Science

THE appearance of Dr. Bastian’s monograph on the “ Mode of Origin of Lowest Organisms ” will add to the interest with which the so-called question of “spontaneous generation ” is now regarded. The great importance of the subject will justify us in giving some account of the controversy which has long been raging, as well as of Dr. Bastian’s ingenious experiments, recently made in London, by which the case is brought to a still more definite issue than by those of the French investigators, Pouchet and Pasteur.

In the chaos of ideas concerning the phenomena of life which prevailed until quite modern times, it was not strange that organisms, even of a high order of complexity such as bees and ants, should have been believed to be now and then directly evolved from lifeless matter, under favorable circumstances. Such a belief, however, clearly belongs to the most rudimentary stage of biological science, when the true character of the difference between living and lifeless matter is wholly unknown, and when the relationships between the myriad forms of organic life are as yet unclassified, To such views, which hardly deserve to be ranked among scientific hypotheses, there succeeded, in the seventeenth century, the doctrine, maintained by the illustrious Redi, and since generally held by philosophic biologists, that under no circumstances can life be originated save under the influence of pre-existing life. The doctrine omne vivum ex vivo consorted admirably with the metaphysical hypothesis of a “ vital principle,” maintained by Paracelsus and Stahl, according to which the peculiar activities displayed by organic bodies are the manifestations of a primordial life-force, distinct from the forces of inorganic nature. And as this hypothesis survived into the present century, the doctrine of Redi was generally received as impregnable. Phenomena which seemed to contravene it were explained away by means of additional hypotheses, the most famous of which is the panspermatist theory, of Spallanzani, — that the atmosphere is full of invisible germs, *— by which the evolution of apparently self-generated organisms was supposed to be satisfactorily accounted for.

But during the present century the attitude of the prevailing philosophic thought with reference to these doctrines has been materially changed. Since the creation of the vast science of organic chemistry, the researches of histologists, and the discovery of the transformation and equivalence of forces, the hypothesis of a“ vital principle” has become generally discredited, and it is held by most biologists that all the activities displayed by any organism result simply from the compounding of the various dynamic properties possessed by the ultimate units of which it is built up. The chasm which the old physiology had dug between the inorganic and the organic worlds has thus been partly bridged over, and it becomes less improbable that between the lowest organisms and the most complex aggregations of non-living matter some genetic relationship may be established. In the second place, owing mainly to the brilliant investigations of Darwin and Wallace, nearly all naturalists — at least in England, Germany, and our own country — have come to believe in the derivation of the more complex organic forms from ancestral forms that were less complex ; so that the hypothesis of the evolution of the least complex organic forms from highly complex non-organic forms finds a less inhospitable reception than formerly. And in the third place, the discovery of organisms far lower in the scale than those which were until lately supposed to be lowest has begun to teach us that the sharp demarcations once thought to exist in the scheme of nature have really existed only in our own ignorance of that scheme.

Indeed, the organisms with which Dr. Bastian’s experiments are chiefly concerned — monads and bacteria and vibriones and leptothrix filaments — are far less widely removed from inorganic matter than even the amoeba and protococcus, which are nothing but simple nucleated cells, resembling those of which the tissues of higher organisms are composed. They rank even lower than Professor Haeckel’s monera, which are merely patches of albumen, possessed — as crystals are — of the power of growing, and of occasionally breaking in two. Dr. Bastian’s monads are simply structureless specks of albuminous matter, no bigger than the motes which float in the sunbeam, and distinguished from inorganic specks only by the capacity of multiplication. Yet upon the filmy surface of sundry organic solutions these motes have the power of growing together, gradually segregating from the liquid medium in which they float, until they have become built up into an amoeba-like cell. Now the great question at issue in the so-called “ spontaneous-generation ” controversy is as fellows : When monads and bacteria are found in solutions containing all the unorganized materials requisite for the production of a living thing, have these living motes been produced, after the fashion of crystals, by the simple union of their inorganic elements, or have they been only reproduced from other monads and bacteria pre-existing in the atmosphere in which the solution is bathed ?

If the former alternative be the one which experiment forces us to adopt, the bridge between the organic and inorganic worlds becomes at last complete, and light is thrown upon the origin of life upon the surface of our planet. But if, on the other hand, we are forced, in this particular instance, to reaffirm the doctrine omne vivum ex vivo, the result is purely negative, and we are not entitled to affirm, on the strength of it, that the genesis of living things from non-living matter does nowhere and under no imaginable circumstances take place. Still less are we entitled to affirm that such primordial genesis of life may not have secured, independently of miraculous origination, in earlier stages of the earth’s history, when its physico-chemical circumstances were certainly different from what they now are. The fact, if it be established, that Dr. Bastian cannot artificially produce bacteria in a flask, is not sufficient to prove a negative with reference to what may now be going on among Professor Haeckel’s albuminous patches on the sea-bottom, or to what may have gone on in days in comparison with which the era of the Canadian eozoon is recent. Not only, therefore, may the consistent evolutionist view with equanimity the overthrow of Dr. Bastian’s conclusions, but we need not be surprised at finding in the ranks of Dr. Bastian’s opponents a thinker like Professor Huxley, who avowedly believes in a primordial genesis of living things from non-living matter. There is no reason whatever why the purely scientific inquirer should not examine Dr. Bastian’s experiments and reasonings, without the least desire to come to one conclusion rather than another.

