Book - Chemical embryology 1 (1900) 1

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Needham J. Chemical Embryology Vol. 1. (1900)

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This historic 1900 volume 1 of a textbook by Needham describes chemical embryology.

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Also by this author: Needham J. Chemical Embryology Vol. 2. (1900)

Modern Notes:
Historic Embryology Textbooks

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Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

Part I The Theory of Chemical Embryology

. . . .to measure all things that can be measured, and to make measurable what cannot yet be measured.


Philosophy, Embryology, and Chemistry

The penetration of physico-chemical concepts into embryology has not been entirely peaceful. "In experimental embryology", it has been said, "concepts borrowed from the physical sciences do not admit of calculations being made, and until they do they are not really playing the same role as they do in the sciences from which they have been borrowed and for which they were devised." "Nothing is more clear", says another writer, "in chemistry and physics than that identical results follow upon identical causes. Introduce a disturbing element, even a small one, into your experiment, and the experiment will fail. Such is not the case with the developing egg." W. McDougall, too, endows the egg with good intentions. "The embryo", he says, "seems to be resolved to acquire a certain form and structure, and to be capable of overcoming very great obstacles placed in its path. The development of the forms of organisms seems to be utterly refractory to explanation by mechanical or physicochemical principles." Finally, J. A. Thomson goes farther than them all, and does not hesitate to say, "It is a mere impious opinion that development will one day be described in terms of mechanics". Chapter iv of his Gifford Lectures illustrates the antagonistic attitude to physico-chemical embryology in its most acute form.

It can hardly be a coincidence that so many among the great embryologists of the past were men of strongly philosophic minds. It would be absurd to support this opinion by citing Aristotle, but it holds less obviously true of William Harvey, whose book on generation is full of thoughts about causation, and in the cases of Ernst von Baer, Ernst Haeckel, Wilhelm Roux, Hans Driesch, dArcy Thompson and J. W. Jenkinson, there is no doubt about it. It is not really surprising, for of all the strange things in biology surely the most striking of all is the transmutation inside the developing egg, when in three weeks the white and the yolk give place to che animal with its tissues and organs, its batteries of enzymes and its dehcately regulated endocrine system. This coming-to-be can hardly have failed to lead, in the minds of those most intimately acquainted with it, to thoughts of a metaphysical character. Nor, it seemed, did those who worked on it do much to diminish its wonder. "Neither the schools of physicians", as Harvey said, "nor Aristotle's discerning brain, have disclosed the manner how the Cock and its seed, doth mint and coine, the chicken out of the Ggg,'^ Or, in the words of Erycius Puteanus, "I will neglect gold, and will praise what is more precious than any metal, I will despise feasts, and will set forth praises of something better than any food or drink. If you would know of what it is that I intend to speak, it is the egg; men marvel at the sun, at meteors flung from heaven, at stars swimming therein, but this is the greatest of all wonders". Here, however, there is one significant thing. It is that the very chapter of Harvey's book in which the preceding remark is found has as its heading "The Efficient Cause of the Chicken, is hard to be found out". It certainly was, but the right clue was in the heading to that exercitation.

This close association of embryology with philosophy, then, made it necessary to discuss at the outset of this book certain points in the more theoretical regions of biology, and, as it were, to defend from a theoretical angle the extension of the domain of physics and chemistry over embryology. I might have entitled this part of the book "The philosophy of embryology", but, in deference to those metaphysicians who rightly insist that the word philosophy should only be used of a definite system of experience which looks at the universe as a corporate whole, I adopted the present heading. Under it I propose to discuss the exact status of the chemical aspect of embryology. For many biologists, having perhaps insufficiently considered the nature of the scientific method, think it likely that the discoveries of modern times may allow of some other basis for biology than mathematical physics and that the scientific niethod may rightly be different in biology from what it is in chemistry. It is this factor in our present intellectual climate which makes it necessary to preface by a philosophical discussion a book in which the concepts of physics and chemistry are extended to a field of biology where they have never before received more than a conventional and formal reverence.

The aim of all studies in physico-chemical embryology must be that expressed by T. H. Huxley when he said, " Zoological Physiology is the doctrine of the functions or actions of animals. It regards animal bodies as machines impelled by certain forces and performing an amount of work which can be measured and expressed in terms of the ordinary forces of nature. The final object of physiology is to deduce the facts of morphology on the one hand and those of oecology on the other hand from the laws of the molecular forces of matter". It may be regarded as very noteworthy that Huxley here puts morphology as secondary to physiology and as it were derivable from it; he does not place morphology and physiology on two high places, "neither afore or after other", as has so often been done, but he plainly states his view that the anatomical aspect of animals, their external and internal forms, could be deduced from the interplay of physico-chemical forces within them, if we only knew enough about those forces. This is the idea of the primacy of function. It seems always to have two meanings, firstly, the Epicurean-Lucretian one which Huxley adopts here and Roux so brilliantly developed, in which shape is regarded as the outward and visible sign of the properties of matter itself, and, secondly, the Aristotelian one emphasised by J. B. de Lamarck's writings in the eighteenth century, and in our time by E. S. Russell's great work Form and Function, in which psychical factors are introduced as the essential elements in the ultimate analysis of shape. In both these interpretations, function has the priority over form, but the meaning of function is the point of difference. Some biologists, however, seem to think that physiology and morphology are categorical, and the latter is emphatically not reducible to or derivable from the former. The two spheres of study represent, for them, correlative and immiscible disciplines, morphology aiming ultimately at solid geometry, physiology at causation, and "rerum cognoscere causas" is not the basic desire of the scientific mind. They object to the view which regards "the ovum as a kind of chemical device wound up and ready to go off on receipt of a stimulus, the task of the causal morphologist being to disentangle the complex of events which constitute the unwinding process" (Woodger), complaining that in this view no account is taken of the past history of the race, which is left to genetics, again a causal discipHne. To some extent these opinions spring from a conviction that the analytical method is inapplicable to a living being because it is an organism, and of that there is more to be said. But they also arise from a profound unwillingness to subsume biology under physics and a desire to uphold "the autonomy of biology". This precludes the promise of an everincreasing homogeneity in the structure of science, and hence an ever-increasing simplicity.

The Historical Perspective

That the older embryologists awaited the extension of physicochemical conceptions to embryology is no mere matter of conjecture. Until the mechanical theory of the universe had been consolidated by the " corpuscularian philosophy" of the seventeenth century it would be useless to look for illustration of this, but by 1674 John Mayow was tracing the part played by the " nitro-aerial particles" in the development of the embryo, and in 1732 Hermann Boerhaave was discussing chemical problems with explicit reference to embryonic development. Many other examples of this point of view in the eighteenth century will be given later. Then, when the second decade of the nineteenth century had nearly gone, von Baer, perhaps the greatest of all embryologists, was careful to preface his Entwicklungsgeschichte by a careful account of all that was known about the chemical constitution of the Qgg, and that, although his philosophical inclinations were deeply vitalistic, and even his practical interests morphological. In Roux, of course, this future reference came out explicitly, and the extension of biochemistry into embryology was allowed for and foreseen. An early instance was the association between Wilhelm His and Hans Miescher. Miescher, writing to HoppeSeyler in 1872 said, "I am now collecting material from fishes, birds, and amphibia to lead to a chemical statics of development. With this end in view I shall do analyses of ash, nuclein, and lecithin".

