Westminster lectures
Aveling, Francis, 1875-1941
HE ss CRI i 01 * HI '! Hi- fiU'tM!-:k CRI - (< I Thf. FREEDOM SANDS & CO, WESTMINSTER LECTURE EDITED BY REV. FRANCIS AVELING, D.D. SERIES II. THE SECRET OF THE CELL THE HIGHER CRITICISM THE DIVINITY OF CHRIST THE FREEDOM OF THE WILL SANDS & CO. LONDON : 15 KING STREET, COVENT GARDEN, W.C. EDINBURGH: 37 GEORGE STREET GLASGOW: 76 CAMBRIDGE STREET PREFACE THIS lecture was delivered at the Cathedral Hall, Westminster, on the evening of the 22nd of March 1906, and is an attempt to bring together some of the arguments which can be advanced for the existence of a factor in the living organism unknown outside living matter, and of a wholly different character to anything within the domain of mechanics, of chemistry, or of physics. At the same time an effort has been made to point out some of the difficulties which exist in the way of such a thesis, and to indicate the direction in which a solution of these difficulties may be expected. B. C. A. WINDLE. QUEEN'S COLLEGE, CORK. THE SECRET OF THE CELL THAT there are two views respecting the nature of every living organism, human, animal, or vegetable, is, I suppose I may take it, r -i- 11 t t Two Views familiar to all persons who have bestowed even a very cursory glance upon bio logical controversies. According to the one party, the living organism is a mere machine, and its operations are the sum of the processes, chemical and physical, which take place in its interior. According to the other party, there is a something over — a something which controls and directs the operations of the organism, a something differing in char acter from the known chemical and physical forces, which can be investigated in the laboratory. As Dr Haldane puts it:1 " In a living organism there is a specific influence at work, which so controls all the movements of the 1 Nineteenth Century, 1898, ii., p. 400. 6 THE SECRET OF THE CELL body and of the material entering or leaving it, that the structure peculiar to the organism is developed and maintained." We may call this force what we please. We may term it a " genetic energy" with Williams, or a " growth- or bathmic-force " with Cope ; we may speak of it as a " property of self-adaptation " with Henslow, or of " direction" with Eimer. Whatever term we may choose to employ, we are really coming back to the long-believed but sometime scouted standpoint of a vital force. It is scarcely necessary to say that Catholic philosophers hold the existence of a vital force. The scholastic view is defined by Fr. Maher1 when he says : " The principle of life in the lower animals was held by the schoolmen to be an example of a simple principle which is nevertheless not spiritual, since it is altogether dependent upon the organism, or, as they The said, completely immersed in the body. Corporeal S. Thomas, accordingly, speaks of the corporeal souls of brutes." Such a view, it will at once be seen, is sharply to be distinguished from that held by Descartes and the "vitalists" of his school, for they believed that the soul or vital 1 Pschychology, 5th ed., p. 469. THE SECRET OF THE CELL 7 principle was something distinct from the body, though reigning, so to speak, in solitary state within it. We gain a clear insight into their views when we learn that Descartes tried to prove that the soul of man had its habitation in the pineal body, a small structure situated near the centre of the brain. Some thirty years ago, when Huxley and other great pundits of the science of that day were at their zenith, it was the custom to teach that there was nothing in the universe, living organisms included, which was not capable of explanation on chemico-physical grounds. It was held and taught that the manufacture of living protoplasm in the laboratory was only a question of time — even, as many thought, of a very short time. "The whole world," wrote Huxley,1 "living and not-living, is the result of the mutual interaction, according to definite laws, of the forces possessed by the molecules of which the primitive nebulosity of the universe was composed." And, again, he stated2 "that the living body is a mechanism ... is now the expressed or implied funda mental proposition of the whole of scientific 1 Belfast Address, 1874. 2 Collected Essay s,\. 163. 8 THE SECRET OF THE CELL physiology." So careful, in fact, was he to make his view clear, that, whereas in the first edition of this article he wrote, " our volition counts for something as a condition of the course of events," in a later edition he adds the note, " or, to speak more accurately, the physical state of which our volition is the expression." And another distinguished physi ologist, the late Professor Burdon Sanderson, declared, in 1889, that "for the future, the word 'vital,' as distinctive of physiological processes, might be abandoned altogether." It must not be supposed, however, that even at this time, and outside the ranks of Catholic philosophers, the doctrine thus enunciated, was held everywhere and by all persons. At an almost identical date, in 1886 to be accurate, we find