Viewed in this impartial light, it must be admitted that in his various papers on the subject Dr. Bastian has made out a very strong case ; and although it would be too much to say that the results of his experiments amount to anything like a demonstration of the inorganic ancestry of his monads and bacteria, we are, nevertheless, bound to say that they present a very hard nut for those to crack who refuse to believe in such inorganic ancestry. Let us glance at one or two of his arguments.

Obviously the first requisite in an experiment of this sort is the absolute exclusion of all organic germs from the solution in which the new organisms are expected to appear ; and a very difficult requisite it is, to be sure, that we have fulfilled. The method ordinarily employed is to isolate the solution in an impervious flask, while raising it to a temperature sufficiently high to destroy any and every living thing. It becomes necessary, then, to ascertain what is the highest degree of temperature compatible with the preservation of such living things as the flask may contain before it is sealed. Now upon this point experimenters have been singularly unanimous. It has been generally admitted that none of the living things of which there is any question in these experiments can withstand, when immersed in liquids, a temperature of 100° C. kept up for fifteen minutes. In Schwann’s experiments the solutions employed were boiled in the flask for this length of time, while the upper portion of the flask was filled with calcined air from which all living germs must have been destroyed during its passage through a red-hot tube. When these precautions were taken to exclude all possible organic sources of life, as in the experiments of Schwann and Pasteur, it was found that no living things afterwards appeared in the flasks ; and this result was for some time held to have settled the question. Nothing could, at first sight, seem more conclusive. When the air, with its contained germs, is allowed to enter, you get bacteria ; when it is kept out, bacteria fail to show themselves ; obviously, therefore, there can be no bacterium without its organic parentage.

But, as Dr. Bastian observes, when you come to examine this argument more critically, it does not look so conclusive. Bear in mind that we do not positively know that the air is full of germs capable of developing into vibriones and bacteria : the existence of the germs, which are themselves invisible, is only an inference from the existence of the bacteria; and, as already noticed, the doctrine omne vivum ex vivo is here on its trial and cannot be summoned as a witness. It is admissible to maintain that with liquids differently constituted the results of the experiments might have been different; or that the process to which the flask was subjected, in order to slay all the contained life, also left the solution unfitted for the production of new life. In Schwann’s experiments, for example, the molecular changes going on in the cooling liquid were often attended by the disengagement of gases, always causing excessive tension, and sometimes bursting the flask. The opponents of the germ-theory are quite at liberty to argue that the non-appearance of new organisms was due, not to the exclusion of germs, but to the abnormal tension created within the flask by the freed gases.

With a view to getting rid of this source of ambiguity, Dr. Bastian decided to leave a vacuum in the upper portion of the flask, rightly judging that a vacuum would be as likely as calcined air to be an inhospitable place for intrusive germs. The vacuum was produced by a simple expedient. The neck of the flask was drawn out by means of the blowpipe to an almost capillary tenuity, and then, while the rapidly boiling liquid was rushing out in puffs of vapor the mouth was hermetically sealed by the blowpipe. On the cooling of the liquid enough empty space remained in the flask to prevent any undue tension from freed gases. A temperature of 100° C. prolonged for fifteen minutes having been generally admitted to be destructive of all the kinds of life in question, Dr. Bastian often subjected his flasks during four hours to a temperature of 140° to 150° C. The results obtained after these precautions were certainly very interesting. For while in some cases living monads, bacteria, vibriones, or leptothrix filaments were found to have been developed within the sealed flasks, in other cases no signs of life were manifested ; but in all cases the presence or absence of living organisms was found to depend upon the character of the liquid solution employed. Infusions containing a large amount of organizable materials were generally found to contain a multitude of living things ; while few living things, or none at all, were found in infusions poor in organizable materials. The menstrua employed were usually infusions of hay, turnip, beef, or urine. But as all these were substances dependent for their existence upon pre-existent organic life, — an element which it was desirable to eliminate entirely from the problem, — Dr. Bastian next proceeded to try what could be done with purely inorganic solutions containing organizable materials, such as sodic phosphate, ammonic tartrate,phosphate, acetate, and oxalate. With these he succeeded in obtaining monads, fungus-spores, spirallytwistcd, organic fibres, and co-nfervokl-leoking filarrnts.

The conditions of a trustworthy experiment, in a question of this sort, are so difficult to satisfy, that it would be altogether premature to say that Dr. Bastian has actually overthrown the theory of the panspermatists. Nevertheless, it can hardly be denied that, until the panspermatists have offered some satisfactory interpretation of Dr. Bastian’s results, the force of the purely negative conclusions reached by Schwann and Pasteur must be regarded as materially diminished. So far from the theory of Rcdi being “ victorious along the whole line,”as Professor ITuxley would have it, we have yet to see how well it can withstand the opening of this new battery. Here, after satisfying all the conditions prescribed by Pasteur, living things are found in the flasks ; and it is incumbent on the panspermatists to point out some way in which they could have got there, otherwise than by development de novo from the organizable materials contained in the solution. Without feeling himself bound to advocate either view of the case, the student of biology will, at least, recognize the extreme interest attaching to the inquiry.