Embryology before Harvey, however, was rigidly Aristotelian, a statement the meaning of which George Santayana has lucidly explained. "Aristotle", said he, "distinguished four principles in the understanding of Nature. The ignorant think that these are all, equally, forces producing change, and the cooperative sources of all natural things. Thus, if a chicken is hatched, they say that the Efficient Cause is the warmth of the brooding hen, yet this heat would not have hatched a chicken out of a stone, so that a second condition, which they call the Material Cause, must be invoked as well, namely, the nature of an egg; the essence of eggness being precisely a capacity to be hatched when warmed gently — because, as they wisely observe, boiling would drive away all potentiality of hatching. Yet, as they further remark, gentle heat-in-general joined with the essence-ofeggness would produce only hatching-as-such and not the hatching of a chicken, so that a third influence, which they call the Final Cause, or the End-in-view, must operate as well, and this guiding influence is the divine idea of a perfect cock or a perfect hen presiding over the incubation and causing the mere eggness in the egg to assume the likeness of the animals from which it came. Nor, finally, do they find that these three influences are sufficient to produce here and now this particular chicken, but are compelled to add a fourth, a Formal Cause, namely, a particular yolk, a particular shell, and a particular farmyard, on which and in which the other three causes may work, and laboriously hatch an individual chicken, probably lame and ridiculous despite so many sponsors." The Aristotelian account of causation could not be better expressed. Santayana puts this description of it into the mouth of Avicenna in his imaginary dialogue, and makes him go on to say, "Thus these learned babblers would put nature together out of words, and would regard the four principles of interpretation as forces mutually supplementary combining to produce material things ; as if perfection could be one of the sources of imperfection or as if the form which things happen to have could be one of the causes of their having it. Far differently do these four principles clarify the world when discretion conceives them as four rays shed by the light of an observing spirit". In this last observation we may perhaps trace the germ of the Copernican revolution in philosophy effected by Kant, if we may take it to enclose the idea of the activity of the experient subject in all perception.

In science generally, however, the x\ristotelian conceptions went without serious contradiction, and thus formed the framework for all the embryological work that was done, as, for instance, by Albertus Magnus. Owing to its association with the idea of the plan of a divine being, the final cause tended in the Middle Ages to eclipse the others. In the seventeenth century this feeling is well shown in a remarkable passage, which occurs in the Religio Medici of Sir Thomas Browne: "There is but one first cause, and four second causes of all things; some are without Efficient, as God; others without Matter, as Angels; some without Form, as the first matter; but every Essence created or uncreated, hath its Final cause, and some positive End both of its Essence and Operation ; this is the cause I grope after in the works of Nature ; on this hangs the providence of God ; to raise so beauteous a structure as the World and the Creatures thereof, was but his Art; but their sundry and divided operations, with their predestinated ends, are from the Treasure of his Wisdom. In the causes, nature, and affections of the EcHpses of the Sun and Moon there is most excellent speculation, but to profound farther, and to contemplate a reason why his providence hath so disposed and ordered their motions in that vast circle as to conjoyn and obscure each other, is a sweeter piece of Reason and a diviner point of Philosophy; therefore sometimes, and in some things, there appears to me as much Divinity in Galen his books De Usu Partium, as in Suarez' Metaphysicks: Had Aristotle been as curious in the enquiry of this cause as he was of the other, he had not left behind him an imperfect piece of Philosophy but an absolute tract of Divinity". This was written in Harvey's time, and in Harvey's thought the four causes were still supreme ; his De Generatione Animalium is deeply concerned with the unravelling of the causes which must collaborate in producing the finished embryo. But the end of their domination was at hand, and the exsuccous Lord Chancellor, whose writings Harvey thought so little of, was making an attack on one of Aristotle's causes which was destined to be peculiarly successful. There is no need to quote his immortal passages about the "impertinence", or irrelevance, of final causes in science, for they cannot but be familiar to all scientific men. Bacon demonstrated that from a scientific point of view the final cause was a useless conception; recourse to it as an explanation of any phenomenon might be of value in metaphysics, but was pernicious in science, since it closed the way at once for further experiments. To say that embryonic development took the course it did because the process was drawn on by a pulling force, by the idea of the perfect adult animal, might be an explanation of interest to the metaphysician, but as it could lead to no fresh experiments, it was nothing but a nuisance to the man of science. Later on, it became clear also that the final cause was irrelevant in science owing to its inexpressibility in terms of measurable entities. From these blows the final cause never recovered. In England the seventeenth century was the time of transition in these aflfairs, and in such books as Josfeph Glanville's Plus Ultra and Scepsis Scientifica, for instance, and Thomas Sprat's Defence of the Royal Society, the stormy conflict between the "new or experimental philosophy" and the Aristotelian "school-philosophy" can be easily followed. Francis Gotch has given a delightful account of the evening of AristoteUanism, but it involved a stormy sunset, and the older ideas did not give way without a struggle. Harvey's work is perfectly representative of the period of transition, for, in his preface under the heading "Of the Method to be observed in the knowledge of Generation", he says, "Every inquisition is to be derived from its Causes, and chiefly from the Material and Efficient". As for the formal cause. Bacon expressly excluded it from Physic, and it quietly disappeared as men saw that scientific laws depended on the repeatableness of phenomena, and that anything unique or individual stood outside the scope of science. Thus in the case of the developing egg, the formal (the particular farmyard, etc.) and the final causes are scientifically meaningless, and if it were desired to express modern scientific explanation in Aristotelian terminology, the material and efficient causes would alone be spoken of, essence-of-eggness being a "chymical matter" as well as the heat of the brooding hen.

Obstacles to Chemical Embryology

The complexity of living systems, however, is such that many minds find it difficult to accept this physico-chemical account as the most truly scientific way of looking at it. This is doubtless due in part to an erroneous notion, which is yet very tenacious of existence, that the mechanical theory of the universe must, if accepted at all, be accepted as an ultimate ontological doctrine, and so involve its supporter in one of the classical varieties of metaphysical materialism. It cannot be too strongly asserted that this is not the case. To imagine that it is, is to take no account of the great space that separates us from the last century. "When the first mathematical, logical, and natural uniformities", said WilHam James, "the first Laws, were discovered, men were so carried away by the clearness, beauty, and simplification that resulted that they believed themselves to have deciphered authentically the eternal thoughts of the Almighty. His mind also thundered and reverberated in syllogisms. He also thought in conic sections, squares, and roots and ratios, and geometrised like Euclid. He made Kepler's laws for the planets to follow, he made velocity increase proportionately to the time in falhng bodies; he made the laws of the sines for light to obey when refracted; he established the classes, orders, families, and genera of plants and animals, and fixed the distances between them."

Far different is the account of itself which science has since learned to give. But this change of attitude is not a revolt against thought as such, or against reason as such ; it is only a loss of belief in the literal inspiration of the formulae proper to science. It would be just as extravagant to claim that the scientific investigator of the twentieth century sets down absolute truths in his laboratory notebook, and, armed with an infallible method, explores the real structure of an objective world, as it would be fantastic to claim that Jehovah dictated an absolute code of the good to Moses on Mount Sinai. To say that the development of a living being can best be described in a metrical or mechanical way is not to say that it is metrical or mechanical and nothing else. The physico-chemical embryologist is not committed to any opinion on what his material really is, but he is committed to the opinion that the scientific method is one way of describing it, and that it is best to apply that method in its full rigour if it is to be applied at all. In other words, following the train of thought of William James, he does not assert that the courts of Heaven as well as those of our laboratories resound with expressions such as "organisers of the second grade," and "so many milHgrams per cent." The mechanical theory of the world, which is, as many beHeve, bound up indissolubly with one of the ultimate types of human experience, can no longer be considered as necessarily involving the exclusion of other theories of the world. Or, put in another way, it is a theory of the world, and not a pocket edition of the world itself

But before bringing forward any arguments in support of this attitude and in defence of physico-chemical embryology, it will be well to consider briefly those theoretical tendencies in modern biology which go together under the inexact adjective "neo-vitalistic", for their influence in scientific thought has been far-reaching. To deal critically with them is not a waste of time, for, were we to adopt any one of them, we should find that the notion of embryology as complicated biophysics and biochemistry would have to be abandoned, and quite other means of approach (never, indeed, very well defined) would have to be used.

