Chapter II: Preface (1)

Having been compelled by the results of my investigations on the question of the Origin of Life to arrive at conclusions adverse to generally received opinions, I found that several persons having high authority in matters of science, were little disposed to assent to these views. To a great extent this seemed due to the fact that a distinguished chemist had previously gone over some of the same ground, and had arrived at precisely opposite conclusions. M. Pasteur has been long known as an able and brilliant experimenter, and some of his admirers seem to regard him as an almost equally faultless reasoner.

Renewed and prolonged experimentation having tended to demonstrate the truth of my original conclusions, and to convince me of the utter untenability of M. Pasteur’s views, it seemed that the best course to pursue would be, at first, to endeavour to show into what errors of reasoning M. Pasteur had fallen, and also how his conclusions were capable of being reversed by the employment of different experimental materials, and different experimental methods. Then, having presented, in a connected form, evidence which might suffice to shake the faith of all who preserved a right of independent judgment, one might hope to have paved the way for the reception of new views--even though they were adverse to those of M. Pasteur. The present volume contains, indeed, only a fragment of the evidence which will be embodied in a much larger work--now almost completed--relating to the nature and origin of living matter, and in favour of what is termed the physical doctrine of Life.

The question of the mode of origin of Living Matter, is inextricably mixed up with another problem as to the cause of fermentation and putrefaction. M. Pasteur’s labours were, at first, undertaken in order to solve the latter difficulty--to decide, in fact, between two rival hypotheses. It was held, on the one hand, that many ferments were mere dead nitrogenous substances, and that fermentation was a purely chemical process, for the initiation of which the action of living organisms was not necessary; whilst, on the other hand, it was also maintained that no fermentation could be initiated without the agency of living things--in fact, that _all_ ferments were living organisms. The former may be called the _physical_ theory of fermentation, of which Baron Liebig is the most prominent modern exponent; whilst the latter may be termed the _vital_ theory of fermentation, and this is the doctrine of M. Pasteur. All the facts which I have to adduce, so far as the subject of fermentation is concerned, are wholly in favour of the views of Baron Liebig.

And, the conclusions arrived at in this work are confirmed by the results of several unpublished experiments, in which living organisms have been taken from flasks that had, a few weeks before, been hermetically sealed and heated for a variable time to temperatures ranging from 260° F. to 302° F.

With the view of aiding some of my readers in their interpretation of the results of some of the experiments contained in this volume, I would call their attention to the following considerations. If fluids _in vacuo_ (in hermetically-sealed flasks), which were clear at first, have gradually become turbid; and if on microscopical examination this turbidity is found to be almost wholly due to the presence of _Bacteria_ or other organisms, then it would be sheer trifling gravely to discuss whether the organisms were living or dead, on the strength of the mere activity or languor of the movements which they may be seen to display. Can dead organisms multiply in a closed flask to such an extent as to make an originally clear fluid become quite turbid in the course of two or three days?

And if any one wishes to convince himself as to whether such turbidity can occur in a flask which is still hermetically sealed, let him take one that has been prepared in the manner I have elsewhere described, carefully heat the neck of it in a spirit-lamp flame, and see how the rapid in-bending of the red-hot glass testifies to the preservation of a partial vacuum within. The vacuum in such cases is only partially preserved, because of the emission of a certain amount of gases within the flask--such as invariably occurs during the progress of fermentation or putrefaction.

In these experiments with heated fluids in closed flasks, nothing is easier than to obtain negative results. The same kinds of infusions which--if care has been taken to obtain them strong enough--will in a few days teem with living organisms, often show no trace of living things after much longer periods, when the solutions are weak. Again, in those cases where only a few organisms exist in a solution which has been made the subject of experimentation, nothing is easier than by a perfunctory examination of the fluid to fail in finding any of these sparsely-distributed living organisms. Experiments, the results of which are positive, may, therefore, in the absence of sufficient care, be cited as negative; and experiments which would otherwise have been crowned with unmistakeably positive results, may be rendered wholly barren by the employment of infusions which have been carelessly made.

A word of explanation seems necessary with regard to the introduction of the new term _Archebiosis_. I had originally, in unpublished writings, adopted the word _Biogenesis_ to express the same meaning--viz., life-origination or commencement. But in the mean time the word _Biogenesis_ has been made use of, quite independently, by a distinguished biologist, who wished to make it bear a totally different meaning. He also introduced the word _Abiogenesis_. I have been informed, however, on the best authority, that neither of these words can--with any regard to the language from which they are derived--be supposed to bear the meanings which have of late been publicly assigned to them. Wishing to avoid all needless confusion, I therefore renounced the use of the word _Biogenesis_, and being, for the reason just given, unable to adopt the other term, I was compelled to introduce a new word, in order to designate the process by which living matter is supposed to come into being, independently of pre-existing living matter.

H. CHARLTON BASTIAN.

_Queen Anne Street, W.,
May 8, 1871._

THE MODES OF ORIGIN

OF

LOWEST ORGANISMS.

The mode of origin of _Bacteria_, and, to a less extent, of _Torulæ_, has been much discussed of late, and many different views have been advocated on this subject by successive writers.

