§ 5. A “New” Theory of Abiogenesis
Since true science is out of sympathy with baseless conjectures and gratuitous assumptions, one would scarcely expect to find scientists opposing the inductive trend of the known facts by preferring mere possibilities (if they are even such) to solid actualities. As a matter of fact, however, there are not a few who obstinately refuse to abandon preconceptions for which they can find no factual justification. The bio-chemist, Benjamin Moore, while conceding the bankruptcy of the old theory of spontaneous generation, which looked for a de novo origin of living cells in sterilized cultures, has, nevertheless, the hardihood to propose what he is pleased to term a new one. Impressed by the credulity of Charlton Bastian and the autocratic tone of Schäfer, he sets out to defend as plausible the hypothesis that the origination of life from inert matter may be a contemporaneous, perhaps, daily, phenomenon, going on continually, but invisible to us, because its initial stages take place in the submicroscopic world. By the time life has emerged into the visible world, it has already reached the stage at which the law of genetic continuity prevails, but at stages of organization, which lie below the limit of the microscope, it is not impossible, he thinks, that abiogenesis may occur. To plausibleize this conjecture, he notes that the cell is a natural unit composed of molecules as a molecule is a natural unit composed of atoms. He further notes, that, in addition to the cell, there is in nature another unit higher than the monomolecule, namely, the multimolecule occurring in both crystalloids and colloids. The monomolecule consists of atoms held together by atomic valence, whereas the multimolecule consists of molecules whose atomic valence is completely saturated, and which are, consequently, held together by what is now known as molecular or residual valence. Moore cites the crystal units of sodium bromide and sodium iodide as instances of multimolecules. The crystal unit of ordinary salt, sodium chloride, is an ordinary monomolecule, with the formula NaCl. In the case of the former salts the crystal units consist of multimolecules of the formula NaB·(H2O)2 and NaI·(H2O)2, the water of crystallization not being mechanically confined in the crystals, but combined with the respective salt in the exact ratio of two molecules of water to one of the salt. Judged by all chemical tests, such as heat of formation, the law of combination in fixed ratios, the manifestation of selective affinity, etc., the multimolecule is quite as much entitled to be considered a natural unit as is the monomolecule.
But it is not in the crystalloidal multimolecule, but in the larger and more complex multimolecule of colloids (viscid substances like gum arabic, gelatine, agar-agar, white of egg, etc.), that Moore professes to see a sort of intermediate between the cell and inorganic units. Such colloids form with a dispersing medium (like water) an emulsion, in which the dispersed particles, known as ultramicrons or “solution aggregates,” are larger than monomolecules. It is among these multimolecules of colloids that Moore would have us search for a transitional link connecting the cell with the inorganic world. Borrowing Herbert Spencer’s dogma of the complication of homogeneity into heterogeneity, he asserts that such colloidal multimolecules would tend to become more and more complex, and consequently more and more instable, so that their instability would gradually approach the chronic instability or constant state of metabolic fluxion manifest in living organisms. The end-result would be a living unit more simply organized than the cell, and evolution seizing upon this submicroscopic unit would, in due time, transform it into cellular life of every variety and kind. Ce n’est que le premier pas qui coûte!
It should be noted that this so-called law is a mere vague formula like the “law” of natural selection and the “law” of evolution. The facts which it is alleged to express are not cited, and its terms are far from being quantitative. It is certainly not a law in the sense of Arrhénius, who says: “Quantitative formulation, that is, the establishing of a connection, expressed by a formula, between different quantitatively measurable magnitudes, is the peculiar feature of a law.” (“Theories of Chemistry,” Price’s translation, p. 3.) Now, chemistry, as an exact science, has no lack of laws of this kind, but no branch of chemistry, whether physical, organic, or inorganic, knows of any law of complexity, that can be stated in either quantitative, or descriptive, terms. We will, however, let Moore speak for himself:
“It may then be summed up as a general law universal in its application to all matter, ... a law which might be called the Law of Complexity, that matter so far as its energy environment will permit tends to assume more and more complex forms in labile equilibrium. Atoms, molecules, colloids, and living organisms, arise as a result of the operations of this law, and in the higher regions of complexity it induces organic evolution and all the many thousands of living forms....
“In this manner we can conceive that the hiatus between non-living and living things can be bridged over, and there awakens in our minds the conception of a kind of spontaneous production of life of a different order from the old. The territory of this spontaneous generation of life lies not at the level of bacteria, or animalculæ, springing forth into life from dead organic matter, but at a level of life lying deeper than anything the microscope can reveal, and possessing a lower unit than the living cell, as we form our concept of it from the tissues of higher animals and plants.
“In the future, the stage at which colloids begin to be able to deal with external energy forms, such as light, and build up in chemical complexity, will yield a new unit of life opening a vista of possibilities as magnificent as that which the establishment of the cell as a unit gave, with the development of the microscope, about a century ago.” (“Origin and Nature of Life,” pp. 188-190.)
Having heard out a rhapsody of this sort, one may be pardoned a little impatience at such a travesty on science. Again we have the appeal from realities to fancies, from the seen to unseen. Moore sees no reason to doubt and is therefore quite sure that an unverified occurrence is taking place “at a level of life lying deeper than anything the microscope can reveal.” The unknown is a veritable paradise for irresponsible speculation and phantasy. It is well, however, to keep one’s feet on the terra firma of ascertained facts and to make one’s ignorance a motive for caution rather than an incentive to reckless dogmatizing.
