LOUIS PASTEUR
LOUIS PASTEUR
HIS LIFE AND LABOURS
_BY HIS SON-IN-LAW_
TRANSLATED FROM THE FRENCH
BY
LADY CLAUD HAMILTON
_WITH AN INTRODUCTION_
BY JOHN TYNDALL
NEW YORK
D. APPLETON AND COMPANY
1, 3, AND 5 BOND STREET
1886.
PREFACE.
In the _salon_ of a distinguished man, or of a great writer, there is
often to be found a person who, without being either a fellow-worker
or a disciple, without even possessing the scientific or literary
qualities which might explain his habitual presence, lives nevertheless
in complete familiarity with the man whom all around him call 'dear
master.' Whence comes this intimate one? who is he? what is his
business? He is only known as a friend of the house. He has no other
title, and he is almost proud of having no other. Stripped of his
own personality, he speaks only of the labours and the success of
his illustrious friend, in the radiance of whose glory he moves with
delight.
The author of this work is a person of this description. Intimately
connected with the life of M. Pasteur, and a constant inmate of his
laboratory, he has passed happy years near this great investigator, who
has discovered a new world--the world of the infinitely little. Since
the first studies of M. Pasteur on molecular dissymmetry, down to his
most recent investigations on hydrophobia, on virulent diseases, and on
the artificial cultures of living contagia, which have been converted
by such cultures into veritable vaccines--passing by the intermediate
celebrated experiments on spontaneous generation, fermentation, the
diseases of wine, the manufacture of beer and vinegar, and the diseases
of silkworms--the author of these pages has been able, if not to
witness all, at least to follow in its principal developments this
uninterrupted series of scientific conquests.
'What a beautiful book,' he remarked one day to M. Pasteur, 'might be
written about all this!'
'But it is all in the Comptes-rendus of the Academy of Sciences.'
'It is not for the readers of the Comptes-rendus that such a book needs
to be written, but for the great public, who know that you have done
great things, but who know it only vaguely, by the records of journals,
or by fragments of biography. The persons are few who know the history
of your discoveries. What was your point of departure? How have you
arrived at such and such principles, and at the consequences which
flow from these principles? What is the connection and rigorous bond
of your method? These are the things which it would be interesting to
put together in a book which would have some chance of enduring as an
historic document.'
'I could not waste my time in going back upon things already
accomplished.'
'No; but my desire is that someone else should consecrate his time to
the work. And listen,' added this friend, with audacious frankness--'do
you know by whom, in my opinion, this book ought to be written? By
a man who, without having been in any way trained to follow in your
footsteps, is animated by the most lively desire to understand the
course which you have pursued; who, while living at your side, has been
each day impregnated with your method and your ideas; who, having had
the happiness of comprehending your life and its achievements, does not
wish to confine the pleasure thus derived to himself alone.'
'Where, then,' interrupted Pasteur with a kindly smile, not without a
tinge of irony, 'is this man, at once so happy, and so impatient to
share his happiness with others?'
'He is now pleading his cause before you. Yes, I would gladly attempt
such a work. I have seen your efforts and observed your success. The
experiments which I have not witnessed you have always freely explained
to me, with that gift of clearness which Vauvenargues called the
"polish" of masters.[1] Initiated by affection, I would make myself
initiator by admiration. It would be the history of a learned man by
an ignorant one. My ignorance would save me from dwelling too strictly
or too long on technical details. With the exposition of your doctrine
I would mingle some fragments of your biography. I would pass from a
discovery to an anecdote, and so arrange matters as to give the book
not only the character of a familiar scientific conversation, which
would hardly be more than the echo of what I have learnt while near
you, but also to make it a reflex of your life.'
'You should postpone that until I am no longer here.'
'Why so? Why, before assigning to them their places, should we wait
till those whose names will endure have disappeared from the scene?
No; it is you, living, that I wish to paint--you, in full work, in the
midst of your laboratory. And, in addition to all other considerations,
I would add, that your presence in the flesh will be the guarantee of
my exactitude.'
_July 1883._
FOOTNOTE:
[1] 'Vernis des maîtres.'
CONTENTS.