Bunge, a celebrated writer on organic chemistry, proclaiming that "the mechanical theories of the present are urging us surely onwards to the vitalistic theory of the Neo- Vitalism M. future. This was no false prophecy. What are now called " neo-vitalistic " theories are to-day being put forward by many men of science. This is particularly the case in Germany and in the United States, countries in which the problems of ontogenesis have received especial THE SECRET OF THE CELL 9 attention. In England, however, where such studies have taken a second place to those of phylogeny, vitalistic views are still stigma tised by many as being mere mysticism. Let me give two examples of recent state ments which show the change which has come over scientific opinion. Both of them shall be from the writings of well-known men. Professor Wilson is perhaps the best-known writer in English on the problems of cellular life. In his classical work1 he says that "the study of the cell has on the whole seemed to widen rather than to narrow the enormous gap that separates even the lowest forms of life from the inorganic world." Dr Haldane, Reader in Physiology in the University of Oxford, states his view as follows:2 "To any physiologist who candidly reviews the progress of the last fifty years it must be perfectly evident that, so far from having advanced towards a physico- chemical explanation of life, we are in appear ance very much farther from one than we were fifty years ago." Subsequently he proceeds to show that operations in the body, once sup- 1 The Cell in Development and Inheritance, Macmillan & Co., 2nd ed., 1900. 2 Loc. cit. io THE SECRET OF THE CELL posed to be purely mechanical in their nature, such as the absorption of digested materials from the intestine and the process of oxidation, have now been shown to be wholly inexplicable in such terms. For the sake of a clearer appreciation of the various sides of the question, let us turn our attention to a limited field of observation. Let us consider the problem from the point of view of the cell, for it becomes more obvious every day that, in the ultimate analysis, it is in the cell that we must seek for the key of every biological problem. "When," says Bunge, "with the help of scalpel and microscope, we have dissected the organism to its last shred, when we are concerned only with the single cell — then the greatest riddle still lies before us. The single cell, the formless, structureless, microscopically small drop of protoplasm — it shows all the essential functions of life : nourish ment, growth, reproduction, motion, sensation — yes, even functions which at least compensate for the 'sensorium/ the conscious life of the higher animals." Schwann, who was the discoverer of the cell, thought that by his discovery he had entirely THE SECRET OF THE CELL u overthrown vitalistic theories. But the theory upon which Schwann based this view has since been shown to be entirely incorrect ; and all that his discovery did was to shift the question to a smaller region. Though smaller, it was not less complex ; for, as we have seen, the processes which take place in the cell are in many respects comparable with those which take place in the entire body. And, as we have also seen, so far from the discovery of the cell having rendered a vitalistic explanation of life less probable, we are told by many of those who have most assiduously studied it, that the more we know of the cell the less we are able to explain the phenomena which it presents on physico-chemical lines. What is a cell, and of what parts is it com posed ? The cell, speaking, as one must, in very general terms, is a more or less spherical mass of protoplasm, and this protoplasm may be divided into two portions. There is the cyto plasm, which makes up the great mass of the cell ; and there is the nucleoplasm, or caryoplasm, of which the nucleus, which we may regard as a highly specialised part of the cell, consists. And what is protoplasm? Chemically, it 12 THE SECRET OF THE CELL appears to be a substance of great complexity, though, so far, it has proved quite impossible to construct its definite chemical Protoplasm ... , formula. Its complexity is not due to the large number of elements, or what we believe to be elements, which enter into its composition. Of these there are but few ; three gases — oxygen, hydrogen, and nitrogen — and one solid — carbon — form by far the larger part, though there are trifling amounts of other substances. It is the com plex manner in which the molecule of proto plasm is built up that renders the construction of a formula difficult. " Protoplasm," says Wallace,1 "is so complex chemically as to defy exact analysis, being an elaborate structure of atoms built up into a molecule in which each atom must occupy its true place, like every carved stone in a Gothic Cathedral." And Pflliger, the celebrated German physiologist, tells us that living proteid is a huge molecule, undergoing constant, never-ending formation and decomposition, and probably behaves to wards the usual chemical molecules as the sun behaves