Transcriber’s notes:
In this transcription, paired underscores denote _italicised text_,
paired asterisks denote *bold text* and a ^ (caret) indicates that the
following bracketed character was superscripted in the original text.
Footnotes have been positioned below the relevant paragraphs.
A small number of errors have been corrected silently, including the
following:
Amæbæ —> Amœbæ
continuea —> continued
translalations —> translations
Harvar —> Harvard
ST. —> St.
missing word ‘in’ inserted
redundant comma deleted
The following misplaced section of text has been correctly positioned:
disowned. But these are not its best features: its sustained power of
reasoning, its wide sweep of observation and reflection, its elevated
ethical and social tone, stamp it as a work of high excellence, and as
such we cordially recommend it to our readers.”--Saturday Review.
Inconsistently labelled passages of text are as in the original, e.g.
a b c d; a b c e; _ b c e;
A title has been added to the original featureless book cover.
_In the Press, in Two Volumes, Crown 8vo., with numerous
Illustrations_,
THE BEGINNINGS OF LIFE.
BY
THE SAME AUTHOR.
London and New York:
MACMILLAN AND CO.
[Illustration: LOWEST ORGANISMS.
Fig. 1.--The simplest forms of Life--_Bacteria_, _Torulæ_, _&c._
Fig. 2.--_Bacteria_, _Vibriones_, and _Leptothrix_ filaments.
(× 800 diameters.)]
THE MODES OF ORIGIN
OF
LOWEST ORGANISMS:
INCLUDING
A DISCUSSION OF THE EXPERIMENTS
OF M. PASTEUR,
AND A REPLY TO SOME STATEMENTS BY PROFESSORS
HUXLEY AND TYNDALL.
By H. CHARLTON BASTIAN, M.A., M.D., F.R.S.,
FELLOW OF THE ROYAL COLLEGE OF PHYSICIANS;
PROFESSOR OF PATHOLOGICAL ANATOMY IN UNIVERSITY COLLEGE, LONDON;
ASSISTANT PHYSICIAN TO UNIVERSITY COLLEGE HOSPITAL,
AND TO THE NATIONAL HOSPITAL FOR THE EPILEPTIC AND PARALYSED.
London and New York:
MACMILLAN AND CO.
1871.
[_All rights reserved._]
“Quant à ce qui concerne la prétendue incubation d’œufs
d’Infusoires dans l’infusion, il faudrait d’abord prouver
l’existence de ces œufs. Les dit-on trop petits pour être aperçus,
c’est avouer qu’on ne peut rien savoir de leur existence. * * *
Croire que partout où l’on rencontre des Infusoires, ils ont été
précédés d’œufs, c’est donc admettre une pure hypothèse, qui n’a
d’autre fondement que l’analogie. * * * Si c’est seulement par
l’analogie qu’on suppose des œufs chez eux, il faut accorder à ces
œufs des propriétés semblables à celles de tous les œufs connus;
car ce serait jouer sur les mots que de supposer qu’ils en ont de
particulières à eux seuls.”--BURDACH’S _Traité de Physiologie_,
Translation by Jourdan, 1837, t. i., p. 22.
LONDON: PRINTED BY WILLIAM CLOWES AND SONS, STAMFORD STREET,
AND CHARING CROSS.
PREFACE.
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.
Seeing however, that we are able, with the aid of the microscope alone,
to demonstrate that _Bacteria_ and _Torulæ_ can develop in situations
where no visible germs had previously existed, it is useless, as I
have said before--so far as the question of their mode of origin is
concerned--to search the atmosphere to ascertain what visible germs
it may contain. If some _Bacteria_ and _Torulæ_ arise from germs at
all, it must be from germs which are invisible to us. The finding of
visible germs in the atmosphere can, therefore, only have an indirect
bearing upon the solution of the problem. Since it _can_ be shown that
some visible spores and ova exist in the atmosphere, this affords a
certain amount of warrant for the supposition that invisible, living,
reproductive particles may also exist--more especially if the existence
of an amount of organic matter, which is ordinarily invisible, can be
revealed in the air, by the agency of the electric beam, or by any
other means.
Nothing can be more illegitimate, however, in the way of inference,
than the assumption at once indulged in by Prof. Tyndall and others
(who might have been expected, by their previous scientific work,
to have learned more caution) that this impalpable organic dust was
largely composed of impalpable germs. Yet, without a shadow of proof,
without even an attempt to prove it, the air was for a time represented
to be a mere stirabout, thick with invisible germs. The briefest
reflection, however, upon the probabilities of the case, should have
sufficed to suggest a totally different interpretation. The surface
of the earth is clothed with living things of all kinds, animal and
vegetal, which are not only continually throwing off organic particles
and fragments during their life, but are constantly undergoing
processes of decay and molecular disintegration after their death. The
actual reproductive elements of these living things are extremely small
in bulk, when compared with the other parts which are not reproductive,
and although _Bacteria_ and _Torulæ_ do exist abundantly, and do
materially help to bring about some of the decay in question, yet their
bulk, also, is extremely small in comparison with the amount of organic
matter itself that is continually undergoing disintegration of a dry
kind, in which _Bacteria_ and _Torulæ_ take no part. When, moreover, it
is considered that in the neighbourhood of populous cities (the air of
which alone exhibits this very large quantity of impalpable, mixed with
palpable, organic dust), there is constantly going on a wear and tear
of the textile fabrics and of the organic products of various kinds
which are daily subservient to the wants of man; and that the chimneys
of manufactories and dwelling-houses are also continually emitting
clouds of smoke thick with imperfectly consumed organic particles, some
idea may be gained of the manifold sources whence the organic particles
and fragments found in the atmosphere may emanate, and also as to
what proportion of them is likely to be composed of living or dead
reproductive elements, or “germs.”
Thus, then, so far as the two rival doctrines of fermentation are
concerned, the investigation of the nature of the solid particles
contained in the atmosphere has revealed facts which are thoroughly
in harmony with all the requirements of Liebig’s physical theory,
though it has almost utterly failed to give anything like a scientific
basis to the vital theory of Pasteur. So far from being able to show
that living _Bacteria_ (which are the first and oftentimes the only
organisms concerned in many processes of fermentation and putrefaction)
are universally diffused through the air, Pasteur admits that these
cannot be detected, and that their “germs” are not recognizable.
If, therefore, M. Pasteur still maintains the truth of his theory, it
should be distinctly understood that it rests originally, not upon
established facts, but upon a mere hypothesis--the hypothesis that
the air teems with multitudes of invisible _Bacteria_ germs. He is
driven to such a doctrine, not only by his own confessions concerning
_Bacteria_, but also by the microscopical evidence to which I have
referred.
So that in explaining the results of any experiments made with the view
of throwing light upon the _cause_ of fermentation or putrefaction, it
is especially necessary to bear in mind two considerations:--
I. That dust filtered from the atmosphere cannot be proved to include
living _Bacteria_; though it is known to contain a multitude of organic
particles which may be capable in the presence of water, in accordance
with Liebig’s hypothesis, of acting as ferments.
II. It must also be recollected that, in the opinion of many, Life
represents a higher function which is displayed by certain kinds of
organic matter; and that this higher function may be deteriorated or
rendered non-existent by an amount of heat which might not be adequate
to decompose the organic matter itself.
It is all the more necessary to call attention to these two
considerations, because M. Pasteur invariably speaks as though it
had been established that the air contains multitudes of living
_Bacteria_, when, really, he had only proved that the air contains
a number of corpuscles resembling spores of fungi, &c. And, as I
have already intimated, the existence of spores of fungi in the
atmosphere, however well established, is of little or no importance as
an explanation of the cause of a very large number of fermentations.
Their presence is even of still less importance, owing to the fact of
the co-existence with these fungus-spores, of multitudes of organic
fragments, which--in accordance with the views of Liebig, Gerhardt,
and other chemists--are capable of acting as ferments. To this latter
consideration M. Pasteur never even alludes when he speaks (_loc. cit._
p. 40) of his “ensemencements,” and of other experiments which are
equally, or even more, capable of being interpreted in accordance with
Liebig’s views than with his own.
Bearing these considerations in mind, we shall be in a better position
to enquire into the real interpretation that may be given to many of
M. Pasteur’s results, and into the question as to how far the facts
which he records are favourable to his own, or to the adverse doctrine
concerning the causes of fermentation.
* * * * *
In the memoir so often alluded to on “The Organized Corpuscles which
exist in the Atmosphere,” M. Pasteur adduced various kinds of evidence,
tending, as he thought, to show that the first _Bacteria_ which make
their appearance in putrefying or fermenting solutions, have been
derived from living _Bacteria_ or their “germs,” which pre-existed in
the atmosphere.
Some of the experiments by which he endeavoured to substantiate this
position were of a very simple nature. Their narration attracted much
attention at the time, as it was supposed that by their means M.
Pasteur had--as he professed--conclusively shown the erroneousness
of the views of those who believed in what was called “spontaneous
generation.” These experiments were soon repeated by other observers,
who, using different fluids, obtained quite opposite results. Thus it
became obvious to impartial critics, that whilst the means adopted by
M. Pasteur might be adequate to check the processes of fermentation or
putrefaction in certain fluids, they were quite powerless to effect
this when many other fluids were employed.
These particular experiments, however, still seem to exercise a very
great influence on the minds of many in this country, who are either
unaware of, or disbelieve in, the possibility of obtaining opposite
results.
The chapter in which M. Pasteur detailed these experiments is thus
entitled:--“_Another very simple method of demonstrating that all the
organized products of Infusions (previously heated) owe their origin
to the corpuscles which exist suspended in the Atmosphere._” Whilst
claiming to have already rigorously established the validity of this
conclusion by the experiments described in previous chapters, M.
Pasteur adds:--“If there remained the least doubt on this subject, in
the mind of the reader, it would be dissipated by the experiments of
which I am now about to speak.” (p. 66.)
Sweetened yeast-water, urine, infusions of pear and of beetroot, were
placed in flasks with long necks, variously drawn out and bent. The
flasks were subsequently treated as follows. M. Pasteur says:--“I then
raise the liquid to the boiling-point for several minutes until steam
issues abundantly from the extremity of the drawn-out neck of the
flask, which is permitted to remain open. I then allow the flask to
cool. But, singular fact--and one well calculated to astonish every one
acquainted with the delicacy of the experiments relating to what is
called ‘spontaneous generation’--the liquid of this flask will remain
indefinitely without alteration. The flask may be handled without any
fear, it may be transported from place to place, allowed to experience
all the seasonal variations of temperature, and its liquid does not
undergo the slightest alteration, whilst it preserves its odour and
its taste.” If, however, the neck of one of these flasks be broken
off close to the flask itself, then, according to M. Pasteur, the
previously unaltered fluid will, in a day or two, undergo the ordinary
changes, and swarm with _Bacteria_ and _Mucedineæ_.
“The great interest of this method is,” M. Pasteur adds, “that it
completes, unanswerably, the proof that the origin of life in infusions
which have been raised to the boiling point, is solely due to the
solid particles[23] which are suspended in the air.” He believes that
any living things pre-existing in the fluid itself would be destroyed
by the high temperature to which it had been raised; and that those
contained in the air of the flask would also be destroyed, if not
expelled, by the process of ebullition. Believing that the air is
the source of germs from which Life is first developed in infusions,
he thinks that what rapidly enters at first, on the cessation of
ebullition, has its germs destroyed by contact with the almost boiling
liquid; whilst the air which enters subsequently, and more slowly, is
supposed to deposit its germs in the various flexures of the tubes,
so that none are able to reach the fluid itself. Infusions, thus
protected, do not undergo putrefaction, says M. Pasteur, because the
access of pre-existing living things is necessary for the initiation of
this change, and such access is prevented by the tortuous and bent neck
of the flask.
[23] As expressed, the proposition may be an approximation to the
truth. M. Pasteur, however, really endeavours to lead his readers to
believe that the “solid particles” which are efficacious, are, in all
cases, living “germs.”
Others say that _some_ fluids submitted to the conditions mentioned,
will undergo putrefactive changes, and that, therefore, these
experiments of M. Pasteur are utterly incapable of settling the general
question as to the cause of fermentation and putrefaction, and also
that concerning the origin of Life. Although acknowledging a certain
difficulty in explaining the results which are sometimes attained by
this method, some of us would rather confess this than confidently
offer explanations--as M. Pasteur did--which may in a short time be
stultified by the results of other experiments with different fluids.
Having previously shown[24] that living things could appear and
multiply in such a flask as M. Pasteur describes--in any flask, in
fact,--which had been hermetically sealed during the ebullition of a
suitable fluid within; this was deemed to be a result so contradictory
to the explanations of M. Pasteur, that it appeared needless to add
my testimony, as I could have done, to that of M. Victor Meunier
and others, as to the different results obtainable by operating, in
M. Pasteur’s fashion, with different fluids. It seemed to me that
if organisms were to be procured in flasks from which air had been
altogether expelled, it was useless still to urge the preservative
virtues of any process of filtration of air--with the object of showing
that living things in infusions derived their origin from atmospheric
germs. Obviously, if there were no atmosphere, there could be no
atmospheric germs present; and if living things were, nevertheless,
developed under these exclusive circumstances, how could M. Pasteur or
his disciples still expect to convince others that the first living
things in infusions always proceeded from pre-existing atmospheric
germs--even although it could be shown, that in many cases, when these
were filtered off by flasks with narrow and tortuous necks, no living
things were developed in such fluids. Granting to the full the truth
of such facts, they could do nothing to establish the doctrine of the
origin of infusorial life from pre-existing atmospheric germs, so long
as it could also be shown that living things might be developed in
boiled solutions to which air, instead of being filtered, was never
allowed to enter at all.