It is of much importance to bear in mind when such views are under consideration, that a short time since nothing was positively known concerning the life-history of these organisms. However strongly, therefore, certain persons are inclined to rely upon the analogy which is supposed to obtain between these doubtful cases, and the multitudes of known cases--in which it can be shown that organisms are the offspring of pre-existing organisms--it must always be borne in mind that in many of the doubtful cases, where the simplest organisms are concerned, there is also an analogical argument of almost equal weight adducible in favour of their _de novo_ origination--after a fashion, and under the influence of laws similar to those by which crystals arise. To rely too exclusively upon an argument from analogy is always perilous: it is more than usually so, however, in a case like this, where what is practically an opposing analogy may be deemed to speak just as authoritatively in an opposite direction.

There is one consideration, moreover, which deserves to be pointed out here, and which does not seem to have occurred to most of those who so firmly pin their faith to the truth of the motto “_omne vivum ex vivo_.” The every-day experience of mankind, supplemented by the ordinary observations of skilled naturalists, does pretty fairly entitle us to arrive at a wide generalization, to the effect that _some representatives of every kind of organism are capable of reproducing similar organisms_. But, whilst this is all that the actual every-day experience of mankind warrants being said, and whilst there is in reality the widest possible gulf between such a generalization and that which is expressed by the motto “_omne vivum ex vivo_,” the latter formula has of late been spoken of as though it were the one which was in accordance with the daily experience of mankind, rather than the other, which gives expression to a generalization of a much narrower description. This experience, in reality, affords no evidence which could entitle us to place implicit belief in the formula “_omne vivum ex vivo_.”

Whilst we do know something about the ability which most organisms possess of reproducing similar organisms, we cannot possibly say, from direct observation, that every organism which exists has had a similar mode of origin, because the cases in which organisms may have originated _de novo_ are the very cases in which their mode of origin must elude our actual observation. Such a statement, too, would be all the more dangerous, in the face of the other analogy, when it can actually be shown that some organisms do make their appearance in fluids after precisely the same fashion as crystals.

Although, therefore, there is a contradiction between the unwarrantable and ill-begotten formula, “_omne vivum ex vivo_,” and the doctrines of what has been called “Spontaneous Generation”; there is no contradiction whatever between such doctrines and the only generalization which we are really warranted in arriving at, to the effect that _some representatives of every kind of organism are capable of reproducing similar organisms_.

_Bacteria_, _Torulæ_, or other living things which may have been evolved _de novo_, when so evolved, multiply and reproduce just as freely as organisms that have been derived from parents.

The views as to the origin of _Bacteria_ and _Torulæ_ which are most worthy of attention, may be thus enumerated:--

_a._ That they are independent organisms derived by fission or gemmation from pre-existing _Bacteria_ and _Torulæ_.

_b._ That they represent subordinate stages in the life-history of other organisms (fungi), from some portion of which they have derived their origin, and into which they again tend to develop.

_c._ That they may have a heterogeneous mode of origin, owing to the more complete individualization of minute particles of living matter entering into the composition of higher organisms, both animal and vegetal.

_d._ That they may arise _de novo_ in certain fluids containing organic matter, independently of pre-existing living things (_Archebiosis_).

I shall make some remarks concerning each of these views, though the evidence I have to adduce mainly concerns the possibility of the origin of _Bacteria_ and _Torulæ_ in the way last alluded to, viz., by _Archebiosis_.

The third mode of origin is what is called _Heterogenesis_; whilst the first and second modes are the representatives of more familiar processes, included under the head of _Homogenesis_. Thus, in accordance with the first view, _Bacteria_ may be regarded as low organisms having a distinct individuality of their own and multiplying by a process of fission--thus affording instances of what I propose to term _direct Homogenesis_. Whilst, in accordance with the second view, _Bacteria_ are supposed to represent merely one stage in the life-history of higher organisms, which are therefore reproduced by an _indirect_ or cyclical process of _Homogenesis_.

The possible modes of origin of _Bacteria_ and _Torulæ_ may, therefore, be tabulated as follows:--

Modes of origin { 1. Homogenesis. { _a._ Direct. of _Bacteria_ { _b._ Indirect. and { 2. Heterogenesis. _Torulæ_. { 3. Archebiosis.

I. HOMOGENETIC MODE OF ORIGIN OF BACTERIA AND TORULÆ.

_Bacteria_ and _Torulæ_ being already in existence, they may, undoubtedly, reproduce organisms similar to themselves by processes of fission and gemmation--in the same way that other low protistic organisms propagate their kind. Although so many reasons rendered this view probable, it was some time before I was able actually to confirm it by personal observations in the case of _Bacteria_. In the ordinary microscopical examination of portions of an infusion containing these organisms, an observer may watch for hours and never see a single instance of such fission occurring. His attention is apt to be distracted by the number of organisms which are constantly flitting before his view, and he is, moreover, perhaps apt to pay particular attention to those which seem by their movements to be most obviously alive.

I have observed the process most plainly when a few _Bacteria_ have been enclosed in a single drop of fluid, pressed into a very thin stratum, in a “live-box” kept at a temperature of about 90° Fahr. by resting on one of Stricker’s warm-water chambers placed on the stage of the microscope. Under these conditions, I have seen a _Bacterium_ of moderate size divide into two, and each of these into two others somewhat smaller, in the course of fifteen minutes.

It is still more worthy of remark, that in all cases (so far as I have been able to observe), this, the most certain sign of vitality which such organisms are capable of manifesting, is shown by those which, from their stillness, might be considered dead. The _Bacteria_ which are about to divide are generally either motionless,[1] or merely present slight oscillating movements. The separation is quickly brought about at the joint, so that the original organism divides into two equal portions; and these, lying close together, soon develop a new construction as they grow, through which a further division may occur.