The Stumbling-block of Hormism

Hormism, or "Psychobiology," may be dealt with in a few words. Chiefly supported by A. Wagner in Germany, and by E. S. Russell and L. T. Hobhouse in this country, it holds that — to use Lloyd Morgan's terminology — a physiological tale cannot be told separately from a psychological tale. Instead of expressing living processes in terms of physical causes and effects, the hormists wish to regard unconscious striving as the essential urge in life, and such conceptions as food, rest, fatigue, etc., as irreducible biological categories. These thinkers do not often acknowledge their debt to Galen of Pergamos, who put forward, as early as a.d. 170, an essentially similar conception as the basis of his biology. In the treatise On the Natural Faculties he says, "The cause of an activity I term a faculty.... Thus we say that there exists in the veins a blood-making faculty, as also a digestive faculty in the stomach, a pulsatile faculty in the heart, and in each of the other parts a special faculty corresponding to the function or activity of that part". He also said, "We call it a faculty so long as we are ignorant of the cause which is operating", but he never actually suggested any such underlying cause, and seems to have thought it impossible to ascertain. So do the hormists. According to them the actions of protozoa are to be described in terms of avoiding responses, seeking responses and the like, language which, as they claim, is much simpler than the complex terminology of surface tension and molecular orientation. Everything, of course, depends on what is meant by simple. To say that a protozoon seeks the light is evidently more naive than to say that a dimolecular photochemical reaction takes place in its protoplasm leading to an increase of lactic acid or what not on the stimulated side, but since the latter explanation fits into the body of scientific fact known already it is open to the biochemist to say that, for his part, he. considers the latter explanation the simpler. It is, in fact, simpler in the long run. Psychobiology or hormism differs from the other forms of neo-vitalism because it insists on retaining " commonsense " explanations in biology as categories of biological thought beneath which it is impossible to go. It dismisses the entelechy of dynamic Teleology, on the ground that it acts, as it were, in addition to the mechanistic schema, accepting the latter fully but interfering in it. It resembles much more finaUsm and organicism, but lays stress rather on the unconscious striving force which seems to animate colloidal solutions of carbohydrates, fats, and proteins. It resembles the Behaviourism of J. B. Watson superficially by emphasising animal behaviour, but it fundamentally differs, for it asks the question — Does an animal see the green light and the red light in this experiment as we do, or does it see them as two shades of grey as colour-blind people do? while the behaviourist asks — Does it respond according to difference of light-intensity or difference of wave-lengths ? Hormism, in fact, recurs continually to psychical factors. Samuel Butler, for instance, one of its principal exponents, wrote, "I want to connect the actual manufacture of the things a chicken makes inside an egg with the desire and memory of the chicken so as to show that one and the same set of vibrations at once change the universal substratum into the particular phase of it required" (cf. ^ rov hwdixei, 6vTo<i ivreXex^ta fj tolovtov) "and awaken a consciousness of and a memory of and a desire towards this particular phase on the part of the molecules which are being vibrated into it". "The Hormist contends", says Lloyd Morgan, "that something which is very difficult to distinguish from a ' plan-in-mind ' on the part of the embryo chick or rabbit does freely determine the course of events in specific growth from egg to adult. This, I urge, is a metaphysical hypothesis which goes beyond biology or psychology as branches of science."

Finalism as a Rock of Offence

Finalism and dynamic Teleology are closely connected, for both of them embody an attempt to go back to the Aristotelian inclusion of the final cause as an integral essential of scientific explanation, and to regard the Baconian attitude to teleology as a mistake. They solve Kant's antinomy of the teleological judgment simply by deleting the proposition, and leaving the counter-proposition. They are weakest on their practical side, for their supporters do not suggest any alterations which might be made in scientific method, although their fundamental assumptions plainly require it. The principal representative of finalism is Eugenio Rignano, and dynamic teleology has been for the most part upheld by Hans Driesch.

Rignano, in his Qii' est-ce-que la Vie? and his Biological Memory has contended that, though the mechanical concept of the universe may be perfectly satisfactory as a description of the world of physics, yet animals and plants show so much purposiveness that mechanical categories are absolutely inadequate for them. Biology, therefore, cannot be complicated physics and chemistry, but must be something sui generis and with its own methods and laws. "The long debate between vitalists and mechanists," he says, "in attempting to give an explanation of life, cannot lead to any conclusion unless that fundamental characteristic common to all vital phenomena of presenting a purposive, teleological, or finaUstic aspect in their most typical manifestations is first thoroughly examined." The most succinct account of his views and of the exact biologist's answer to them will be found in his Man Not a Machine, and in the volume Man a Machine in the same series. The way in which they affect embryology is significant, and may be found in his chapter called "Finalism of the generative and regenerative phenomena". "Even if", he says, "the organism could be explained as a physico-chemical machine, there would still remain to be explained the most fundamental thing — how the machine constructed itself The purposiveness of the ontogenetic development is too evident to be denied. It results from the convergence of manifold morphogenetic activities to one sole end, that is, to the formation of a marvellous functional unity, every part of which serves to maintain the life and guarantee the well-being of the whole. The embryo in its development manifests at every stage a ' harmony of composition ' as Driesch calls it, which has a touch of the marvellous ; parts and elements of an organ develop independently, but when they have finished their development they are found to fit together perfectly like the parts of a machine and the one so answers to the other that they unitedly form one complex organ. Thus the mouth and intestine of the sea-urchin begin their development at two points distant from each other and develop independently, but as they grow the one moves towards the other, so that when development is ended they fit together perfectly and form a single canal." This passage illustrates the line of argument found throughout Rignano, and I will not remark on it further than to draw attention to the mention of the marvellous in it, another hint, if any were needed, of that strain of misplaced "numinous instinct" which seems to be present in all biological vitaHsts. Omnia exeunt in mysterium would seem to be "a discouraging maxim" for the scientific worker. "The direction", Rignano goes on to say, "of ontogenetic development toward a predetermined end is also influenced by the fact that the embryo overcomes early disturbances which might deflect it from its course. Ontogenesis thus seems to be marshalled by some occult intelligence or entelechy in the same way that the construction of a machine and the direction of its work is presided over by the mind of the engineer."

Rignano's arguments are open to grave objection on two main grounds, first, that he regards biology as suffering more than physics from the teleology of things, and, second, that he wishes to bring the concept of purposiveness back into natural science.