towards small meteors. Beyond a general idea of vast complexity, 1 Mail's Place in the Universe, p. 199. THE SECRET OF THE CELL 13 then, we get no help from the chemical com position in trying to understand the function. Can we obtain any assistance from the physical structure ? The fundamental activities of protoplasm being everywhere the same, it was thought that some morphological basis ought to be ph • , discoverable underlying the varia- Structure of tions and special modifications of given cells. Hence most careful investiga tion has been made on this point, and every resource of the microscopist has been brought to bear upon its solution, but, so far, all in vain. "The attempt," says Wilson, "to find in visible protoplasmic structure any adequate insight into its fundamental modes of physiological activity has thus far proved fruit less." Of the mutual relations of the cell and its nucleus we are perhaps a little less ignorant. If we deprive the cell of its nucleus by artificial means, we know that whilst that cell can go on exhibiting some of the characteristic activities of life, such as irritability, for a certain time, it has lost its powers of assimilation, of growth, and of repair. In a word, it is on the high road to death. Hence, according to Roux and H THE SECRET OF THE CELL others, the nucleus is the controlling agency in the cell. But, on the other hand, the nucleus cannot get on without the cell-body, The Nucleus . 7 the protoplasm of which seems to act as a stimulant upon the nuclein and hence may "indirectly regulate the process of cleavage."1 We may conclude, then, with Balbiani 2 that "the cellular life neither resides exclusively in the protoplasm3 nor within the nucleus, but results from the reciprocal relations which are established between these two elements. Iso lated one from the other, neither of them is capable of life by itself." In a word then, the cell is a whole. One might almost speak of it as an individual when it forms, with other like and unlike cells, an organism. One can cer tainly speak of it as an individual when existing in an independent condition as a unicellular organism. Complicated chemical changes and elaborate physical processes no doubt take place continually within this cell. That all will admit. But we may certainly say that the totality of these changes and processes, the 1 Morgan, The Development of the Frog's Egg, p. 128. 2 Annales de Micrographie, 1893. 3 He is here using this word as meaning cytoplasm or cell-protoplasm, as opposed to karyoplasm, or nucleo- plasm. THE SECRET OF THE CELL 15 manner in which they are induced, and the results to which they tend, present us with phenomena wholly different from those which we can study in non-living matter either in the laboratory or in nature. Bitter Living matter is always changing, yet ever the same. It is like a river which remains the same to outward eye, though the water in it is ever different. " For, backward, Duddon ! as I cast my eyes, I see what was, and is, and will abide ; Still glides the Stream, and shall for ever glide ; The Form remains, the Function never dies." We have seen of how few elements the protoplasm is composed. Yet from this trifling collection of materials it is able to build up an almost endless series of highly varied deriva tives. Look at the vegetable world alone and consider the essential oils, the turpentines, the subtle poisons, the medicinal and edible sub stances which are elaborated from this scanty list of elementary substances. Yet the cell itself goes on its way unchanged. These metabolic changes, in fact, in no way resemble ordinary chemico-physical operations. Take, for example, the case of assimilation. In an ordinary chemical process, two substances 16 THE SECRET OF THE CELL come into combination with one another, and the result is the formation of a third substance wholly unlike those out of which it Metabolism. has been built up. I he cell, m its assimilative processes, also takes up sub stances and combines them with itself, or with substances which it contains. But in so doing, the cell does not become a third substance, but remains what it was before and from the beginning. Again, in the course of the metabolic changes by which the oils and other products mentioned a moment ago come into being, the cell, with all its characteristics, remains unchanged, and is not converted into something other than itself by the chemical changes which have taken place within it. Some have thought that the assimilative changes in the cell were comparable with the phenomena of crystallisa tion, but surely there is only an apparent resemblance between these two processes, a resemblance not even apparent on close consideration. A crystal is a mass of rytion1Sa" h°m°geneous particles which, when collected together, build up a regular edifice. Add new material to this and all that happens is that new molecules, of a similar char- THE SECRET OF THE CELL 17 acter, are placed side by side with the old ones. But in the cell the chemical substances which are taken in are moulded to the purposes of the