[1] Those which are quite motionless are always in close apposition either with the under surface of the covering glass, or with the surface of the glass on which they are situated.

That the _Bacteria_ which reproduce should be in a comparatively quiescent condition, seems not difficult to understand. Such rudimentary organisms do not appear to possess cilia or other locomotory appendages: their movements are, therefore, in all probability dependent upon the mere molecular changes which are taking place within them, and upon which their life and nutrition depend. The process of fission must, however, be considered as the result of a new effort at equilibrium, which has, perhaps, been necessitated by molecular changes that have occurred during a preceding period of growth. The living matter which is no longer able to exist round a single centre, re-arranges itself around two centres,--as a result of which, fission occurs. It seems only natural, therefore, that whilst this active work of molecular re-arrangement is going on, those other molecular movements which occasion the actual locomotion of the organism from place to place, should be more or less interfered with.

This is the one and only mode of multiplication of _Bacteria_ and of _Torulæ_ which is actually known to occur; and such a limitation is in accordance with the more general fact, that processes of fission or gemmation are the only means of reproduction that are known to occur in the lower kinds of organisms, belonging to the PROTISTIC kingdom.

However well this process of fission may have been established, as a frequent mode of reproduction of _Bacteria_, such a fact does not lend any support to the notion that these are necessarily distinct and independent organisms. _Torulæ_ (of which beer-yeast is the most familiar example) may similarly undergo this process of mere vegetative repetition to an indefinite extent, whilst only some of the products develop into fungi. The gonidia of lichens may also reproduce indefinitely in this fashion, and only some of the products of multiplication may go on to the production of lichens similar to that from which the gonidia had been derived.

It is a fact, however, admitted by many, and which any patient microscopist is capable of verifying for himself, that some _Bacteria_ do develop into _Leptothrix_ filaments, and that these are capable of passing into a dissepimented mycelial structure of larger size and undoubtedly fungus nature--from which fructification of various kinds may be produced. Some _Bacteria_ may therefore develop into some fungi, just as certainly as some _Torulæ_ may develop into other fungi, or, just as surely as some multiplying gonidia may develop into lichens.

In order to prove, however, that the _Bacteria_ which happen to go through this development into _Leptothrix_ and thence into fungi, are strictly to be considered as _necessary_ links in the life-history of fungi, it would be essential for the person holding such views, to show that _Bacteria_ could not arise independently--or at least that no independently evolved _Bacteria_ could develop through _Leptothrix_-forms into a fungus. And, similarly, for the other kinds of organisms: in order to establish that the _Torula_ cell is a necessary link in the life-history of certain fungi, or the gonidial cell a necessary link in the life-history of lichens, it would be necessary to show that _Torulæ_ or gonidial cells could not originate _de novo_--that no independently evolved _Torula_ or gonidial cell could develop into a fungus or a lichen.

An easier position to establish would be, that the _Bacterium_ or the _Torula_ were _occasionally_ links in the life-history of fungi, or that the gonidial cell was an occasional link in the life-history of a lichen. This doctrine would leave the other more difficult problems,--as to the possible existence of supplementary modes of origin for such organisms by Heterogenesis or by Archebiosis--perfectly open questions.

To establish the position that _Bacteria_ are occasional links in the life-history of fungi, it would be only necessary to show that some of the _Bacteria_ which develop into fungi through _Leptothrix_ have derived their origin from pre-existing fungi. This is the view which Hallier[2] has endeavoured to establish; it is also the doctrine of M. Polotebnow,[3] and one, moreover, to which Professor Huxley[4] inclines. Even this mode of origin for _Bacteria_, however, has not been so decisively established as might be desired. With regard to _Torulæ_, we do possess sufficient evidence tending to show that some of them may arise from pre-existing fungi, and we are equally certain that some gonidial cells are thrown off from lichens. The analogical evidence is, therefore, in favour of the view that minute particles which are budded off from the mycelium of certain fungi, may subsequently lead an independent existence, and multiply in the form of _Bacteria_--although many of the cases in which such buds _seem_ to be given off, may be merely cases in which co-existing _Bacteria_ have become adherent to fungus filaments or to _Torulæ_.[5]

[2] Phytopathologie, 1867. Hallier seems, however, strongly inclined to disbelieve in the origin of these organisms by Heterogenesis or by Archebiosis.

[3] Sitzungsber. der K. Akad. zu Wien, 1870, Band lx., Heft iv.

[4] Quarterly Journal of Microscopical Science, Oct., 1870.

[5] Notwithstanding what Professor Huxley has said, I believe it to be almost certain that in many cases _Bacteria_ exist in a solution in which there are neither _Torulæ_ nor developed fungi. And, on the other hand, I have seen fungi growing in a simple (boiled) solution of tartrate of ammonia, for weeks together, without the appearance of _Bacteria_ or the occurrence of any turbidity of the solution; and on two or three occasions I have seen _Torulæ_ swarming in an infusion without the presence of _Bacteria_.

But, with reference to these supposed cases of budding, and also to those others in which the contents of a spore or sporangium break up into what Professor Hallier calls “micrococci” (which are generally incipient _Bacteria_), it would be difficult for us to decide whether such processes are normal or abnormal. When we have to do with such organisms, in fact, there may be the nicest transitions between what is called Homogenesis, and what, when occurring in other organisms, we term Heterogenesis. It may be that the production of such “micrococci” from the spore or sporangium of the fungus is not an invariable incident in the life-history of the species, but rather an occasional result of the influence of unusual conditions, or of failing vigour on the part of the organism. In this latter case we should have to do with a process of Heterogenesis; although, as I have just stated, in respect to such low and changeable organisms, scarcely any distinct line of demarcation can be drawn between Homogenesis and Heterogenesis.