[24] ‘Nature,’ 1870, No. 36, p. 193.
It is not, therefore, because I think that some of the experiments
which will subsequently be related afford any stronger or more direct
support to my own conclusions, but because I think they may do this
indirectly--by shaking the faith of many in some of the reasonings of
M. Pasteur--that I am induced to give an account of them.[25]
[25] If his reasonings can be shown to be quite inconclusive, and if
his results can be otherwise explained, some people may, at last, begin
to recognize that their blind and mistaken faith in M. Pasteur’s work
has been somewhat misplaced.
What has been hitherto said, also applies to the more recent statements
concerning the efficacy of cotton-wool as an agent for filtering germs
from the atmosphere. Prof. Huxley says he has never seen putrefaction
or fermentation occur after certain organic fluids have been boiled
for ten or fifteen minutes, if a good plug of cotton-wool has been
inserted into the neck of the flask in which they are contained whilst
ebullition is going on, and has, subsequently, been allowed to remain
in the same situation. Using other or perhaps stronger fluids, however,
I have found that such a method of proceeding is by no means adequate
to stop the growth and development of organisms. And, also, even if it
had been always efficacious--the reason adduced could not hold good, in
the face of my other experiments, which had shown that a development
of life might go on in cases where the air, which had been similarly
driven out, was subsequently, in place of being filtered, prevented
from gaining access to the fluid.
If germs derived from the air are the sole causes of putrefaction,
then, surely, deprivation from air ought to be just as efficacious as
any process of filtration of air--more especially when the filtration
or the deprivation have a common starting point. And the mode of
procedure, in both cases, is precisely the same up to a certain point.
A fluid is boiled for a short time in order to kill the germs which may
be within the flask, and to expel its previously contained air. At a
certain stage of the ebullition, this may be arrested, if we have to do
with a bent-neck flask, or one whose neck is plugged with cotton-wool,
and no change, it is said, will subsequently take place in the
contained fluid, because the air which enters is, by either of these
means, filtered from its germs. But if, whilst ebullition continued,
the neck of the flask had been hermetically sealed--so as altogether
to prevent the re-ingress of air--and if the fluid, thus contained _in
vacuo_, would nevertheless undergo fermentation, obviously the former
explanation must be altogether shelved.
In the face of M. Pasteur’s explanations, and those of Professor
Huxley, these frequent positive results with fluids contained _in
vacuo_ are absolutely contradictory. There may naturally arise,
therefore, a very grave doubt as to the validity of the explanation
adduced by M. Pasteur, and adopted by Professor Huxley and others.
All these experiments to which I have been alluding are based upon the
supposition (assented to by Pasteur and Huxley) that _Bacteria_ which
pre-existed in the solution would certainly be destroyed by its being
raised for a few minutes to a temperature of 212° F. This conclusion
is, I believe, perfectly correct,[26] and in support thereof I will
adduce the following additional information.
[26] M. Pasteur attempted to make a distinction in the case of slightly
alkaline or neutral fluids (loc. cit., pp. 60–65). I have endeavoured
to show the untenability of his conclusion in ‘Nature,’ 1870, No. 37,
pp. 224–227.
_Limits of ‘Vital Resistance’ to Heat displayed by Bacteria and Torulæ._
After stating elsewhere[27], that _Vibriones_ are partly broken up
or disintegrated by an exposure for a few minutes to a temperature
of 212° F. in an infusion which is being boiled, and also that, in
all probability, the life of _Bacteria_ would be destroyed by such a
treatment, I made the following remarks:--“With reference to these
organisms, however, one caution is necessary to be borne in mind by
the experimenter. The movements of monads and Bacteria may be, and
frequently are, of two kinds. The one variety does not differ in the
least from the mere molecular or Brownian movement, which may be
witnessed in similarly minute, not-living particles immersed in fluids.
Whilst the other seems to be purely vital--that is, dependent upon
their properties as living things. These vital movements are altogether
different from the mere dancing oscillations which not-living particles
display, as may be seen when the monad or Bacterium darts about over
comparatively large areas, so as frequently to disappear from the
field. After an infusion has been exposed for a second or two to the
boiling temperature, these vital movements no longer occur, though
almost all the monads and Bacteria may be seen to display the Brownian
movement in a well-marked degree. They seem to be reduced by the
shortest exposure to a temperature of 100° C. to the condition of mere
not-living particles, and then they become subjected to the unimpaired
influence of the physical conditions which determine these movements.”
I now have various facts to add in confirmation of these conclusions,
and in extension of our knowledge concerning the vital resistance to
heat of _Bacteria_ and _Torulæ_.
[27] ‘Nature,’ 1870, No. 35, p. 171.
It would be a most important step if we could ascertain some means
by which these primary movements of living _Bacteria_ might be
distinguished from the secondary, or communicated, movements of
not-living particles. In many cases, organisms that are truly living
may only exhibit very languid movements, which, as movements, are quite
indistinguishable from those that the same _Bacteria_ may display
when they are really dead. Because the movements, therefore, are of
this doubtful character, persons are apt, unfairly, to argue that
the _Bacteria_ which present them, are no more living than are the
minute particles of carbon obtained from the flame of a lamp, which
may exhibit similar movements. This, however, is a point of view which
becomes obviously misleading if too much stress is laid upon it; and
it is more especially so in this case, when those _Bacteria_ which
display the most characteristic sign of vitality--viz., “spontaneous”
division or reproduction--do, at the time, almost always exhibit only
the same languid movements. Mobility is, in fact, not an essential
characteristic of living _Bacteria_, whilst _the occurrence of the
act of reproduction is the most indubitable sign of their life_. It
should be remembered, therefore, that any _Bacteria_ which are almost
motionless, or which exhibit mere Brownian movements, _may_ be living,
whilst those which spontaneously divide and reproduce, are certainly
alive--whatever may be the kind of movement they present.
In any particular case, however, can we decide whether _Bacteria_,
that have been submitted to a given temperature, and which exhibit
movements resembling those known as Brownian, are really dead or
living? If the movements are primary, or dependent upon the inherent
molecular activity of the organism itself, they ought, it might be
argued, to continue when the molecules of the fluid are at rest;
if, on the other hand, they are mere secondary or communicated
movements, impressed upon the organisms as they would be upon any
other similarly minute particles, by the molecular oscillations of
the fluid in which they are contained, then the movements ought to
grow less, and gradually cease, as the fluid approaches a state of
molecular rest--if this be attainable. Following out this idea,
some months ago, I first tested the correctness of the assumption
by experimenting with fluids containing various kinds of not-living
particles; such as carbon-particles from the flame of a lamp, or
freshly precipitated baric sulphate. However perfect may have been the
Brownian movements when portions of these fluids were first examined
beneath a covering-glass, they always gradually diminished, after the
specimen had been mounted by surrounding the covering-glass with some
cement or varnish. Thus prepared, no evaporation could take place from
the thin film of fluid, and after one, three, four, or more hours--the
slide remaining undisturbed--most of the particles had subsided, and
were found to have come to a state of rest. In order still further to
test these views, I took an infusion of turnip, containing a multitude
of _Bacteria_ whose movements were of the languid description, and
divided it into two portions. One of these portions was boiled for
about a minute, whilst the other was not interfered with. Then,
after the boiled solution had been cooled, a drop was taken from
each and placed at some little distance from one another on the same
glass slip; covering-glasses half an inch in diameter were laid
on, and the superfluous fluid beneath each was removed by a piece
of blotting-paper. When only the thinnest film of fluid was left,
the covering-glasses were surrounded by a thick, quickly-drying
cement.[28] Examined with the microscope immediately afterwards, it was
generally found that the _Bacteria_ which had been boiled presented a
shrunken and shrivelled aspect--whilst some of them were more or less
disintegrated--though, as far as movement was concerned, there was
little to distinguish that which they manifested, from that of their
plumper-looking relatives which had not been boiled.
[28] I always employ a solution of gum mastic and bismuth in
chloroform. If a different varnish be employed, it is of course
necessary to ascertain whether its application is injurious to the
enclosed _Bacteria_.
If the specimens were examined again after twenty-four or more hours,
there was still very little difference perceptible between them, as
regards their movements. And the same was the case when the specimens
were examined after a lapse of some days or weeks. One important
difference does, however, soon become obvious. The _Bacteria_ which
have not been boiled, undergo a most unmistakeable increase within
their imprisoned habitat; whilst those which have been boiled, do not
increase. The two films may be almost colourless at first (if the
_Bacteria_ are not very abundant), but after a few days, that composed
of unboiled fluid begins to show an obvious and increasing cloudiness,
which is never manifested by the other. Microscopical examination shows
that this cloudiness is due to a proportionate increase in the number
of _Bacteria_.
Is the continuance of the movements of the organisms which had been
boiled attributable to their extreme lightness, and to the slight
difference between their specific gravity and that of the fluid in
which they are immersed? I soon became convinced that this was one,
if not the chief reason, when I found that _Bacteria_ which had been
submitted to very much higher temperatures, behaved in precisely the
same manner as those which had been merely boiled, and also that
other particles which--though obviously dead--had a similar specific
lightness, also continued to exhibit their Brownian movements for
days and weeks. This was the case more especially with the minute fat
particles in a mounted specimen of boiled milk,[29] and also with very
minute particles which were gradually precipitated[30] from a hay
infusion that had been heated to 302° F. for four hours. Trials with
many different substances, indeed, after a time convinced me that the
most rapid cessation of Brownian movements in stationary films,[31]
occurred where the particles were heavy or large; and that the
duration of the movement was more and more prolonged, as the particles
experimented with, were lighter or more minute. So that, when we have
to do with _Bacteria_, the minute oil globules of milk, or with other
similarly light particles, the movements continue for an indefinite
time, and are, in part, mere exponents of the molecular unrest of the
fluid. They are always capable of being increased or renewed by the
incidence of heat or other disturbing agencies.
[29] If an unboiled specimen of milk be mounted, a multiplication of
living particles takes place here and there amongst the fat globules,
just as the multiplication of _Bacteria_ occurs in a vegetable
infusion; but in the boiled specimen no trace of such multiplication
can ever be detected.
[30] Those particles which come to rest, in such cases, are always in
contact with one or other of the contiguous surfaces of glass.
[31] The specific gravity of the fluid being constant. Where this is
dense or viscid, as with glycerine, Brownian movements do not occur at
all.
In respect of the movements which they may exhibit, therefore, really
living, though languid, _Bacteria_, cannot always be discriminated from
dead _Bacteria_. Both may only display mere Brownian movements.
It becomes obvious, then, that in doubtful cases we ought not to rely
very strongly upon the character of their movements, as evidence of the
death of _Bacteria_--although these may frequently be of so extensive a
nature as to render it not at all doubtful whether the _Bacteria_ which
display them are living. In the experiments which I am about to relate,
we shall be able to pronounce that the _Bacteria_ are living or dead,
by reference to the continuance or cessation of their most essentially
vital characteristic. If _Bacteria_ fail to multiply in a suitable
fluid, and under suitable conditions, we have the best proof that can
be obtained of their death.
Having made many experiments with solutions of ammonic tartrate
and sodic phosphate, I have almost invariably observed that such
solutions--when exposed to the air without having been boiled--become
turbid in the course of a few days owing to the presence of myriads
of _Bacteria_ and _Vibriones_, with some _Torulæ_. These organisms
seem to appear and multiply in such a solution almost as readily as
they do in an organic infusion. On the other hand, having frequently
boiled such solutions, and closed the flasks during ebullition, I have
invariably found, on subsequent examination of these fluids, that
whatever else may have been met with, _Bacteria_ and _Vibriones_ were
always absent. The difference was most notable, and it seemed only
intelligible on the supposition that any living _Bacteria_ or dead
ferments which may have pre-existed in the solution, were deprived of
their virtues by the preliminary boiling. These experiments also seemed
to show that such solutions, after having been boiled, and shut up in
hermetically-sealed flasks, from which all air had been expelled, were
quite incapable of giving birth to _Bacteria_. The unboiled fluid,
exposed to the air, might have become turbid, because it was able to
nourish any living _Bacteria_ which it may have contained, or because
it was capable of evolving these _de novo_, under the influence of dead
ferments whose activity had not been destroyed by heat. Hence we have
a fluid which is eminently suitable for testing the vital resistance
of _Bacteria_,--one which, although quite capable of nourishing and
favouring their reproduction, does not appear capable of evolving them,
when, after previous ebullition, it is enclosed in a hermetically
sealed flask from which all air has been expelled. Three flasks were
half-filled with this solution.[32] The neck of the first (_a_) was
allowed to remain open, and no addition was made to the fluid. To the
second (_b_), after it had been boiled and had become cool, was added
half a minim of a similar saline solution, which had been previously
exposed to the air, and which was quite turbid with _Bacteria_,
_Vibriones_ and _Torulæ_. From this flask--after its inoculation with
the living organisms--the air was exhausted by means of an air-pump,
and its neck was hermetically sealed during the ebullition of the
fluid, without the flask and its contents having been exposed to a heat
of more than 90° F. The third flask (_c_) was similarly inoculated with
living _Bacteria_, although its contents were boiled for ten minutes
(at 212° F.), and its neck was hermetically sealed during ebullition.
