ON THE

ATMOSPHERIC GERM THEORY

AND

ORIGIN OF INFUSORIA.

A LECTURE DELIVERED TO THE ROYAL COLLEGE OF SURGEONS
OF EDINBURGH, 17th JANUARY 1868.

BY

JOHN HUGHES BENNETT, M.D., F.R.S.E.,

PROFESSOR OF THE INSTITUTES OF MEDICINE AND SENIOR PROFESSOR OF CLINICAL MEDICINE
IN THE UNIVERSITY OP EDINBURGH :
Honorary Fellow of the King and Queen's College of Physicians in Ireland; Memher and
Corresponding Member of various Scientific and Medical Societies in Edinburgli ,
St Andrews, Philadelphia, New York, Paris, Brussels, Vienna, Berlin,
St Petersburgh, Jena, Stockholm, Athens, Buda-Pesth,
Copenhagen, Amsterdam, etc., etc.

EDINBURGH: 3r'
ADAM & CHARLES BLACK.

MDCCCLXVIII.

REPKINTEO FKOM THE EDINBURGH MEDICAL JOURXATi FOR MARCH 1868.

NOTE.

Since this lecture was delivered my attention has been directed to
two papers, by Dr George Child, in the Proceedings of the Royal
Society, vols. xiii. and xiv., in which several careful experiments
are described, and in which microscopical examinations with high
powers, some of which were made by Dr Beale, show that infusoria
occur under circumstances altogether opposed to the statements
of M. Pasteur. It w^ould appear, also, that Dr Wyman, of
Cambridge, U. S., had previously made similar experiments with
like results; but I am ignorant where an account of them is to
be found. In the Annales des Sciences Naturelles, Botanique,
Mars et Avril 1867, will be found a Memoir by M. Trecul on
Amylobacteria. He has observed bacteria forming in the interior
of the cells of decomposing plants, where no previous germs could
exist, and says they are frequently coloured blue by iodine.
Several other recent memoirs on the origin of Infusoria may be
found scattered through the scientific works and journals of Great
Britain, France, and Germany. (See especially Botanische Zeitung
and Archiv fur Mikroskopische Anatomic.) A careful perusal
of these has only tended to confirm in my mind the correctness
ot the views which, after long consideration and repeated inves-
tigations, I now put forth.

J. H. B.

THE ATMOSPHERIC GERM THEORY.

Mr President and Gentlemen, — The subject which I have the
honour of bringing before you this evening is one which has en-
gaged the attention of physiologists since the days of Aristotle.
That distinguished man, as well as most of the naturalists who
lived previous to the time of Harvey, were of opinion that dust,
decomposed flesh, and other dead substances might, under the in-
flaence of heat, air, and water, give rise to living beings indepen-
dently of parents. This mysterious process, by a singular perver-
sion of language, has been called spontaneous generation. We all
know the story of the shepherd recounted by Virgil, who thought
he saw bees spring up in the dead body of an ox, which was
implicitly believed by Pliny ; and we have read accounts of rats
and frogs which were supposed to be engendered by the fruitful
earth^^or teeming waters.

Francis Redi, a physician of Florence, was the first who clearly
demonstrated, in 1638, that the larvae and worms found in a dead
body were not produced by putrefaction, but originated from flies'
eggs deposited in the flesh. ^ Even he, however, says that he is
inclined to believe the entozoa to have a spontaneous origin. The
researches into generation, which alone would have conferred undy-
ing honour on the name of William Harvey, had it not been
associated with the discovery of the circulation, led him to announce
the law, Omne vivum ex ovo." Since his day the Ibelief has been
general, that all animals and plants are derived from eggs or
seeds ; that vitality is always transm.itted, and never created ; and
that, where these fundamental principles cannot be recognised, the
minuteness of the germs and their wide diffusion throughout nature,
and more especially in the atmosphere, offer a sufficient explanation
of what may appear mysterious. Nature, it was argued, must be
uniform in her operations, and analogy warrants our supposing that
the same law of generation which applies to the higher animals and
plants, is equally applicable to the lower.^

' Experiraenta circa Generationem Insectorum.

^ Most of the arguments on the other side, that is, in favour of Heterogenesis,
will be found well stated by Burdach (Physiologic, tome 1. p. 8, et seq.) — argu-

6

THE ATMOSPHERIC GERM THEORY.

The cell theory of growth , which was brought forward by Schlei-
den and Schwann in 1840, gave a new impulse to investigation by
means of the achromatic microscope. With this instrument, physi-
ologists have now traced the changes which ova and seeds undergo
during their development in a vast number of animals and plants,
and have even followed the former in their wanderings from the
body of one animal where they originate, into that of another where
they are fully developed. In this way we have an alternate gene-
ration, as explained by Steenstrup. In the mouse, for example,
we find a cystic worm which, in its body, would be no further
developed, but when the mouse is eaten by the cat, the cystic
is transformed into the tapeworm, which infests the last named
animal. But it has also been shown that certain insects are pro-
duced from others without generation by parents. This interruption
in descent Owen has called Parthenogenesis, from ^ra^^jji/gia^ virginity.
Thus, two winged insects will produce an animal without wings,
from which ten or twelve generations of individuals may be derived
without a fresh act of conception, until the last in the chain gives
forth another winged insect, when the process is repeated — as in the
case of the aphis.^ These generalizations, by clearing up some very
obscure points in embryology, were thought to have given the
coup de grace to the old notion of spontaneous generation.

The ova, seeds, and primary cells, however, which were supposed
to be floating in the atmosphere, though constantly looked for,
could nowhere be found, and more careful investigation of the
numerous forms of life which spring up in putrescent and fermented
fluids utterly failed in connecting them with pre-existing germs.
It is perhaps unnecessary to remark, that our modern microscopes
have reached such perfection that we can examine with the greatest
accuracy particles of only one fifty-thousandth of an inch in dia-
meter, which are much more minute than the smallest recogniz-
able ova or seeds. As all eflbrts, therefore, to discover the supposed
germs in the atmosphere with our best instruments have failed,
many scientific men w^ho had personally investigated the subject
were once more led into the belief of, at least, an equivocal or
doubtful generation of the lowest forms of animal and vegetable
life. This belief was strengthened by the appearance, in 1859, of
a remarkable work by M, Pouchet, Professor of Natural History at
Rouen, and a corresponding member of the French Academy of
Sciences, entitled ^' Heterogenesis, or Spontaneous Generation,"
as distinguished from Homogenesis, or Generation from Parents.
This book contains not only a full history of all that had been previ-
ously written and thought on the subject, but gives an account of
numerous original experiments and observations made by the author,

ments admitted by Allen Thomson to throw the balance of evidence in favour
of the spontaneous production of Infusoria, mould, and the like." (Todd's
Cyclopaedia, article Generation, vol. ii. p. 430, 1839.)
' Owen on Parthenogenesis.

THE ATMOSPHERIC GEEM THEOEY.

7

proving, as he thinks, that infusoria originate in a finely molecular,
or, as he calls it, proligerous pellicle on the surface of decomposing
fluids, without pre-existing cells or germs of any kind, and there-
fore independently of parents.

The publication of this book has led to a controversy which has
continued up to the present moment. The theory of atmospheric
germs, or that of the Panspermatists, has been ably sustained by M.
Pasteur, who, by new experiments, has revived the doctrine that
fermentation and putrefaction are not chemical processes, as has
been maintained by Liebig, but physiological phenomena dependent
on living germs derived from the atmosphere. These experiments
gained for him, in 1859, the Grand Prize for Physiology annually
awarded by the French Academy of Sciences. They have all,
however, been since repeated by Pouchet and others, and their ac-
curacy as well as the correctness of his conclusions are by them
utterly denied. An extraordinary amount of research, ingenuity,
and talent has been displayed by the advocates on either side, the
results of which will be found recorded in numerous communica-
tions printed in the " Comptes Eendus " of the proceedings of the
Academy.