The evidence seems, therefore, against the notion that _Bacteria_ or _Torulæ_ are ordinary, independent living things, which merely reproduce their like.

That some _Bacteria_ are produced from pre-existing _Bacteria_, just as some _Torulæ_ are derived from pre-existing _Torulæ_, may, it is true, be considered as settled. But, so far as we have yet considered the subject, there may be just as good evidence to show that _Bacteria_ and _Torulæ_ are capable of arising _de novo_, as there is that some of them are capable of developing into fungi.

If this were the case, such types could only be regarded as the most common forms assumed by new-born specks of living matter; and, by reason of their origin--which would entail an absence of all hereditary predisposition--they might be supposed to be capable of assuming higher developmental forms.

Now, as a matter of fact, worthy of arresting our attention, we do find that some _Bacteria_ are capable of growing into _Leptothrix_, whilst this is able to develop continuously into a fungus; just as we also know that some _Torulæ_ are capable of growing into other fungi.

Should it be established, therefore, that _Bacteria_ and _Torulæ_ are capable of arising _de novo_, the facts concerning their mutability are harmonious enough with theoretical indications.

But, as I have before indicated, although it is quite true that some _Bacteria_ develop into fungi, such forms may constitute no necessary links in the life-history of other fungi. I have suggested that in those (occasional) cases in which they do occur as links in the life-history of fungi, there is room for doubt whether these _Bacteria_ are to be considered as normal products, or as abnormal results (heterogeneous offcasts), brought about by some unusual conditions acting upon the parent fungus. That is to say, we may be doubtful whether in such a case their origin ought to be considered Homogenetic or Heterogenetic. It may be that many of the lower fungi are such changeable organisms, and so prone to respond to the various “conditions” acting upon them (which would be almost certainly the case if they had been developed from a _Bacterium_ in two or three days--the _Bacterium_ itself having been evolved _de novo_) that no very valid distinction can here be drawn between Homogenesis and Heterogenesis. Our whole point of view, in fact, concerning such fungi as are seen to develop through _Leptothrix_ forms from _Bacteria_ must be entirely altered, if it is once conceded that _Bacteria_ may arise _de novo_. Such simple _Mucedineæ_ would then have to be regarded as mere upstart organisms only a few removes from dead matter, and--in view of the greater molecular mobility of living matter--capable of being modified in shape and form even more than the most changeable crystals under the influence of altering “conditions.” We should have no longer to do with the members of a stable species, which had been reproducing its like through countless geologic ages anterior to the advent of man upon the earth. Indeed, in order to reconcile such a possibility with the seemingly contradictory fact of the known extreme changeability of these lower forms of life, we hear only vague hints thrown out about our imperfect knowledge of the “limits within which species may vary.” As if, in the face of what we do know concerning hereditary transmission, this changeability did not make it almost impossible to conceive that there should have been an unbroken series of such organisms since that remote epoch of the earth’s history, when the first organisms of the kind made their appearance. It does not seem to me that the presumed permanence of a very changeable organism is consistent with, or rendered more explicable by, the supposition that _some_ representatives of the species _have_ constantly been undergoing progressive modifications which have been successively perpetuated by inheritance, in the shape of distinct specific forms. Why should some be presumed to have undergone so much change, whilst others (presenting an equal and an extreme degree of modifiability, even to the present day) are supposed to have preserved the same specific form through a countless series of changing influences?

2. HETEROGENETIC MODE OF ORIGIN OF BACTERIA AND OF TORULÆ.

It has been long known that _Bacteria_ and _Torulæ_ are frequently to be found within vegetable cells, taken even from the central parts of plants, whenever these are in a sickly condition or are actually dying. They are apt to exist also within epithelial cells taken from the inside of the mouth; and the frequency and abundance with which such organisms are met with in these cells, is almost in direct proportion to the malnutrition and lack of vital power in the individual who is the subject of observation. Then, again, in persons who have died of adynamic diseases, in the course of twenty-four or thirty-six hours (during warm weather) _Bacteria_ may be found in abundance within the blood-vessels of the brain and of other parts, although no such _Bacteria_ were recognizable in the blood of the individual during life.

In these cases we must, in order to account for the presence of the _Bacteria_ and _Torulæ_, either suppose that such organisms, in an embryonic state, are almost universally disseminated throughout the various textures of higher organisms, both animal and vegetal (though they are only able to develop and manifest themselves when the higher organisms, or the parts of them in which the _Bacteria_ or _Torulæ_ are met with, are on the eve of death), or else we must imagine that when the vital activity of any organism, whether simple or complex, is on the wane, its constituent particles (being still portions of living matter) are capable of individualizing themselves, and of growing into the low organisms in question. Just as the life of one of the cells of a higher organism may continue for some time after the death of the organism itself, so, in accordance with this latter view, may one of the particles of such a cell be supposed to continue to live after even cell-life is impossible.

