LUDWIG AND MODERN PHYSIOLOGY.'

By J. BURDON-SANDERSON.

I. INTRODUCTION.

The death of any discoverer-of anyone who has added largely to the sum of human knowledge-affords a reason for inquiring what his work was and how he accomplished it. This inquiry has interest even when the work has been completed in a few years, and has been limited to a single line of investigation-much more when the life has been associated with the origin and development of a new science and has extended over half a century.

The science of physiology, as we know it, came into existence fifty years ago, with the beginning of the active life of Ludwig, in the same sense that the other great branch of biology, the science of living beings. (ontology), as we now know it, came into existence with the appearance of the "Origin of Species." In the order of time physiology had the advantage, for the new physiology was accepted some ten years before the Darwinian epoch. Notwithstanding, the content of the science is relatively so unfamiliar, that before entering on the discussion of the life and work of the man who, as I shall endeavor to show, had a larger share in founding it than any of his contemporaries, it is necessary to define its limits and its relations to other branches of knowledge.

The word physiology has in modern times changed its meaning. It once comprehended the whole knowledge of nature. Now it is the name for one of the two divisions of the science of life. In the progress of investigation the study of that science has inevitably divided itself into two: ontology, the science of living beings; physiology, the science of living processes, and thus, inasmuch as life consists in processes, of life itself. Both strive to understand the complicated relations and endless varieties which present themselves in living nature, but by different methods. Both refer to general principles, but they are of a different nature.

To the ontologist, the student of living beings, plants, or animals, the great fact of evolution, namely, that from the simplest beginning our own organism, no less than that of every animal and plant with its

Founded upon a lecture delivered at the Royal Institution, January 24, 1896. Printed in Science Progress, Vol. V, No. 25, 1896, pages 1-21.

infinite complication of parts and powers, unfolds the plan of its existence-taken with the observation that that small beginning was, in all excepting the lowest forms, itself derived from two parents, equally from each is the basis from which his study and knowledge of the world of living beings takes its departure. For on these two factsevolution and descent-the explorer of the forms, distribution, and habits of animals and plants has, since the Darwinian epoch, relied with an ever-increasing certainty, and has found in them the explanation of every phenomenon, the solution of every problem relating to the subject of his inquiry. Nor could he wish for a more secure basis. Whatever doubts or misgivings exist in the minds of "nonbiologists" in relation to it may be attributed partly to the association with the doctrine of evolution of questions which the true naturalist regards as transcendental, partly to the perversion or weakening of meaning which the term has suffered in consequence of its introduction into the language of common life, and particularly to the habit of applying it to any kind of progress or improvement, anything which from small beginnings gradually increases. But, provided that we limit the term to its original sense-the evolution of a living being from its germ by a continuous, not a gradual process-there is no conception which is more free from doubt either as to its meaning or reality. It is inseparable from that of life itself, which is but the unfolding of a predestined harmony, of a prearranged consensus and synergy of parts.

The other branch of biology, that with which Ludwig's name is associated, deals with the same facts in a different way. While ontology regards animals and plants as individuals and in relation to other individuals, physiology considers the processes themselves of which life is a complex. This is the most obvious distinction, but it is subordinate to the fundamental one, namely, that while ontology has for its basis laws which are in force only in its own province, those of evolution, descent, and adaptation, we physiologists, while accepting these as true, found nothing upon them, using them only for euristic purposes, i. e., as guides to discovery, not for the purpose of explana tion. Purposive adaptation, for example, serves as a clue, by which we are constantly guided in our exploration of the tangled labyrinth of vital processes. But when it becomes our business to explain these processes-to say how they are brought about-we refer them not to biological principles of any kind, but to the universal laws of nature. Hence it happens that with reference to each of these processes, our inquiry is rather how it occurs than why it occurs.

It has been well said that the natural sciences are the children of necessity. Just as the other natural sciences owed their origin to the necessity of acquiring that control over the forces of nature without which life would scarcely be worth living, so physiology arose out of human suffering and the necessity of relieving it. It sprang, indeed, out of pathology. It was suffering that led us to know, as regards our

own bodies, that we had internal as well as external organs, and probably one of the first generalizations which arose out of this knowledge was, that "if one member suffer all the members suffer with it”—that all work together for the good of the whole. In earlier times the good which was thus indicated was associated in men's minds with human welfare exclusively. But it was eventually seen that nature has no less consideration for the welfare of those of her products which to us seem hideous or mischievous, than for those which we regard as most useful to man or most deserving of his admiration. It thus became apparent that the good in question could not be human exclusively, but as regards each animal its own good-and that in the organized world the existence and life of every species is brought into subordination to one purpose-its own success in the struggle for existence.1

From what has preceded it may be readily understood that in physiology adaptation takes a more prominent place than evolution or descent. In the prescientific period adaptation was everything. The observation that any structure or arrangement exhibited marks of adaptation to a useful purpose was accepted, not merely as a guide in research, but as a full and final explanation. Of an organism or organ which perfectly fulfilled in its structure and working the end of its existence nothing further is required to be said or known. Physiologists of the present day recognize as fully as their predecessors that perfection of contrivance which displays itself in all living structures the more exquisitely the more minutely they are examined. No one, for example, has written more emphatically uonp this point than did Ludwig. In one of his discourses, after showing how nature exceeds the highest standard of human attainment-how she fashions, as it were, out of nothing and without tools instruments of a perfection which the human artificer can not reach, though provided with every suitable materialwood, brass, glass, india rubber-he gives the organ of sight as a signal example, referring among its other perfections to the rapidity with which the eye can be fixed on numerous objects in succession and the instantaneous and unconscious estimates which we are able to form of the distances of objects, each estimate involving a process of arithmetic which no calculating machine could effect in the time.2 In another

1I am aware that in thus stating the relation between adaptation and the struggle for existence, I may seem to be reversing the order followed by Mr. Darwin, inasmuch as he regarded the survival of organisms which are fittest for their place in nature, and of parts which are fittest for their place in the organism, as the agency by which adaptedness is brought about. However this may be expressed it can not be doubted that fitness is an essential of organisms. Living beings are the only things in nature which by virtue of evolution and descent are able to adapt themselves to their surroundings. It is therefore only so far as organism (with all its attributes) is presupposed, that the dependence of adaptation on survival is intelligible.