Such, then, is an outline of the history of this matter. Before
stating more particularly the arguments advanced by the controver-
sialists, on one side or the other, I propose describing shortly the
results of some investigations undertaken by myself, with a view of
determining precisely the .facts of the case, and the nature of the
phenomena which have excited so much discussion.

My attention was originally directed to the origin of fungi in
1841, when examining the parasitic plants found growing on living
animals, an account of which was published in the Transactions of
the Eoyal Society of this city in 1842. In October 1863, after
studying the memoir of M. Pasteur, I commenced a series of obser-
vations, with the aid of my former assistant, Dr Argyll Eobertson,
which were directed (1st) to determine with exactitude, by means of
the microscope, the changes which occurred on the surface of infu-
sions during the development of plants and animals there ; and (2d)
to ascertain what influence the air treated in various ways exercised
on such growths. These observations were carefully repeated and
extended in October 1864. They have again been recently repeated,
and numerous other experiments have been performed, with the aid
of my present assistant, Dr Eutherford. These investigations natu-
rally divide themselves into (1st) observations by means of the
microscope as to the development of infusoria ; and (2d) experiments
directed to destroy the supposed germs in the atmosphere so as
to prevent putrefaction.

8 THE ATMOSPHERIC GERM THEORY.

1. Mode of Development of Infusoria.

On making a cold or hot infusion of any vegetable or animal sub-
stance^ covering the vessel with a piece of paper so as to exclude the
dust, and then watching it every twelve hours, the first change
visible to the eye is a slight opalescence, and the formation of a thin
scum or pellicle that floats upon the surface. This appears at times,
varying from a few hours to several days, according to the tempera-
ture of the atmosphere or the nature of the infusion. On examining
the pellicle or film under high magnifying powers,^ it is seen to be
composed of a mass of minute molecules, varying in size from the
minutest visible point to that of one thirty-thousandth of an inch in
diameter. These molecules are closely aggregated together, and
must exist in incalculable numbers. They constitute the primor-
dial mucous layer of Burdach,^ and the proligerous pellicle of
Pouchet.^ The same pellicle, examined six hours later, shows the
molecules to be somewhat enlarged, and these separated by the pres-
sure of the upper glass are already seen here and there to be strongly
adhering together in twos and fours, so as to form a little chain.
Many twos, also, have apparently melted together so as to form a
short staff or filament — bacterium. (Fig. 1, h.) Twelve hours after
this, it may be seen that the grouping of the molecules in twos,
threes, and fours has become more general, and that several of
these form new groups of eight lengthways. Many of them have
melted together to produce longer bacteria. At the edges of the
molecular mass, and in the fluid surrounding it, may now be seen a
vibratile movement in the shorter bacteria and a serpentine move-
ment in the longer ones, whereby they are propelled forwards in
the fluid — vibrio. (Fig. 1, c, d.) From the second or third to the

Fig. 1.

a h c d e f

Fig. 1.— a, Molecular structure of the proligerous pellicle on its first appearance in a clear
animal infusion. &, Molecular structure of the same, six hours afterwards. The mole-
cules have been separated, and several are seen grouped together in twos and fours. Some
of these have melted together so as to produce bacteria, which exhibit a trembling move-
ment, c, The structure of the proligerous pellicle on the second day. rf, The same sepa-
rated. The molecules are coalescing in rows and melting together to form longer bacteria
or vibrios, which move rapidly across the field of the microscope. As their development
proceeds, they present tlie appearance seen in e, and in Fig. 2. /, Long filaments com-
posed of adhering molecules. 800 diameters linear.

^ The powers I have employed for the investigation were an excellent lens
of ith of an inch focus, by Eoss ; but I also frequently used a -^\t.h. of an inch
by the same maker, and the immersion lens No. 10 of Hartnach, with varying
powers of from 600 to 800 diameters linear. Occasionally 1 confirmed my ob-
servations with a lens recently made for me by Messrs Powell & Lealand, of
J^th of an inch focus, whereby I obtained an enlargement varying from 1250
to 2000 diameters linear.

2 Physiologic, par Jourdan, tome ii. p. 123. ^ H^t«?.rogenie, p. 383.

DEVELOPMENT OF INFUSORIA.

9

fifth or seventh days, the vibrios are lengthened, evidently by appo-
sition of groups of other molecules, to their ends. These melt
together to form a filament, which may extend a third or half, and in
a few cases entirely across the field of the microscope. (Fig. 2.)

Fig. 2.

Fig'. 2. — [a) Vibrio with a serpentine movement. (&) Vibrio with one flexui'e, evidently
formed by the union of two bacteria, (c) Elongated vibrio with one flexure, the area of
the movement marked by a dotted line, [d] An elongated vibrio, not moving; a bacterium
evidently added at one extremity, (e) An elongated vibrio with two flexures, moving
rapidly across the field of the microscope. An observation of these vital structures
evidently indicates aggregations of bacteria and vibriones of a certain length endways, the
flexures occurring at the points of junction. 800 diameters linear.

The movements visible in the molecules and filaments vary accord-
ing to the amount of development. At first the molecules which float
loose in the fluid exhibit gyrations which cannot be distinguished
from Brunonian movements. When short bacteria are formed,
these exhibit peculiar vibrations, — often turn round on their own
axis in various directions, and slowly change their place. They
rarely dart rapidly through tlie fluid, or exhibit a serpentine
motion. But when the vibrio is formed, the filament is pushed
forward with greater or less velocity, at first presenting a wriggling,
but, as it becomes longer, a more decided serpentine motion. A
distinct flexure can be seen at certain points in the filaments,
between the groups of molecular chains or filaments. Dumas says
he has seen the molecules and bacteria uniting endways, a state-
ment the correctness of which Pouchet doubts.^ On two occasions,
however, I was fortunate enough to see this occurrence as repre-
sented in the accompanying figures. (See Figs. 3 and 4.)

Fig. 3. Fig. 4.

abed a h c d e f g

V\l/ VVl///^

Fig. 3.— a. Position of two short bacteria. 5, The lower bacterium was seen to sink
down and unite itself to the upper, and then the two turned round in unison as in c and d.

Fig. 4.— a, Position of two bacteria. 6, Altered position of the same, c, The lower
one adhering to the upper, d, The two turning together to e. /, Vital flexure at the
middle ; and g, four flexures, when I saw the vibrio so formed move forward out of the
field of the microscope. 800 diameters linear.

Pouchet thought that the vibriones exuded a mucous matter,
whereby one stuck to the other. If so, such exudation can only

^ Nouvelles Experiences, p. 115.

10

THE ATMOSPHERIC GERM THEORY.

be poured out at their extremities, as they always unite lengthways,
never crossways. I feel satisfied, however, that the reason the
actual union has so seldom been seen is, Ist^ That it only occurs
at certain periods of development, and can only be followed by the
eye, when the movements are slow ; 2d, That amidst such a multi-
tude of minute moving bodies it requires a long time before two can
be found exactly on one plane, and can be brought so accurately
into focus that they can be watched for a sufficient time. Having,
however, in the two instances described and figured, actually seen
the coalescence, I can have no doubt whatever that such is the
true method of elongation. Numerous other facts seen among
elongated vibriones support this view (see Fig. 2).

It may frequently be seen, on again examining the fluid in
which these bodies have been moving actively, that they are all
motionless, evidently dead. This occurs at various periods. They
now rapidly disintegrate, and thus a second molecular mass or
pellicle is produced. In this, rounded masses may be seen to form,
which strongly refract light not unlike pus corpuscles, or the
colourless corpuscles of the blood. These soon begin to move with
a jerking motion dependent upon a vibratile cilium attached to one
of Ufi extremities — Monas lens. In a day or two other cilia are
produced, the corpuscle enlarges, is nucleated, and swims through
the fluid evenly. Varied forms may now occur in the molecular
mass, dependent on the temperature, season of the year, ex-
posure to sun-light, and nature of the infusion, all having in-
dependent movements. They have been denominated Amcebce,
Paramecia, Vorticellce^ Kolpoda^ KeronoSj Glaucoma^ Trachelius,
etc., etc}

Pouchet describes the Paramecium as originating in the pro-
ligerous pellicle, formed by the breaking down of the primary
bacteria and vibriones. It is the secondary histolytic mass of
molecules which arrange themselves as seen in Fig. 5.