Now, to many persons, the latter seems to be a much simpler hypothesis than the former, and one, moreover, which is more in accordance with known facts. People’s views, however, on this subject are likely to be much influenced by their notions as to the possibility of _Bacteria_ arising by a process of Archebiosis. Although some may be inclined to accept the doctrine of Heterogenesis, the same persons, being “vitalists,” may not readily believe in the doctrine of Archebiosis, because this implies the vivification of dead matter--the conversion of not-living elements into a living combination. Those, however, who do believe in Archebiosis will--if the necessary evidence be forthcoming--all the more readily yield their assent to the doctrine of Heterogenesis, because it is a much less novel thing to have to believe in the mere transformation of living matter, than in the possibility of its origin _de novo_.

Evidence of a tolerably satisfactory nature, however, is forthcoming, which may speak independently in favour of the doctrine of _Heterogenesis_.

It has been affirmed by Crivelli and Maggi[6] that they have actually seen the particles within granular epithelial cells (taken from the back of the tongue of a patient suffering from diabetes) grow and elongate, so as to give rise to _Bacteria_, or fuse in longitudinal series, so as to form a _Vibrio_.[7] And, moreover, as I have myself ascertained, if one takes healthy-looking epithelial scales scraped from the inside of the mouth, which appear to contain nothing but the finest granules, and places them with a little saliva in a “live-box” (and this within a damp chamber kept at a temperature of about 90° Fahr.), in the course of from 5 to 10 hours, the cells may be found to be studded throughout with motionless _Bacteria_. Of course it may be said that the granules originally seen in the cells were offcasts from pre-existing _Bacteria_[8] which had gained access to the cell. And although, to many, this may seem an extremely improbable supposition, it is, nevertheless, one which it would be very difficult to disprove. The improbability of the notion is increased, moreover, when we find that _Bacteria_, and even _Torulæ_, will develop just as freely within closed cells taken from the very centre of a vegetable tuber, as they will in the midst of the more solid epithelial cell from the inside of the mouth. If it be urged that in this latter situation, there is the greatest chance of the cells being brought into contact with _Bacteria_, and that it must be considered possible for imaginary minute offcasts from these _Bacteria_ to make their own way into the substance of the epithelial cell, I am quite willing to grant the desirability of taking such possibilities into consideration. But, at the same time, it seems all the less likely that the actual occurrence of the _Bacteria_ is explicable on these grounds, because we find them developing just as freely within the cells freshly cut from the centre of a tuberous root, or we may find them already developed within these cells, if the root has begun to decay. To suppose that actual germs of _Bacteria_ and of _Torulæ_ are uniformly distributed throughout the tissues of higher organisms, is to harbour a hypothesis which would appear to many to be devoid of all probability--more especially when the heterogenetic mode of origin of larger and higher organisms is a matter of absolute certainty.

[6] Rendiconti del R. Istit. Lombardo, Ser. II. Vol. 1, p. 11.

[7] However novel such a mode of origin of independent _Bacteria_ and _Vibriones_ may appear to some, it will seem much less strange and unlikely to others who have seen, as I have done, an _Amœba_, or an _Actinophrys_-like body, originate from the progressive molecular modifications taking place in a mass of chlorophyll and protoplasm within the filament of an alga. Many independent observers have watched all the stages of this process, and some have even seen Ciliated Infusoria originate by such a metamorphic change.

[8] Or offcasts from pre-existing fungi,--constituting the “micrococci” of Professor Hallier.

3. ORIGIN OF BACTERIA AND OF TORULÆ BY ARCHEBIOSIS.

The evidence on this part of the subject is, I think, sharply defined and conclusive. Simple experiments can be had recourse to, which are not admissible in the discussion of the question as to the origin of _Bacteria_ and _Torulæ_ by Heterogenesis. There, we wish to establish the fact that living matter is capable of undergoing a certain metamorphosis, and consequently, we must deal with living matter. Here, however, with the view of establishing the fact that living matter can arise _de novo_, if we are able, shortly after beginning our experiment, to arrive at a reasonable and well-based assurance that no living thing exists in the hermetically sealed experimental vessel--if the measures that we have adopted fully entitle us to believe that all living things which may have pre-existed therein have been killed--we may feel pretty sure that any living organisms which are subsequently found, when the vessel is broken, must have originated from some re-arrangements which had taken place amongst the not-living constituents of the experimental solutions, whereby life-initiating combinations had been formed.

The possibility of the _de novo_ origination of _Bacteria_, _Torulæ_, and other such organisms, is one which is intimately associated with the doctrine as to the cause of fermentation and putrefaction. With regard to the almost invariable association of such organisms with some of these processes, almost all are agreed. There is, moreover, a very frequent association of particular kinds of organisms with particular kinds of fermentation. Hence the assumption is an easy and a natural one to many persons, that the organisms which are invariably met with in some cases are the causes of these fermentations,[9] although it is quite obvious that the facts on which this view is based, are equally explicable on the supposition that the organisms are concomitant results or products (due to new chemical combinations) of the fermentative changes. In the one case the fermentative changes are believed to be initiated by the influence of living organisms; and those who regard living things as the only true _ferments_, for the most part also believe that living things are incapable of arising _de novo_. They think that those organisms which serve to initiate the changes in question, have been derived from a multitudinous army of omnipresent atmospheric germs, which are always ready, in number and kind suitable for every emergency. This is the doctrine of M. Pasteur and others. On the other hand, fermentations and putrefactions may be regarded as sets of chemical changes, which are apt to occur in organic and other complex substances--these changes being due either to the intrinsic instability of the body which manifests them, or to molecular movements communicated to it by a still more unstable body. Baron Liebig says:--“Many organic compounds are known, which undergo, in presence of water, alteration and metamorphosis, having a certain duration, and ultimately terminating in putrefaction; while other organic substances that are not liable to such alteration by themselves, nevertheless, suffer a similar displacement or separation of their molecules, when brought into contact with the ferments.”

