural selection, not exercise, seems to afford an explanation. Secondly, plants, which are not less adaptable in their way than animals, do not enjoy exercise. A few phenomena of plant life, reminding us of callus, and traceable back to nutritive and formative stimulation, belong rather to the region of healing and restoration, which is at this point closely connected with exercise. Thirdly, and finally, we require natural selection in order to explain the origin of the adaptability to exercise itself.
Indeed, the usefulness of exercise in its most diversified forms is in itself a deep problem. If we do not concede, as we can not scientifically, that the adaptive quality originated otherwise than mechanically, we must conclude that in the struggle for existence those creatures prevailed which, by exercise of their natural functions, casually increased their fitness for those functions, or did this more than others, and that the beings so favored transmitted this their happy gift to their posterity for further increase. Thus originated an animal world susceptible of exercise; thus was originated natural selection itself, in the exercise of an important aid; finally, thus became the whole of life, like the individual, a self-improving machine. Herr Ewald Hering was also led to the conclusion that "even those properties of an organism may be transmitted to its posterity which it has not itself inherited, but has appropriated to itself under the particular circumstances in which it has lived, and that, in consequence of this, every organic being imparts to the germ that separates from it a small patrimony which it has acquired in the individual life of the mother organism and laid up for the grand inheritance of the whole race." The more perfectly this conception agrees with the one just unfolded, the more I am sorry that I can not follow Herr Hering when he represents the capacity of living beings to transmit acquired properties as an original power of organic matter, and explains it as a power of reproduction of the same kind with memory. To make the manifold processes on which the different kinds of exercise depend the expression of an original power, appears to me to be rather a darkening than an illuminating generalization. Herr Hering finds the tertium comparationis between the transmission of acquired bodily properties and memory in reproduction. But I see no similarity between the facile rolling-off of a definite molecular process in the ganglion-cells of the individual—which is memory—and the return in the offspring of a molecular arrangement imposed, in consequence of external conditions, upon the parent, which would be the transmission of acquired properties; and, if I did see a similarity, it would for me retire before the distinction that, as the name (Geddächtniss) indicates, memory is an attribute only of thinking beings. Herr Hering's unconscious recollection is a side-piece to the idea which men since Plato, to the injury of science, have suspected as a shaping force in the "great and little world," or to the life-force, in the face of which all the problems of physics and chemistry should lie open. Unconscious recollection is, moreover, not acceptable to me, because Herr Haeckel has eagerly appropriated it, and given it an important part in his plastidule theory.
I hold this play with groundless analogies to be the more hazardous, since, finally, it can not be strongly enough sounded that the transmission of acquired properties which we have thought of, with Darwin, Herbert Spencer, Hering, and many others, as possible and real under certain conditions, is proved, on further reflection, to be perfectly incomprehensible.
We are indeed indebted to the mechanical theory of gases for more just conceptions of the minuteness and the number of molecules; viewed in its light, the number of possible arrangements in the ovum and spermatozoön grows into immensity. If we could imagine the head of a spermatozoön as large as the Great Eastern, and the space represented by it filled with a wheel-work as fine as that of the smallest lady's watch, our figure would still be far from giving any kind of a representation of the ultimate division of matter. It is thus clear that the head of a spermatozoön affords space and opportunity for the endlessly numerous arrangements and various motions on which the innumerable types and properties, with which this apparently so simple organism is charged, finally depend. It may then, at all events, be conceived that parental dyscrasies communicate themselves through the blood to the germs in the testicles and ovaries. But now let a group of ganglion-cells in the brain, if we may speak thus, be played upon to a certain molecule-dance-figure. The blood can not be changed by that. Consequently, the threads of the plexus spermaticus internus must so work upon the semen-cells in the seminal canal, the egg-cells in the after-growing Graafian pustules, that each act of exercise in the course of growth leaves its mark on the egg or on the spermatozoön, and that it is followed after years by the natural culmination of the same molecule-dance-figure in the corresponding group of ganglion cells in the man or animal that has grown up out of that egg, or with the aid of that spermatozoön. How the plexus spermaticus internus, the connection of which with the brain is only of the loosest character, brings this to pass, can not be found out. The conditions are no more favorable for the comprehension of the kinds of exercise resting upon nutritive and formative stimulation.