The results were as follows:--the solution in the first flask (_a_),
became turbid in four or five days; the solution in the second (_b_),
became turbid after thirty-six hours; whilst that in the third flask
(_c_), remained perfectly clear. This latter flask was opened on the
twelfth day, whilst its contents were still clear, and on microscopical
examination of the fluid no living _Bacteria_ were to be found. This
particular experiment was repeated three times with similarly negative
results, although on two occasions the fluid was only boiled for one
minute instead of ten.
[32] In the proportion of ten grains of neutral ammonic tartrate, with
three grains of neutral sodic phosphate, to an ounce of distilled water.
It seemed, moreover, that by having recourse to experiments of the
same kind, the exact degree of heat, which is fatal to _Bacteria_
and _Torulæ_ might be ascertained. I accordingly endeavoured to
determine this point. Portions of the same saline solution, after
having been boiled[33] and allowed to cool, were similarly inoculated
with a drop[34] of very turbid fluid, containing hundreds of living
_Bacteria_, _Vibriones_, and _Torulæ_. A drying apparatus was fixed to
an air-pump, and the flask containing the inoculated fluid was securely
connected with the former by means of a piece of tight india-rubber
tubing,[35] after its neck had been drawn out and narrowed, at about
two inches from the extremity. The flask containing the inoculated
fluid was then allowed to dip into a beaker holding water at 122° F.,
in which a thermometer was immersed. The temperature of the fluid was
maintained at this point for fifteen minutes,[36] by means of a spirit
lamp beneath the beaker. The air was then exhausted from the flask by
means of the pump, till the fluid began to boil; ebullition was allowed
to continue for a minute or two, so as to expel as much air as possible
from the flask, and then, during its continuance, the narrowed neck
of the flask was hermetically sealed by means of a spirit-lamp flame
and a blowpipe. Other flasks were similarly prepared, except that
they were exposed to successively higher degrees of heat--the fluid
being boiled off, in different cases, at temperatures of 131°, 140°,
149°, 158°, and 167° F. All the flasks being similarly inoculated with
living _Bacteria_, _Vibriones_, and _Torulæ_, and similarly sealed
during ebullition, they differed from one another only in respect to
the degree of heat to which they had been submitted. Their bulbs were
subsequently placed in a water bath, which during both day and night
was maintained at a temperature of from 85° to 95° F. The results have
been as follows:--The flasks whose contents had been heated to 122° and
131° F. respectively, began to exhibit a bluish tinge in the contained
fluid after the first or second day; and after two or three more days,
the fluid in each became quite turbid and opaque, owing to the presence
and multiplication of myriads of _Bacteria_, _Vibriones_ and _Torulæ_;
the fluids in the flasks, however, which had been exposed to the higher
temperature of 140°, 149°, 158°, and 167° F., showed not the slightest
trace of turbidity, and no diminution in the clearness of the fluid
while they were kept under observation--that is, for a period of twelve
or fourteen days. One kind of conclusion only is to be drawn from
these experiments, the conditions of which were in every way similar,
except as regards the degree of heat to which the inoculated fluids
were subjected--seeing that the organisms were contained in a fluid,
which had been proved to be eminently suitable for their growth and
multiplication.[37] If inoculated fluids which have been raised to 122°
and 131° F. for ten minutes, are found in the course of a few days to
become turbid, then, obviously, the organisms cannot have been killed
by such exposure; whilst, if similar fluids, similarly inoculated,
which have been raised to temperatures of 140°, 149°, 158°, and 167° F.
remain sterile, such sterility can only be explained by the supposition
that the organisms have been killed by exposure to these temperatures.
[33] It was necessary to boil the solution first, in order to destroy
any living things or dead ferments which it might contain. It must
contain one or the other, because an unboiled solution of this kind,
in a corked bottle about half full, will always become turbid; whilst,
after it has been boiled, it may be kept indefinitely under similar
conditions without becoming turbid.
[34] The proportion was one drop of the fluid, opaque with organisms,
to an ounce of the clear solution.
[35] Into which a piece of glass tube had been slipped to prevent
collapse.
[36] Allowing even five minutes for the temperature of the 1 oz. of
fluid to become equal to that of the bath, it would then have remained
exposed to this amount of heat for about ten minutes.
[37] Fluids which had remained sterile would always, in the course
of thirty-six or forty-eight hours after inoculation with living
_Bacteria_, become more or less turbid.
Some of these experiments have been repeated several times with the
same results. On three occasions, I have found the fluid speedily
become turbid, which had only been exposed to 131° F. for ten minutes,
whilst on three other occasions I have found the inoculated fluid
remain clear, after it had been exposed to a heat of 140° F. for ten
minutes.[38]
[38] There is, however, another point of extreme interest in
connection with these experiments, bearing upon the supposed universal
distribution of “germs” of _Bacteria_ and other organisms, which I will
now mention. One of the flasks, which had been exposed to 140° F., and
which had been hermetically sealed at this temperature, had its neck
cracked (accidentally) about half an hour afterwards. Thinking it would
be as well, notwithstanding this, to keep it and observe the result,
its bulb was immersed in the same water-bath with the other flasks
which had been prepared at the same time. Whilst the fluid in one of
these which had been exposed to a heat of 131° F., became turbid in
the course of a few days, this, which had been exposed to a heat of
140° F. and whose neck was also extensively cracked, remained quite
clear for seven days, although to such an extent exposed to the access
of germs. Its eminent suitability for nourishing the germs of such
organisms was also shown, because, on the seventh day, the fluid being
still clear, the blade of a penknife was dipped into it, after having
been previously immersed in a solution containing living _Bacteria_ and
_Torulæ_, and in thirty-six hours after this inoculation, the fluid had
become turbid, owing to the presence of myriads of these organisms.
So that even where obvious cracks occur, and the vacuum is altogether
impaired by the consequent inrush of air, such air does not necessarily
carry with it germs of _Bacteria_--which have been supposed to be
universally diffused, and capable of passing through cracks so minute
as to be invisible. These results, important as they are, have not at
all surprised me, because one may frequently find a previously boiled
solution of the kind under consideration, remaining free from turbidity
for two weeks or more, although the neck of the flask has been merely
covered by a loose paper-cap (see p. 30).
In experimenting upon rather higher organisms, with which there is
little difficulty in ascertaining, by microscopical examination,
whether they are living or dead, I have found that an exposure even to
the lower temperature of 131° F. for five minutes, always suffices to
destroy all signs of life in Vibrios, Amœbæ, Monads, Chlamydomonads,
Euglenæ, Desmids, Vorticellæ, and all other Ciliated Infusoria which
were observed, as well as in free Nematoids, Rotifers, and other
organisms contained in the fluids which had been heated.
These results are quite in harmony with the observations and
experiments of M. Pouchet and of Professor Wyman, as to the capability
of resisting heat displayed by _Vibriones_ and all kinds of ciliated
infusoria. According to the former,[39] the majority of ciliated
infusoria are killed at, or even below, the temperature of 122° F.,
whilst large _Vibriones_ are all killed at a temperature of 131° F.[40]
According to the observations of Professor Wyman, the motions of
all ciliated infusoria are stopped at less than 130° F., whilst
_Vibriones_, taken from the most various sources, also seemed to be
killed at temperatures between 130°–136.4° F. Similarly, we find
Baron Liebig quite recently making the following remarks concerning
a species of _Torula_:--“A temperature of 60° C. [140° F.] kills
the yeast cells; after exposure to this temperature in water, they
no longer undergo fermentation, and do not cause fermentation in a
sugar solution.... In like manner, active fermentation in a saccharine
liquid is stopped when the liquid is heated to 60° C., and it does not
recommence again on cooling the liquid.”
[39] ‘Nouvelles Expériences,’ etc., 1864, p. 38.
[40] ‘American Journal of Science and Arts,’ Oct. 1867.
That the organisms in question--being minute naked portions of living
matter--should be killed by exposure to the influence of a fluid at
these temperatures will perhaps not seem very improbable to those who
have attempted to keep their fingers for any length of time in water
heated to a similar extent. With watch in hand I immersed my fingers in
one of the experimental beakers containing water at 131° F., and found
that, in spite of my desires, they were hastily withdrawn, after an
exposure of less than _five-and-twenty seconds_.
Wishing to ascertain what difference there would be if the inoculated
fluids were exposed for a very long time, instead of for ten minutes
only, to certain temperatures, I prepared three flasks in the same
manner--each containing some of the previously boiled solution, which,
when cold, had been inoculated with living _Bacteria_, _Vibriones_,
and _Torulæ_. These flasks and their contents were then submitted to
the influence of the following conditions:--One of them was heated for
a few minutes in a beaker containing water at 113° F., and then by
means of the air-pump a partial vacuum was procured, till the fluid
began to boil. After the remainder of the air had been expelled by
the ebullition of the fluid, the neck of the flask was hermetically
sealed, and the flask itself was subsequently immersed in the water of
the beaker, which was kept for four hours at a temperature between 113°
and 118-1/2° F.[41] The two other flasks similarly prepared were kept
at a temperature of 118-1/2° - 127-1/2° F. for four hours. In two days,
the fluid in the first flask became slightly turbid, whilst in two days
more the turbidity was most marked. The fluid in the two other flasks
which had been exposed to the temperature of 118-1/2° - 127-1/2° F.
for four hours, remained quite clear and unaltered during the twelve
days in which they were kept in the warm bath under observation.
These experiments seem to show, therefore, that the prolongation of
the period of exposure to four hours, suffices to lower the vital
resistance to heat of _Bacteria_ and _Torulæ_ by 14-1/2° - 18° F.
[41] During nearly the whole of the time the temperature was kept at
113° F. It only rose to the higher temperature for about ten minutes.
Such experiments would seem to be most important and crucial in their
nature. They may be considered to settle the question as to the vital
resistance of these particular _Bacteria_, whilst other evidence points
conclusively in the direction that all _Bacteria_, whencesoever they
have been derived, possess essentially similar vital endowments[42].
Seeing also that the solutions have been inoculated with a drop of a
fluid in which _Bacteria_, _Vibriones_, and _Torulæ_ are multiplying
rapidly, we must suppose that they are multiplying in their accustomed
manner, as much by the known method of fission, as by any unknown and
assumed method of reproduction. In such a fluid, at all events, there
would be all the kinds of reproductive elements common to _Bacteria_,
whether visible or invisible, and these would have been alike subjected
to the influence of the same temperature. These experiments seem
to show, therefore, that even if _Bacteria_ do multiply by means
of invisible gemmules as well as by the known process of fission,
such invisible particles possess no higher power of resisting the
destructive influence of heat than the parent _Bacteria_ themselves
possess. This result is, moreover, as I venture to think, in
accordance with what might have been anticipated _à priori_. _Bacteria_
seem to be composed of homogeneous living matter, and any gemmule,
however minute, could only be a portion of such living matter, endowed
with similar properties.
[42] The _Bacteria_ and _Vibriones_ with which Professor Wyman
experimented were derived from different sources; and so far as I also
have been able to ascertain, the _Bacteria_ of different fluids are
similarly affected by exposure to similar degrees of heat. Thus, if
on the same slip, though under different covering glasses, specimens
of a hay infusion, turbid with _Bacteria_, are mounted, (_a_) without
being heated, (_b_) after the fluid has been raised to 122° F. for
ten minutes, and (_c_) after the fluid has been heated to 140° F. for
ten minutes, it will be found that, in the course of a few days, the
_Bacteria_ under _a_ and _b_ have notably increased in quantity, whilst
those under _c_ do not become more numerous, however long the slide
is kept. Facts of the same kind are observable if a turnip infusion,
containing living _Bacteria_, is experimented with; and the phenomena
are in no way different if a solution of ammonic tartrate and sodic
phosphate (containing _Bacteria_) be employed instead of one of these
vegetable infusions. The multiplication of the _Bacteria_ beneath the
covering-glass, when it occurs, is soon rendered obvious, even to the
naked eye, by the increasing cloudiness of the film.
_Extent to which boiled Fermentable Fluids may be preserved in Vessels
with Bent Necks, or in those whose Necks are guarded by a Plug of
Cotton-Wool._
Having thus satisfied ourselves as to the truth of the conclusion that
_Bacteria_ are killed when the fluid containing them is boiled (at
212° F.), we are in a position to proceed with the inquiry as to the
evidence which exists in respect to the statements made by M. Pasteur,
Professor Huxley, and others, that fermentable fluids which have been
boiled, will not undergo fermentation, either in vessels whose necks
have been many times bent, or in those into whose necks a plug of
cotton-wool has been inserted during the ebullition of their contained
fluid. Organisms are not found in such cases, they say, because the
“germs” from which the low organisms of infusions are usually produced,
are arrested either in the flexures of the tube or in the cotton-wool.