It would occupy too much time to follow the development of all
the forms that may arise. They originate always long after the
primary vibrios are produced, in the secondary, tertiary, or even
later molecular masses, resulting from the disintegration of previous
forms.

It frequently happens that soon after some of these higher
infusoria are seen, that the pellicle falls to the bottom of the fluid,
where it constitutes a dense precipitate, and slowly breaks down ;
then another scum forms on the surface, and molecules, bacteria,
and vibrios are again produced.

The varied forms produced are spoken of by Ehrenberg and other
naturalists as being diflerent species ; ^ but I think it will be found
that the laws, not only of molecular but of alternate generation and
parthenogenesis, prevail among them, and one frequently passes into
another. Their production is largely dependent on temperature,
^ See Ehreiiberg's Infusoria. ^ Ibid.

DEVELOPMENT OF INFUSORIA.

11

state of the atmosphere, light, — especially the sun's rays,— and
other physical conditions.

At other times, it happens that the molecular mass, instead of
being transformed into animalcules, gives origin to minute fungi.
In this case the molecules form small masses, which soon melt
together to constitute a globular body, from which a process juts
out on one side. These are Torulce^ which give off processes
which are soon transformed into jointed tubes of various diameters.

Fig. 5.

€

Formation of Ova in the proligerous Membrane.

a, Coalescence of molecules. The same more advanced, c, Still larger mass. d. The
same assuming a rounded form, e, A membrane formed externally. /, Complete differentia-
tion of the now perfect ovum from the surrounding molecular mass, A nucleus apparent.
— Pouchet. 250 diameters.

terminating in rows of sporules [Pemcillmm) ^ or capsules containing
numerous globular seeds [Aspergillus). Occasionally filaments are
formed from the direct melting together of molecules arranged
longways {Leptothrix) (See Fig. 1,/.)

Here also I think various forms regarded as distinct plants pass
into one another — especially torulse, which are only embiyonic forms
of higher fungi. In all these cases no kind of animalcule or fungus
is ever seen to originate from pre-existing cells or larger bodies,
but always from molecules.

That we should sometimes have animalcules, and at others
fungi, is a well-known fact, the exact causes or conditions producing
which are not yet explained. The Panspermatists, of course, are
of opinion that the germs in the atmosphere are of many kinds,
and that as they fall into various infusions they produce different
results, in the same manner that varieties in ova or seeds develop

12

THE ATMOSPHERIC GERM THEORY.

themselves in peculiar localities or special soils. This assumption,
however, seems to me opposed by the following experiment : —

If an infusion be placed in a deep glass vessel, which again
stands in the centre of a shallow vessel containing the same in-
fusion, and the whole covered with a large bell glass, it will be
found in eight days that on the surface of the former are numerous
ciliated animalcules, while on that of the latter only bacteria and
vibrios exist. Tlie experiment may be reversed, for if the shallow
vessel be filled to the brim, and the deep vessel has. only its bottom
covered, then the ciliated microzoa will appear in the former, and
the non-ciiiated in the latter/

As a result of these experiments, Pouchet has formularized a law
to the effect that the production of ciliated animalcules is in an
inverse ratio to the square of the surface, and that the production
of monads is in a direct ratio to the cube of the mass of the
same fluid.^ To this law I have met with some exceptions,
animalcules having been produced in some of our recent experi-
ments in the shallow dish, and vegetations in the deep vessel, and
vice versa.

It is difficult to explain how germs falling from the air on
the same infusion, under identically similar conditions, with the
exception that the fluid is in vessels of different forms, can vary
the results. Whereas the fact that the higher infusoria are
formed secondarily out of the disintegrated mass of the simpler
ones, which can only take place where that mass is considerable
and floating on the surface of deep fluids, directly conhrms the
molecular theory of growth, and offers an illustration of how
successive disintegrations give origin to different formations.^

That the infusoria originate and are developed in the molecular
pellicle which floats on the surface of putrefying or fermenting
liquids, has been admitted by all who have carefully watched that
pellicle with the microscope, more especially by Kutzing,* Pineau,^
Nicolet,^ Pouchet,'' Jolly and Musset,^ Schaafhausen,^ and Mante-
gazza.^^ The question therefore is, are the molecules that constitute
that pellicle derived from the air or the fluid, — are they precipitated
from above, or do they float to the surface from below, like the
globules of the milk which produce cream ?

Now, it was in consequence of having professed to demonstrate

' Pouchet's Nouvelles Experiences, etc., pp. 135, 243-245. Paris, 1864.
^ Nouvelles Experiences, p. 134.

^ See On the Molecular Theory of Organization, by the Author. Pro-
ceedings of Royal Society of Edinburgli, 1861.

See SchaafFhausen, Comptes Rendus, tome liv. p. 1046.
^ Annales des Sciences Naturelles, 3me serie, tome iii., p. 182. This
observer thinks he saw disintegrated fibres of meat and of other substances
formed directly into vibriones, — in this he was incorrect.
^ Arcana Naturae, tome i. p. 2.

Heterogenic, p. 353. Nouvelles Experiences, p. 111.
Comptes Rendus, tome 1., p. 934. ^ Ibid, tome liv. p. 1046.

10 Institut Lombard, 1852, tome iii.

RESEARCHES OF M. PASTEUR.

13

what had escaped ail previous observers, — viz., the germs in tlie air, —
that M. Pasteur has made his name so famous. He tells us ^ that
he did this by causing a current of air to pass through a glass tube
in which a pledget of gun-cotton had been placed. This was then
dissolved in ether, and the sediment allowed to collect in a watch-
glass. This sediment, after being repeatedly washed, and allowed
to remain in distilled water for twenty-four hours at a time, is
allowed to dry. A portion of the dried matter is then put upon a
slide moistened with a weak solution of potash, and, being covered
with another glass, is examined with the microscope. The results
he has figured ; and, very properly, he has given the scale of mag-
nifying power under which they were drawn (Fig. 10), and which,
by careful measurement, I have ascertained to be 180 times linear.
I show you his drawings, carefully copied.

Fig. 6.

0 ^ 0

®

0

0

Fig. 7.

Fig. 8.

Fig. 9. Fig. 10.

Exact copies of the figures given by M. Pasteur of the dust he collected on gun-cotton,
magnified 180 diameters. These should be compared with Fig. 1, magnified 800 diameters,
showing what is seen to take place when infusoria are forming. Fig. 10, scale of one hun-
dredth of a millimetre.

He says Figs. 6 and 7 represent organized corpuscles from dust
collected in twenty-four hours, from the 16th to 17th November 1859.
The manner in which these drawings, giving the volume and
outline of the bodies, were made, is as follows : — After the dust has
been prepared in the manner described, I took a portion of it from
the watch-glass, and diluted it with a solution of potash, consisting
of 5 parts of potash in 100 of water. As soon as I perceived a
globule evidently organized under the microscope, I drew it. This
is how figure 4 was drawn." ^ This description leaves it uncertain
whether an exact copy was taken of any portion of the field of the
microscope, and, therefore, whether the figure represents the exact
number of corpuscles present, and their relation to each other. It
only gives their form. But, assuming that the same kind of
demonstration was made in each case, we have the relative numbers
of these bodies taken from the gun-cotton in Fig. 6. Fig. 7 is
another demonstration of the same after the addition of an aqueous
solution of iodine. Fig. 8 represents the organized corpuscles
associated with amorphous particles obtained on the 25th and 26th
of June 1860 ; Fig. 9, the dust of an intense fog in the month of
February 1861. In all these demonstrations he admits the organ-

^ Annales des Sciences Naturelles, 4me s^rie, tome xvi. p. 25. ^ Ibid.