PAGE
INTRODUCTION, BY PROFESSOR TYNDALL xi
RECOLLECTIONS OF CHILDHOOD
AND YOUTH--FIRST DISCOVERIES 1
FERMENTATION 40
ACETIC FERMENTATION--
THE MANUFACTURE OF VINEGAR 66
THE QUESTION OF SPONTANEOUS GENERATION 89
STUDIES ON WINE 112
THE SILKWORM-DISEASE 127
DECISIVE EXPERIMENTS 164
STUDIES ON BEER 168
VIRULENT DISEASES--SPLENIC FEVER,
SEPTICÆMIA 176
FOWL CHOLERA 212
ATTENUATED VIRUS, OR VACCINATION--
THE FOWL CHOLERA VACCINE 220
THE VACCINE OF SPLENIC FEVER 231
THE RETURN TO VIRULENCE 246
ETIOLOGY OF SPLENIC FEVER 250
METHOD OF DISCUSSION AND CONTRADICTIONS 262
THE LABORATORY OF THE ÉCOLE NORMALE--
VARIOUS STUDIES--HYDROPHOBIA 271
INTRODUCTION.
In the early part of the present year the French original of this work
was sent to me from Paris by its author. It was accompanied by a letter
from M. Pasteur, expressing his desire to have the work translated and
published in England. Responding to this desire, I placed the book in
the hands of the Messrs. Longman, who, in the exercise of their own
judgment, decided on publication. The translation was confided, at my
suggestion, to Lady Claud Hamilton.
The translator's task was not always an easy one, but it has, I
think, been well executed. A few slight abbreviations, for which I
am responsible, have been introduced, but in no case do they affect
the sense. It was, moreover, found difficult to render into suitable
English the title of the original: '_M. Pasteur, Histoire d'un Savant
par un Ignorant_.' A less piquant and antithetical English title was,
therefore, substituted for the French one.
This filial tribute, for such it is, was written, under the immediate
supervision of M. Pasteur, by his devoted and admiring son-in-law, M.
Valery Radot. It is the record of a life of extraordinary scientific
ardour and success, the picture of a mind on which facts fall like
germs upon a nutritive soil, and, like germs so favoured, undergo rapid
increase and multiplication. One hardly knows which to admire most--the
intuitive vision which discerns in advance the new issues to which
existing data point, or the skill in device, the adaptation of means
to ends, whereby the intuition is brought to the test and ordeal of
experiment.
In the investigation of microscopic organisms--the 'infinitely little,'
as Pouchet loved to call them--and their doings in this our world,
M. Pasteur has found his true vocation. In this broad field it has
been his good fortune to alight upon a crowd of connected problems
of the highest public and scientific interest, ripe for solution,
and requiring for their successful treatment the precise culture and
capacities which he has brought to bear upon them. He may regret his
abandonment of molecular physics; he may look fondly back upon the
hopes with which his researches on the tartrates and paratartrates
inspired him; he may think that great things awaited him had he
continued to labour in this line. I do not doubt it. But this does not
shake my conviction that he yielded to the natural affinities of his
intellect, that he obeyed its truest impulses, and reaped its richest
rewards, in pursuing the line that he has chosen, and in which his
labours have rendered him one of the most conspicuous scientific
figures of this age.
With regard to the earliest labours of M. Pasteur, a few remarks
supplementary to those of M. Radot may be introduced here. The days
when angels whispered into the hearkening human ear, secrets which had
no root in man's previous knowledge or experience, are gone for ever.
The only revelation--and surely it deserves the name--now open to the
wise arises from 'intending the mind' on acquired knowledge. When,
therefore, M. Radot, following M. Pasteur, speaks with such emphasis
about 'preconceived ideas,' he does not mean ideas without antecedents.
Preconceived ideas, if out of deference to M. Pasteur the term be
admitted, are the vintage of garnered facts. We in England should
rather call them inductions, which, as M. Pasteur truly says, inspire
the mind, and shape its course, in the subsequent work of deduction and
verification.