The first of these is inadmissible both on philosophic and scientific grounds. Bernard Bosanquet best expresses the former attitude. He was led to his conclusions by the conviction that James Ward and other opponents of scientific naturalism had gone too far in their polemics against the mechanical theory of the universe, and had rested the case for teleology only "on the capacity of the finite consciousness for guidance and selection". This he considered a mistake. "Things are not teleological", he said, "because they are de facto purposed but necessary to be purposed because they are teleological.,.. The foundations of teleology in the universe are far too deeply laid to be accounted for by, still less restricted to, the intervention of finite consciousness. Everything goes to show that such consciousness should not be regarded as the source of teleology but as itself a manifestation falling within wider manifestations of the immanent individuality of the real." Bosanquet proceeds, following out the thought of his teacher, Lotze, "The contrast, then, of mechanism with teleology, is not to be treated as if elucidated at one blow by the antithesis of purposive consciousness and the reactions of part on part. It is rooted in the very nature of totality, which is regarded from two complementary points of view, as an individual whole, and as constituted of interacting members". But Rignano's arguments are unsatisfactory also from a scientific angle, and here the objection comes from Lawrence J. Henderson, whose book The Fitness of the Environment, probably the most important contribution to biological thought in this century, is never referred to by Rignano. It cannot now be necessary to recount how Henderson examined the question of the finality of our present scientific knowledge, and, judging that it was considerable, went on to enquire into the properties of the elements and compounds principally associated with life. His conclusion was that living animals and plants exist in an environment just as fitted for them as they are for it, that the Darwinian concept of fitness works, indeed, both ways, and that there is a reciprocity between organism and environment so that every teleological action done by an individual organism bears upon it the image and superscription of universal teleology. Thus the conclusion of the thought of Bosanquet and Henderson was that, though teleology was a conception which it was impossible to do without, yet any limitation of it to, or special association of it with, living organisms, was inadmissible. The question remained, What has teleology to do with science?

This point has been approached best by J. W. Jenkinson with his usual clarity. "Those who uphold teleological doctrine", he said, "seem to have fallen into a confusion between two different things, the formal and the final cause. The material, efficient, and formal causes, if we mean by the last the idea of the effect in the mind of a sentient being, all precede in time the occurrence of the effect; and this kind of teleology is not, as it is asserted to be, a doctrine of final, but one of formal causes. The final cause stands for the use to which an object is to be put, the effect it will produce, the function it will perform, which obviously succeed in time the existence of the object itself The final cause, then, cannot be taken as ever determining in time the existence of the object itself, and is therefore a conception which belongs not to science but to metaphysics. The only necessary conditions of a phenomenon ascertainable by science are those material and efficient causes which precede it." Or, as Streeter puts it, "If there is purpose in nature, we ought not to expect science to reveal it. Purpose is activity, the direction of which is determined by an end, that is, by an apprehension of quality or value. But quaUty cannot be measured, and therefore from its essential nature it — and along with it purpose — lies outside the sphere of science". Or, finally, to go straight to the fountain-head, "If I say", says Kant, "that I must judge according to merely mechanical laws of the possibility of all events in material nature and consequently of all forms regarded as its products, I do not therefore say: they are possible in this way alone. All that is impUed is: I must always reflect on them according to the principle of the mere mechanism of nature and consequently investigate this as far as I can ; because unless this Ues at the basis of investigation there can be no proper knowledge of nature at all". Purposiveness, in fact, is not a conception which interlocks with quantitative treatment; that mathematical expression of relationships which is the ideal type of all science has here nothing upon which to impinge, and the pulling force, perpetually going on before, eludes and must always elude, if this analysis is correct, the advancing web of mechanical explanation.

If, then, Bacon and his successors were right in banishing the concept of teleology from scientific thought, the physico-chemical embryologist need not be alarmed by the finalism with which, according to Rignano, the whole of ontogenetic development is suffused. In fact, it is not the phenomenon, but only one way of looking at it, that is finalistic, and it is this aspect of it that must be neglected in scientific work if the gravest confusion is to be avoided. Is there need for the biologist to be any more afraid of the Drieschian entelechy (Aristotle's eVreXe^em Actuality) making what might be into what is and directing from within the development of the embryo in the egg or the uterus? The word "entelechy" as used by Aristotle meant that which exists in the highest sense of the word, whether actually or potentially, e.g. the sword in the mind of the swordmaker before a single one of the necessary operations of manufacture had been begun. The entelechy therefore operated on the process in question by means of the final cause, and did not reside in the changing entity if it was dead like the sword, though it did if it was alive like the embryo. Driesch frequently says that he uses the word in a quite different sense from Aristotle, but the majority of his readers find it impossible to discover any essential point of divergence. He does at any rate make it much more precise than Aristotle, for he defines it as a non-spatial element in the living being, which at one time suspends possible action and at another time relaxes such suspension, acting in this way as the bearer of "individualising causality" and bringing the animal from potentiality into actuality.

It seems that this inherent immanent formative power has been translated by biologists of every period since Aristotle into the language of their time. Just as Driesch now tries to acclimatise it to the unfavourable environment of a post-Cartesian world, so St Gregory of Nyssa, who lived about a.d. 370, clothed it in patristic terminology, and produced a theological variety of neo-vitalism. His most important biological works, the irepl KaraaKevrjq dvdpcoirov, On the making of Man, and Trepl '^v^V'^i On the Soul, contained such passages as these, "The thing so implanted by the male in the female is fashioned into the different varieties of limbs and interior organs, not by the importation of any other power from without, but by the power which resides in it transforming it". And elsewhere, "For just as a man when perfectly developed has a soul of a specific nature, so at the fount and origin of his life, he shows in himself that conformation of soul which is suitable for his need in its preparing for itself its peculiarly fit dwelling-place by means of the matter implanted in the maternal body, for we do not suppose it possible that the soul is adapted to a strange building, just as it is not possible that a certain seal should agree with a different impression made in wax".

Thus the soul makes its body as if it were a gem making a stamp upon some soft substance, and acting during embryogeny from within — a conception essentially like that of Driesch. We shall see later how many Renaissance authors adopted similar views, e.g. Fienus. "No unsouled thing", says Gregory, "has the power to move and to grow. Yet there is no doubt that the embryo moves and waxes big as it is fed in the body of the mother." There is nothing new about dynamic teleology; it is by no means the outcome of newly ascertained facts : it recurs from time to time in the history of biological thought because it is the natural result of an unscientific attitude.

I do not propose to discuss here the facts which originally led Driesch to the views expressed in his Science and Philosophy of the Organism, for they are very well known, and have been shown by J. W. Jenkinson, H. S. Jennings, H. C. Warren and A. E. Boveri, among others, to be interpretable on quite other lines. Nor shall I demonstrate by a comparison of passages from Driesch and Paracelsus how closely the conception of immanent formative force or entelechy approaches the master-archaeus of Paracelsus and the later iatrochemists such as Stahl, for Driesch has done it himself in his History and Theory of Vitalism. The inference from it is that the Drieschian entelechy has been and will be of no more use as a practical working hypothesis for the laboratory than the archaeus was in the past.

Driesch's dynamic teleology is open to more serious and fundamental objections. These were not obvious at the first appearance of his Gifford Lectures, but were clearly brought to light through the controversy which Jacques Loeb had with H. S. Jennings and which resulted in the publication of their respective books, Forced Movements, Tropisms, and Animal Conduct and The Behaviour of the Lower Organisms. Loeb's theory of tropisms entirely dispensed with any psychological factors, but Jennings upheld the view that they might be legitimately brought under scientific discussion, provided they were regarded as being determined as well as determining. This led him to make a new enquiry into scientific methodology, and he published his results in a valuable series of papers from 1911 to 191 8. He concluded that the pursuance of laboratory work demands as its minimum of system what he called "Radical Experimental Determinism", and that there was difference of opinion as to whether this might regard conscious or unconscious mental processes as links in the chain of determinate causation. On this point Jennings and Loeb were antagonists, but both were united against Driesch, from whose writings it now appeared that psychical events might or might not affect physical events according to circumstances, and that the entelechy was subject to no general laws. Neal had maintained that the experimentally discoverable perceptual determiners in living things were insufficient to account for the effects produced in them. Jennings pointed out that, if this meant that the non-perceptual (mental) determiners acted supplementarily to the others and not instead of them, it was compatible with radical experimental determinism. But, if it was said that some of the determiners were nonperceptual and could not be known at all, then it was incompatible. Now it was just this that Driesch had been saying. "A complete knowledge", he wrote, "of all physico-chemical things and relations (including possible relations) of a given system at a time t would not give a complete characterisation of that system if it is a living system. . . . Practically we may say that complete knowledge of the physico-chemical constitution of a given egg in a given state and of the behaviour following this constitution in one case, implies the same knowledge for other cases (in the same species) with great probability. But this is a probability in principle and can never be more. It would not even be a probability if we did not know the origin of a given egg in a given state, i.e. that the egg was the tgg, say, of an ascidian. But to know this history or origin, is of course, already more than simply to know its physico-chemical constitution and its consequences in one case, which suffices in the realm of the inorganic. It may be that the eggs of echinoidea, fishes, and birds, are the same in all the essentials of physico-chemical constitution. Something very different happens in each case on account of the different entelechies. In spite of this we know with great probability what will happen from one case if we know that this egg comes from a bird and that from an echinoid. Therefore, practically, experimental indeterminism is not a great danger for science."