To begin with, it is not to a single dispersed particle or ultramicron that protoplasm has been likened, but to an emulsion, comprising both the dispersed particles and the dispersing medium, or, in other words, to the colloidal system as a whole. Moreover, even there the analogy is far from being perfect, and is confined exclusively, as Wilson has pointed out, to a rough similarity of structure and appearance. The colloidal system is obviously a mere aggregate and not a natural unit like the cell, and its dispersed particles (ultramicrons) do not multiply and perpetuate themselves by growth and division as do the living components or formed bodies of the cell. As for the single ultramicron or multimolecule of a colloidal solution, it may, indeed, be a natural unit, but it only resembles the cell in the sense that, like the latter, it is a complex of constituent molecules. Here, however, all resemblance ceases; for the ultramicron does not display the typically vital power of self-perpetuation by growth and division, which, as we have seen, is characteristic not only of the cell as a whole, but of its single components or organelles. Certainly, the distinctive phenomena of colloidal systems cannot be interpreted as processes of multiplication. There is nothing suggestive of this vital phenomenon in the reversal of phase, which is caused by the addition of electrolytes to oil emulsions, or in gelation, which is caused by a change of temperature in certain hydrophilic colloids. Thus the addition of the salt of a bivalent cation (e.g. CaCl2 or BaCl2) to an oil-in-water emulsion (if soap is used as the emulsifier) will cause the external or continuous phase (water) to become the internal or discontinuous phase. Vice versa, a water-in-oil emulsion can be reversed into an oil-in-water emulsion, under the same conditions, by the addition of the salt of a monovalent cation (e. g. NaOH). Solutions of hydrophilic colloids, like gelatine or agar-agar, can be made to “set” from the semifluid state of a hydrosol into the semisolid state of a hydrogel, by lowering the temperature, after which the opposite effect can be brought about by again raising the temperature. In white of egg, however, once gelation has taken place, through the agency of heat, it is impossible to reconvert the “gel” into a “sol” (solution). In such phenomena, it is, perhaps, possible to see a certain parallelism with some processes taking place in the cell, e. g. the osmotic processes of absorption and excretion, but to construe them as evidence of propagation by growth and division would be preposterous.
Nor is the subterfuge of relegating the question to the obscurity of the submicroscopic world of any avail; for, as a matter of fact, submicroscopic organisms actually do exist, and manage, precisely by virtue of this uniquely vital power of multiplication or reproductivity, to give indirect testimony of their invisible existence. The microörganisms, for example, which cause the disease known as Measles are so minute that they pass through the pores of a porcelain filter, and are invisible to the highest powers of the microscope. Nevertheless, they can be bred in the test tube cultures of the bacteriologist, where they propagate themselves for generations without losing the definite specificity, which make them capable of producing distinctive pathological effects in the organisms of higher animals, including man. Each of these invisible disease germs communicates but one disease, with symptoms that are perfectly characteristic and definite. Moreover, they are specific in their choice of a host, and will not infect any and every organism promiscuously. Finally, they never arise de novo in a healthy host, but must always be transmitted from a diseased to a healthy individual. The microscopist is tantalized, to quote the words of Wilson, “with visions of disease germs which no eye has yet seen, so minute as to pass through a fine filter, yet beyond a doubt self-perpetuating and of specific type.” (Science, March 9, 1923, p. 283.) Submicroscopic dimensions, therefore, are no obstacle to the manifestation of such vital properties as reproduction, genetic continuity, and typical specificity; and we must conclude that, if any of the ultramicrons of colloids possessed them, their minute size would not debar them from manifesting the fact. As it is, they fail to show any vital quality, whereas the submicroscopic disease germs give evidence of possessing all the characteristics of visible cells.
In fine, the radical difference between inorganic units, like atoms, molecules, and multimolecules, and living units, like protozoans and metazoans, is so obvious that it is universally admitted. Not all, however, are in accord when it comes to assigning the fundamental reason for the difference in question. Benjamin Moore postulates a unique physical energy, peculiar to living organisms and responsible for all distinctively vital manifestations. This unique form of energy, unlike all other forms, he calls “biotic energy,” denying at the same time that it is a vital force. (Cf. op. cit., pp. 224-226.) Moore seems to be desirous of dressing up vitalism in the verbal vesture of mechanism. He wants the game, without the name. But, if his “biotic energy” is unlike all other forms of energy, it ought not to parade under the same name, but should frankly call itself a “vital force.” Somewhat similar in nature is Osborn’s suggestion that the peculiar properties of living protoplasm may be due to the presence of a unique chemical element called Bion. (Cf. “The Origin and Evolution of Life,” 1917, p. 6.) Now, a chemical element unlike other chemical elements is not a chemical element at all. Osborn’s Bion, like Moore’s biotic energy, ought, by all means, to make up its mind definitely on Hamlet’s question of “to be, or not to be.” The policy of “It is, and it is not,” is not likely to win the approval of either mechanists or vitalists.