14

THE ATMOSPHERIC GERM THEORY.

ized corpuscles are comparatively scarce, because, he observes
(p. 31), it is frequently necessary to change the field in order to
see one of them, whilst at other times several could be seen together.

M. Pasteur thinks that these drawings indicate the number of
organized corpuscles that may be arrested in a small mass of cotton
through which 1500 litres of air, in one of the less-frequented streets
of Paris, have passed in twenty-four hours, about three or four yards
from the ground. These he estimates at several millions in a litre
(p. 29). _

Now, it must be remembered that M. Pasteur is a chemist, and it
will be admitted by every histologist that no method could be more
unsatisfactory for determining either the nature or the number of
the corpuscles than the one he adopted. The solution of the cotton
in ether, the frequent soakings in water, the desiccation, and then
the addition of a solution of potash, must completely alter the cha-
racter of any living corpuscles in the atmosphere. Then the forms
he assumes to be organic, are not necessarily so. They are exceed-
ingly frequent among mineral substances, and siliceous rounded
forms are common, which of course resist sulphuric acid.

Numerous investigations have been made, both before and since
M. Pasteur wrote, to determine the nature of dust floating in the
atmosphere — of that dust, for example, which a ray of sunlight
reveals to us, when admitted into a chamber. It consists, for the
most part, of different kinds of starch corpuscles; the debris of
clothing, especially filaments of cotton, silk, and wool ; the results
of different kinds of combustion, whether of coal or of wood ; vari-
ous mineral bodies, globular or ovoid, amorphous or crystalline ;
and minute fragments of insects and vegetables ; very rarely small
seeds and microscopic animalcules.

These constituents vary to such an extent in different localities,
as to enable the observer, in some cases, to determine whence
the dust was collected. Starch corpuscles abound in the neighbour-
hood of flour-mills and bakeries ; fragments of clothing where there
have been crowded assemblies of persons, cotton and wool being
predominant if the persons belong to the poorer classes, and silk if
the upper classes have been present; the produ.cts of combustion
predominate in smoky localities ; mineral particles on the roads
and highways ; seeds, fragments of vegetables and insects, in market
places, gardens, etc., etc. But although these constituents of the
air vary in different places, infusoria, produced in all of them, are
identically the same.^

This has been tested in various ways. The dust has been ran-
sacked to discover organic germs, — collected and carefully examined
with the microscope, near the soil, and on the summits of the highest
buildings, not only in frequented, but in desert places ; in crowded
assemblies, as^ well as in empty Gothic cathedrals and ancient
vaults — in the ancient palace of Karnack, on the banks of the Nile ;
1 Pouchet's Nouvelles Experiences, p. 73, et seq.

ORIGIN OF INFUKOSIA.

15

in the tomb of Khamses II. at the extremity of the Desert ; as well
as in the central chambers of the great pyramid of Ghizeh. The
chief element of the dust collected in these places has been found
to be starch corpuscles.^ Large quantities of air have been drawn
through tubes by aspirators, and collected on cotton, in distilled
water, or projected on glass. The feathery snow, which, falling
through the atmosphere, may be well supposed to collect its con-
tents, has been melted, and the precipitate carefully collected. The
emanations of marshy places, such as those of the Maremma in
Tuscany, have been specially investigated.^ The larynges and
mucous pulmonary surfaces of numerous animals have been ex-
plored, even to the inmost bone cavities of birds. On the summit
of Mont Blanc, amidst eternal snow ; on the glaciers of the Jura and
of the Pyrenees, and in the deep crevasse;^ on the burning plains
of Egypt, and in the markets of Constantinople, the dust of the
atmosphere has been microscopically examined, — and in all with a
like negative result as to the existence of germs. Nowhere could
they be seen, or if a few, in the opinion of some, were visible, could
they in any way account for the multitude of minute infusoria,
which, in all these localities, not only readily spring up in putrid
fluids, but in every instance are identically the same.*

Indeed, on examining the drawings of M. Pasteur (see Figs. 6 to 9),
let us suppose that the few bodies he has figured are truly sporules, as
he believes them to be, w^hich have preserved their form — after the
action of ether, several soakings of twenty-four hours each in water,
the desiccation, and subsequent mixture with a weak solution of potash.
How, it may be asked, could these bodies produce the incalculable
millions of minute molecules in the smallest fragment of the pellicle
we can transfer to our microscopes, in which, as we have seen, the
infusoria originate ? It has been supposed that, on falling from the
air, they undergo rapid division, and spread over the surface with the
greatest rapidity ; but no one has ever seen this remarkable phenome-
non, and the slightest consideration must show that such an assump-
tion is completely adverse to what can be readily demonstrated on the
surface of every infusion. Thus, there can be no doubt that the minute
molecules are formed first, and the bacteria, vibrios, and filaments,
last. Supposing that the primary molecules, figured No. 1, in Fig. 11 ,
enlarge to a certain point. No. 2, and then divide, how is it pos-
sible to explain the formation of elongated filaments at all? Surely
the idea of their rapid multiplication by division is opposed to that
of their power of elongating into bacteria and vibrios, whether by
aggregation or growth from their extremities. It may frequently
be seen that No. 3 is composed of molecules of exactly the same
^ Pouchet's H^terog^nie, p. 446.

^ L. Gigot's Recherches experiinentales sur la Nature des Emanations mar^
cageuses, Paris, 1859. E^cherches sur I'Air des Maremmes de la Toscane, par
M. E. Bechi. Comptes Rendus, tome lii. p. 852.
Comptes Rendus, tome Ivii. p. 658.

* Nouvelles Experiences, p. 75,

16

THE ATMOSPHERIC GERM THEORY.

Fig. 11.

1. 2. 3. 4. 5. 6.

CQQCtXCB

Stages in the Development of Vibriones. 800 diameters linear.

size as No. 2, which are floating loose, — a fact in favour of their
coalescence rather than of their division, as then they would be re-
duced to half the size. - It is more probable that although the smaller
molecules may increase by imbibition of fluids, they have yet a con-
stant tendency to aggregate together and melt into one another.
No. 3 is not a proof of No. 2 dividing, but of two molecules coalesc-
ing ; and when they unite, they form No. 4. Two or more of
these uniting, form Nos. 5 and 6. When a similar process to this
goes on in mineral bodies, as shown by Mr Eainey,^ it cannot
suggest division, but union ; and this for the obvious reason, that
the former would lead to disintegration, whereas, it can be seen in
one case as in the other, that development is the result. In short,
in the same manner as a tube is formed by a coalescence of cells, so
is this minute vibratile vibrio formed by the coalescence of mole-
cules. It may be argued, however, that each molecule elongates
itself — that is, No. 2 is converted into No. 4 ; this into Nos. 5 and
6 ; and that No. 3 are sporules or ova, caused by the disintegration
of No. 6. But this view is opposed by the fact that Nos. 1, 2, and
3 are seen before Nos. 4, 5, and 6 are produced. Of this all have
satisfied themselves who have examined animal and vegetable infu-
sions; and the conclusion, therefore, cannot be resisted, that the
vibrios are derived from the molecules, and not the molecules from
the vibrios.