cell and are broken up and converted into the very substance of the cell itself, or into by products of various kinds. Moreover, addition of new substance to a crystal is a superficial process, but the assimila tion and growth of the cell is interstitial in its character, and there is a fundamental difference between these two processes. But we can go a step beyond this in connection with the matter of crystallisation, and perhaps it will be as well to do so, since the point has been raised. Living organisms do construct crystals within themselves, so that if the parallel were a fair one we should have an instance of a process of crystallisation making use of another kind of crystallisation for its own purposes. But what do we learn from the study of these living crystals ? Professor Minchin shall tell us.1 " An ordinary crystal owes its peculiar characteristics entirely to the action of the laws of inorganic matter, laws which admit of 1 u Living Crystals," Proceedings of Royal Institution, vol. xv. B i8 THE SECRET OF THE CELL being accurately formulated and accurately calculated. Crystalline bodies are, however, known to occur which have been deposited within living bodies, and which owe their origin to vital activities. In such c/ state cases» tne crystals, while identical in their chemical composition and mole cular structure with crystals of inorganic origin, may exhibit, at the same time, certain peculi arities which are due entirely to the circum stances of their origin. . . . The relation of the spicules to the structure of the sponge shows that they have a definite function to perform and an important part to play in the economy of the organism which produced them. . .. We may, therefore, sum up in regard to the living crystals as follows — their composition is that of calcite crystals, but their external form is that which the sponge requires, and not that which they would naturally assume. They furnish us, in fact, with a beautiful instance of what is called adaptation ; that is to say, the fact that any living organism - tends to have just that form, structure, and organisation in all its parts which it requires in order to maintain its existence in its peculiar mode of life, whatever it may be." THE SECRET OF THE CELL 19 Chemistry and morphology, then, alike reveal a condition of things quite different from anything in existence in non-living matter. A physical examination of the most striking intracellular processes teaches us the same lesson. Prior to and during the pro cess by which a cell divides into x?el!" Division two, there occur, at least in a large number of instances, a singular series of events involving the protoplasm of the nucleus as well as that of the cell-body, which are known under the name of karyo- kinesis. It would be impossible to give here any adequate account of these happenings. Suffice it to say that a portion, perhaps the most important portion of the nucleus, nay, even of the cell itself, becomes broken up into fragments.1 These fragments pass through a series of complicated figures, like some country dance, and are finally deposited in a regular manner in the two portions which have been constituted from the originally single cell. Many efforts have been made to explain this 1 Whether it is the chromatin or the interstitial protoplasm which is of first importance is of no conse quence as regards the present argument. 20 THE SECRET OF THE CELL remarkable series of events, but, so far, no one has succeeded in clearing up their causa tion. Hartog's 1 careful experiments, so far as they go, certainly seem to point to the fact that these changes are the result of a force or energy unknown outside living matter, and, whether we regard it, for the present, as a mere form of words or not, it seems difficult to go beyond the statement of Boveri — himself one of the most distinguished of the observers of the phenomena which we have been con sidering — that the splitting of the chromosomes —one of the steps in the process — is "an independent vital manifestation." From the natural let us turn to the artificial. Curious investigators are daily playing all kinds of tricks upon the cell, partic- Expen- ujar]v on the ovum with a view ments ' of finding out what are its powers and what its limitations. One is sometimes told that living things are provided with adaptations, and a great deal of ignorance is covered by a word which, if it means anything at all, can only have a teleological significance. But those who, like Weismann, argue most freely about adaptations, proclaim 1 Proc. Royal Society, B. 76, 1905. THE SECRET OF THE CELL 21 that Nature — herself, by the way, only a personification — only provides these adapta tions in view of occurrences likely to take place. It would be going rather far to argue that the experimental embryologist was one of these occurrences foreseen by " Nature," yet, when the ovum is confronted with him, it manages to get its own way in a surprising number of cases. It will be instructive to examine a few instances of this kind. The normal process of cleavage through