At the time when M. Pasteur undertook his investigation of the diseases
of silkworms, which led to such admirable results, he had never seen a
silkworm; but, so far from this being considered a disqualification,
M. Dumas regarded his freedom from preconceived ideas a positive
advantage. His first care was to make himself acquainted with what
others had done. To their observations he added his own, and then,
surveying all, came to the conclusion that the origin of the disease
was to be sought, not in the worms, not in the eggs, but in the moths
which laid the eggs. I am not sure that this conclusion is happily
described as 'a preconceived idea.' Every whipster may have his
preconceived ideas; but the divine power, so largely shared by M.
Pasteur, of distilling from facts their essences--of extracting from
them the principles from which they flow--is given only to a few.
* * * * *
With regard to the discovery of crystalline facets in the tartrates,
which has been dwelt upon by M. Radot, a brief reference to antecedent
labours may be here allowed. It had been discovered by Arago, in 1811,
and by Biot, in 1812 and 1818, that a plate of rock-crystal, cut
perpendicular to the axis of the prism, possessed the power of rotating
the plane of polarisation through an angle, dependent on the thickness
of the plate and the refrangibility of the light. It had, moreover,
been proved by Biot that there existed two species of rock-crystal,
one of which turned the plane of polarisation to the right, and the
other to the left. They were called, respectively, right-handed and
left-handed crystals. No external difference of crystalline form was
at first noticed which could furnish a clue to this difference of
action. But closer scrutiny revealed upon the crystals minute facets,
which, in the one class, were ranged along a right-handed, and, in
the other, along a left-handed spiral. The symmetry of the hexagonal
prism, and of the two terminal pyramids of the crystal, was disturbed
by the introduction of these spirally-arranged facets. They constituted
the outward and visible sign of that inward and invisible molecular
structure which produced the observed action, and difference of action,
on polarised light.
When, therefore, the celebrated Mitscherlich brought forward his
tartrates and paratartrates of ammonia and soda, and affirmed them to
possess the same atoms, the same internal arrangement of atoms, and
the same outward crystalline form, one of them, nevertheless, causing
the plane of polarisation to rotate, while the other did not, Pasteur,
remembering, no doubt, the observations just described, instituted a
search for facets like those discovered in rock-crystal, and which,
without altering chemical constitution, destroyed crystalline identity.
He first found such facets in the tartrates, while he subsequently
proved the neutrality of the paratartrate to be due to the equal
admixture of right-handed and left-handed crystals, one of which, when
the paratartrate was dissolved, exactly neutralised the other.
Prior to Pasteur the left-handed tartrate was unknown. Its discovery,
moreover, was supplemented by a series of beautiful researches on the
compounds of right-handed and left-handed tartaric acid; he having
previously extracted from the two tartrates, acids which, in regard
to polarised light, behaved like themselves. Such was the worthy
opening of M. Pasteur's scientific career, which has been dwelt upon so
frequently and emphatically by M. Radot. The wonder, however, is, not
that a searcher of such penetration as Pasteur should have discovered
the facets of the tartrates, but that an investigator so powerful and
experienced as Mitscherlich should have missed them.
The idea of molecular dissymmetry, introduced by Biot, was forced
upon Biot's mind by the discovery of a number of liquids, and of some
vapours, which possessed the rotatory power. Some, moreover, turned the
plane of polarisation to the right, others to the left. Crystalline
structure being here out of the question, the notion of dissymmetry,
derived from the crystal, was transferred to the molecule. 'To produce
any such phenomena,' says Sir John Herschel, 'the individual molecule
must be conceived as unsymmetrically constituted.' The illustrations
employed by M. Pasteur to elucidate this subject, though well
calculated to give a general idea of dissymmetry, will, I fear, render
but little aid to the reader in his attempts to realise _molecular_
dissymmetry. Should difficulty be encountered here at the threshold
of this work, I would recommend the reader not to be daunted by it,
or prevented by it from going further. He may comfort himself by the
assurance that the conception of a dissymmetric molecule is not a very
precise one, even in the mind of M. Pasteur.
One word more with regard to the parentage of preconceived ideas.