But the matter was taken up by various writers, and Lovejoy, especially, defended Driesch from the charge of interfering with the fundamental necessities of scientific thought. Jennings, however, was able to publish in reply letters from Driesch in which these implications of his position were fully admitted. "Two systems absolutely identical in every physico-chemical respect may behave differently under absolutely identical conditions if the systems are living systems. For the specificity of a certain entelechy is among the complete characteristics of a living organism and about this entelechy knowledge of physico-chemical things and relations teaches absolutely nothing." Such a basis for experimental work was generally felt to carry with it its own condemnation.

It is interesting to recall, in this connection, the vivid account given by Claude Bernard of the polemic he had with Gerdy at

the Philomathic Society in Paris, for the Driesch-Lovejoy-Jennings controversy simply repeated on a larger scale the arguments

of the two Parisian biologists sixty years before. "In 1859,"

says Claude Bernard, "I made a report to the Philomathic

Society in which I discussed the experiments of Brodie and

Magendie on ligature of the bile-duct, and I showed that the divergent

results which the two experimentalists reached depended on the fact

that one operated only on dogs and tied only the bile-duct, while

the other operated only on cats, and, without suspecting it, included

in his ligature both the bile-duct and a pancreatic duct. Thus I

explained the difference in the results they reached and concluded

that in physiology as everywhere else experiments are rigorous and

give identical results wherever we operate in exactly similar Conditions.

A propos of this a member of the Society took the floor to attack my

conclusions ; it was Gerdy, a surgeon at the Charite, professor in the

faculty of medicine and known through various works in surgery

and physiology. 'Your anatomical explanation of these experiments',

said he, 'is correct, but I cannot accept your general conclusions.

You say, in fact, that the results of experiments in physiology are

identical; I deny it. Your conclusion would be correct for inert

nature but cannot be true for living nature. Whenever life enters

into phenomena', he went on, 'conditions may be as similar as we

please, the results may still be different.' To support his opinion Gerdy

cited cases of individuals with the same disease, to whom he had

given the same drugs with different results. He also recalled cases

of like operations for the same disease, but followed by cure in one case and death in another. These differences, according to him, all depended on life itself altering the results, though the experimental conditions were the same, but this could not happen, he thought, in the phenomena of inert bodies, where life does not enter. Opposition to these ideas was prompt and general in the Philomathic Society. Everyone pointed out to Gerdy that his opinions were nothing less than a denial of biological science, but he would not give up his ideas and entrenched himself behind the word 'vitality'. He could not be made to understand that it was only a word, devoid of meaning and corresponding to nothing, and that saying that something was due to vitality amounted to calling it unknown." The only difference between Driesch and Gerdy seems to be that Driesch's arguments rested on a more solid basis of fact, and were put forward with greater eloquence.

It is worth while to study the thought of Claude Bernard more closely. Bernard was so subtle a thinker that it has always been difficult to classify him with any of the main currents of biological thought, but the following passage seems to me to sum up as well as any other the main shape of his ideas. "When a chicken develops in an egg", said he, "the formation of the animal body as a grouping of chemical elements is not what essentially distinguishes the vital force. This grouping takes place only according to laws which govern the physico-chemical properties of matter ; but the guiding idea of the vital evolution is essentially of the domain of life and belongs neither to chemistry nor to physics nor to anything else. In every living germ is a creative idea which develops and exhibits itself through organisation. As long as a living being persists it remains under the influence of this same creative vital force, and death comes when it can no longer express itself; here, as everywhere, everything is derived from the idea which alone creates and guides ; physico-chemical means of expression are common to all natural phenomena and remain mingled pell-mell, like the letters of the alphabet in a box, till a force goes to fetch them to express the most varied thoughts and mechanisms. This same vital idea preserves beings by reconstructing the vital parts disorganised by exercise or destroyed by accident or disease. To the physico-chemical conditions of this primal development, then, we must always refer our explanation of life, whether in the normal or pathological state." Here Bernard seems to recognise the significance of universal teleology, for he says, "here, as everywhere, everything is derived, etc.", and at the same time he lays stress on the identification of the physico-chemical aspect with the scientific aspect, going on, indeed, to say that "physiologists can only act indirectly through animal physico-chemistry, i.e. physics and chemistry worked out in the field of life, where the necessary conditions of all living organisms develop, create, and support each other according to a definite idea and obedient to rigorous determinism". It is true that elsewhere he identifies this "force that goes to arrange the letters of the alphabet" with the "mediating nature" of Hippocrates and the archaeus faber of van Helmont. Had he read more in Lucretius than in Aristotle, he might rather have spoken of it as a necessary outcome of the constitution of nature, a suggestion more profoundly in harmony, perhaps, with the natural bent of the scientific consciousness (cf Bacon's remarks on Democritus in De Augmentis Scientiarum) . But, even so, he evidently regards it as the subject-matter of metaphysics and not of science, for he says in the next paragraph, "The term 'vital properties' is only provisional because we call properties ' vital ' which we have not yet been able to reduce to physico-chemical terms, though doubtless we shall succeed in that some day".

Organicism as an Occasion of Falling

By making use of the thought of Bernard, we pass by an imperceptible transition from finalism and dynamic teleology to organicism, another of the principal forms which the opposition to mechanistic biology has taken. This, like some of the other doctrines I have mentioned, has a long history behind it. The notion, "We murder to dissect", finds clear expression as early as a.d. 200, when Q^. Septimius Tertullianus, of Carthage, one of the Western Fathers, spoke thus of Herophilus, the Alexandrian anatomist, "Herophilus, the physician, or rather butcher, dissected 600 persons that he might scrutinise nature; he hated man that he might gain knowledge. I know not whether he explored clearly all the internal parts of man for death itself changes them from their state when alive, and death in his hands was not simply death, but led to error from the very process of cutting up". No more excellent statement of the organicistic viewpoint could be devised. Sir Kenelm Digby in 1644 gave a still clearer summary of this point of view, and even in the rationalistic eighteenth century there were scientific men who objected to the use of the term machine-like as applied to animals, and insisted that