which the ovum of the frog passes, in developing from the unicellular to the adult condition, is perfectly well known. For experimental purposes this normal sequence of events has been materially altered by various artificial processes. What has resulted from these interferences with Nature ? Let us take one example and see. When the egg is developed under compression— that is between two plates of glass instead of free in the water — the sequence of the cell- division takes place in a very different manner from that which occurs under normal , Abnormal circumstances, but the embryo which Develop- is finally developed from this com pressed ovum is of a perfectly normal char acter. A similar experiment with a similar 22 THE SECRET OF THE CELL result has been tried on the ova of the Sea - Urchin. Here again the cells into which the ovum divides have a normal pattern of arrangement. If they are prevented from forming this normal pattern by artificial pressure, they spread themselves out in a plane instead of arranging themselves in three dimen sions of space with regard to one another. Let the pressure now be removed : the cells re-group themselves and a normal embryo is the result. From these facts it is clear that the ovum is not rigid in its processes ; it is clear, on the contrary, that it has elasticity and adaptability ; it is clear that it is able to reach its desired goal by paths hitherto untrodden by any ovum. Let us examine one more sample of artificial interference with the normal courses of nature. It is now well established that in the case of the developing ova of certain forms, such as the Sea-Urchin or the Lancelet (Amphioxus), a still more startling experiment can be performed. Here, as in other cases, the originally single ovum cell divides into two ; each of these again becomes two ; this four-celled stage is succeeded by one of eight ; that again by one of sixteen cells, and so on. Under ordinary circumstances THE SECRET OF THE CELL 23 this group of cells goes on to its normal develop ment, which is the production of a single indi vidual, let us say a Sea- Urchin. Now, however, the experimenter enters upon the scene. He takes the group of eight cohering cells and carefully shakes them apart. What happens ? Bear in mind that each of these cells, if let alone, would, one may roughly put it, have turned into one-eighth of an individual. But now, when they are shaken apart, each becomes a whole individual. Could one ask for a better example of the adaptability of a living cell ? But adapta bility to what ? To a purpose in the future, namely, the production of a complete individual of the species. Those who consider that crystallisation and growth are really parallel conditions may argue that this is only a case of pouring the fluid which would have formed one crystal into eight glasses whereby eight crystals have resulted. But, as we have already seen, the facts of crystallisation, when carefully examined, are not found in any way to tally with those which take place in the cell. To me the two series of phenomena are about as unlike one another as it is possible for any two series of phenomena to be, Indeed it seems 24 THE SECRET OF THE CELL abundantly clear that the absence of rigidity of behaviour shown by the ovum and by living matter generally, when contrasted with the rigidity of chemical and physical processes, is a very important and characteristic distinction between the two, and a very powerful argument in favour of the view that in living matter there is a "something over" which is unknown in chemistry or physics. The study of phenomena, such as those described, and many others might have been cited, led Driesch, one of the most prominent workers in this field, to declare that the egg seems to act like an intelligent being.1 In the preface to Wilson's work, that author says, "'One is sometimes tempted to conclude,' was recently remarked by a well- known embryologist, ' that every egg is a law unto itself!' The jest, perhaps, embodies more of the truth than the author would seriously have maintained, expressing, as it does, a growing appreciation of the intricacy of cell-phenomena, the difficulty of formulating their general aspects in simple terms, the inadequacy of some of the working hypotheses which have been our guides." Let us leave this branch of the subject and 1 Morgan, op. cit, p. 136, THE SECRET OF THE CELL 25 turn for a moment to the cell in a permanently unicellular condition — the unicellular organism. Here, too, we shall find abundant evidence in favour of the "some- Unicellular Organisms thing over " which distinguishes living from non-living matter. Take the case of Vampyrella spirogyrae, a unicellular naked organism described by Cienkowski. This little creature, which lives in the water, and is possessed of amoeboid movements, seeks out from amongst all other algae — and there are myriads of them — spirogyra, a lowly water vegetable, and invariably attaches itself for feeding purposes to that form and that alone. Why ? Well, why do we eat beef in preference to horse-flesh ? Because we prefer