M. Radot informs us that at Strasburg M. Pasteur invoked the aid of
helices and magnets, with a view to rendering crystals dissymmetrical
at the moment of their formation. There can, I think, be but little
doubt that such experiments were suggested by the pregnant discovery of
Faraday published in 1845. By both helices and magnets Faraday caused
the plane of polarisation in perfectly neutral liquids and solids to
rotate. If the turning of the plane of polarisation be a demonstration
of molecular dissymmetry, then, in the twinkling of an eye, Faraday was
able to displace symmetry by dissymmetry, and to confer upon bodies,
which in their ordinary state were inert and dead, this power of
rotation which M. Pasteur considers to be the exclusive attribute of
life.
The conclusion of M. Pasteur here referred to, which M. Radot justly
describes as 'worthy of the most serious consideration,' is sure
to arrest the attention of a large class of people, who, dreading
'materialism,' are ready to welcome any generalisation which
differentiates the living world from the dead. M. Pasteur considers
that his researches point to an irrefragable physical barrier between
organic and inorganic nature. Never, he says, have you been able to
produce in the laboratory, by the ordinary processes of chemistry, a
dissymmetric molecule--in other words, a substance which, in a state
of solution, where molecular forces are paramount, has the power of
causing a polarised beam to rotate. This power belongs exclusively to
derivatives from the living world. Dissymmetric _forces_, different
from those of the laboratory, are, in Pasteur's mind, the agents of
vitality; it is they that build up dissymmetric molecules which baffle
the chemist when he attempts to reproduce them. Such molecules trace
their ancestry to life alone. 'Pourrait-on indiquer une séparation plus
profonde entre les produits de la nature vivante, et ceux de la nature
minérale, que cette dissymmétrie chez les uns, et son absence chez les
autres?' It may be worth calling to mind that molecular dissymmetry
is the _idea_, or _inference_, the observed rotation of the plane of
polarisation, by masses of sensible magnitude, being the _fact_ on
which the inference is based.
That the molecule, or unit brick, of an organism should be different
from the molecule of a mineral is only to be expected, for otherwise
the profound distinction between them would disappear. And that
one of the differences between the two classes of molecules should
be the possession, by the one, of this power of rotation, and its
non-possession by the other, would be a fact, interesting no doubt, but
not surprising. The critical point here has reference to the power
and range of chemical processes, apart from the play of vitality.
Beginning with the elements themselves, can they not be so combined
as to produce organic compounds? Not to speak of the antecedent
labours of Wöhler and others in Germany, it is well known that various
French investigators, among whom are some of M. Pasteur's illustrious
colleagues of the Academy, have succeeded in forming substances which
were once universally regarded as capable of being elaborated by plants
and animals alone. Even with regard to the rotation of the plane of
polarisation, M. Jungfleisch, an extremely able pupil of the celebrated
Berthelot, affirms that the barrier erected by M. Pasteur has been
broken down; and though M. Pasteur questions this affirmation, it is at
least hazardous, where so many supposed distinctions between organic
and inorganic have been swept away, to erect a new one. For my part, I
frankly confess my disbelief in its permanence.
Without waiting for new facts, those already in our possession tend, I
think, to render the association which M. Pasteur seeks to establish
between dissymmetry and life insecure. Quartz, as a crystal, exerts
a very powerful twist on the plane of polarisation. Quartz dissolved
exerts no power at all. The molecules of quartz, then, do not belong to
the same category as the crystal of which they are the constituents;
the former are symmetrical, the latter is dissymmetrical. This, in my
opinion, is a very significant fact. By the act of crystallisation, and
without the intervention of life, the forces of molecules, possessing
planes of symmetry, are so compounded as to build up crystals which
have no planes of symmetry. Thus, in passing from the symmetrical to
the dissymmetrical, we are not compelled to interpolate new forces; the
forces extant in mineral nature suffice. The reasoning which applies
to the dissymmetric crystal applies to the dissymmetric molecule. The
dissymmetry of the latter, however pronounced and complicated, arises
from the composition of atomic forces which, when reduced to their
most elementary action, are exerted along straight lines. In 1865 I
ventured, in reference to this subject, to define the position which I
am still inclined to maintain. 'It is the compounding, in the organic
world, of forces belonging equally to the inorganic that constitutes
the mystery and the miracle of vitality.'[2]
Add to these considerations the discovery of Faraday already adverted
to. An electric current is not an organism, nor does a magnet possess
life; still, by their action, Faraday, in his first essay, converted
over one hundred and fifty symmetric and inert aqueous solutions into
dissymmetric and active ones.[3]
Theory, however, may change, and inference may fade away, but
scientific experiment endures for ever. Such durability belongs, in
the domain of molecular physics, to the experimental researches of M.