the living being was an organism. Cuvier took a very definite stand on this question when he said, "All the parts of a body are interrelated, they can act only in so far as they all act together; trying to separate one from the whole means transferring it to the realm of dead substance and entirely changing its essence". But the name most familiarly associated with biological organicism in this country is that of J. S. Haldane, who has frequently set forth his views upon this subject. His attitude is so well known that it need not be described here at any length, but, in brief, he points out that the living animal is an entity with a far higher degree of internal relatedness than any non-living system, and holds that the organic cannot be understood by a study of its parts though the inorganic very possibly can. In other words, an organism is an entity whose parts lose all their characteristic properties when they are studied away from the organism itself; they fall, as it were, into meaninglessness as soon as they are abstracted from the whole of which they are parts. Consequently that kind of physiology, and a fortiori biophysics and biochemistry, which analyses living organisms, is insufficient as an apparatus for understanding living things and should give place to studies in which organisms are regarded intact. Moreover, it is only in the untouched organism that those wonderfully wellbalanced actions are seen by which the animal or plant holds to its own niche in the economy of nature, resisting every attempt to dislodge it, provided the attempt be not so successful as to disorganise the living thing. This power of maintaining a constancy in its external and internal environment is what Haldane regards as the deus ex machina, the property of living things essentially inexplicable by physico-chemical hypotheses and requiring special biological language for its formulation. (For a discussion of the "inconceivability argument" in biology, see Mackenzie and Needham.) "All attempts", he says, "to trace the ultimate mechanism of life must be given up as meaningless. The aim of biology becomes a very different one — to trace in increasing detail, and with increasing clearness, the organic determination which the organic conception formulates." It is to be noted, however, that Haldane vigorously criticised Drieschian neovitalism, adducing against it the argument of impossibility of interference with the second law of thermo-dynamics, and the dubiousness of the theory of guidance without work done, a discussion of which on much better foundations was subsequently given by Lotka.


Haldane was not convincing in his criticism of Driesch, and there can be little doubt that Driesch's position is a perfectly tenable one, provided its supporter closes his eyes to the nature of the scientific method on the one hand, and the actual history of recent scientific progress on the other. Another side of Haldane's teaching was the view that the living animal was in some way less abstract than the world of physics ; physics and biology, he thought, might some day coalesce, but it would then be found that physics would not have swallowed up biology; rather the contrary would occur and biology would swallow up physics. "The idea of life", he said, "is nearer to reality than the ideas of matter and energy, and therefore the presupposition of ideal biology is that inorganic can ultimately be resolved into organic phenomena, and that the physical world is thus only the appearance of a deeper reality which is as yet hidden from our distinct vision and can only be seen dimly with the eye of scientific faith."

There had been precursory voices of all this in the nineteenth century, as when, in spite of the discoveries of Cagniard de Latour and others that the yeast-cell played an essential part in fermentation, Justus von Liebig refused to credit them, fearing that their suggestions were a return to explanations by vital force. "Chemical actions may very well explain physiological actions, but certainly not vice versa ", said Moritz Traube. Claude Bernard, moreover, discussed the matter with his usual subtlety. "Physiologists", he said, "must not forget that a living being is an organism with its own individuality. Since physicists and chemists cannot take their stand outside the universe they study bodies and phenomena in themselves and separately without necessarily having to connect them with nature as a whole. Physiologists, on the contrary, find themselves outside the animal organism which they see as a whole, even when trying to get inside so as to understand the mechanism of every part. The result is that physicists and chemists reject all idea of final causes for the facts which they observe while physiologists are inclined to acknowledge an harmonious and pre-established unity in an organised body, all of whose actions are independent and mutually generative. If we break up an organism for the sake of studying its parts it is only for the sake of ease in experimental analysis, and by no means in order to conceive them separately. Indeed, when we wish to ascribe to a physiological quality its value and true significance we must


always refer it to this whole and draw our final conclusions only in relation to its effect on the whole. It is doubtless because he felt this necessary interdependence among the parts of an organism that Cuvier said that experimentation was not applicable to living beings since it separated organised parts that should remain united. For the same reason vitalists proscribe experiments in medicine. These views, which have their correct side, are nevertheless false in their general outcome and have greatly hampered the progress of science." Bernard did not commit himself to an absolutely unambiguous statement as to the correct and incorrect sides of organicism, and seems to have regarded it as true only in the sense that imaginative synthesis must follow radical experimental analysis. He was therefore quite opposed to that true and keen-edged organicism represented by Cuvier and other biologists, which denied the bare utility and legitimacy of the experimental analysis, and which was not unjustly satirised by Woolf in 1927:

You cannot demonstrate the soul

Except upon the animal as a whole;

Spiritual autolytic changes begin

As soon as you push a needle through the skin.

Haldane's writings and those of his school, such as J. A. Thomson and G. G. Douglas, had extremely little effect on the direction taken by biological science in the first years of this century. As A. D. Ritchie pointed out, it is extraordinarily difficult to find out anything about living systems, unless their parts are treated in isolation, even if that be recognised as but the preliminary for imaginative synthesis, and, as many observers said, Haldane's own researches in the physiology of breathing afforded an excellent example of the usual scientific method. Biological research proceeded steadily on the usual lines, for Haldane's practical counsels could only be followed by those who were willing to abandon causal explanations in biology or to give up the hope of biology becoming an exact science.

An influence was at hand, however, which was to lessen very much, if not to destroy altogether, the attraction of Haldane's opinions for biologists. A. N. Whitehead had in his earlier works, The Concept of Mature and The Principles of Natural Knowledge, elaborated his theory of extensive abstraction, but it was not until the publication of his Science and the Modern World that it began to exercise any wide


spread effect upon scientific men other than mathematical physicists. Whitehead boldly extended the concept of the organism to cover all objects, i.e. all events, non-living as well as living. The word "inorganic" would thus cease to apply to non-living nature and all physical systems would be regarded as in a sense incomprehensible, except when regarded as wholes composed of parts owing their very existence to their share and arrangement in the whole in question. Quoting Tennyson's, '"The stars', she whispers, 'blindly run'", he says, "An electron within a living body is different from an electron outside it, by reason of the plan of the body. The electron blindly runs within or without the body, but it runs within the body in accordance with the general plan of the body and this plan includes the mental state. But this principle of modification is perfectly general throughout nature, and represents no property peculiar to living bodies".

Lloyd Morgan recognised in Whitehead's organisms his "systems of relations going together in substantial unity", which he had conceived of as stretching in degrees of ever vaster complexity from the smallest physical event to the universe itself. It was Lloyd Morgan, indeed, who pointed out first the significance of Whitehead's arguments for biological thought. He showed that the extension of organicism to cover the entire world of physics had no serious consequences for biological mechanists (who would continue to employ physico-chemical methods as before), provided that they had not adopted some form of scientific naturalism. At the same time, it could have little help for those who had insisted that the principal characteristic of living things was their organismic character, and had been led by this to propose far-reaching alterations in scientific logic or to give up the hope of causal explanation in biology. If, as it would seem, there are organisms everywhere, then the position that there are organisms nowhere turns out to be better placed than the position that living things are organisms and not other things ; for, in the former case, peace can be at once secured by attention to definitions, while in the latter case the irreducible characteristic of life is not organicism, whatever else it may be. The difference between the living and the non-living becomes a quantitative one, expressible in degrees of organisation. As has been pointed out, Haldane's prophetic observations concerning the eventual meetingplace of physics and biology have perhaps at last been justified, but, if so, with a barren benefit to neo- vitalism.


Organicism and Emergence

We may now pass by another small transition, from organicism to theories of emergence. Neo- vitalism in this form practically ceases to have any claim to the name, and approaches extremely closely to neo-mechanism. The principle of emergence in its simplest form is the statement that there are levels of existence in the universe, at each of which some more complicated form of being comes into existence, containing some essence absolutely new, and which could not have been predicted, even if all the properties of the constituents of the lower order had been known. This is evidently a conception very close to that of the organism, for just as the living or non-living system, looked at from one point of view, ceases to be itself as soon as it is dismembered, so the new level of complexity, looked at from one point of view, consists of lower levels of complexity joined together in a way that could not have been foreseen, because its properties and peculiarities are not the sum of the properties and peculiarities of its constituents. But it is important to note that there are here two parentheses, namely, "looked at from one point of view", implying that there is another point of view, and though the discussion is complicated here by the doubt as to whether Whitehead intends his organisms to be taken as a metaphysical theory, or as a scientific theory, yet in Lloyd Morgan the statement is clear that the emergent point of view has always a complementary one, the resultant point of view, "the emergent web and the resultant woof" as he calls it. This is really a new and more accurate way of putting the ancient antithesis of mechanism and teleology, for the scientific method involves the concept of resultance, since it continually seeks for the predetermining causes which must be in some way uniform with their effects, while the advent of something absolutely new at each level, i.e. atom to molecule, colloidal aggregate to living cell, etc., is a speculation hardly germane to science and resembling the final cause.