As I have before stated, however, it is obvious that if this
explanation be the correct one, the preservation should be equally well
marked in all cases--quite irrespectively of the amount of albumenoid
or other nitrogenous material which may be contained in the fluid. Any
exceptions to the rule should at once suggest doubts as to the validity
of the explanation.
It was shown[43] in 1865 by M. Victor Meunier that some fluids were
preserved after having been boiled in a vessel of this kind, whilst
others, submitted to the same treatment, speedily became turbid
from the presence of _Bacteria_ and other organisms.[44] By these
experiments he ascertained that strong infusions did frequently change,
whilst weak ones might be preserved; and that even a strong infusion
might be prevented from undergoing change if the period of ebullition
were sufficiently prolonged.
[43] ‘Compt. Rend.,’ t. lxi. p. 1060.
[44] When boiled solutions, containing mannite, with a little nitrate
and phosphate of ammonia, were employed, they always remained sterile.
Similar negative results followed the employment of ox-gall. Of three
decoctions of beef with which M. Meunier experimented, the two stronger
of them were found to contain swarms of _Bacteria_ in about twelve
days. Of three other flasks containing boiled urine, two also proved
fertile.
The fluids most frequently employed by M. Pasteur were yeast-water, the
same sweetened by sugar, urine, infusion of beetroot, and infusion of
pear.
Taking urine as a fair example of such a fluid, I have found that
the statements of M. Pasteur and of Professor Lister are perfectly
correct. This fluid may generally remain for an indefinite period in
such vessels[45] without becoming turbid, or undergoing any apparent
change. The same is generally found to be the case with an infusion of
turnip, and occasionally an infusion of hay may be similarly prevented
from undergoing fermentation. On the other hand, if the turnip-solution
be neutralized by the addition of a little ammonic carbonate, or
liquor potassæ; or, better still, if even half a grain of new cheese
be added to the infusion before it is boiled, then I have found
that the fluid speedily becomes turbid, owing to the appearance of
multitudes of _Bacteria_. In an infusion to which a fragment of cheese
had been added, I have seen a pellicle form in three days, which, on
microscopical examination, proved to be composed of an aggregation
of _Bacteria_, _Vibriones_, and _Leptothrix_ filaments. A mixture of
albuminous urine and turnip-infusion has also rapidly become turbid
in a vessel of this kind owing to the appearance of multitudes of
_Bacteria_, and so has a mixture containing one-third of healthy urine
with two-thirds of infusion of turnip.
[45] I have employed flasks of about 1-1/2 oz. in capacity, provided
with necks two feet in length. In each case, after the flask has been
half filled with the fluid, the neck has been bent eight times at an
acute angle.
Other infusions have been boiled for ten minutes in a vessel with
a horizontal neck two feet long, into which, during ebullition, a
good plug of cotton-wool had been carefully pushed down for a depth
of twelve or fourteen inches, and cautiously increased in quantity
during the continuance of the ebullition; whilst immediately after the
withdrawal of the heat, the plug was pressed closer, and all the outer
unoccupied portion of the tube was rapidly filled up in the same manner.
Preserved in such a vessel, a specimen of urine remained unchanged;
a hay-infusion also underwent no apparent alteration; whilst a very
strong infusion of turnip became turbid in five days, and ultimately
showed a large quantity of deposit.[46]
[46] These are the only experiments which I have performed with the
very long plugs of cotton-wool, though in other previous trials with
plugs about 1-1/2 in. long, I have several times obtained positive
results.
Thus the rules laid down by Pasteur and others are not universal, and
therefore, as I have previously pointed out, the explanation which he
adduced of the preservation of those particular fluids which remained
unchanged is at once rendered doubtful. More especially is there
room for doubt on this subject when, as I have found, the result of
the experiment can be, within certain limits, predicated beforehand,
according to the nature of the fluid employed. If all organisms proceed
from pre-existing germs, and these can be filtered from the air by a
certain mechanical contrivance, then, if it be alleged that it is on
account of such filtration that certain boiled fluids do not change,
all fluids placed under these conditions ought, on this theory, to be
similarly preserved. Exceptional cases cannot be accounted for on this
hypothesis. To others, however, who say that organisms are capable of
arising _de novo_, and that fermentation can be initiated without the
agency of living things, the above facts appear quite natural. The more
complex the nitrogenous or protein materials contained in a solution,
the more is it fitted to undergo fermentative changes, which may be
accompanied by the _de novo_ origination of living things. Therefore
the above results are just as compatible with the notions of M. Liebig
and his school, as they are antagonistic to those of M. Pasteur.
Certain fluids, it is found, do not undergo change; whilst other
fluids, of a more complex description, will ferment under the influence
of similar conditions. Prolonged ebullition also, by breaking up some
of the more unstable compounds of a solution (those which most easily
initiate these changes) will retard or prevent its fermentation.
The complete untenability of M. Pasteur’s explanations are, however,
best revealed by having recourse to a series of comparative
experiments, in which portions of the same fluid are boiled for an
equal length of time in vessels of different kinds, and are then
subsequently submitted, in a water-bath, to the influence of the same
temperature.
I have made many experiments of this kind with different solutions,
some of which I will now record. Owing to the different behaviour of
the same fluids under different conditions, we are enabled to draw some
most important conclusions; and owing to the different behaviour of
different fluids under these respective conditions, our attention is
strongly drawn to other facts which ought considerably to influence our
judgment as to the relative merits of the two doctrines concerning the
cause of fermentation and putrefaction.
COMPARATIVE EXPERIMENTS.
In the following experiments, each fluid (unless a statement is made to
the contrary) was _boiled continuously for ten minutes_, after having
been placed in its flask. Then, with the neck either open, sealed, or
plugged, the bulb of the flask was immersed in a water-bath maintained
at a temperature of 80°–95° F., during both day and night.[47]
[47] When infusions have been employed, these have all been made as
strong as possible, and have been filtered before use. _Warm_ water
has been added in quantity just sufficient to cover the substance to
be infused (cut into very small pieces), and the mixture has then been
kept at a temperature of from 110°–130° F. for three or four hours.
FIRST SET OF EXPERIMENTS (I.–XV.).
_a. Fluid exposed to Air in a Flask with a short Open Neck._
*No. I.--Urine* in twenty-four hours was still clear and free from
deposit. In forty-four hours the fluid was very slightly turbid, and on
microscopical examination _Bacteria_ and _Torulæ_ were found, though
not in very great abundance. In sixty-eight hours the fluid was quite
turbid.
*No. II.--Hay Infusion* in twenty-four hours was still clear. In
forty-four hours the fluid was very turbid, and a drop on examination
showed multitudes of _Bacteria_ of different kinds, exhibiting languid
movements. In sixty-eight hours the turbidity had become much more
marked, and there was also a certain amount of sediment.
*No. III.--Turnip Infusion* in twenty-four hours showed a very slight
degree of turbidity. A drop examined microscopically revealed a number
of very minute, but very active, _Bacteria_. In forty-four hours the
turbidity had become very well marked.
_b. Fluid in contact with Ordinary Air and its Particles; Neck of Flask
Sealed after the Fluid had become Cold._
*No. IV.--Urine* remained quite bright and clear during the fifteen
days in which it was kept under observation in the water-bath.[48]
*No. V.--Hay Infusion* after forty-four hours showed a well-marked
turbidity. In sixty-eight hours there was an increase in the amount of
turbidity, and also some sediment. During the next forty-eight hours
turbidity and sediment gradually increased, whilst the colour of the
fluid (originally that of port wine) became several shades lighter.
Except that it grew still lighter in colour, and that the amount of
sediment increased, it underwent no further obvious change during the
fifteen days in which it remained in the bath.[48]
*No. VI.--Turnip Infusion* underwent no change during the fifteen days
in which it was kept in the bath under observation.[48]
_c. Fluid in a Flask with a Neck two feet long, and having Eight acute
Flexures._
*No. VII.--Urine* remained quite bright and clear during the fifteen
days in which it was kept under observation in the water-bath.[48]
[48] Flask still in my possession, unopened.
*No. VIII.--Hay Infusion* remained bright and clear for twelve days.
On the thirteenth day a very slight (almost inappreciable) sediment
was seen, which scarcely underwent any obvious increase during the
next eight days, though on the two following days (twenty-second and
twenty-third) the turbidity became most obvious: much sediment was
deposited, and the fluid assumed a much lighter colour.[49] (On the
twenty-second day the temperature of the bath was raised to 100° F.,
for two or three hours.)
[49] Flask still in my possession, unopened.
*No. IX.--Turnip Infusion* remained for four days without undergoing
any apparent change. Its neck was then accidentally broken at the
fourth joint--a certain amount of fluid still filling the third joint.
In this condition the flask was allowed to remain in the water-bath,
and the fluid continued quite unchanged in appearance for five days. It
was then boiled[50] for three minutes, and the neck of the flask was
_hermetically sealed_ whilst the fluid was boiling. The flask being
re-immersed in water-bath, the fluid continued quite clear for thirteen
days. Its neck was then carefully heated in the spirit-lamp flame till,
when red-hot, the rapid inbending of the glass showed that the vacuum
was still preserved. This being ascertained, the flask was, after a few
minutes, replaced in the bath. The next day the temperature of the bath
was allowed to go up to 100° F. for three or four hours, and in the
evening the fluid was observed to be very slightly turbid. In two days
more (_i.e._, after sixteen days _in vacuo_) the turbidity was well
marked, and when the fluid was examined microscopically it was found
to contain an abundance of very languid _Bacteria_ and _Vibriones_.
On opening the flask there was an outrush of very fœtid gas, and the
reaction of the fluid was acid.[51]
[50] The vapour had lost all odour of turnip. Some of the fluid which
splashed over was found to be still slightly acid.
[51] This experiment is very interesting in two or three respects. A
neck of half the usual length--with only four bendings--sufficed to
preserve the fluid for several days; and when this fluid (which had
been in the bent-neck apparatus for nine days) was sealed up in the
same flask during ebullition, it remained _in vacuo_ for thirteen
days without undergoing any apparent change, and then only became
turbid under the influence of a higher temperature. Yet some of the
same fluid, in a flask which was hermetically sealed during the first
ebullition (No. XV.) behaved as such an infusion usually does, and
became quite turbid in forty-eight hours.
_d. Fluid in a Flask having a Neck two feet long, bent at right angles
shortly above the bulb, and provided with a firm Plug of Cotton-Wool
twelve inches in length._
*No. X.--Urine* remained quite bright and clear during the fifteen days
in which it was kept under observation in the water-bath.[52]
*No. XI.--Hay Infusion* showed a very slight amount of sediment after
forty-four hours, which seemed to increase somewhat during the next
three days. The fluid afterwards appeared to undergo no further change,
though it remained in the warm water-bath for fifteen days.[52]
*No. XII.--Turnip Infusion* in four days showed a well-marked
turbidity, and also very many flakes of a broken pellicle.[52]
[52] Flask still in my possession, unopened.
_e. Fluid (in vacuo) in a Flask, the Neck of which was hermetically
Sealed by means of the Blowpipe Flame during Ebullition._
*No. XIII.--Urine* in forty-four hours showed a very slight amount
of sediment. During the next two days the sediment very slightly
increased, but was still small in amount. At the expiration of fifteen
days, no further increase in the turbidity having taken place, the
fluid was examined. The vacuum was still partially preserved, as
evidenced by the rapid inbending of a portion of the neck of the flask
after it had been carefully made red-hot. When opened, the odour of
the fluid was stale, but not fœtid, and its reaction was still faintly
acid. On microscopical examination _Bacteria_ and _Torulæ_ were found
in tolerable abundance.
*No. XIV.--Hay Infusion* in forty-four hours showed a very slight
amount of turbidity. In sixty-eight hours the turbidity was most
marked, and there was also a small amount of sediment. In another
twenty-four hours it was noticed that the colour of the fluid had
become much lighter, whilst the turbidity and sediment had increased.
It subsequently continued in much the same state, and the flask
was opened on the sixteenth day. The vacuum was found to be almost
wholly impaired, whilst the odour of the fluid was sour, and not at
all hay-like. On microscopical examination _Bacteria_, _Vibriones_,
_Leptothrix_, and _Torulæ_, were found in abundance, and the former
were very active.
*No. XV.--Turnip Infusion* after forty-eight hours showed a well-marked
turbidity. In seventy-two hours the turbidity was more marked, and
there was a slight amount of sediment. The turbidity also increased
during the next twenty-four hours; though, after that, the infusion
seemed to undergo no further change. The flask remained in the warm
bath for fifteen days, when the fluid was examined. Its odour was not
fœtid, but was somewhat like that of baked turnip. _Bacteria_ and
_Vibriones_ existed in abundance, though their movements were extremely
languid.
SECOND SET OF EXPERIMENTS (XVI.–XXI.).