[9] From this view the transition is also easy, though none the less illegitimate, to the doctrine that _all_ fermentations are caused by organisms; just as it has been easy to start, and find converts for, the doctrine expressed by the phrase “_omne vivum ex vivo_.” The distinction between _all_ and _some_ is only too often overlooked.

Each substance belonging to the first class, would be at the same time, therefore, both ferment and fermentable substance; whilst a small portion of such substance, when brought into contact with a less unstable substance, might induce such molecular movements as to make it undergo a process of fermentation. With regard to the cause of such induced fermentative changes, Gerhardt[10] says, in explaining Liebig’s views:--“Every substance which decomposes or enters into combination is in a state of movement, its molecules being agitated; but since friction, shock, mechanical agitation, suffice to provoke the decomposition of many substances (chlorous acid, chloride of nitrogen, fulminating silver), there is all the more reason why a chemical decomposition in which the molecular agitation is more complete, should produce similar effects upon certain substances. In addition, bodies are known which when alone are not decomposed by certain agents, but which are attacked, when they exist in contact with other bodies incapable of resisting the influence of these agents. Thus platinum alone does not dissolve in nitric acid, but when allied with silver, it is easily dissolved; pure copper is not dissolved by sulphuric acid, but it does dissolve in this when it is allied with zinc, &c. According to M. Liebig it is the same with ferments and fermentable substances; sugar, which does not change when it is quite alone, changes--that is to say ferments--when it is in contact with a nitrogenous substance undergoing change, that is, with a ferment.”

[10] ‘Chimie organique,’ 1856, t. iv. p. 589.

Thus, in accordance with this latter view, living ferments are not needed--mere dead, organic or nitrogenous matter suffices to initiate the processes in question.[11] Those who hold this opinion may or may not believe that organisms are capable of arising _de novo_;[12] though there can be little doubt that a belief in the truth of such a doctrine does, almost inevitably, entail a belief in the _de novo_ origination of living things. No one who has looked into the evidence, doubts the fact of the association between some of these processes and the presence of organisms; the only question is, as to the relation in which they stand to one another. If organisms are not the causes of those fermentative changes with which they are invariably associated, then they are, in all probability, the results of such changes; and they must certainly have been produced _de novo_ if it can be shown that fermentation or putrefaction may take place under the influence of conditions which make it certain that pre-existing living organisms could have had nothing to do with the process.

[11] Those who hold this opinion do not of course deny that living ferments can initiate fermentations. Every-day experience convinces them of the truth of this. They merely affirm that the intervention of vital action is not essential: they look upon fermentation as a purely chemical process, and believe that even in those cases where fermentation is initiated by living organisms (such as beer-yeast), these--although living--act chemically upon the matter which undergoes fermentation.

[12] They may not believe this, because they may be unaware of the fact of the invariable association of some organisms with some kinds of fermentations, and may consequently have never concerned themselves with the evidence bearing upon this part of the question. (See Gerhardt, _loc. cit._)

Now, in order to lend some air of probability to the former hypothesis, concerning the necessity for the existence of living ferments, it was incumbent upon its supporters to endeavour to show that the air did contain such a multitude of “germs,” or living things, as were demanded by the requirements of their theory. Spallanzani and Bonnet had, as far as the imagination was concerned, done all that was necessary. They had proclaimed the universal diffusion of “germs” of all kinds of organisms throughout the atmosphere--which were ready to develop, whenever suitable conditions presented themselves. So far, however, this was but another hypothesis. To establish the doctrine that fermentation cannot take place without the agency of living ferments, we cannot receive hypotheses in evidence: facts are needed. These, no one attempted to supply in an adequate manner[13] anterior to the investigations of M. Pasteur. Speaking of his researches, even M. Milne-Edwards says,[14] “Previous to this time, the existence of reproductive particles, or infusorial germs in the atmosphere was nothing more than a _plausible hypothesis_, put forward in order to explain the origin of such creatures in a manner conformable with the general laws of reproduction; but it was only a mere supposition, and no one had been able actually to see or to handle these reproductive corpuscles.”

[13] M. Pouchet and others had examined the dust which _settles_ on objects, and amongst much débris of different kinds had found comparatively few ova or spores. He had not, however, up to this time, filtered the air, so as to see what germs might be detected floating about in the atmosphere.

[14] ‘Anat. et Physiol. compar.’ t. viii. p. 264.

We have to look, therefore, to M. Pasteur’s investigations, and to others which may have been since conducted, for all the scientific evidence in support of what has been called the “Panspermic hypothesis.”