it, and find it the more suitable food, and no other answer can be given with regard to Vampyrella. The writer just mentioned describes another form, also a monad, named Colpodella pugnax, which lives only on Chla- mydomonas, whose chlorophyll it sucks. He says that the behaviour of this monad in seeking for and obtaining its nourishment is so remark able, that one is led to believe that one sees the operations of conscious life in it. Take one further example, given by Bunge 26 THE SECRET OF THE CELL from the observations of Engelmann. In this instance we have to do with a foraminifer, named Arcella. Foraminifera are provided with calcareous shells from openings in which they can protrude protoplasmic processes, called pseudopodia. Arcella has a round concavo- convex shell, and protrudes its pseudopodia from a central round opening on the concave side. When it accidentally falls on its back and cannot restore itself to its former position by means of its pseudopodia, what does it do ? One of two things. It develops gas-bubbles in its interior, and these are either unilaterally formed so that it is raised upon its edge and tilts over on the right side, or they are generally formed throughout the protoplasm. When the latter takes place, the whole organism finds its specific weight decreased. It is raised to the top of the water and there is able to rectify its position.1 In these purposive actions Telic r 11 i • ... Actions unicellular organisms it is impos sible to see only the actions of chemico-physical forces. Such forces look entirely backwards for their explanation. They are the result of what has been, and 1 For the facts just mentioned see Pauly, Darwinismus imd Lamarckismus, Miinchen, 1905, s. 147. THE SECRET OF THE CELL 27 the end of the series of occurrences is an equilibrium. Add sulphuric acid to carbonate of lime and gas is evolved, sulphate of lime is formed, and there is an end of the operation. The disengagement of the gas and the forma tion of the sulphate are explained by the bringing together of the original substances, and no future occurrences have to be taken into consideration. The operations of the living cell are telic in their character ; they look forward, and are to be explained by what is to come. The Arcella does not primarily form the gas-bubbles in its interior because it has fallen on its back, but because it wants to get right side upwards. I turn now to a further line of evidence in favour of the vitalistic theory, and that is the question of regeneration, a process widely known in both the animal and vegetable kingdoms. Take the case of Hydra, a lowly metazooan, or multicellular organism e^^ra~ which lives in the water. Hydra may be divided up into twenty fragments, may even be chopped up into almost in numerable bits, yet, under favourable circum stances, each of these bits can reform itself into an entire new Hydra. In the vegetable kingdom numerous instances, such as that 28 THE SECRET OF THE CELL of Begonia, will at once occur to the mind. But the phenomena of regeneration are even more remarkable than would appear from what has just been said. Take the case of the Tubularia polyp. This animal has a head-end and a root-end, and lives in the water with its root in the sand. Now, suppose one cuts off the head-end, leaving the root where it was. The organism promptly grows a new head with proboscis and tentacles. Suppose, however, that, instead of leaving the root undisturbed, the animal is pulled up and turned head down wards in the sand. Then the former head-end develops roots whilst the root-end turns into a head. Finally, if the beheaded polyp is suspended horizontally in the water, a head will grow out of each end. Planaria, a parasitic worm, can be cut up into pieces, each of which will reconstruct a perfect individual. Moreover, extra heads or tails or both can be produced along the sides of this creature by making incisions in it. Amongst higher animals the water-newt can re-grow his limbs, and has been observed to do so six times in succession after they have been removed for purposes of experiment. Wolff extirpated the lens from the eye of Triton larvae and found THE SECRET OF THE CELL 29 that it was formed anew and from a different tissue source to that from which the original lens sprang. The living organism, then, has the power of self-repair, and sometimes this power reaches to very remarkable manifestations. It is true that this power is, one might almost say, capriciously distributed, but it is there to a greater or less extent in all living forms. When we watch the healing of wounds in our selves or our fellow-creatures, we are watching a minor manifestation of the regenerative process. Weismann very fully con- we{smann»s siders these phenomena, and frankly Expiana- admits that they lend no special assistance to his theory — composed for the purpose of getting rid of a vitalistic explana tion. But in attempting to explain the phenomena, he is obliged to make use of a purely teleological terminology. For example, with regard to the Tubularia just alluded to, he says : 1 " This also appears to us to be adaptive, and does not surprise us, since we have long been accustomed to recognise that what is adapted to an end will realise this if it be possible at all." And again, in another con- 1 The Evolution Theory, ii. 9. 