_b. Fluid in contact with Ordinary Air and its Particles; Neck of Flask
Sealed after the Fluid had become Cold._
*No. XVI.--Simple Turnip Infusion* in twenty-four hours had undergone
no apparent change. In thirty-six hours there was slight turbidity,
and in forty-eight hours this was most marked and uniform. When the
flask was opened, after seventy-two hours, there was an outrush of
very fœtid gas; the reaction of the fluid was acid, and, when examined
microscopically, it was found to contain multitudes of very languid
_Bacteria_.
*No. XVII.--Neutralized Infusion of Turnip + 1/2 gr. of Cheese*,[53]
in thirty-six hours showed a well-marked pellicle.[54] When the flask
was opened, after seventy-two hours, there was a violent outrush of
gas, though the fluid was still neutral. Portions of the thick pellicle
were found, on microscopical examination, to be made up of _Bacteria_,
_Vibriones_, and an abundance of long, interlaced _Leptothrix_
filaments. _Bacteria_ also existed abundantly in the fluid, though
their movements were very languid.
[53] The filtered infusion of turnip was neutralized by liquor potassæ.
The cheese (Cheddar) was new and not in the least mouldy.
[54] The fluid itself being somewhat opaque, the first stages of
increased turbidity from presence of _Bacteria_ could not be detected.
_c. Fluid in a Bent Neck Flask, having Eight acute Flexures._
*No. XVIII.--Simple Turnip Infusion* after forty-eight hours showed no
change. It was kept in water-bath for twelve days, and during the whole
of this time the fluid remained quite clear. The tube was then broken
1-1/2 inch above the bulb (which was re-immersed in the bath), _leaving
the fluid exposed to the air_ through the straight open tube. The fluid
at this time was odourless, and its re-action was still faintly acid.
The infusion remained thus exposed for six days without undergoing any
apparent change. On the eighth day a very slight whitish sediment was
noticed, which had increased in quantity by the tenth day, though there
was still no trace of general turbidity. On the eleventh day some of
the sediment was examined in a drop of the fluid, and it was found to
be wholly composed of rather large _Torulæ_ cells--the largest being
about 1/3000 in diameter, though all the smaller sizes were abundantly
represented. Not a single _Bacterium_ or _Vibrio_ could be detected,
and the fluid was still quite odourless.[55]
[55] This again is a most instructive experiment when compared with
Nos. XVI. and XX., in which portions of the same infusion were
employed. The results in No. IX. would lead us to believe that a
vegetable infusion which does not ferment, does, nevertheless,
undergo some changes in molecular composition, and this notion seems
to derive confirmation from the present experiment. Some of the same
solution which has been kept for a time (twelve days) from contact
with atmospheric particles, subsequently, even when fully exposed to
the air, undergoes no apparent change for six days, and then, instead
of becoming filled with _Bacteria_, swarms only with _Torulæ_. Yet
the infusion in this condition was perfectly capable of nourishing
_Bacteria_, as I subsequently proved by inoculating it. Why then was it
not inoculated by the living _Bacteria_, with which the air is thought
by some to be teeming?
*No. XIX.--Neutral Turnip Infusion + 1/2 gr. of Cheese*, showed no
perceptible change in twenty-four hours, though in thirty-six hours
there was a well-marked pellicle on the surface. When the neck of the
flask was broken after seventy-two hours, the fluid was found to be
very fœtid, whilst its re-action had become slightly acid. Portions of
the pellicle were found to be made up by aggregations of _Bacteria_,
_Vibriones_, and an abundance of _Leptothrix_ filaments. The _Bacteria_
all exhibited very languid movements.
_e. Fluid (in vacuo) in a Flask which had been Sealed during
Ebullition._
*No. XX.--Simple Turnip Infusion* in twenty-four hours showed a very
slight amount of turbidity; in thirty-six hours this had increased, and
in forty-eight hours there were multitudes of curdy flocculi floating
in a tolerably clear fluid. The flask was opened after seventy-two
hours, when there seemed to be only a very slight inrush of air. The
odour of the fluid was somewhat fœtid, and its re-action was acid.
There were multitudes of _Bacteria_ and _Vibriones_, partly separate
and partly aggregated (constituting the flocculi above mentioned). The
separate _Bacteria_ exhibited only very languid movements.
*No. XXI.--Neutral Turnip Infusion + 1/2 gr. of Cheese*, showed a
well-marked pellicle on its surface in twenty-four hours. In thirty-six
hours the first pellicle had, in great part, sunk to the bottom of
the flask, though its place on the surface was already taken by a new,
though thin, scum-like layer. After seventy-two hours, the flask was
opened; there was _no fœtid_ odour of the fluid, and its re-action was
_still neutral_. Examined microscopically the fluid showed an abundance
of Bacteria, and also of short monilated filaments. There were,
however, none of the ordinary kind of _Vibriones_, and no _Leptothrix_.
All the _Bacteria_ exhibited very languid movements.
THIRD SET OF EXPERIMENTS (XXII.–XXX.).
_a. Fluid exposed to Air in a Flask with a short Open Neck._
*No. XXII.--Urine* in twenty-four hours showed no change; though
in forty-six hours the turbidity was well marked.[56] Examined
microscopically it was found to contain an abundance of _Bacteria_.
[56] Some of the same fluid, exposed in a similar flask, without
previous boiling, became turbid in eight hours, and lighter in colour;
whilst, after twenty hours, the turbidity was extremely well-marked.
_b. Fluid in contact with Ordinary Air and its Particles; Neck of Flask
Sealed after the Fluid had become Cold._
*No. XXIII.--Urine* in eighteen hours showed a distinct pellicle,
though there was not much general turbidity. During the next few days
the old pellicle fell to the bottom, and a new one formed.
_c. Fluid in a Bent Neck Flask, having Eight acute Flexures._
*No. XXIV.--Urine* in forty-eight hours showed no change. After twelve
days there was still no general turbidity, though there was a slight
flocculent deposit of an uncertain nature. Two days afterwards the
flask was broken, when the odour of the fluid was still found to
resemble that of fresh urine, and its re-action was acid. The flocculi
were made up of granular aggregations, in the midst of which were a few
bodies closely resembling _Torulæ_, though they were somewhat doubtful
in nature. Neither _Bacteria_ nor _Vibriones_ could be found. The
flask, having a short open neck, was then replaced in the warm bath. In
sixteen hours the whole fluid had become turbid; it was also slightly
fœtid; and on microscopical examination it was found to be swarming
with _Bacteria_, _Vibriones_, and _Leptothrix_.
*No. XXV.--Turnip Infusion + 1/2 gr. of Cheese* in forty-eight hours
showed no change, though in seventy-two hours there was a well-marked
pellicle, in which some bubbles of gas were engaged. After ninety-six
hours the neck of the flask was broken; the fluid was found to be
fœtid, and it had an acid re-action. On microscopical examination,
a portion of the pellicle was seen to consist of multitudes of
_Bacteria_, _Vibriones_, and jointed _Leptothrix_ filaments.
*No. XXVI.--Simple Turnip Infusion* remained clear, and showed no
appreciable change for seven days. On the eighth day a slight general
turbidity of the fluid was noticed. On the ninth, the turbidity was
rather more marked, though there was no trace of a pellicle; the neck
of the flask having been broken, the fluid was found to be _odourless_
and very faintly acid. On microscopical examination, multitudes of
languid _Bacteria_ of medium size were found, and also short monilated
chains with from two to ten segments. There were no _Vibriones_,
_Leptothrix_ or _Torulæ_.[57]
[57] The condition of the fluid, and the nature of its contents, were
very similar to that met with in No. XXI.
_e. Fluid (in vacuo) in a Flask, Sealed during Ebullition._
*No. XXVII.--Healthy Urine* after twenty-four hours showed no change.
After eleven days there was still no apparent change, though on the
thirteenth a slight amount of flocculent sediment was noticed. This
deposit increased in amount, very slowly, during the next fortnight;
though afterwards the fluid seemed to undergo no further change, and
did not become generally turbid.[58]
[58] Still in my possession, unopened. In all probability the flocculi
which formed would be found to be similar in their microscopical, as
they certainly were in their naked-eye characters, to those met with in
No. XXXV.
*No. XXVIII.--Healthy Urine (1/3) and Filtered Turnip Infusion (2/3)*
after forty-eight hours showed a very slight turbidity, which, however,
became quite marked in another twenty-four hours.
*No. XXIX.--Albuminous Urine (1/3) and filtered Turnip Infusion (2/3)*
after twenty-four hours, showed a slight turbidity, which became much
more marked in forty-eight hours; whilst in seventy-two hours there was
a considerable deposit at the bottom of the flask.
*No. XXX.--Simple Turnip Infusion* showed no change in forty-eight
hours, though in seventy-two hours there was well-marked turbidity. The
turbidity and sediment continued to increase for several days, and both
were most marked on the tenth day, when the flask was opened. There
was an outrush of gas, having an extremely fœtid odour. The fluid
had an acid re-action, and when examined microscopically, multitudes
of _Bacteria_, _Vibriones_ and _Leptothrix_ filaments were found--the
movements of the _Bacteria_ being very languid.
FOURTH SET OF EXPERIMENTS (XXXI.–XXXVII.).
_b. Fluid in contact with ordinary Air and its Particles; Flask Sealed
after the Fluid had become Cold._
*No. XXXI.--Healthy Urine* remained in the warm bath for twenty-eight
days without undergoing the least change.
*No. XXXII.--Simple Turnip Infusion* remained in the warm bath for
twenty-eight days without undergoing any appreciable change.[59]
On breaking the neck of the flask, the fluid was found to be quite
odourless. With its neck quite open, the flask was replaced in the
water-bath. During the first forty-eight hours it underwent no
apparent change, though at the end of seventy-two hours a slight
general turbidity was noticeable, and an examination of a drop of the
fluid (still odourless), showed a number of minute but very active
_Bacteria_.[60]
[59] Experiment No. 8, recorded in ‘Nature,’ 1870, No. 36, p. 194, may
be compared with this and No. XXXIII.
[60] This experiment should be compared with Nos. XVIII. and XXXIII. It
seems to show that if some fermentable fluids can be kept for a time
under conditions in which they will not ferment, the constitution of
the fluid, instead of remaining the same, undergoes a slow alteration
by which it is rendered absolutely less fermentable, even when exposed
to the most favouring influences.
_c. Fluid in a Bent-Neck Flask, having Eight acute Flexures._
*No. XXXIII.--Simple Turnip Infusion* showed no change after eight
days’ immersion in the warm bath. After _eleven_ days, the fluid being
still clear, the tube was broken just beyond the second bending from
the bulb, and then the flask was re-immersed in the bath. After three
days’ exposure, the fluid being still clear, it was boiled in the flask
for one minute, when it was noticed that the steam was quite odourless.
The flask was then replaced in the water-bath, where it remained for
twenty-two days (still with the neck open and broken just beyond its
second bending) without showing any change.[61] It was then submitted
to examination; the fluid was found to be devoid of all odour, it had
a slightly bitter taste, and its re-action was very faintly acid. On
microscopical examination no living things were found; there were no
_Bacteria_, no _Vibriones_, and no _Torulæ_, only some mere granules, a
small amount of amorphous matter, and a few fibres.[62]
[61] After this experiment had been completed, a fresh-filtered
infusion of turnip was placed in the same flask (having the neck open
just beyond its second bending), and after having been boiled for a
few minutes it was immersed in the same water-bath. This fluid became
turbid in thirty-six hours, and was then found to contain multitudes
of _Bacteria_; and the characteristic odour of the turnip infusion was
still appreciable.
[62] The results of this experiment are most interesting, especially
if compared with what takes place when some of the same fluid is
neutralized by ammonic carbonate (No. XXXIV.), with what occurs when a
similar fluid (as in No. XXX.) is contained in a flask sealed during
the continuance of ebullition, or also with what occurred in Nos.
XIII. and XXXII. In the present case the second boiling seems to have
destroyed what small amount of fermentability there was still remaining
in the solution; but in No. IX. fermentation did take place after
the second boiling--though this occurred only under the influence of
diminished pressure and a higher temperature.
*No. XXXIV.--Turnip Infusion Neutralized by Ammonic Carbonate* in
forty-eight hours showed a slight turbidity, which slowly increased
during the next two days. In two days more the turbidity was very
great, and there was also a considerable amount of sediment. The fluid
was then examined microscopically, and found to contain myriads of
large but very languid _Bacteria_.
_e. Fluid (in vacuo) in a Flask which had been Sealed during
Ebullition._
*No. XXXV.--Healthy Urine* underwent no apparent change for the first
twelve days, then (the bulk of the fluid still remaining clear and
bright) small greyish white flocculi began to collect at the bottom
of the flask, which very slowly increased in quantity during the
succeeding twelve days. At the expiration of this time the flocculi
were pretty numerous, though the fluid was otherwise bright. The vacuum
was ascertained to be still good, and on breaking the flask, the fluid
was found to have a slightly acid re-action, though no appreciable
odour. When examined microscopically, the flocculi were seen to be made
up for the most part of mere granular aggregations (simple, and not in
the form of _Bacteria_). Small _Torula_ cells, however, existed in some
quantity; also a few necklace-like chains, and a comparatively small
number of _Bacteria_, some of which were tolerably active.