By an ingenious method of filtration, which is fully described in his memoir,[15] M. Pasteur separated from the air that passed through his apparatus the solid particles which it contained. This search convinced him that there were, as he says, “constantly in ordinary air a variable number of corpuscles whose form and structure declare them to be organized.” Some of these, he thinks, resemble the spores of fungi, and others the ova of ciliated infusoria, though he adds:--“But as to affirming that this is a spore, much less the spore of any definite species, and that one is an egg, and belonging to such an infusorium, I believe that this is not possible.” He limits himself, in fact, to the statements, that the corpuscles which he found, were (in his opinion) evidently organized; that they resembled in form and appearance the germs of the lower kinds of organisms; and that, from their variety in size, they probably belonged to many different sorts of living things. Even here, therefore, we have to do with the impressions of M. Pasteur, rather than with verified statements. All that has been established by his direct investigation as to the nature of the solid bodies contained in the atmosphere is this: that the air contains a number of round or ovoidal corpuscles, often quite structureless, which he could not distinguish from the spores of fungi[16]--some of which, being about the right size, were round or ovoidal, and structureless. In addition, however, it has been shown that the air contains other rounded corpuscles which are similarly structureless, though composed of silica or starch. It may therefore be asked, in the first place, whether the conclusion is a sufficiently safe one that many of the corpuscles found by M. Pasteur were spores of fungi; and in the next place, supposing this to have been established, whether such spores were living or dead. These questions would have been answered satisfactorily if M. Pasteur could state that he had actually watched the development of such corpuscles, in some suitable apparatus, into distinct organisms. But any such development, he distinctly states, he never witnessed. He says[17]:--“What would have been the better and more direct course would have been to follow the development of these germs with the microscope. Such was my intention; but the apparatus which I had devised for this purpose not having been delivered to me at a convenient time, I was diverted from this investigation by other work.” The evidence which he does adduce, in subsequent portions of his memoir, in order to prove that some of these corpuscles were really “fertile germs,” is almost valueless, because all the facts are open to another interpretation, which is just as much, nay, even more, in accordance with Baron Liebig’s than with his own doctrine of fermentation.

[15] ‘Annales de Chimie et de Physique,’ 1862, t. lxiv. p. 24.

[16] Those which he believed to be eggs of ciliated infusoria, may be at once dismissed from consideration, as we are not at present concerned with the origin of organisms of this kind.

[17] _Loc. cit._ p. 34, note ^{1}.

But another most important consideration presents itself. M. Pasteur’s researches as to the nature of the dust contained in the atmosphere enable him to say nothing concerning the presence of _Bacteria_, although he himself admits that these are generally the first organisms which display themselves in fermentations or putrefactions, and that in a very large majority of the cases in which fermentation occurs in closed vessels they are the only organisms which make their appearance.[18] And yet, notwithstanding these facts, M. Pasteur says, in reference to the common form of _Bacterium_:--“This infusorial animal is so small that one cannot distinguish its germ, and still less fix upon the presence of this germ, if it were known, amongst the organized corpuscles of the dust which is suspended in the air.”

[18] _Loc cit._ p. 56.

Here, then, we have a confession from M. Pasteur himself, that all evidence fails, where it is most wanted, in support of his hypothesis.

If a large number of fermentations begin with the presence of _Bacteria_ as the only living things, and if in a number of cases no other organisms ever occur, it is useless to adduce as evidence, in proof of the view that fermentations are _always_ initiated by air-derived organisms, the fact that certain corpuscles (supposed to be spores of fungi) are recognizable in the atmosphere--capped by the distinct statement[19] that _Bacteria_ or their germs are not recognizable. If _Bacteria_ are not recognizable in the atmosphere, what scientific evidence is there that the fermentations in which these alone occur are initiated by _Bacteria_ derived from the atmosphere, or from certain imaginary _Bacteria_ germs,[20] which we are supposed to be unable to distinguish? M. Pasteur may, moreover, be reminded that when he resorts to the supposition of _Bacteria_ possessing “germs” which are indistinguishable, he is again resorting to hypothesis rather than to fact, in order to prove the truth of the particular doctrine of fermentation which he advocates. _Bacteria_ are known to reproduce and multiply only by a process of fission; each of the parts into which they divide being nothing more than a part of the original _Bacterium_, and therefore endowed with similar properties of resisting heat, desiccation, and other agencies. Any resort to invisible germs to account for the multiplication of _Bacteria_, which are known to reproduce freely in other ways, is obviously not permissible, unless such postulation be more or less necessitated by the occurrence of facts otherwise inexplicable.

[19] See p. 57.

[20] M. Pasteur’s use of this term, in which he is followed by others holding similar opinions, is much to be deprecated. Having said that he had found certain corpuscles which resembled spores of fungi, or ova of infusoria, he subsequently speaks of them as “germs,” and also applies the same name to the reproductive particles of _Bacteria_, which he merely _assumes_ to be present in the atmosphere. Thus, having only proved that corpuscles resembling spores of some fungi, are to be found in the atmosphere, he subsequently speaks of the presence of a multitude of atmospheric germs as an established fact, without at all prominently pointing out that, so far as the most important of these are concerned--germs of _Bacteria_--their existence had only been inferred, and not proved.