30 THE SECRET OF THE CELL nection, "It was, so to speak, not worth Nature's while to make such adaptations." But, as we have seen, this telic explanation is wholly alien to the phenomena of chemistry and physics. In fact, when one considers these manifestations of living matter, one is more ready to ask how they resemble ordinary mechanical or chemico-physical phenomena than how they may be differentiated from them. The most delicate and complicated machine requires someone to start it before it can do its work, and chemical compounds will lie for ever unaltered unless someone or something brings them into contact with an agency capable of reacting upon them. On the other hand, Vampyrella starts out on its own initiative and finds the alga most suitable to be its host, and the Triton, by virtue of its own innate forces, renews its amputated limb. " The structure Stras °^ a machine," savs Strasburger,1 a burger's very distinguished German botanist, " might be called its organisation ; and the fact that, when provided with a store of energy, it can be started by the opening of a valve to perform work con formable to its structure — this property 1 Das Pl'otoplasma nnd die Reizbarkeit, 1891, s. 24. THE SECRET OF THE CELL 31 might be called its sensibility. But the living substance is entirely distinguished from the dead machine by the ability to provide itself with the energy needful for its work ; to set itself in motion and keep itself going ; to repair itself, within certain limits, the defects that may arise ; and above all, by the fact that it constructs itself. In short, an organism — in contradistinction to the dead machine — is a living machine, one that does not depend upon external impulses for its movements, one that regulates its own course, and continues going as long as the environ ment will allow — only through the hostility of this or through irreparable misfortune is it brought to a halt." Perhaps, however, the weakness of the mechanical theory is best shown by the ex pedients to which its adherents are reduced in their endeavours to account for the phenomena with which they are confronted. Herbert Spencer, for example, who repudiated with considerable scorn the hypothesis of a nisus formativus or vital principle, explained things by saying that "the polarities of the molecules deter mine the direction in which the power (of 32 THE SECRET OF THE CELL environing forces) is turned." Here we have either a mere logomachy or an excellent instance of the kind of thing which Professor Ward alludes to when he points out that the system of explaining everything which is "going" because it is "going" is excellent "once you have got inside the system," but does not approach to being a full explanation. If "polarities " are mere mechanical forces, they must have acquired their remarkable faculties — faculties not possessed by any other mechanical forces — from somewhere. If "polarities" are non-mechanical and purposive, then to talk of them as "polarities," and to suppose that one has thereby explained things, is to cover one self with the cloak of delusion. We have already seen the effort made by Weismann to deal with the phenomena of regeneration. He is far too eminent a biol°gist not to see that a11 vital phenomena require some explana tion. He is persuaded that the vitalistic theory is untenable. What does he offer in its place ? It may be well to deal with his views in some detail since he is the latest and the most eminent exponent of a non- vitalistic theory of life. "The botanist THE SECRET OF THE CELL 33 Reinke," Weismann admits,1 "has recently called attention once again to the fact that machines cannot be directly made up of primary chemico-physical forces or energies, but that, as Lotze said, forces of a superior order are indispensable, which so dispose the fundamental chemico-physical forces that they must act in the way aimed at by the purpose of the machine." Thus, in making a watch, gold, steel, jewels, etc., must not only be brought together, but brought into a definite relation with one another. Here it is human intelligence which effects the conjunction. " But organisms also are machines which perform a particular and purposeful kind of work, and they are only capable of doing so because the energies which perform the work are forced into definite paths by superior forces ; these superior forces are thus the steersmen of the energies." Reinke considers that these superior forces are put into the organism by a "cosmic intelligence." Weis mann will have none of that. Why not? " Because, in the first place, these superior 'forces' are not 'forces' at all." What, then, one asks, are they ? The reply is ready. 