But it may also be supposed, that while some have the property of
dividing, others are capable of elongating or aggregating ; but this
view is not only opposed to observation, but is at variance with all that
we know of embryonic development in plants and animals. When a
plant consists of a single structural element, such as a cell or a tube,
it will, I think, be admitted that growth in the sense of increased
bulk, and growth in the sense of multiplication of parts by division,
do not proceed at the same moment of time. Every plant and
animal follows, in this respect, the same law. Nutrition is carried
on up to a certain point of maturity, and then, and not till then,
does generation, or the separation of parts to form new creatures,
take place. When plants and animals are complex in their struc-
ture, one organ or segment may be growing, while another is disin-
tegrating ; but in individual organs there is a period for growth and
reparation, and a period for division or separation. Hence, it seems
to me, I am correct in thinking that if the primary molecules on the
surface of an infusion possess the property of dividing, they cannot
also, at the same moment, possess the property of elongating and
1 On the Mode of Formation of Shells, etc., 8vo. London, 1855, p. 12.

CHEMICAL EXPERIMENTiS.

17

forming filaments. The one function is subversive of the other.
While, then, a cell or a vibrio may possess the property of growth
and division, these two functions must be exercised at different
periods of time, — so that, in reference to the early stage of forma-
tion, if the molecules divide, bacteria, vibrios, and filaments could
not be formed. A mass of vibrionic molecules is not. a compound
organism ; it is a mere aggregation of similar simple elements.
Each of these in passing through certain phases of development
may be arrested, or reach maturity at various periods, so that we
frequently see different forms present at one time; but that the
same forms and the same stages of growtli sliould exhibit directly
opposite functions, is surely not in accordance with physiological
knowledge.

The conclusion we must arrive at therefore is, that the mole-
cules seen on the surface of infusions out of which animalcules and
fungi are produced, are not derived from the air.

Neither can they be supposed to pre-exist in the fluid, as then
they would be readily seen, which they never are at the commence-
ment. On this point nothing can be clearer than the microscopical
evidence, so that it results from the facts and arguments I have
brought before you, that the more simple infusoria do not origi-
nate from cells or minute germs at all, whether in the atmosphere
or in the fluid. This is the almost universal conviction of histolo-
gists who have carefully investigated the matter.

2. Chemical Experiments ivhich have heen directed to destroy the sup-
posed Germs in the Atmosphere^ so as to prevent Fermentation and
Putrefaction.

Schutze, in 1837,^ after heating an infusion to the boiling
point, connected it with two of Liebig's bulbs, one containing sul-
phuric acid, and the other concentrated solution of potash. The
air forced through these liquids he thought capable of destroying
the atmospheric germs.

Schwann also, in 1837,^ forced air, with the same view, through
metallic tubes heated to redness ; and found, when so calcined, it
occasionally prevented infusorial growth. He thought that oxygen
alone was not the cause of fermentation, but some substance in the
air capable of being destroyed by heat.

Schrgeder and Dusch, in 1859, filtered the air through cotton
before bringing it in contact with organic fluids. They found that
some did and others did not undergo putrefaction, and were induced
to believe that the presence of oxygen, and the formation of an
acid, were the cause of fermentation. Schrgeder afterwards found
that the yolk of an egg, milk, and the juice of meat without water,

^ Poggendorf's Annalen, 1837, p. 41 ; and Edinburgh New Philosophical
Journal, 1837.

Poggendorf's Annalen, 1837, p. 184.

18

THE ATMOSPHEKIC GERM THEORY.

putrefied in air filtered through cotton, and supposed it to contain
an active substance, the nature of which was unknown/

The experiments of Schutze, Schwann, Schraeder, and Dusch
have been frequently repeated without preventing the growth of
fungi. ^

Again, it is almost universally considered that the heat of
boiling water or cold at zero w^ill destroy all kinds of animal and
vegetable life. Indeed, to imagine that the minute molecules or
vibrios of which we have been speaking, or small ova and sporules
consisting of oleo-albuminous matter without any envelope, would
remain in boiling water for hours and retain, their vitality, must
be regarded as a violent assumption. Three or four minutes'
boiling of a hen's egg not only kills it, but converts its whole sub-
stance into a hard mass. There is no seed known which, when
taken out of its indurated shell or case, is capable of germina-
ting after being boiled for a short time.^ Yet nothing is more
certain than that long ebullition of various infusions has wholly
failed to prevent the formation in them of animal and vegetable
growths.

Pouchet and others have frequently performed the following ex-
periment : — An open flask was plunged into and filled with a
decoction of barley which had been boiling for six hours. A
stopper was introduced into it below the liquid, and on taking it
out the whole neck of the flask was immediately plunged into
melting sealing-wax, and hermetically closed. In six days some
yeast was observed in it, at a temperature of 18° Cent. The follow-
ing day the temperature was raised suddenly to 27°, when the flask
burst, and then it was seen by the naked eye, and by the micro-
scope, that it contained a notable quantity of yeast.* Now, yeast
is a plant, which was thus proved to have grown in an infusion
that had long been boiling, and from wdiich all atmospheric air had
been expelled. As, therefore, neither calcined air, sulphuric acid,
liquor potassse, gun-cotton, or a boiling temperature have failed to
prevent the production of infusoria, or destroy the supposed germs
in the air or infusion, I determined, in 1863, to try the effects of
all these destructive agents, with the exception of the first, at
once, and with the greatest possible care.

First Series of Eoxperiments.

On the 17th and 18th of October 1864, I performed the follow-
ing experiments in my laboratory, with the assistance of Dr Argyll
Robertson : —

1 Quoted by Pasteur, opus cit., p. 16.

2 See Pasteur, opus cit., pp. 34, 35. Pouchet's Heterogenic, pp. 252, et seq.

3 See some conclusive experiments recently performed on this subject by
Meunier. Comptes Rendus, tome Ixii. p. 992. See also Pouchet's Experi-
ments on the Seeds of Medicago from Brazil. Comptes Rendus, tome Ixii.
p. 941.

* Heterogenic, p. 629.

CHEMICAL EXPERIMENTS.

19

Decoctions of liquorice root, of tea, and of hay were kept at the
boiling temperature in a porcelain basin, over a gas flame. Flasks
filled with and inverted in the boiling fluid, had air pumped into
them to the extent of three-fourths of their volume, which had
passed through (1st) a U-shaped tube containing liquor potassse ;
(2d) Liebig bulbs, containing sulphuric acid; (3d) a hollow glass
ball containing gun-cotton ; and (4th) another U-shaped tube with

Fig. 12.

a h c d e

f

Arrangement of the Apparatus employed.

a, Bent tube containing liquor potassse and pumice-stone, h. Hollow glass ball containing
gun-cotton, c, Liebig's bulbs, containing sulphuric acid, d, Bent tube containing sul-
phuric acid and pumice-stone, e, Infusion kept at the boiling point, when air was pumped
into it. /, Caoutchouc pump.

sulphuric acid. All the bent tubes were filled with fragments of
pumice-stone, to break up the air, so as to prevent the possibility
of any germs passing through in the centre of bubbles. The bent
glass tube leading from the last U-shaped tube, filled with sulphuric
acid and pumice-stone, was also filled with the acid, so as to destroy
any germs that might be supposed to adhere to the interior. After
the air so prepared had entered the flask, corks, which had been for
some time boiled in the infusion, were by means of iron forceps
inserted in the necks of the flasks, and the entrance of fresh air
prevented. Further^ on removing the flask from the boiling infu-
sion, the cork and neck were hermetically closed by plunging them
into melted sealing-wax. At the same time bottles or flasks con-
taining the same infusion, but having a similar proportion'' of ordi-
nary air, were sealed or corked up, so as to be contrasted with the
influence of the prepared air.

The results were that the infusions in all the flasks in contact with
ordinary air, five in number, were rendered turbid, or covered with
fungi in from six to twelve days ,* whereas all the infusions, with
one exception, which were exposed to the prepared air, eight in
number, also became turbid and contained fungi, but at periods
varying from four to nine months.

Some of these flasks I have recently opened (January 7, 1868),
and found that they contained deposits of bacteria and vibriones,
with molecular debris of an indeterminate character.

20

THE ATMOSPHERIC GERM THEORY.