Although, therefore, no direct evidence has been adduced tending to show that _Bacteria_ are present in the atmosphere, even if this evidence had been forthcoming, it would have been necessary, in reference to M. Pasteur’s hypothesis, for it to be supplemented by further evidence to the effect that _Bacteria_ were well capable of resisting such an amount of desiccation as must have been involved by their presence for an indefinite time in the atmosphere even of the hottest and driest regions of the earth. For, organic substances in solution do not only putrefy in moist weather or moist climates; they putrefy most rapidly and surely when the temperature is high, and quite irrespectively of the amount of moisture contained in the atmosphere. A property of resisting the effects of desiccation--the possession of which, by _Bacteria_, is so necessary for the truth of M. Pasteur’s argument--ought to have been shown by scientific evidence to be a real attribute of such organisms; though it seems, on the contrary, to have been assumed to exist, with almost equal readiness by both parties, in the controversies concerning the possibility of “spontaneous generation.” This error may be ascribed to the misguiding influence of a treacherous analogy. Whilst it may be true that certain seeds and spores, and also that Rotifers, “Sloths,” and some Nematoids are capable of resisting the influence of a prolonged exposure to desiccating influences, it may well be asked, whether the same fact necessarily holds good for organisms such as _Bacteria_, which have no chitinous or other envelopes to protect them, and which are merely minute fragments of naked protoplasm. Having elsewhere[21] shown how far presumptions had stolen a march upon established facts, in reference to the supposed possession of a similar property by the Free Nematoids, my eyes were opened to the reality of this uncertainty with regard to _Bacteria_. It is, however, no easy matter definitely to prove or to disprove the possession of this property by organisms so minute as _Bacteria_, and therefore so difficult to identify. If dried _Bacteria_ are added to a drop of a suitable solution--similar to that in which they had been bred--it soon becomes quite impossible to distinguish those which have been added from those which arise in the fluid. Taking into consideration the fate of other simple organisms, however, it is by no means improbable that they should be killed even by a short desiccation. I have found, for instance, that desiccation for half-an-hour in a room at a temperature of 65° F. suffices to kill all the larger, naked, lower organisms with which I have experimented--including long Vibrios, Amœbæ, Monads, Chlamydomonads, Euglenæ, Desmids, Vorticellæ and all other Ciliated Infusoria.

[21] ‘Philosophical Transactions,’ 1866, pp. 616–619.

But, certain indirect evidence seems to speak most authoritatively against the supposition that the air contains any notable quantity of living _Bacteria_, or _Bacteria_ germs, whether visible or invisible. I have always found that a simple solution of ammonic tartrate, which has been placed--without previous boiling--in a corked bottle of greater capacity, will become turbid in two or three days, owing to the presence of myriads of _Bacteria_; whilst a similar solution, previously boiled, may remain for ten days, three weeks, or more, without showing the least trace of turbidity, although the open neck of the bottle or flask in which it is contained, may be covered only by a loose cap of paper. And yet, at any time, in order to make this fluid become turbid in from 24 to 48 hours, all that one has to do is to bring it into contact with a small glass rod which has just been dipped into a solution containing living _Bacteria_.[22]

[22] The solution, during the whole time, being exposed to a temperature of 75° to 85° F.

If we find that an eminently inoculable fluid will remain for two or three weeks, or perhaps more, in contact with the air without becoming turbid, though it will always become turbid in two or three days if brought into contact with living _Bacteria_, what can we conclude, but that living _Bacteria_ are not very common in the atmosphere? These most striking facts can be easily verified by other observers.

Thus we find ourselves, at present, in this position. After all that has been said and done to prove the wonderful prevalence of “germs” in the atmosphere, we are really still in the region of hypothesis--no further advanced than we were in the time of Bonnet and of Spallanzani, so far as it concerns the organisms which are all important--_Bacteria_. Neither these nor their germs have been shown to exist in any recognizable abundance in the atmosphere, and yet in most fermentations they are the first organisms which display themselves; whilst in many such fermentations _Bacteria_ alone occur. Nay more, even were they present in any great abundance, there is some reason to believe that the majority of them would exist as mere dead, organic particles--because _Bacteria_ are more than likely to be unable to resist anything like an extreme or prolonged exposure to desiccating influences.

The first and essential data in support of M. Pasteur’s hypothesis must, therefore, be regarded as entirely unproved in respect to _Bacteria_--which are the most important of all organisms, in relation to the cause of fermentation and putrefaction.

Without the aid of elaborate experiments, however, the evidence which the microscope can supply is capable of leading us to the conclusion that such search for atmospheric _Bacteria_ germs, was comparatively useless. If it can be shown that _Bacteria_ can arise in a fluid independently of _visible_ germs, then, obviously, any inquiries as to the nature of the visible contents of the atmosphere, can have only a very indirect bearing upon the question as to the mode of origin of these organisms. And yet by the aid of the microscope, as I have elsewhere stated, one can watch the appearance of almost motionless specks, more or less uniformly diffused through a motionless film of fluid, and can see them gradually develop into moving _Bacteria_ or into _Torulæ_. So that, where no _visible_ germs previously existed, visible particles of living matter develop, and more or less rapidly grow into distinct _Bacteria_. This may be best seen in a drop of a fresh and very strong turnip infusion, which has been filtered several times through the finest paper. The drop, placed in a live-box, should be flattened into a thin film by the application of the cover.

Thus protected, evaporation takes place very slowly, and with the live-box resting on one of Stricker’s hot-water plates, at a temperature of 85° to 90° F., and the latter upon the stage of the microscope, one can easily select a portion of the field in which either no particles or only a countable number exist. If, therefore, around and between any mere granules which may pre-exist, or in a clear space, one gradually sees in the course of two or perhaps three hours, a multitude of almost motionless specks (at first about 1/100000″ in diameter) in positions where no such specks previously existed; and if these specks may be seen gradually to increase in size and develop into _Bacteria_ and _Torulæ_, then, at all events, we are able to say that these organisms can be developed without pre-existing _visible_ germs, and we have just the same amount of actual evidence for believing that they have been formed _de novo_, as we should have for believing that crystals had been formed _de novo_, if we had seen them appearing under our eyes in the same manner. Whether they really arise after the fashion of crystals, without the aid of pre-existing though invisible germs, is a matter which can only be settled inferentially, by a subsequent resort to strict methods of experimentation.