*No. XXXVI.--Simple Turnip Infusion* after twenty-four hours showed no
sign of change, though in thirty-six hours it was slightly turbid. On
the fourth day the turbidity was well-marked and general, though there
were no flake-like aggregations. When examined microscopically, the
fluid was found to contain multitudes of _Bacteria_.
*No. XXXVII.--Turnip Infusion,[63] Neutralized by Ammonic Carbonate*
in twenty-four hours was decidedly turbid. In thirty-six hours the
turbidity was more marked, and there was a slight sediment. By the end
of forty-eight hours both turbidity and sediment had notably increased.
On the fourth day, there was a moderately clear fluid, containing an
abundance of curdy or flake-like masses. When the flask was opened,
these were found to be made up principally by the aggregation of
myriads of _Bacteria_.
[63] Some of same as that which was used (unaltered) in last experiment.
FIFTH SET OF EXPERIMENTS (XXXVIII.–XLVII.).
_Fluids not boiled, but half-filling hermetically Sealed Flasks,
containing Ordinary Air._
*No. XXXVIII.--Turnip Infusion* in ten hours showed a slight amount of
turbidity. After forty-eight hours this was very well-marked: there
was a thick pellicle on the surface, and, in addition, a small amount
of deposit. On examination, the fluid and the pellicle were found
to contain an abundance of _Bacteria_, _Vibriones_ and _Leptothrix_
filaments.
*No. XXXIX.--Turnip Infusion + 1/20 of Carbolic Acid* after eight
days showed no appreciable alteration in appearance,[64] no trace of
pellicle or deposit. When examined microscopically, however, the fluid
was found to contain some very minute _Bacteria_, though they were by
no means abundant.
[64] It had been rendered turbid from the first, by the carbolic acid.
*No. XL.--Hay Infusion* had become quite turbid in twenty-four hours,
and several shades lighter in colour. After forty-eight hours the
colour of the infusion was still lighter; there was more turbidity, and
some sediment. On microscopical examination, the fluid was found to
contain an abundance of _Bacteria_, _Vibriones_ and short _Leptothrix_
filaments.
*No. XLI.--Hay Infusion + 1/20 of Carbolic Acid* showed no apparent
change[65] after forty-eight hours, and when examined microscopically
it revealed no trace of _Bacteria_, or other organisms. The neck of the
flask was then again closed. On the twelfth day the fluid had still
undergone no change in appearance, and when examined microscopically,
it still showed no trace of organisms, though the fluid was--as it had
been at the time of the first examination--full of minute, undissolved
particles of carbolic acid.
[65] The fluid had been rendered paler and turbid from the first, by
the addition of the carbolic acid.
_Fluids boiled for five minutes, and half-filling hermetically Sealed
Flasks containing Ordinary Air._
*No. XLII.--Hay Infusion*, after forty-eight hours, showed no change,
and continued to remain quite clear and free from deposit until the
twelfth day, when it was examined microscopically. No organisms of any
kind could be detected.
*No. XLIII.--Hay Infusion + 1/20 part of Carbolic Acid* showed no
apparent change[66] for the first five days, though, on the sixth day,
a slight deposit was noticed at the bottom of the flask. The deposit
had increased, and was well-marked by the twelfth day, when, on
microscopical examination, there were found amongst the granular flakes
of the deposit, _Torulæ_ of several varieties of size and shape. Many
were spherical, others ovoid, or having an elongated oat-like shape:
some were of the ordinary colour, and others were brownish in tint. The
variety was most striking. No _Bacteria_ were seen, though there were
multitudes of active particles which seemed to differ from the minute
spherules of undissolved carbolic acid.
[66] The alteration in colour was less marked than in the similar
mixture which had not been boiled, though the turbidity was just as
obvious.
_Fluids (in vacuo)--boiled for five minutes, and Flasks Sealed during
Ebullition._
*No. XLIV.--Turnip Infusion*, in seventy-two hours, showed a slight
turbidity, which gradually increased. On the eighth day there was
a considerable quantity of flake-like sediment, and some amount of
general turbidity. On the thirteenth day the vacuum was found to
be still partly preserved. When the flask was opened the fluid was
perceived to have a fœtid odour, and an acid re-action; and, on
microscopical examination, multitudes of _Bacteria_ and _Vibriones_
were seen. In the flake-like aggregations also (made up almost wholly
of these organisms) there were a number of large thick-walled spores;
some already formed, and others in process of formation by coalescence.
*No. XLV.--Turnip Infusion + 1/20 part of Carbolic Acid* showed no
increase of turbidity[67] for the thirteen days during which it was
kept under observation. Before the flask was opened it was ascertained
that the vacuum was well preserved. The odour of the fluid was
unaltered, and on microscopical examination no _Bacteria_, or other
living things, were found.[68]
[67] This fluid was whitish, and somewhat opaque, from the first.
[68] For other experiments showing a similar sterility, induced by a
slight acidification with acetic acid, see ‘Nature,’ 1870, No. 37,
pp. 226 and 227.
*No. XLVI.--Hay Infusion*, after forty-eight hours, showed no change,
though, in seventy-two hours, there was perceptible a very small amount
of a dirty greyish deposit. By the fifth day the deposit had slightly
increased, and on the seventh day there was a trace of turbidity in
the fluid. It did not undergo much further change, so that, on the
twelfth day, the flask was opened. The vacuum was found to have been
very slightly impaired; the odour of the fluid was almost natural, and
its re-action was slightly acid. On microscopical examination of the
deposit, _Bacteria_, _Vibriones_, short _Leptothrix_ filaments, and
_Torulæ_, were found, though not in very great abundance.
*No. XLVII.--Hay Infusion + 1/20 part of Carbolic Acid* showed no
apparent change for the first four days. On the fifth day there was a
small quantity of powder-like sediment, and one dirty greyish-coloured
flake. On the seventh day there were more small flakes at the bottom,
and a slight general turbidity of the fluid. On the twelfth day, the
turbidity and deposit having increased, the flask was opened--after
it had been first ascertained that the vacuum had only been slightly
impaired. The re-action of the fluid was still strongly acid. On
microscopical examination of some of the deposit, there was found,
amongst granular flakes and aggregations, a large number of _Torulæ_
cells, of most various shapes and sizes; also in the midst of the
granule heaps many large, rounded or ovoidal, densely granular
nucleated bodies, whose average size was 1/1500″ in diameter, though
there were many of them much larger, and others even less than half
this size. Intertwined amongst the granular matter also were a large
number of algoid-looking filaments, 1/20000 in diameter, containing
segmented protoplasmic contents. There were also in the fluid itself
a number of medium-size, unsegmented _Bacteria_, whose movements were
somewhat languid.[69]
[69] The results of this experiment, and of No. LXIII. are decidedly
opposed to the reality of the germ-killing powers with which carbolic
acid has been endowed by Professor Lister and others. I, however, had
previously found that specimens of _Torulæ_ and _Bacteria_, obtained
from freshly opened flasks, and then mounted as microscopical specimens
in a mixture of glycerine and carbolic acid (in the proportion of
15:1), not unfrequently grew and multiplied under such conditions. MM.
Béchamp and Estor, also found that _Bacteria_ multiplied in carbolized
fluids, and similar facts have been testified to by some Italian
observers. But, organic fluids differ much from one another, so that
the influence of carbolic acid may well be different upon different
fluids. And, accordingly, we find that whilst its addition to, and
subsequent boiling with, a hay infusion increases the fermentability
of this, precisely the opposite effects are produced when the hay
is replaced by a turnip infusion (see No. XLV.). Without wishing to
undervalue in the least the system of treatment introduced, and so
admirably carried out by Professor Lister, I am strongly of opinion
that he explains his results by theories which are almost wholly
incorrect.
SIXTH SET OF EXPERIMENTS (XLVIII.–LXV.).
_Ammoniacal Solutions, unboiled, and exposed to Ordinary Air in a
Corked Bottle._[70] (_Temp. 60°–65° F._)
[70] All the simple ammoniacal solutions were in the proportion of
ten grains of the salt to the fluid ounce of distilled water; and to
those which also contained sodic phosphate, three grains of this were
added. About half an ounce of each solution was put into a one-ounce
wide-mouthed bottle, and then tightly corked.
*No. XLVIII.--Ammonic Acetate Solution.*--On the tenth day the fluid
was still quite clear, and free from sediment.
*No. XLIX.--Ammonic Oxalate Solution.*--On the tenth day there was no
distinct opalescence of the fluid, but a well-marked whitish flocculent
deposit. On microscopical examination no _Bacteria_ were found in the
fluid, and the deposit was made up by an aggregation of blackish and
colourless granules, mixed with a few crystals and a very few _Torula_
cells--all being held together by a sort of mucoid matrix. In the midst
of this matter were found two or three very small, much branched,
mycelial tufts of a fungus-growth.
*No. L.--Ammonic Carbonate Solution.*--On the tenth day the fluid
showed a very faint opalescence, with a small amount of deposit, and
a partial non-coherent scum on the surface, which, on microscopical
examination, was found to be composed partly of amorphous granules, and
partly of minute _Bacteria_, mixed with small necklace-like organisms.
The fluid itself contained, in suspension, a few small and sluggish
_Bacteria_, with a minute _Torula_ cell here and there.
*No. LI.--Ammonic Tartrate Solution* after twenty-four hours showed
the faintest opalescence of the fluid; in forty-eight hours there was
a bluish-white turbidity, and in seventy-two hours the turbidity was
well marked. When examined microscopically the fluid was found to
contain multitudes of very active _Bacteria_. On the thirteenth day
the turbidity was not so well marked, though there was a very thin
pellicle on the surface, and also the dirty-looking crumpled remains of
another pellicle at the bottom, which, on examination, was found to be
composed of an aggregation of _Bacteria_. The pellicle on the surface
was very thin, and composed only of a single layer of _Bacteria_. In
the fluid itself many _Bacteria_ were seen, of medium size, and mostly
sluggish in movement, though a few of them exhibited very active
rotatory movements. No _Vibriones_, _Leptothrix_, or _Torulæ_, were
found.
*No. LII.--Ammonic Tartrate and Sodic Phosphate Solution* after
twenty-four hours showed the faintest opalescence; in forty-eight
hours there was a bluish-white turbidity, which, in seventy-two hours,
had become more marked. When examined microscopically multitudes of
_Bacteria_ were found whose movements were very sluggish. On the
thirteenth day there was a well-marked whitish turbidity, due to
_Bacteria_ and _Vibriones_, a slight amount of deposit, and a firm
pellicle which was found to be composed, almost wholly, of long
unjointed _Vibriones_ and unsegmented _Leptothrix_ filaments, all of
which, when separate, exhibited the most distinct eel-like movements,
accompanied by an actual progression from place to place.
_Ammoniacal Solutions, unboiled, and exposed to Air in a Corked Bottle,
after Inoculation with a Drop of Fluid containing living_ BACTERIA_and_
TORULÆ. (_Temp._ 60°–65° F.)
*No. LIII.--Ammonic Acetate Solution* after twenty-four hours was
faintly opalescent, and in forty-eight hours showed a very slight
bluish tint. In seventy-two hours it was in the same state, and, on
microscopical examination, the fluid showed no distinct _Bacteria_
or other living things, though there were a number of very minute
particles distributed, singly or in small groups, throughout the fluid.
On the thirteenth day there was no change in appearance, except that
the sediment had somewhat increased in amount. Still, no _Bacteria_
could be found in the fluid or the sediment,--only the above-mentioned
particles, and a few somewhat larger, which resembled very minute
_Torulæ_. Amongst the sediment, however, there were two or three very
small mycelial tufts of a developing fungus.
*No. LIV.--Ammonic Oxalate Solution.*--On the eighth day the fluid
showed a very faint opalescence, though there was a well-marked,
greyish, flocculent deposit, which was found to be composed of an
aggregation of colourless and blackish granules, of a multitude of
minute crystalline particles (mostly diamond-shaped), and some rounded
or ovoidal, thick-walled, spore-like bodies; amongst which, and
enveloped in part by them, were several mycelial tufts of a fungus.
A number of minute _Bacteria_ were found distributed throughout the
fluid, and also a quantity of minute star-like bodies (crystalline),
about 1/12000 in diameter.
*No. LV.--Ammonic Carbonate Solution.*--On the eighth day the fluid
showed a very faint opalescence, and a slight deposit, which was found
to be composed principally of amorphous granules. Distributed through
the fluid were some small and sluggish _Bacteria_, though no other
organisms were seen.
*No. LVI.--Ammonic Tartrate Solution.*--After twenty-four hours the
fluid showed the faintest opalescence, and in forty-eight hours there
was a slight bluish-white turbidity. In seventy-two hours the turbidity
was well marked, and there was a very thin pellicle on the surface.