Pasteur.
* * * * *
The weightiest events of life sometimes turn upon small hinges; and
we now come to the incident which caused M. Pasteur to quit a line
of research the abandonment of which he still regrets. A German
manufacturer of chemicals had noticed that the impure commercial
tartrate of lime, sullied with organic matters of various kinds,
fermented on being dissolved in water and exposed to summer heat. Thus
prompted, Pasteur prepared some pure, right-handed tartrate of ammonia,
mixed with it albuminous matter, and found that the mixture fermented.
His solution, limpid at first, became turbid, and the turbidity he
found to be due to the multiplication of a microscopic organism, which
found in the liquid its proper aliment. Pasteur recognised in this
little organism a _living ferment_. This bold conclusion was doubtless
strengthened, if not prompted, by the previous discovery of the
yeast-plant--the alcoholic ferment--by Cagniard-Latour and Schwann.
Pasteur next permitted his little organism to take the carbon
necessary for its growth from the pure paratartrate of ammonia. Owing
to the opposition of its two classes of crystals, a solution of this
salt, it will be remembered, does not turn the plane of polarised
light either to the right or to the left. Soon after fermentation
had set in, a rotation to the left was noticed, proving that the
equilibrium previously existing between the two classes of crystals
had ceased. The rotation reached a maximum, after which it was found
that all the right-handed tartrate had disappeared from the liquid.
The organism thus proved itself competent to select its own food. It
found, as it were, one of the tartrates more digestible than the other,
and appropriated it, to the neglect of the other. No difference of
chemical constitution determined its choice; for the elements, and the
proportions of the elements, in the two tartrates were identical. But
the peculiarity of structure which enabled the substance to rotate the
plane of polarisation to the right, also rendered it a fit aliment for
the organism. This most remarkable experiment was successfully made
with the seeds of our common mould, _Penicillium glaucam_.
Here we find Pasteur unexpectedly landed amid the phenomena of
fermentation. With true scientific instinct he closed with the
conception that ferments are, in all cases, living things, and that
the substances formerly regarded as ferments are, in reality, the food
of the ferments. Touched by this wand, difficulties fell rapidly
before him. He proved the ferment of lactic acid to be an organism of a
certain kind. The ferment of butyric acid he proved to be an organism
of a different kind. He was soon led to the fundamental conclusion
that the capacity of an organism to act as a ferment depended on its
power to live, without air. The fermentation of beer was sufficient to
suggest this idea. The yeast-plant, like many others, can live either
with or without free air. It flourishes best in contact with free
air, for it is then spared the labour of wresting from the malt the
oxygen required for its sustenance. Supplied with free air, however,
it practically ceases to be a ferment; while in the brewing vat, where
the work of fermentation is active, the budding _torula_ is completely
cut off by the sides of the vessel, and by a deep layer of carbonic
acid gas, from all contact with air. The butyric ferment not only lives
without air, but Pasteur showed that air is fatal to it. He finally
divided microscopic organisms into two great classes, which he named
respectively _ærobies_ and _anærobies_, the former requiring free
oxygen to maintain life, the latter capable of living without free
oxygen, but able to wrest this element from its combinations with other
elements. This destruction of pre-existing compounds and formation of
new ones, caused by the increase and multiplication of the organism,
constitute the process of fermentation.
Under this head are also rightly ranked the phenomena of putrefaction.
As M. Radot well expresses it, the fermentation of sugar may be
described as the putrefaction of sugar. In this particular field
M. Pasteur, whose contributions to the subject are of the highest
value, was preceded by Schwann, a man of great merit, of whom the
world has heard too little.[4] Schwann placed decoctions of meat in
flasks, sterilised the decoctions by boiling, and then supplied them
with calcined air, the power of which to support life he showed to
be unimpaired. Under these circumstances putrefaction never set in.