As we have already pointed out, it appears that we might, in order to verify the transmission of acquired properties, invoke the example of hereditary diseases, from which our ancestors were in all probability free, which chiefly visit more highly developed manhood, and the transmission of which consequently resembles the transmission of acquired properties. Still, we may question whether the first epileptic attack, the first migraine, followed injuries which came upon a sound adult, or whether the foundation for them was not laid in the egg or the spermatozoön out of which the first sufferer grew. There remains, for the confirmation of this view—we will be honest—the transmission of acquired peculiarities, an hypothesis drawn solely from the facts illustrating it, yet quite obscure in itself, which receives only doubtful light through Darwin's "pangenesis."
I believe now, gentlemen, that I have justified the expression with which I introduced to you my intention to speak of exercise—that is, that it deserved a place in the scientific order of the day; yet I need not say explicitly how far I am from entertaining the thought that I have contributed anything essential to the fulfillment of that object. I consider that I have succeeded no further than more sharply to define the eventual phylogenetic office of exercise and the direction of the evidences to be supplied than is usually done in the presentations of the Darwinian theory. In the immense field of research opened by Darwin after the fall of the zoölogical-paleontological dogma, the cultivation of which will employ the plowshares of many generations, we have plainly indicated to us one point where the work is urgent. On the other hand, a surer foundation might now be laid for the determination of one of the practical questions relating to exercise.
All are agreed as to the importance of bodily exercise for modern civilized mankind. With the knightly tournaments of the middle ages, in which, moreover, only an extremely small minority ever took part, physical training has more and more declined. Jean Jacques Rousseau, by his educational romance, gave the impulse to a movement that was fast taken up, especially in Germany, and, borne through the national and military struggles of the war of freedom, has culminated in the German turning.
Physical exercise had been pursued by us in this form for half a century when doubts were raised as to its fitness. To the German turning was opposed a theoretically devised form of physical training, the so-called Swedish movement, or gymnastics, the ground thought of which was the limitation of the exercises to extremely simple, although varied, motions. Since these movements were performed against resistance, a methodical strengthening of all the individual muscles was thought to result from them, and the true ideal of an athletic muscular system to be reached.
Again, from another point of view do we hear the superior fitness of the German turning doubted. The European nation which stands foremost in physical accomplishments, and which attaches the highest value to bodily vigor, the English, has till very recently known nothing like the German turning. Separated more than ever from the Continent during the French Revolution and the Empire, it was little affected by the movement of which Rousseau was the pioneer. Jahn's arguments, with their somewhat German-chauvinistic coloring, found but little acceptance there. The English, however, had less use for turning than the nations of the Continent. Thanks to the rural life of the wealthy classes and the common training of the youth in public institutions, a number of national games and contests (riding, rowing, games of ball of various kinds) had been formed, which afforded a superior empirical schooling in the various movements called forth in them; as the achievements of the English mountain-climber, who has just put Chimborazo under his feet, sufficiently illustrate. The passionate interest felt through the length and breadth of Sir Charles Dilke's "Greater Britain" in the annual contest between the dark-blue Oxford and the light-blue Cambridge oarsmen on the Thames can only be compared with the enthusiasm of the Greeks for their national games of competition, and goads the youth to the most earnest exertion.
Here we have the other extreme. The κατ' ὲζοχἠν practical people rejects our physical exercises as too theoretical for its taste. The English at least did not understand at all, when, in answer to the question what sports we played at, an effort was made to explain our tool-gymnastics to them.
When we undertake to judge, in the light of our view into the nature of physical exercise, between these three forms, the German turning, the Swedish movement, and the English sport, the utter worthlessness of the second form for the bodily improvement of a healthy youth manifests itself at once. We have found that physical culture is not only exercise of the muscles, as it appears on a superficial view to be, but is quite as much, yes, more, exercise of the gray substance of the central nerve-system. The physiological value of the Swedish movement is expressed in the simple remark that it can strengthen the muscles, but has not power to make composite movements fluent. Now, in an extremely theoretical case, a physical training is thinkable, by which single muscles of a Caspar Hauser could be cultivated by gymnastics to a lion-like strength without the victim of such an experiment even learning to walk. The Swedish movement is only good for the purposes of physicians, to keep up or restore the efficiency of single groups of muscles.