1 Op. cit., i. 402. C 34 THE SECRET OF THE CELL " They are constellations of energy, co-ordina tions of matter, and the energies immanent therein, under complex and precisely defined conditions, and it is a matter of indifference whether chance or human intelligence has brought them together." Now, is this a mere throwing of the dust of words into the eyes of the mind, or have these mysterious " constellations of energy " any real existence under some other name? Let us pursue our search. Yes, we find that these " constellations " are defined as being " the biophors, the determinants, and the 'groups of determinants ' which we may think of as dis posed in a manifold overlapping series." What are the objects so confidently dealt with in the last quotation ? Have they any real existence ? The great majority of biologists utterly deny that they have. What of their describer? He admits that they cannot be seen by any microscope, or recognised by any objective test. What, then, are these biophors and deter minants? They are hypothetical objects, postulated by Weismann himself for the purpose of explaining the phenomena of nature, and, inter alia, of disproving the existence of a vital force in the living organism. Weismann's THE SECRET OF THE CELL 35 explanation, then, is a mere word-explanation, and we have no true evidence that it in any way corresponds to reality. But then it may be urged, -your own explana- tion is a mere verbal one, too." Let me allow an eminent physiologist to answer this objection. Dr Haldane1 says: "It is frequently urged that vitalism amounts to nothing more than the mere assertion that a physico-chemical explanation of vital pheno mena has not been found ; and that even though this assertion be correct, the only possible way of advance in physiology is by the further application of the principles of physics and chemistry, since there are, and can be, no other kinds of explanation but the causal ones which these sciences afford. This argument in its widest form is undoubtedly based on the metaphysical assumption that the universe, interpreted as it is in the physical sciences as a universe of matter and energy, corresponds to absolute reality, and is for this reason incapable of any further interpreta tion. The work of modern philosophy since Berkeley and Hume has shown that the assumption in question is without foundation." Loc. supra cit. 36 THE SECRET OF THE CELL From what has been said it will be gathered that there are a vast number of phenomena exhibited by the living cell or organism which cannot be explained in chemico-physical terms. I hope at least that I have been able to show that such is the opinion of many men of science, whose lives have been spent in investigating the phenomena of Nature. One must not leave untouched one difficulty, sometimes held to be an insuperable difficulty, which has often been brought forward The Law of . . . . ..... the Conser- m connection with a vitahstic expla- vation of nation of life. This is the difficulty Energy presented, or supposed to be pre sented, by what we call the Law of the Conservation of Energy. Physical energy or the capacity for doing work may be of two kinds. It may be kinetic, as it is in the case of a flying bullet ; or it may be poten tial, as it is in the case of an elevated weight. A large number of experiments have shown that when one form of energy is transmuted into another, nothing is lost, 'nor is anything gained. So that we formulate the laws that (i) the sum of the kinetic and potential energies of any isolated system of bodies remains constant, and (2) that the sum-total THE SECRET OF THE CELL 37 of the energy in the universe remains the same. But if this be the case, how are we to account for the power which we have seemed to discover directing and, still more, initia ting chemico-physical processes in the living organism ? Is it subject to the laws above detailed ? Where does it come from, and whither does it go ? Many attempts have been made to clear up this difficulty. It has been urged that the power which frees the energy is so small that it may be regarded as inappreciable when incorporated in the total result. To some extent, no doubt, this is true. "As far as we can judge," says Balfour Stewart,1 "life is always associated with machinery of a certain kind, in virtue of which an extremely delicate directive touch is magnified ultimately into a very considerable transmutation of energy." But this is never theless not a satisfactory explanation. The disengaging power is either something, or it is nothing. If it is nothing, it can do nothing. If it is something, it must be accounted for. If this and some other attempts to solve the difficulty do not seem to help us very far, must 1 On the Conservation of Energy, p. 163. 38 THE SECRET OF THE CELL we then conclude that the Law of the Conserva tion of Energy excludes the possibility of the existence of a power controlling the operations of the cell? Certainly not. "The very advance of physics," says Ward,1 " is proving the most effectual cure for this ignorant faith in matter and motion as the inmost substances rather than the most abstract symbols of the sum of existence." To which statement may be added the dictum of Lord Lord Kelvin. 