When examined microscopically the fluid was found to contain multitudes
of very active _Bacteria_, and the pellicle was also composed of an
aggregation of _Bacteria_. On the thirteenth day the opacity had
somewhat increased; there was also a well-marked pellicle, and an
obvious deposit. The pellicle was found to be composed of _Bacteria_,
and in the fluid there were multitudes of medium-size _Bacteria_ and
_Vibriones_, with here and there a small _Torula_ cell.[71]
[71] On comparing the corresponding experiments of series XLVIII.-LI.
with those of series LIII.-LVI. less difference is found than might
have been expected by many. The comparison of the numbers of each
series with one another, also reveals the interesting fact, that
the mere presence of N, C, O, and H, is not all that is required,
even for the growth and nutrition of the lower living things. These
elements seem to lapse into the new combinations constituting living
matter of various kinds, more easily from certain pre-existing states
of combination than from others. Solutions of ammonic tartrate are
much more favourable starting points for the new combinations than
solutions of ammonic acetate. The comparison of experiment No. LI.
with No. LII. is extremely interesting in reference to the dogma that
phosphorus is a necessary ingredient in living matter. Solutions of
the ammonic tartrate in distilled water have been twice analyzed for
me by a skilled chemist, without revealing the least trace either of
phosphorus or sulphur. This result is very remarkable when compared
with the amount of living matter which may so soon appear in such
a solution: the number of the organisms and the rapidity of their
evolution, being almost equal to that which occurs in a similar
solution to which a phosphate has been added. However much, therefore,
phosphorus may aid the development of organisms in many fluids, there
is still an important difference between _many_ and _all_, which if
more frequently borne in mind, would render universal propositions more
scarce (see ‘Journal of Chemical Society,’ March, 1871, pp. 72–74). The
truth of the dictum “_Ohne Phosphor gar kein Leben_,” is, I venture to
think, far from being proved. If on insufficient evidence (referring
only to particular fluids) such a dictum is arrived at; and if then,
the presence of organisms in any fluid is to be taken as evidence of
the existence of phosphorus (even though this cannot be otherwise
substantiated), the case of phosphorus in relation to Life comes to be
similar to the case of the much abused germs.
Mutato nomine, de te
Fabula narratur.
_Ammoniacal Solutions (in vacuo) in Flasks which were hermetically
Sealed during Ebullition of their Fluids at a Temperature of 90 F.°[72]
(Subsequently exposed in water-bath to a Temperature of 75°–85° F.)._
[72] The fluids were boiled at the low temperature, with the aid of an
air-pump, merely in order to be able to procure a more perfect vacuum
in the flasks; these experiments being destined to show whether the
simple (uninoculated) solutions would become turbid _in vacuo_--that is
to say, without the oxidizing influence of the air--when they had not
been exposed to an amount of heat sufficient to destroy any living or
dead ferments which they might contain.
*No. LVII.--Ammonic Tartrate Solution* after sixty hours showed a
slight sediment, with bluish flakes attached to sides of flask. In
eighty-four hours there was a general bluish opalescence, and on
microscopical examination the fluid was found to contain multitudes of
_Bacteria_.
*No. LVIII.--Ammonic Tartrate and Sodic Phosphate Solution.*--After
sixty hours there was a slight general bluish opalescence. In
eighty-four hours the general opalescence was not more marked, but
there were many flake-like aggregations in the fluid, which on
microscopical examination were found to be aggregations of _Bacteria_.
_Ammoniacal Solutions boiled (at 212° F.), and exposed to Air in Flasks
whose Open Necks were only loosely covered with Paper Caps: subsequent
Inoculation. (Temp. 75°–85° F.)._
*No. LIX.--Ammonic Tartrate Solution.*--The fluid remained quite clear,
and free from all trace of turbidity up to the ninth day, when it
was inoculated with some living _Bacteria_. In fifty hours after the
inoculation there was a very faint opalescence of the fluid, which,
in another 24 hours, had become much more marked. On microscopical
examination it was found to contain multitudes of _Bacteria_.
*No. LX.--Ammonic Tartrate and Sodic Phosphate Solution.*--After four
days the fluid was still quite clear. In seven days no trace of general
turbidity, though there was a minute dirty-grey aggregation about
1/14″ in diameter at the bottom of the flask. On the sixteenth day the
grey aggregation had very slightly increased in size, though the fluid
above was still perfectly clear. The grey mass was removed by a small
pipette, and, on microscopical examination, it was found to be composed
of an aggregation of minute extraneous fibres, mixed with blackish
particles and amorphous granular matter, in which were growing many
_Torula_-cells in all stages of development, and also a minute mycelium
composed of branched _Leptothrix_-like fibres.[73] The clear fluid was
then inoculated with some living _Bacteria_, and the bulb of the flask
was replaced in the warm bath. After fifty hours the solution showed a
bluish turbidity, which, in thirty-six hours more, had increased to a
well-marked whitish opacity, and when examined, the fluid was found to
be swarming with active _Bacteria_.
[73] A deposit of this kind is almost invariably found in such
solutions after their fermentability has been lowered by previous
boiling. Growth takes place very slowly in these cases, and also when
similar boiled fluids are contained _in vacuo_.
_Solutions of Ammonic Tartrate and Sodic Phosphate were heated, in
their respective Flasks, for Fifteen Minutes to the Temperatures
mentioned below. The Necks of the Flasks were afterwards loosely
covered with Paper Caps, whilst the Bulbs were immersed in a Water-Bath
kept at a Temperature of 75°–85° F._
*No. LXI.--Solution heated to* 149° F.
*No. LXII.* " " " 158° F.
*No. LXIII.* " " " 158° F.
*No. LXIV.* " " " 167° F.
*No. LXV.* " " " 167° F.
All these solutions remained quite clear and free from any trace
of general turbidity for ten days. Each fluid was then inoculated
with some living _Bacteria_, and in the space of thirty-six to
seventy-two hours, all had become more or less obviously turbid, and on
microscopical examination this turbidity was found in each case to be
almost wholly due to the presence of multitudes of _Bacteria_.
_Interpretation of the Experiments: Conclusions as to the Cause of
Fermentation, and as to the Occurrence of_ *Archebiosis*.
These experiments seem to show quite conclusively that M. Pasteur’s
explanations are altogether inadequate to account for the occasional
preservation of boiled fluids in bent-neck flasks. They show that the
preservation, far from being universal, is only occasional, and that
preservation or non-preservation of different fluids is almost wholly
dependent upon their nature. They lend no countenance, moreover, to his
particular theory, that fermentation cannot be initiated without the
agency of living ferments,--they are, on the contrary, wholly opposed
to this restriction.
The plug of cotton-wool, or the narrow and bent tube may, it is
true, protect the boiled fluid from subsequent contact with living
“germs”; but that the fluids do not undergo change on account of such
deprivation cannot be safely affirmed, when the same means would also
filter from the fluid some of the multitudinous particles of organic
matter (dead), which the air undoubtedly contains, and which may
act as ferments. It must be remembered that the main object of M.
Pasteur’s investigation was to determine whether fermentation took
place under the agency of mere dead nitrogenous matter, as Liebig and
others affirm; or whether it is only initiated by living organisms, as
he himself supposes. Obviously, therefore, the same filtration which
purified the air from any living organisms would filter from it its
nitrogenous particles, which are the other possible ferments: so that
no conclusion could be drawn from such experiments, more favourable
to the one than to the other of these hypotheses. All that could
have been safely affirmed was, that by boiling the fluid, and then
protecting it from subsequent contact with everything that could act as
a ferment, fermentation would not take place.
Even this however,--as the preceding experiments fully show--cannot be
truly affirmed to be a general rule. Some infusions do undergo change,
notwithstanding this treatment and deprivation, whilst others do not:
that is to say, some still preserve a first degree of fermentability
even after boiling, whilst others are reduced by this process to the
second degree of fermentability. These latter are unable to initiate
changes by virtue of their own inherent instability; molecular
re-arrangements require to be set on foot in them by contact with some
more unstable substance, which is itself undergoing change.
That such is the correct explanation of the reason why _some_ fluids
do not ferment in bent-neck flasks, seems obvious from the discordant
results obtained in many other experiments, after the free admission
of uncalcined air to the fluids which had been boiled. The fluids were
deprived of their virtues in some cases by the heat to which they had
been subjected, so that whether they underwent change or not, may
have depended upon the accidental presence or absence, in the air
which was subsequently admitted to the fluid, of some unheated organic
fragments, capable of initiating fermentative changes. If germs were
as omnipresent as they have been represented to be, such fluids ought
always to have undergone fermentation.
Whilst I have found that any given fluid, whose strength is about
equal on different occasions, acts in a definite manner when the flask
is hermetically sealed after expulsion of all its air and during the
continuance of ebullition; and, whilst a like definite result can
generally be obtained, when calcined air is admitted to the boiled
fluid before the vessel is hermetically sealed; it is found, on the
other hand, that the result is in no way predicable when uncalcined
air is admitted. Sometimes fermentation takes place, and sometimes in
other flasks--sealed at the same time, and subsequently placed under
the same conditions--no change whatever occurs. My own experience
in this respect accords perfectly with that of M. Pasteur.[74] He,
however, at once came to the conclusion that the only inference from
such facts was that “germs” are not so universally distributed as they
had been supposed to be by Bonnet and Spallanzani.[75] The unprejudiced
inquirer, however, will perceive that M. Pasteur was entitled to
come to no such conclusion concerning germs which was not equally
applicable to minute fragments or débris of organic matter floating
in the air. And, similarly, the evidence which he adduces with regard
to the diminution in the number of the fertile flasks when they were
filled with some of the still air of the caves of the observatory,
or else with some from the peaks of the Jura,[76] far away from the
haunts of men, had no bearing upon the distribution of germs which
was not equally applicable to that of dead organic particles. Such
evidence, therefore, was valueless for settling between the rival
doctrines of fermentation--it could not possibly help us to decide
whether living or dead ferments were necessary. Dead organic particles
would sink in still air in the same manner as living organisms;[77]
and similarly, dead organic particles, have been shown to be less
and less numerous in the atmosphere in proportion to the elevation
obtained.[78] In these latter experiments M. Pasteur made use of
yeast-water (alone or sweetened), and of urine--all three of them
fluids, which, after having been boiled, are apt to possess only the
second degree of fermentability. Shortly afterwards, M. Pouchet, in
concert with MM. Joly and Musset,[79] repeated these experiments, with
the sole difference that they employed strong infusions of hay--which
experiment has shown almost invariably to possess the first degree
of fermentability. And seeing that all their flasks, after a time,
yielded organisms from whatever mountain elevation the air had been
taken--the combined evidence tends strongly against the view of M.
Pasteur. Since the germs in the fluids and in the flasks, in each set
of experiments, had been previously destroyed by ebullition, and since
in each set, also, air of the same character had been admitted to the
boiled fluids, the different results seemed to show that fermentation
or non-fermentation, in such cases, depends wholly upon the quality of
the fluids employed.
[74] Loc. cit. p. 71.
[75] Loc. cit. pp. 75 and 76.
[76] Loc. cit. pp. 83 and 84.
[77] The subsidence of the atmospheric particles has been ably
demonstrated by Professor Tyndall.--See ‘Nature,’ 1870.
[78] See M. Pouchet’s ‘Nouvelles Expériences sur la Génération
Spontanée,’ &c., p. 69.
[79] See various communications in ‘Compt. Rend.’ (1863), t. LVII.
Other evidence which is so much vaunted by M. Pasteur and his
supporters, as to the possibility of inducing fertility in previously
sterile flasks, by the addition of a portion of asbestos containing
the solid particles filtered from the atmosphere,[80] is also equally
valueless for confirming the proposition that fermentation is only
capable of being initiated by living ferments. The same asbestos which
_may_ contain living spores or organisms (“germs”), does undoubtedly
contain many decomposable particles and fragments of organic
matter.[81] The previously barren solution may therefore be rendered
fertile by the mere addition of those portions of unstable organic
matter, whose molecular mobility has not been impaired by the agency
of heat, and which are therefore capable of initiating fermentations.
This view is strengthened, as M. Pouchet has pointed out, by the fact
that in these cases, instead of meeting some of the _various_ kinds
of organisms which are supposed to have representatives in the air,
and whose spores or ova may be supposed to have been sown, it is often
merely _Bacteria_ which are encountered,--differing in no respect from
those that may present themselves in a somewhat similar infusion, which
has undergone change in a closed flask without any such hypothetical
sowing of living spores or germs. It is more especially important to
bear in mind this consideration, when portions of organic matter can
always be easily demonstrated amongst such atmospheric dust; whilst
living _Bacteria_, or other organisms, such as are first produced as a
result of the supposed sowing of spores, either cannot be demonstrated,
or would seem, from other evidence, to be at least very sparingly
distributed.[82]
[80] Loc. cit., p. 40.
[81] Speaking of experiments in closed flasks, in which the air has
been either calcined or filtered, Gerhardt (‘Chimie Organique,’ t.
IV. p. 545) says:--“Si dans les premières expériences l’air calciné
ou tamisé s’est montré beaucoup moins actif que l’air non soumis à ce
traitement, c’est que la chaleur rouge ou le tamisage enlève à l’air
non seulement les germes des infusoires et des moisissures, mais
encore les débris des matières en décomposition qui y sont suspendues,
c’est-à-dire les ferments dont l’activité viendrait s’ajouter à celle
de l’oxygène de l’air.”
[82] On what other supposition can one explain the results of
experiments LVII.-LXV., and of others alluded to on p. 100?