We find ourselves back again, then, at the distinction between metaphysics and science, which was first seriously studied by Kant. Most of the confusion has arisen in the past through an insufficiently clear decision as to the nature of biology. Biology cannot be philosophical and scientific, emergent and resultant, indeterminate and determinate, teleological and mechanical at one and the same time.


No doubt the most powerful solvent of vitalism will turn out to be the set of changes now taking place in physics. It is as yet too early to describe very definitely the effects of these, and several modern writers on the subject are rather free in their use of the word "mysticism", but it is at any rate clear that physicists are coming to see more clearly than before the impHcations and the limitations of the study of the metrical aspects of the world, which is what science is. Behind these sets of numbers and quantities the background of the world is enigmatic, and Heisenberg's Principle of Indeterminacy indicates that extreme accuracy can only be obtained at a cost. Again, the abandonment of the model in physics is a highly important step, and physics seems to have reached a point at which there is no analogy in our everyday experience for the phenomena with which it is dealing, so that we cannot even picture in ordinary words what is happening. Eddington, in his great work The Nature of the Physical World, also shows that physics no longer speaks of the motion of every individual particle in the universe being rigidly determined but rather of the relative probabilities of its motions, i.e. the odds on them. If this funeral of Laplace's Calculator should turn out to be enduring, a good deal of difficulty may vanish from the biological sphere. But I should prefer to leave the working out of these possibilities to those better qualified than myself, and to suggest simply that if the mechanical theory of the world is being reconstructed by modern physics, there may be a widespread sapping of the force of neo-vitaHstic contentions in the near future. I have often thought that neo-vitalists were thinkers whose religious sense had got into the wrong place; unable to set up commonsense watertight compartments on the one hand, or to work out a philosophy of the forms of experience on the other, they brought the numinous into biology and abused biophysics. The fundamental contention of the mechanists always was that science and the scientific method were one and that biology was complicated physics — this remains unaltered. But if physics is more and more obviously throwing off the links which bound it in the past to metaphysical materiahsm, and admitting itself to be the study of the metrical aspects of the world, there will be perhaps less excuse for the misplacement of the numinous, as it might be called; and the affirmation that biology must be based upon physics will cause less antagonism than in the past. In a word, the vitaHsts wished to introduce mysticism at the wrong level; the right


level would seem to be, as it were, underneath the metrical abstractions of physics, i.e. outside science altogether, and if this is realised, the vitalist and the mechanist will fuse into one and the same person — a happy consummation. It is curious that at the present time, when physics is so markedly freeing itself from scientific naturalism, biologists are sometimes found to support that untenable world-view, while still farther away from the inorganic world, literary criticism tries to make itself modern by using a psychological jargon, and applying to its problems all the rigour of a materialist metaphysic.

Neo-mechanism as a Theory for Chemical Embryology

The principal philosophical obstacles to physico-chemical embryology have now been assessed and nothing remains but to outline its own theoretical basis. Anyone who was dissatisfied twenty years ago with the various forms of neo-vitalism which have already been discussed would have had no alternative but to accept the simple, though rather incredible, scientific naturalism of the preceding century, unless, indeed, he was acquainted with German philosophy, and understood the momentous consequences which flowed from the apparently technical question, "How are a priori synthetic judgments possible?" The varieties of neo-vitalism may perhaps be thought of, in so far as they are not modern forms of difficulties which have for many centuries perplexed philosophers, as a series of reactions against mechanistic biology insufficiently distinguished from scientific naturalism. This confusion is well seen in the earlier phases of the American discussion which led up to the symposium of 191 8. It is often difficult to tell, as in the papers of Nichols; Ritter; More and Fraser Harris, whether the writer is attacking the mechanical theory of the universe regarded as an ultimate metaphysical faith or the mechanical methodology of science.

Before the eighteenth century, of course, there had always been thinkers who felt the necessity of including both teleology and its antithesis in their systems of thought. This pull in two directions accounts for those very interesting mediaeval theologians, such as Siger of Brabant and John of Jandun, who wished to acknowledge two kinds of truth, theological and philosophical (see Maywald and Gilson). A right balance had to be struck in some way between Democritus and Plotinus, and in the seventeenth century, for in


stance, Sir Thomas Browne wrote to his son advising him to studyLucretius yet not to read too much in him, "there being divers impieties in him". Perhaps the greatest figure in this line of descent is the Cardinal Nicholas of Cusa, who, in his book De Docta Ignorantia of 1440, contended that the principle of contradiction was only valid for our reason, and so foreshadowed Kant and Hegel (cf. Vansteenberghe) . But the starry heavens with their infinite spaces that terrified Pascal and their mechanical order and metrical uniformity revealed by Kepler and Copernicus, on the one hand, and the moral law with its tremendous purposiveness and its theological implications, on the other hand, were never really faced at one and the same moment and taken seriously together until the time of Kant, who first subjectivated what had before struggled in the external world, and suggested that the contradictions of our thought might spring from the constitution of our own intelligence. "It has always been assumed", he said, "that all our knowledge must conform to objects. The time has now come to ask, whether better progress may not be made by supposing that objects must conform to our knowledge."

Omnis enim longe nostris ab sensibus infra primorum natura jacet. . .

Lucretius had said, but Kant went farther, and suggested that our intelHgence can help us no more than our senses in the attempt to see things as they really are.

This was the great service that Kant performed for philosophy, and in the light of it the scientific mind was relieved of the burden of having to believe finally in its own account of the world. But in the scientific controversies of the last century, Kant was forgotten, and the continual successes of the scientific method led to a naturaUstic outlook, which was wholly unsatisfactory. It had been supported by T. H. Huxley, Herbert Spencer, W. K. CUfford, Tyndall, Ray Lankester, and many others: it apparently still is by Chalmers Mitchell. But, as a widely accepted attitude, it did not live long into the present century, and from such blows as James Ward's Naturalism and Agnosticism and Antonio Aliotta's The Idealistic Reaction against Science, it never recovered. Physico-chemical biologists were thus left, as it were, without visible means of support, and existed for some time on a purely pragmatic basis, devoid of any epistemological comfort. Gradually, however, a more satisfactory attitude came into being.


Karl Pearson pro\-ided an intimation of it when he remarked, "Those who say that mechanism cannot explain life are perfectly correct, but then mechanism does not explain anything. Those, on the other hand, who say that mechanism cannot describe hfe are going far beyond what is justifiable in the present state of our knowledge". A clear enunciation of it, informed with the charm of all his writings, was given by d'Arcy Thompson in the .\ristoteUan Society^ S\Tnposium of 191 8. "In the concepts of matter and energy", he said, " the Whole is not enshrined, mechanism is but one aspect of the world. These are the proper categories of objective science, but they are no more: the physicist is, ipso facto, a mechanist, but he is not by impHcation a materialist; nor is the biologist of necessity a materiahst, even though he may study nothing but mechanism in the material fabric and bodily acti\ities of the organism." R. S. Lillie's paper of 1927 might be taken as one of the best expositions of this point of \-iew. "Every biologist is aware", he says, "in his non-professional moments that the possibiUties of hfe are larger than the mechanistic \iew impHes. This is only another way of acknowledging that the whole mechanistic conception is an incomplete, derivative, or abstract one. To regard it as philosophically final is a grave mistake." Thus Lillie remains cominced of the adequacy of physico-chemical biologv', but expressly repudiates the elevation of mechanism into a metaphysic.