*I summarize here from a very interesting lecture entitled "Leid und Freude in der Naturforschung," published in the Gartenlaube (Nos. 22 and 23) in 1870.

discourse that given at Leipzig when he entered on his professorship in 1865-he remarks that when in our researches into the finer mechanism of an organ we at last come to understand it, we are humbled by the recognition "that the human inventor is but a blunderer as compared with the unknown Master of the animal creation.”

Some readers will perhaps remember how one of the most brilliant of philosophical writers, in a discourse to the British Association delivered a quarter of a century ago, averred on the authority of a great physiologist that the eye, regarded as an optical instrument, was so inferior a production that if it were the work of a mechanician it would be unsalable. Without criticising or endeavoring to explain this paradox, I may refer to it as having given the countenance of a distinguished name to a misconception which I know exists in the minds of many persons, to the effect that the scientific physiologist is more or less blind to the evidence of design in creation. On the contrary, the view taken by Ludwig, as expressed in the words I have quoted, is that of all physiologists. The disuse of the teleological expressions which were formerly current does not imply that the indications of contrivance are less appreciated, for, on the contrary, we regard them as more characteristic of organism as it presents itself to our observation than any other of its endowments. But, if I may be permitted to repeat what has been already said, we use the evidences of adaptation differently. We found no explanation on this or any other biological principle, but refer all the phenomena by which these manifest themselves to the simpler and more certain physical laws of the universe.

Why must we take this position? First, because it is a general rule in investigations of all kinds to explain the more complex by the more simple. The material universe is manifestly divided into two parts, the living and the nonliving. We may, if we like, take the living as our Norma, and say to the physicist: "You must come to us for laws; you must account for the play of energies in universal nature by referring them to evolution, descent, adaptation." Or we may take these words as true expressions of the mutual relations between the phenomena and processes peculiar to living beings, using for the explanation of the processes themselves the same methods which we should employ if we were engaged in the investigation of analogous processes going on independently of life. Between these two courses there seems to me to be no third alternative, unless we suppose that there are two material universes, one to which the material of our bodies belongs, the other comprising everything that is not either plant or animal.

The second reason is a practical one. We should have to go back to the time which I have ventured to call prescientific, when the world of

The words translated in the above sentence are as follows: "Wenn uns endlich die Palme gereicht wird, wenn wir ein Organ in seinem Zuzammenhang begreifen, so wird unser stolzes Gattungsbewusstsein durch die Erkenntniss niedergedruckt, dass der menschlicher Erfinder ein Stümper gegen den unbekannten Meister der thierischen Schöpfung sei."

life and organization was supposed to be governed exclusively by its own laws. The work of the past fifty years has been done on the opposite principle, and has brought light and clearness where there was before obscurity and confusion. All this progress we should have to repudiate. But this would not be all. We should have to forego the prospect of future advance. Whereas by holding on our present course, gradually proceeding from the more simple to the more complex, from the physical to the vital, we may confidently look forward to extending our knowledge considerably beyond its present limits.

A no less brilliant writer than the one already referred to, who is also no longer with us, asserted that mind was a secretion of the brain in the same sense that bile is a secretion of the liver or urine that of the kidney; and many people have imagined this to be the necessary outcome of a too mechanical way of looking at vital phenomena, and that physiologists, by a habit of adhering strictly to their own method, have failed to see that the organism presents problems to which this method is not applicable, such, e. g., as the origin of the organism itself or the origin and development in it of the mental faculty. The answer to this suggestion is that these questions are approached by physiologists only in so far as they are approachable. We are well aware that our business is with the unknown knowable, not with the transcendental. During the last twenty years there has been a considerable forward movement in physiology in the psychological direction, partly dependent on discoveries as to the localization of the higher functions of the nervous system, partly on the application of methods of measurement to the concomitant phenomena of psychical processes; and these researches have brought us to the very edge of a region which can not be explored by our methods, where measurements of time or of space are no longer possible.

In approaching this limit the physiologist is liable to fall into two mistakes; on the one hand, that of passing into the transcendental without knowing it; on the other, that of assuming that what he does not know is not knowledge. The first of these risks seems to me of little moment; first, because the limits of natural knowledge in the psychological direction have been well defined by the best writers, as, e. g., by Du Bois-Reymond in his well-known essay "On the limits of natural knowledge," but chiefly because the investigator who knows what he is about is arrested in limine by the impossibility of applying the experimental method to questions beyond its scope. The other mistake is chiefly fallen into by careless thinkers, who, while they object to the employment of intuition even in regions where intuition is the only method by which anything can be learned, attempt to describe and define mental processes in mechanical terms, assigning to these terms. meanings which science does not recognize, and thus slide into a kind of speculation which is as futile as it is unphilosophical.

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