The fact revealed by M. Pasteur, that _some_ fluids remain unchanged
for an indefinite period, after having been boiled in flasks, with long
and bent necks, is easily explicable in accordance with the physical
theory of fermentation, and now that it has been thoroughly proved
that _other_ fluids--submitted to precisely similar conditions--do
nevertheless undergo fermentation, this fresh fact is just as
completely adverse to the explanations and views of M. Pasteur, as
it is thoroughly harmonious with the doctrines of Baron Liebig. The
fluids which are capable of being preserved--generally not presenting
a high degree of fermentability--do not undergo change, _at ordinary
atmospheric pressure_, after having been boiled, unless they are
brought into contact either with some pre-existing living things or
with some unaltered organic particles from the atmosphere. Neither of
these, however, can gain access to the fluid, in such a vessel; because
all the air which enters, after the first inrush into the still almost
boiling fluid, has to pass, more or less slowly, through the numerous
flexures of the narrow neck of the flask and the two or three strata of
fluid which always remain therein.
Some of the fluids which do not undergo change in these bent-neck
vessels are, however, by no means notable for possessing a low degree
of fermentability. This is the case, for instance, with infusions of
turnip, which, under other conditions, have been found to be most
prone to undergo fermentation. And, I have found in several cases
in which such an infusion had been exposed in a bent-neck vessel,
and had remained unchanged for twelve or fourteen days (even though
subjected to a temperature of 85°–95° F.), that if the neck of the
flask were then broken shortly above the bulb, the solution would still
continue without alteration for a week, ten days, a fortnight, or even
more--although freely exposed to the air, and therefore to the access
of any living germs which might be floating about in the atmosphere.[83]
[83] See notes on pp. 73 and 79. It was not that these fluids were
incapable of being inoculated, or that they were unsuitable for
the development of the lower forms of life, as was shown by their
subsequent fate, and by the fact that they can always speedily be made
to become turbid if they are really inoculated with living _Bacteria_.
Almost similar facts in opposition to the prevalent Panspermic views
have been noted by Professor Cantoni (Rend. del R. Istit. Lombardo,
Novembre, 1869). He found (as I have also frequently found) that when
fluids had been subjected to the influence of high temperatures,
and had subsequently remained sterile in closed flasks, they might
be freely exposed to the air for one or two weeks, or more, without
becoming turbid--although at any time a general turbidity could be
speedily induced, by introducing a few living _Bacteria_ into the fluid.
The views hitherto expressed with reference to the causes of
fermentation and putrefaction, and to the interpretations which M.
Pasteur’s experiments are capable of receiving, seem to derive all
the additional support that can be needed, from the results of my own
experiments with boiled fluids, in sealed flasks, from which all air
had been expelled.
Some of the same fluid being taken and divided into three parts, each
portion is placed in a separate flask, in which it is boiled for a
period of ten minutes. One of the flasks (A) is provided with a long
and bent neck, so that the air which re-enters is deprived of its germs
and organic particles; another (B) has only a short neck, and to this,
the access of germs and organic particles is freely permitted till the
fluid has become cool, and then the neck of the flask is hermetically
sealed; whilst the last (C) is sealed during ebullition, after all air
has been expelled. Now, if Pasteur’s theory of fermentation, and the
prevalent notions concerning the universal distribution of “germs”
throughout the atmosphere were true, it might be expected that the
fluid in B would always rapidly change; that that in A would always
remain pure; and that the fluid in C would, similarly, undergo no
alteration. The facts, however, are quite the reverse: if a strong
turnip infusion be employed, the fluid in A will almost always remain
unchanged; that in B will sometimes rapidly change, and at other
times will remain quite pure; whilst that in C will almost invariably
become turbid in from two to six days. But, even if it were not the
case that some fluids, different from those used by M. Pasteur, will
almost invariably undergo change in bent-neck vessels, M. Pasteur’s
explanation of the cause of the preservation would have been altogether
upset by the fact that _some of the very fluids which remain pure in
the bent-neck apparatus will become fœtid if shut up in vacuo_. It
is, therefore, of course useless to talk of a particular boiled fluid
having been saved from putrefaction on the ground that the living
atmospheric germs (whose presence is supposed to be necessary for the
initiation of such a process) have been altogether filtered from the
re-entering air, when some of the same fluid will putrefy, if placed
under different conditions by which it is freed both from the influence
of the atmosphere and from its germs--_i.e._, when, instead of
filtering the re-entering air, no air is permitted to enter. Germs and
atmospheric particles being equally got rid of in both sets of cases,
the great difference between them is that the weight of the atmosphere
is also got rid of in my experiments--the fluids being contained
_in vacuo_. Now it has been ascertained by Mr. Sorby, that pressure
undoubtedly influences “chemical changes taking place slowly, and
therefore, probably due to weak or nearly counterbalanced affinities;”
and he also states, in the Bakerian Lecture for 1863,[84] that “a
considerable number of facts have been described, showing that pressure
will more or less influence such chemical actions as are accompanied by
an evolution of gas, so that it may cause a compound to be permanent,
which otherwise would be decomposed.” If increase of pressure retards,
a diminution of pressure will facilitate such chemical changes, so that
one can only explain the results which I have obtained, on the ground
that many boiled fluids, which will not undergo change when protected
from the influence of atmospheric particles (living or not living)
at the same time that they are subjected to ordinary or increased
pressure, will, on the contrary, pass through such changes when
pressure is removed, and the fluids are preserved _in vacuo_. It is not
pretended that this is a rule applicable to _all_ organic fluids--far
from it. Diminution of pressure does seem, however, to be a very
potential cause of change in some fluids. The extent to which changes
of a fermentative character can progress in the absence of atmospheric
oxygen, is also evidently subject to much variation, in accordance with
the nature of the dissolved fermentable substances.
[84] ‘On the Direct Correlation of Mechanical and Chemical
Forces.’--Proceedings of the Royal Society, vol. xii. pp. 539 and 546.
These facts are not so new and exceptional, however, as they
may at first sight appear. It has been long known that a boiled
fluid extremely prone to change, will not yield infusoria if the
vessel in which it is contained is filled with the fluid. Burdach
says[85]:--“Gruithuisen a reconnu que des infusions, même très fécondes
d’ailleurs, celles du foin par exemple, ne donnaient point d’infusoires
dans des flacons de verre dont le bouchon était assez enfoncé pour
toucher à la surface de l’eau.” On the other hand, no experiments
with which I am acquainted, in which heated fluids and calcined air
have been shut up in closed flasks, have yielded so many positive
results as those of Professor Wyman of Cambridge, U.S.,--and his were
performed under precisely the reverse conditions. Large flasks were
used, and only 1/15–1/20 of their bulk was filled by the experimental
fluids.[86] Gruithuisen’s results were explained by Burdach on the
ground that a certain amount of air was necessary, and it was also
with the view of subjecting his fluids to as large an amount of air
(calcined) as possible, that Professor Wyman employed small quantities
of fluids in large flasks. These views were dictated by the chemical
doctrines of Gay-Lussac and others, to the effect that the oxygen of
the air is the initiator or _primum movens_ of fermentative changes.[87]
[85] ‘Traité de Physiologie.’ Translated by Jourdan. 1837. t. i., p. 18.
[86] ‘American Journal of Science,’ July, 1862.
[87] See Gerhardt’s, ‘Chimie Organique,’ t. iv. pp. 540 and 547.
Now, without doubting in the least that in some instances this may be
the case, it seems to me quite obvious, from my own experiments, that a
different interpretation may be given of Gruithuisen’s results--which I
have myself verified,--and of the fact that meats and vegetables will
often remain unchanged for years after having been heated in closed
tins from which all air has been expelled.[88]
[88] It was, indeed, the consideration of these latter facts which
originally forced Gay-Lussac to the conclusion, that fermentation
would not take place _in vacuo_, or without the presence of free
oxygen, which was and still is, believed by many, to be the immediate
determining cause of fermentation.
If we ponder only upon the fact that certain fluids, in contact with
a very small quantity of air, in an hermetically-closed vessel, will
not undergo change; though these same fluids will change when exposed
to a much larger quantity of calcined air, there may be strong reason
for coming to an opinion similar to that of Gay-Lussac. When, however,
it is also ascertained that provisions which have been subjected to
the long-continued influence of heat, do not undergo change in closed
vessels, if all air has been expelled from the _very small space above
the level of the provisions_; though many organic infusions will
putrefy if they occupy only one half, or less, of a hermetically closed
vessel from which all air has been similarly expelled by ebullition of
its fluid contents, it is impossible that the same explanation can hold
good. And at the same time another interpretation is suggested for the
first set of facts.
The last-mentioned experiments prove[89] that fermentation can take
place _in vacuo_, when the conditions are more favourable than those
which present themselves within the almost full tins containing
provisions. The change in these latter cases cannot (in the great
majority of instances) proceed far[90], because there is no adequate
space into which residual gases may be emitted. When this emission
(which is almost always one of the accompaniments of a fermentative
change) has taken place to a slight extent, the meats are in the very
best condition for preservation. There is an utter absence of light, an
absence of free oxygen, and also an absence of that diminished pressure
which my experiments seem to show is favourable to the promotion of
many kinds of fermentative change. So that if fermentation does not
take place in a closed flask which is _full_ of a boiled infusion of
hay,[91] it may be owing to the fact that there is no space for the
residual gases, and that undue pressure retards many fermentative
changes. This is also perfectly compatible with the other fact that the
same kind of fluid will undergo change when a small quantity of it is
contained in a comparatively large flask--owing to there being, in such
a case, plenty of room for residual gases to be effused, before that
undue amount of pressure is brought about, in the presence of which
such a fluid will no longer ferment or putrefy. Fluids, therefore,
whose putrefaction is hindered by increased pressure and favoured
by diminution of pressure, may be placed under conditions which are
successively more favourable than the last, by putting a gradually
smaller and smaller quantity of fluid into a flask, to which calcined
air is admitted, and, better still--if the stimulus of oxygen is
not absolutely needed in order to incite fermentation in the fluid
employed--by only half filling the flask, and procuring a more and more
perfect vacuum.
[89] This proof is more severe in certain other experiments (not
yet published) in which I had the benefit of Professor Frankland’s
assistance. The vacuum in these cases was perhaps more perfect,
having been procured by means of a Sprengel’s pump and a simultaneous
ebullition of the fluid, during which the flasks were hermetically
sealed. The closed flasks were subsequently exposed to a temperature of
293° F. for a short time.
[90] An examination of tins of “perfectly good” meats has convinced me
that a very small number of _Bacteria_ and _Leptothrix_ filaments are
occasionally to be met with.
[91] It has, however, been ascertained by M. Pouchet, that beer-yeast,
even after prolonged ebullition, will undergo change in a flask which
is full and hermetically sealed; and the manufacturers of preserved
meats also find that occasionally, in some of their best prepared tins,
the meats become putrid, and that the putridity is accompanied by the
presence of organisms. Some fermentations are doubtless attended by
a less copious emission of waste gases than that which characterizes
other fermentations; and some fermentations will progress in spite of a
moderate amount of pressure.
In accordance with the doctrines of Baron Liebig, therefore, my
experiments, as well as those of many other investigators, tend to
show that fermentative and putrefactive changes are merely processes
of chemical re-arrangement, which frequently take place--as it
were “spontaneously”--owing to the inherent instability of certain
nitrogenous compounds in the presence of free oxygen. My experiments
have, however, also revealed the additional fact that, under the
combined influence of heat and diminished pressure, some fluids will
undergo fermentation even in closed vessels, from which all air has
been expelled. They lend no support to the idea that the air is so
thickly laden with _living germs_ as some would have us suppose; and
in view of the mass of positive information now in our possession
concerning the degree of heat which suffices to kill the lowest
organisms, they also, as I think, entitle us to come to the conclusion
that such organisms are (as the microscopical evidence might lead us
to believe) really capable of being evolved _de novo_. These lowest
organisms are, in fact, to be regarded as occasional concomitant
products, rather than as invariable or necessary causes of all
fermentative changes.
It would thus appear that specks of living matter may be born in
suitable fluids, just as specks of crystalline matter may arise in
other fluids. Both processes are really alike inexplicable--both
products are similarly the results of the operation of inscrutable
natural laws, and what seem to be inherent molecular affinities.
The properties of living matter, just as much as the properties of
crystalline matter, are dependent upon the number, kind, and mode of
collocation of the atoms and molecules entering into its composition.
There is no more reason for a belief in the existence of a special
“vital force,” than there is for a similar belief in the existence of
a special “crystalline force.” The ultimate elements of living matter
are in all probability highly complex, whilst those of crystalline
matter are comparatively simple. Living matter develops into Organisms
of different kinds, whilst crystalline matter grows into Crystals of
diverse shapes. The greater modifiability of living matter, and the
reproductive property by which it is essentially distinguished from
crystalline matter, seem both alike referable to the great molecular
complexity and mobility of the former. Crystals are statical, whilst
organisms are dynamical aggregates, though the evolution of both,
marked by their peculiar characteristics, may be regarded as visible
expressions testifying to the existence of one all-pervading Power
“Whose dwelling is the light of setting suns,
And the round ocean, and the living air,
And the blue sky, and in the mind of man:
A motion and a spirit that impels
All thinking things, all objects of all thought,
And rolls through all things.”
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