Turning our attention to the relative worth of the German turning and the English sport, the latter evidently responds more than the former to the demands arising out of our physiological anatomy. Were the end masterhood in running, jumping, climbing; in dancing, fencing, riding; in swimming, rowing, or skating—then nothing could be more advisable than to practice equally and directly the necessary concatenations in the actions of the ganglion-cells, without pausing at the not practically applicable preliminary and intermediate steps of the German turning.
The German turning, however, offers not only the advantage of furnishing to any number of youth, of every age and condition, opportunity for exercise with the smallest amount of external preparations, and independent of often unattainable external conditions; it not only implies the moral earnestness of an effort that proposes self-improvement without immediate practical advantage as an ideal aim, wherein the superiority of the intellectual training sought in the German gymnasium may also be discerned; but, furthermore, the ingenious selection of German exercises, approved and refined through a long experience, results incontestably in a more equable perfecting of the body than can be attained where, as in England, the individual, following his own casually determined inclination, applies himself with ambitious enthusiasm to rowing or riding, to ball-playing or mountain climbing. The youthful body, thoroughly trained after the German method, enjoys the extraordinary advantage that, like a well-instructed mathematician, it is provided with methods for every problem, with ready forms of movement for every situation of the body. Put, for example, an English boy and a German boy on a road across which hurdles are thrown: the English boy will be sure to climb over somehow. According to the height of the impediment, the German boy jumps, or he climbs, props himself, and swings himself over.
Nothing prevents the German turner at pleasure carrying his more theoretical training into practical and immediately available forms of exercise, in which he, since he has learned to learn, speedily attains the skill which his natural ability permits to him; so we have been told that the gymnasiast soon does as well as the real-scholar in the laboratory.
After all this there can be no doubt that German turning, in its wise mingling of theory and practice, exhibits the happiest, yes, the most adequate solution of the great problem with which pedagogics has been busy since Rousseau—a truth which, after a short obscurity, is now hardly contested, but the physiological principle of which a few are beginning to understand.
I further remark that I do not class with German turning the so called order-exercises, which, over-estimated as preparatives to exercising, and a lazy-bench for inefficient teachers of turning, belong, in my opinion, to the Kindergarten.
Hardly any progress in the knowledge of the laws of exercise has been made since Milo of Croton's famous experiment with the calf. Yet we are indebted to the creator of psychophysics for the beginning of the inquiry which is here possible. Herr Fechner daily for two months raised and dropped a pair of nine-and-a-half-pound dumbbells conformably to the beat of a second-pendulum, from the hanging position of the hands to over his head, raised them and dropped them again, till fatigue compelled him to stop. The curves, the ordinates of which indicated the number of elevations daily, are instructive in a double respect. At first the exercise appeared to bear no fruit, then the results came out all at once; but they soon reached their limit. Volkmann had a similar experience in exercise of the senses. Herr Fechner's curves, in the second place, do not rise steadily, but in a serrated manner, according as weariness or increasing facility prevailed. These experiments might be made of useful application in the inspection of recruits for particular purposes.
Like individuals, so are whole peoples susceptible to exercise and of being-trained; and here also an originally higher talent often does not go so far as continuous practice. The hardy, tough, North-German stock resemble the unpromising land, conquered only by obstinate labor, which we till. The Prussian is the self-made man among the peoples, yet he has not made himself without some help sent him by a favoring destiny. He has been eminently made, trained, and exercised through the care of a series of chiefs, unique in the world's history, culminating in the Emperor William. The present memorial day recalls one of the numerous acts of wise care whose blessed fruits we meet everywhere in this city, in this state. This institution, created when Prussia was still a feeble, small power, has grown with the state in importance and certainty of aim, and is now the nursery of physicians for by far the largest part of the Prussian-German army and for the Imperial German fleet. Whether scholar or teacher, each one of us feels how, with this elevated position of the school, his duty increases to perfect himself by means of incessant conscientious exercise.
- An address at the anniversary of the Institute for Military Surgeons, Berlin, August 2, 1881.