Second Series of Escperhnents.

About a year afterwards, on the 3d and 13th of October 1865,
the experiment was repeated in exactly the same manner, with
separate decoctions of liquorice and dulcamara roots, and with tea.
Again, flasks holding similar decoctions with ordinary air were
contrasted with those which held the prepared air. In these last,
three in number, fungi appeared in from six to twelve days ; and in
the former, all, nine in number, with one exception, contained
fungi, or were very turbid, in periods varying from four to nine
months.

The exception, which I now show^ you in the first series of ex-
periments, was a decoction of hay; and in the second series,. a
decoction of dulcamara root. It will be observed that both these
infusions in the flasks remain clear and without the slightest sedi-
ment or pellicle, although the prepared air they contain, the fluid,
the flask itself, and the mode of closing and sealing it, were iden-
tically the same as in all the other flasks which were filled and
closed at the same time. To suppose that these two flasks were
the only ones from which atmospheric germs were excluded, must
appear to those who will examine them all, a strong assumption.
Neither can it be true that in all the flasks, except one in each
series, air could have entered since they were closed. I have
placed the whole in vacuo under the bell-glass of an air-pump, and
from none could any air whatever be extracted.

Three of the flasks in the second series of experiments I have
opened, and found in two the same molecules and indeterminate
debris as in the others ; but in the third, a white cottony fungus, the
size of a small pea, was floating in a tolerably clear decoction of
dulcamara, which, on microscopic examination, w^as composed of
minute jointed filaments forming a dense network.

Third Series of Experiments.

A third series of experiments was performed with the assistance
of I)r Rutherford, October 14, 1867. In this case glass stoppered
bottles were used, it having been suggested that sporules or
germs might have been concealed in the corks formerly employed,
although they had been well boiled. In this case we employed
w^eak decoction of tea, of beef, and of hay, taking care as before,
that one bottle having ordinary instead of prepared air introduced,
should be kept for the purpose of comparison. In all the bottles
with common air, six in number, fungi appeared in from one to
two months and a half. In one bottle air was passed through car-
bolic acid only, and you see that it presents a distinct proligerous
membrane ; all the others as yet remain unchanged, but we cannot
as yet regard the experiments as complete.

CHEMICAL EXPERIMENTS.

21

Fourth Series of Experiments,

In all these cases it will be observed, that the prepared air was
passed through a boiling fluid and was consequently rarefied. It
occurred to me to allow the fluid in the inverted bottles to get
cold before introducing the prepared air. This was done in four
cases, December 28, and I show you that a fungus has appeared in
all. It would seem, therefore, that rarefaction of the air greatly
influences the result. It may easily be conceived that air subjected
to a boiling temperature is so expanded as scarcely to merit the name
of air, and that it becomes more or less unfit for the purpose of sus-
taining animal or vegetable life.

Fifth Series of Exjoeriments.

A fifth series of experiments was performed on the 4th of the
present month (January 1868), with the same precautions, and with
an infusion of dulcamara only. We filled sixteen bottles. Into
four of these we pumped ordinary air into a cold infusion. Into
four others ordinary air was pumped into a boiling infusion, and we
repeated this experiment with four bottles each of the boiling and
of the cold infusion with prepared air. The result, up to the
present moment is, that the fluid has become turbid only in the four
which contained ordinary air not rarefied.^ This experiment also is
not yet complete, but serves to show the great influence of rarified
air.

Sixth Series of Ex/periments.

A sixth series of experiments was performed on the 11th of the
present month. It having been asserted by M. Pasteur^ that pass-
ing air through bent tubes, by hindering the access of germs and
allowing them to be deposited on the sides of the glass, prevented
the growth of infusoria, twelve bottles were prepared, four of which
contained an infusion of dulcamara, another four a decoction of putrid
meat, and a third four, yeast water. The bottles were plunged into
and filled with the infusion when boiling, inverted in it, and allowed
to get cold. Through a bent tube, five feet in length, having fourteen
sharp zig-zag bends, four inches long, the air was pumped gently
into three bottles of each series, and ordinary air was admitted to the
fourth. The result is, that already, January 17, the fluids in all
are turbid, with the exception of two bottles containing infusion of
dulcamara,^ so that bent tubes appear to intercept none of the sup-
posed germs.

These experiments, on the whole, appear to me to be totally ad-
verse to the atmospheric germ theory, and to indicate that the pro-

' A fungus has since appeared in one of the bottles containing non-rarified
prepared air. (Feb. 12).

^ Comptes Kendus, tome 1. p. 306.

^ These also have since become turbid. (Jan. 30),

22

THE ATMOSPHERIC GERM THEORY.

duction or non-prod action of infusoria depends, for the most part,
on the temperature, chemical constitution, density, and other physi-
cal properties of the air, rather than on living organisms there, which
^ire developed in the fluid. Still, in every series of experiments, it
will be noticed that there are one or two exceptions. This has also
been observed by Pasteur in most of his experiments, and he attri-
butes them to some currents or limited portions of air being rich in
germs, whilst others are free from them.^ But that this explanation
applies to my laboratory, in which all the experiments described
were made, is not probable.

It is now admitted by M. Pasteur that the boiling temperature,
that is 100° Centigrade, does not prevent the growth of the supposed
germs in the atmosphere ; but instead of considering this fact hostile
to his theory, he concludes from it that the germs have the power
of resisting that amount of heat, and of being most tenacious of life ;
but he says, 130" Centigrade always destroys their vitality. M.
Pouchet, however, has shown that the air, and the organic matter
placed in boiling water, will germinate after they have been ex-
posed to a heat of even 150°, and he says it may be raised to 200°
Centigrade, and yet animalcules and fungi will develop themselves.^

In the same manner, air and infusions exposed to intense cold
still produce animalcules, but, according to Pasteur, not so readily.
Twenty flasks containing boiled infusions, and from which the air
was expelled, were opened by him with excessive precaution on the
Mer de Glace at Montanvert on the Jura. Notwithstanding the
purity and extreme coldness of the air, infusoria appeared in live
of his flasks.

As an illustration of the manner in which the controversy on this
subject has been carried on in the Imperial Academy of Sciences in
Paris, I may give a short account of that portion of it referring to
the Glacier experiments. M.M. Pouchet, Jolly, and Musset opened
eight similar flasks used by M. Pasteur at Montanvert, on the
Glacier of the Maladetta, in the Spanish Pyrenees, 9000 feet above
the sea, and 3000 feet higher than that of Montanvert, using all
the precautions required by M. Pasteur. In addition, before cut-
ting ofl" the ends of their hermetically sealed tubes with a file, pre-
viously heated by a lamp, they held the flasks above their heads.
Notwithstanding, infusoria appeared in all the infusions a few days
afterwards.^

To this communication, presented to the Academy, Sept. 21,
1863, M. Pasteur replies, Nov. 2,^ saying that he is rejoiced that
his learned adversaries have gone to such an altitude to repeat his
experiments; but observes that they did not take the necessar}^
precautions. They only had eight flasks, whereas he had twenty ;
they shook their flasks before opening them, which he took care not
to do ; and they had the imprudence to use a file, instead of a pair

1 Comptes Rendus, tome li. pp. 350, 351. ^ i^id. tome 1. p. 1015.
3 Ibid, tome Ivii. p. 558. ^ Ibid. p. 724.

CHEMICAL EXPERIMENTS.

23

of pincers with long branches, heated in the flame of a lamp. He
says that the thumb and fingers holding the file were too near the
opening into the flask, and may have conveyed germs there, espe-
cially as they were not passed through the flame, as the file was.^
He defies them^ if they take sufficient precautions, to obtain infu-
soria in all their flasks.^

MM. Jolly and Musset accept the defiance of M. Pasteur, Nov.
16,^ and, in fact, on the 13th June following, they send a memoir
to the Academy, stating that they had returned to the Maladetta, this
time with twenty-two flasks — that is two more than were used by M.
Pasteur — fulfilled all his conditions, not forgetting the pincers with
long branches, properly heated, and found that infusoria appeared
in every flask without exception in four days and so ended this
part of the controversy.