LilUe goes on to discuss the abstract, distorted and incomplete character of the world which is presented to us by the employment of the scientific method. "To say", he proceeds, "that Hfe is 'nothing but' a combination of chemical reactions in a colloidal substratum is unscientific. Life may be and apparently is that in part but to regard any such scientific formulation as a complete and adequate representation of its total reaUt}- is simply to misconcei\-e the structure of science." This is well said; Ufe is indeed a "dynamic equihbrium in a polyphasic system", but also "Life is a manifest of emergent creativity", "Life is a pure flame and we five by an imisible sun within us", "Life is a sad composition, we five with death and die not in a moment", and — if you will,

Life, like a dome of many-coloured glass, Stains the white radiance of eternity Until death tramples it to fi-agments.


"The dilemma of vitalism is irresolvable", says Lillie, "so long as we regard the units, concepts, and formulae found vaHd in physical science not as abstractions but as primary and self-existent reaUties, by a combination of which all the properties of living beings as of other natural phenomena can be derived."

In a former discussion I contrasted what might be called the Democritus-Holbach-Huxley attitude in biology with the DrieschHaldane-Russell-Rignano attitude, and concluded after examining them that both involved insuperable difficulties. Lotze was the philosopher to whom I went for help in the elaboration of a better standpoint. "The true source of the life of science", said he, "is to be found, not indeed in admitting now a fragment of one view and now a fragment of the other, but in showing how absolutely universal is the extent and at the same time how completely subordinate is the significance of the mission which mechanism has to fulfil in the structure of the world." And in another place, "We granted v^aUdity to the mechanical view in so far as concerns the examination of the relations between finite and finite and the origin and accomplishment of any reciprocal action whatever; we as decidedly denied its authority when it claimed acceptance, not as a formal instrument of investigation, but as a final theorv' of things". "Nowhere is mechanism", says Lotze, "the essence of the matter, but nowhere does being assume another form of finite existence except through it."

I went on to argue that, although Lotze made everv^ effort to demonstrate how mechanism and teleolog)' could fit together in the universe, he failed to do so convincingly, and that it was more satisfactory to make them necessary results of the a priority of our ways of thought. "We may regard", I said, "the mechanistic view of the world as a legitimate methodological distortion, capable of appHcation to any phenomenon whatever, and possessing no value at all as a metaphysical doctrine." Mechanism, whichever of its forms ^defined by C. D. Broad, M. R. Cohen and Y. H. Krikorian turns out to be the minimum requirement of science, is, in fact, not metaphysical materiahsm. It is necessary to maintain it on methodological grounds, but it is pernicious to allot it any v\ider value. It stands, in fact, as one of the kinds of way in which the human spirit reacts to the universe in which it finds itself, and it springs, as R. G. CoUingwood puts it, directly from the ultimate root of all science, the assertion of the abstract concept. "He who generaUses is an idiot", said William Blake, but that was a revelation of the poetic or the religious mind. The scientific spirit is as profound as these, but it sets out upon a different path from the very beginning and reaches in the end a country different in every way. It directs its interest from the first to the correlation of differences between phenomena rather than to individual phenomena themselves, and the impulse to classify leads inevitably to the supremacy of the mechanical cause and the mathematical formula. It stands "at diameter and sword's point" with such aphorisms as "Everything is itself and not something else" or "Nothing is ever merely anything".

R. G. Collingwood has expressed this in a memorable passage: "Mathematics, mechanics, and materialism are the three marks of all science, a triad of which none can be separated from the others, since in fact they all follow from the original act by which the scientific consciousness comes into being, namely, the assertion of the abstract concept. They are all, it may be said, products of the classificatory frame of mind, corollaries from the fact that in this frame of mind the universal and the particular are arbitrarily separated and the universal asserted in its barren an'd rigid self-identity. It is this barrenness and this rigidity which confer their character upon the doctrines of scientific materialism. Hence it is idle to imagine that materialism is justified in some sciences and not in others. It is idle to protest that science ought to surrender its materialistic prejudices when it finds itself face to face with a non-material object such as the soul. No object is material, in the metaphysical sense of the word, except in so far as scientific thinking conceives it so; for materiality means abstractness, subjection to the formulae of mechanical determination and mathematical calculation, and these formulae are never imposed upon any object whatever except by an arbitrary act which falsifies the object's nature. This only appears paradoxical when we fail to see the gulf which separates the common-sense materiaHty of a table, its sensible qualities, from its metaphysical materiality, the abstract conceptual substrate of those qualities. It is this substrate whose transcendent or abstract existence is asserted by materialism. Hence we cannot distinguish objects like tables which are really 'material' from objects in whose presence science must unlearn its materialistic habits of thought. MateriaHsm is no more the truth in physics than in psychology, and no less. It is the truth about any object, just in so far as this object is by abstraction reducible to terms of pure mathematics; and no object is so reducible except by consciously or unconsciously shutting our eyes to everything which differentiates it from anything else. This conscious or unconscious act of abstraction is the very being of the scientific consciousness; and it is therefore no matter for pained surprise when science shows a bias towards determinism, behaviourism, and materiaHsm generally".

By this time the general outlines of this theoretical excursus should have become clear. Embryology, to put it plainly, has been for so many years the happy hunting-ground of vitaHstic and neo-vitalistic theory that the first treatise on the physico-chemical aspect of it could hardly go without some kind of theoretical introduction. "VitaHstic conceptions", said Claude Bernard in 1875, with the voice of authentic prophecy, "can no longer hover over physiology as a whole. The developmental force of the egg and the embryonic cells is the last rampart of vitalism, but in taking refuge there, it transforms itself into a metaphysical concept and snaps the last link connecting it with the physical world, and the science of physiology."

It is to be hoped that what has now been said will place in a right light the aims of physico-chemical embryology, and provide it, as it were, with its decretals. That they are not false will be the hope of every exact biologist.

Chemical embryology is now indeed at a critical point in its history. On the one hand, it links up with the morphological work of the classical embryology and the experimental work of the Entwicklungsmechanik school, while on the other hand it has affinities with genetics, a science which is every day becoming more physiological and which will more and more seek for the effects of its factors in the biochemistry of development. Goldschmidt's book, and the work of Dunn, who found a lethal gene in an inbred strain of fowl which caused a regular chick mortaUty at the seventeenth day of incubation, are important examples of this. Another relationship of chemical embryology is to obstetric medicine, for such problems as the toxaemias of pregnancy will not be solved by Hippocratic observation unassisted by a knowledge of the chemistry of the embryo and the placenta. The attention devoted by the Medical Research Council to such problems is an acknowledgment of this fact. Nor is veterinary physiology in a position to do without the aid of chemico-embryological researches, as is shown by the incident


of the myxoedematous pig foetuses of western America in the work of Smith.

But all practical applications, how valuable soever, must give place to the increase of knowledge itself, and therefore the physicochemical history of embryonic development, from the egg-cell to the loosing of the individual into the activity of post-natal life, is to be the theme of this present book. "The history of a man for the nine months preceding his birth", said S. T. Coleridge, "would probably be far more interesting, and contain events of far greater moment than all the three-score and ten years that follow it."

Cite this page: Hill, M.A. (2020, August 6) Embryology Book - Chemical embryology 1 (1900) 1. Retrieved from

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