Numerous other important questions have been debated before
the Academy ; among these are the changes which take place in
the air confined in the flasks, founded on numerous analyses f the
observations of Jolly and Musset Avith regard to vibrios living in
distilled water;® the statement by M. Pasteur that neither free
oxygen nor atmospheric air are necessary for the growth of infu-
soria/ and that they will develop themselves in carbonic acid gas
only. Lastly, the same chemist declares that, notwithstanding his
often declared opinion that ferments are living beings and not dead
matter, that he can produce fermentation with the ashes of yeast.^
Some of these statements are confirmed by Donne,^ who found that
hens' eggs became putrid witliout the formation of vibrios or other
infusoria. This observation, wliile it might serve to prove that
atmospheric air passing through the egg-shell separated the germs
by filtration, is wholly opposed to the idea that putrefaction is neces-
sarily caused by such germs.

The only conclusion I can draw from the numerous contra-
dictory and ingenious communications presented to the Academy
of Sciences during the last eight years on this matter is, that
not the slightest proof is given by the chemists, with M.
Pasteur at their head, that fermentation and putrefaction are
necessarily dependent on living germs existing in the atmosphere.
They rather tend to show that these are phenomena of a chemical
nature, as was ably maintained by Liebig.^*^ Did we indeed con-
fine our reading to the papers of M. Pasteur — that is, to one side of
the case — we could easily persuade ourselves of his correctness

1 Comptes Rendus, p. 725. ^ ibj^. p. 726. s Ibid. pp. 842-845.

4 Ibid. Ivi. p. 1122. 5 Ibid. pp. 734-739. ^ ibid. Iv. p. 491.

7 Ibid. li. pp. 345, 346 ; liv. p. 267 ; Ivi. p. 1191. » Ibid. Ivi. pp. 418, 419.
9 Ibid. Iviii. pp. 951, 952 ; Ixv. p. 602.
^0 Letters on Chemistry, letters 18 and 19.'

This is what unfortunately seems to have been done by the Commission
of the Academy, which made a report on this subject, Feb. 20, 1865 (Comptes
Rendus, tome xl. p. 384). No histologist was on the Commission, wliich
refused to enter upon any kind of microscoi)ical inquiry; Messrs Poucliet,

24

THE ATMOSPHERIC GERM THEORY.

but every one of his experiments has been repeated by several
independent investigators, who have shown his imagined proofs as
to the existence of atmospheric germs to be altogether erroneous.
We may conclude, therefore, that living germs are not necessarily
the cause of putrefaction and fermentation ; neither is it necessary
to believe that ferments are living at all — they may be dead. This,
if not admitted, seems to be Implied by Pasteur himself, who tells
us he can now excite these processes, not by fresh yeast only, but
by the ashes of yeast.^ That they may be induced by dead organic
matter, which has been subjected to a direct temperature of 150°
or 200° Centigrade — a heat utterly, incompatible with the existence
of life — we have seen to have been proved by Pouchet, Jolly,
Musset, and others.

The idea that these imaginary germs were the cause of putre-
faction, of disease, of blights among vegetables, and other evils,
originated with Kircher and the pathologists of the seventeenth
century. It has been frequently revived, but always shown
to be erroneous. In 1852, cholera was supposed to be occasioned
by a fungus that really existed in the dejections, but which Mr
Busk pointed out was the uredo segetmn of diseased wheat, which
entered the body in the form of bread. Certain well-known para-
sitic diseases are spread by contact, such as scabies, which, as it
depends upon an insect burrowing in the skin, may be understood
to crawl from one person to another. Favus, also, I succeeded, in
1841, in proving might be made to grow on diseased surfaces of
otherwise healthy persons ; but many of our unquestionably infec-
tious diseases, such as smallpox, scarlatina, measles and typhus,
have no such origin. It has been attempted to be proved, indeed,
by Lemaire,^ that in the condensed vapours of hospitals and other
putrid localities, vibrios may be found ; but that vibrios are the
cause of these various diseases, is not only not proved, but from,
what has been stated, is highly improbable.

What, then, it may be asked, is the origin of the infusoria, vege-
table and animal, that we find in organic fluids during fermentation
and putrefaction ? In answer to this question, I say they originate
in oleo-albuminous molecules, which are formed in organic fluids,
and which, floating to the surface, form the pellicle or proligerous
matter. There, under the influence of certain conditions, such as
temperature, light, chemical exchanges, density, pressure, and com-
position of atmospheric air, and of the fluid, etc., the molecules,
by their coalescence, produce the lower forms of vegetable and
animal life.

Hallier, describing the development of Penicillium crustaceum,
tells us, that after all movement in the primary molecular mass has
ceased, the molecules arrange themselves in long lines, which he

Jolly, and Musset, under such circumstances, very properly took no part in
the investigation, which, consequently, was altogether one-sided, and of no
scientific value.

^ Comptes Rendus, tome Ivi. pp. 418, 419. Ibid, tome lix. pp. 317-428.

MOLECULAR THEORY OF ORGANIZATION.

25

calls Leptothrix chains. (Fig. 1, /) From the melting together
of these, the delicate filaments forming Leptothrix buccalis are evi-
dently produced ; and these, according to him, by fm-ther develop-
ment, pass into Penicillium crustaceum.^ Why the molecules
should sometimes arrange themselves in long rows, and at others
into rounded masses (compare Fig, 1, /, and Fig. 5, a), is probably
dependent on varying degrees of limpidity and viscosity. But why
both these forms of molecular matter should sometimes possess an
inherent power of contractility, and at others not, it is impossible
as yet even to surmise. But on the determination of this point,
the variations existing between the different kinds of fermentation
and putrefaction are evidently dependent.

But the ultra vitalist will ask. If so, what becomes of the doctrines
— "Every living thing from an egg;" " Every cell from a cell
and " All life from life ?" To this I reply, these expressions are
formulae, which only impose upon the understanding, check the
search after truth, and are already completely overthrown by the
advance of science. A few words with regard to each of them Avill,
I think, show this.

I. — After what has been said, I need not dwell upon the first of
these views, viz., omne vivum ex ovo, for the facts we have de-
scribed are quite hostile to it.

II. — That every cell comes from a cell, is a recent doctrine, which,
from its first enunciation, was rejected by almost all the first histo-
logists of Europe. The illustrious founders of the cell theory,
Schleiden and Schwann, clearly showed that primary cells origi-
nated in a molecular mass which they called a blastema. Max.
Schultze in 1861,^ and Bruecke in 1862,^ demonstrated that a cell
wall had nothing to do with the development of molecular masses, and
now it is not considered essential to the conception of a cell by the
most inveterate cellulists. Having thus discarded from this far-
famed elementary organ its external wall or boundary — which can
alone entitle it to be called a cell at all — they have only to carry
their conceptions a step farther, and banish the nucleus also. There
will then remain an organic fluid or molecular material, the true
potential substance, in which all growth takes its origin.

That molecular, nuclear, and cell forms are not necessarily organic
has been proved by the researches of Ascherson,* Rainey,^ and
Montgomery.^ They have succeeded in producing from various
viscous substances, more especially oil and albumen, different kinds
of gums,^ and a material obtained from yolk of egg called protagon,
appearances resembling almost every kind of elementary texture.

1 Gahrungsercheinungen, p. 51, and fig. 12. Leipzig, 1867.

2 Reichert and Du Bois-Reymond's Archiv., 1861, p. 9.

^ Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften, 1862
p. 382.

4 Muller'« Archiv, 1840.

5 Mode of Formation of Shells, etc., London, 1858.
The Formation of so-called Cells, etc., London, 1867.

^ Rainey in Medical Times, January 1868.

26

THE ATMOSPHERIC GERM THEORY.

The idea that there are such things as histological organic forms,
which are necessarily indicative of life, must now be regarded as
fallacious. It has deceived many, and among the rest, as we have
seen, M. Pasteur. What now interests us are the transformations
which these forms undergo, and the passage of one into the other.
This inquiry must lead us to the molecular theory of organization,
which inculcates that all the tissues are formed by the successive
production of histogenetic or formative, and histolytic or disinte-
grative molecules ;^ and it appears to me that its correctness is sin-
gularly confirmed by the investigations that have been brouglit
before you this evening. In short, we have first molecular deposi-
tions in organic fluids ; these aggregate to form nuclei, cells, and
other tissues ; and these again, by constantly breaking down and
re-forming, gradually elaborate and build up the higher organisms.
It would appear that nature is constantly operating in the or-
ganic and inorganic worlds by the process of molecular coalescence ;
that the notion of every particle being necessarily derived from its
like is erroneous ; and that the law of descent from parents, which
we recognise in the higher animals, changes, as we descend in the
scale, first to parthenogenesis^ whereby this direct descent is broken,
and ultimately to heterogenesis, in which it is lost.

This theory irresistibly recalls to our recollection the philosophical
speculations of the Greeks, and especially of Deraocritus, Anaxagoras,
and Empedocles, and suggests to us that history in science, like
history in morals or in politics, often repeats itself, so that our pre-
decessors may often be regarded not only as the originators of spec-
ulative opinions in the past, but also as prophets, who have foretold
in the cycle of events the deductive truths of the future.

III. — The doctrine that life must necessarily spring from life is
essentially connected with the view of direct descent from parents.
Previous to the time of Harvey, life was considered to be an inde-
pendent principle, capable of being added to or removed from inert
matter. Such was the opinion of the ancient philosophers, as alle-
gorically explained by the fable of Prometheus, who animated the
marble statue by fire stolen from heaven. In later times, BufFon
imagined life, like matter, to be indestructible. According to him
every living molecule had a life of its own, and the method by
which it manifested its function depended on its association with
other molecules. Thus, the body of an animal or a plant was the
aggregation of a multitude of minute living beings arranged in a
particular way. The death of the complex compound was simply
a dissolution of one of these associations, and the organic molecules
thus set at liberty wandered about until they once more combined
with a plant or animal — herewith a monad, there with a quadruped.
The materia vitce diffusa of John Hunter was something similar.

Our modern view of life is, not that it is independent of matter,

^ See the author's paper on the Molecular Theory of Organization. Proceed-
ings of the Royal Society of Edinburgh, April 1, 1861 ; and Microscopical Jour-
nal, 1861.

MOLECULAK THEORY OF ORGANIZATION.

27

but a condition of matter : in nther words, that material substances
found in the atmosphere, and in plants and animals, influenced by
certain forces, have peculiar properties communicated to them.
These properties are contractility, sensibility, the power of
growth in certain directions, and mental acts ; the exercise of any
one of which constitutes life. That accidental causes are capa-
ble of communicating one or more of these properties to tissues
that did not previously possess them, is certain. Thus, exposure to
light may influence the movement of the pigment molecules in the
skin of the frog and other animals, so that it at once becomes dark
or light.^ The entrance of a spermatozoid into the ovum — that is a
vibratile fibre, much like a vibrio, pushing a molecule before it —
excites those changes in the yolk which produce an embryo. An un-
impregnated uterus is not contractile, but if impregnated, its fibres
have, at a certain period and then only, a vital property communi-
cated to them, and they expel the foetus. I think no one can
doubt that an aggregation of molecules produces a vibrio, which,
at first motionless, has contractility communicated to it, and thereby
lives.

M. Onimus has shown, by careful experiment, that if the clear
serum from a blister be placed in a bag of gold-beater's skin, and
put below the skin of a rabbit, so as to be exposed to warmth and
endosmotic currents, bodies like pus or the colourless cells of the
blood, called by Robin, Leucocytes, are formed. He has even
filtered the fluid, and shown that they arise spontaneously by mole-
cular deposition, so long as the fibrin it contains is not coagulated.
Hence, he says, all substances which produce coagulation — such as
alcohol, corrosive sublimate, iodine, to which we may add car-
bolic acid — prevent such purulent formations. Their production,
however, he points out, is identical with that of molecular growth.
He further ascertained, that when white of egg or fresh blood was
placed in a glass vaccination tube, or vessel deprived of air, they did
not putrefy ; but if placed in a sac of gold-beater's skin, although
not exposed to fresh air, they shortly putrefied, and contained nume-
rous vibrios. In the first case, he says there is no exchange of air
between the organic substances and the fluid, under which circum-
stances no organic fprms are produced. He therefore maintains that
vibrios and fungi in fluids are not the result of atmospheric germs,
but of conditions necessary to the putrefaction of organic fluids.^

These conclusions are confirmed by the numerous facts which
have long been recognised in pathology,^ and indicate that it is to
a knowledge of these conditions that science must now apply
itself. So long as the origin of infusoria was ascribed to atmo-
spheric germs, we rested contented, and all inquiry was stopped. I

^ See Professor Lister on the Cutaneous Pigmentary System of the Frog. —
Phil. Trans. 1858.

^ Journal de I'Anatomie et de la Physiol ogie, 1867, p. 47.

See the author's Clinical Lectures on the Principles and Practice of Medi-
cine, 4th edition, more especially pp. 164, 182, 233, 689.

28

THE ATMOSPHERIC GERM THEORY, ETC.

shall be satisfied if, in supporting another doctrine this evening, I
have stimulated even one inquiring mind to investigate the truth.

Gentlemen, I see by the public papers that a great legal autho-
rity in this city has been lecturing on the contradictions which exist
among scientific men, and the want of proper evidence leading to
their conclusions. He complains, also, that he everywhere sees a
tendency to place new scientific views in opposition to religious
beliefs.^ I shall not reply to his good-natured criticisms by dwelling
on the glorious uncertainties of the law, but shortly point out, in
conclusion, that the theory I have placed before you this evening
should recommend itself to the Biblical student. Man, he learns,
was created from the dust of the earth, and he may well ask, — why
should such molecular matter have been chosen for the purpose?
How many histogenetic and histolytic transformations it underwent
before the form was perfected, he is not told ; but being made, it is
distinctly said that living properties were added to it He is nowhere
taught that life invariably springs from life. On the contrary, the
great doctrine everywhere impressed upon him is, that life springs
from death. Thou fool," says St Paul, " that which thou
sowest is not quickened unless it die." In quoting this remarkable
passage, I do not seek from it scientific evidence at all, but I
believe it contains a deep philosophy consistent with all kinds of
development — religious, moral, political, and certainly physio-
logical. There is a manifest inconsistency in supposing that the
same kind Providence which alone can create life, should have done
so once only in ages past. The idea that a seed can retain vitality
for thousands of years has hitherto been a stumbling-block to
physiologists. What it really possesses is a certain arrangement
of dried molecular matter, which, when exposed to peculiar condi-
tions, enables it to exhibit the vital property of growth. The truth
seems to be, that new life springs from the molecular death of pre-
existing tissues and organisms. The vibratile and germinal mole-
cules concerned in the process are not new productions, but old ones,
and these, submitted to conditions which it is the office of the
physiologist to investigate, undergo a rejuvenescence, and enter into
and constitute the living substance of the new being. This theory,
1 venture to think, is not only consistent with all known facts, but
unites in one grand conclusion the physiological science of the
present day, the intellectual speculations of ancient Greece, and the
direct teachings of our sacred records.

^ Address to the Stockbridge Working-men's Institute, by James Moncreiff,
Esq., Dean of Faculty, etc.— Scotsman Newspaper, 14th January 1868.

EDINBURGH : PRINTED BY OLIVER AND BOYD,