Hence the conclusion of Schwann, that putrefaction was not due to the
contact of air, as affirmed by Gay-Lussac, but to something suspended
in the air which heat was able to destroy. This something consists of
living organisms which nourish themselves at the expense of the organic
substance, and cause its putrefaction.
* * * * *
The grasp of Pasteur on this class of subjects was embracing. He
studied acetic fermentation, and found it to be the work of a minute
fungus, the _mycoderma aceti_, which, requiring free oxygen for its
nutrition, overspreads the surface of the fermenting liquid. By the
alcoholic ferment the sugar of the grape-juice is transformed into
carbonic acid gas and alcohol, the former exhaling, the latter
remaining in the wine. By the _mycoderma aceti_ the wine is, in its
turn, converted into vinegar. Of the experiments made in connection
with this subject one deserves especial mention. It is that in
which Pasteur suppressed all albuminous matters, and carried on
the fermentation with purely crystallisable substances. He studied
the deterioration of vinegar, revealed its cause, and the means of
preventing it. He defined the part played by the little eel-like
organisms which sometimes swarm in vinegar casks, and ended by
introducing important ameliorations and improvements in the manufacture
of vinegar. The discussion with Liebig and other minor discussions of a
similar nature, which M. Radot has somewhat strongly emphasized, I will
not here dwell upon.
* * * * *
It was impossible for an inquirer like Pasteur to evade the
question--Whence come these minute organisms which are demonstrably
capable of producing effects on which vast industries are built and on
which whole populations depend for occupation and sustenance? He thus
found himself face to face with the question of spontaneous generation,
to which the researches of Pouchet had just given fresh interest.
Trained as Pasteur was in the experimental sciences, he had an immense
advantage over Pouchet, whose culture was derived from the sciences of
observation. One by one the statements and experiments of Pouchet were
explained or overthrown, and the doctrine of spontaneous generation
remained discredited until it was revived with ardour, ability, and,
for a time, with success, by Dr. Bastian.
A remark of M. Radot's on page 103 needs some qualification. 'The
great interest of Pasteur's method consists,' he says, 'in its proving
unanswerably that the origin of life in infusions which have been
heated to the boiling point is solely due to the solid particles
suspended in the air.' This means that living germs cannot exist _in
the liquid_ when once raised to a temperature of 212° Fahr. No doubt a
great number of organisms collapse at this temperature; some indeed,
as M. Pasteur has shown, are destroyed at a temperature 90° below
the boiling point. But this is by no means universally the case. The
spores of the hay-bacillus, for example, have, in numerous instances,
successfully resisted the boiling temperature for one, two, three, four
hours; while in one instance _eight hours'_ continuous boiling failed
to sterilise an infusion of desiccated hay. The knowledge of this fact
caused me a little anxiety some years ago when a meeting was projected
between M. Pasteur and Dr. Bastian. For though, in regard to the main
question, I knew that the upholder of spontaneous generation could not
win, on the particular issue touching the death temperature he might
have come off victor.
The manufacture and maladies of wine next occupied Pasteur's attention.
He had, in fact, got the key to this whole series of problems, and he
knew how to use it. Each of the disorders of wine was traced to its
specific organism, which, acting as a ferment, produced substances
the reverse of agreeable to the palate. By the simplest of devices,
Pasteur, at a stroke, abolished the causes of wine disease. Fortunately
the foreign organisms which, if unchecked, destroy the best red
wines are extremely sensitive to heat. A temperature of 50° Cent.
(122° Fahr.) suffices to kill them. Bottled wines once raised to
this temperature, for a single minute, are secured from subsequent
deterioration. The wines suffer in no degree from exposure to this
temperature. The manner in which Pasteur proved this, by invoking
the judgment of the wine-tasters of Paris, is as amusing as it is
interesting.
* * * * *
Moved by the entreaty of his master, the illustrious Dumas, Pasteur
took up the investigation of the diseases of silkworms at a time
when the silk-husbandry of France was in a state of ruin. In doing
so he did not, as might appear, entirely forsake his former line
of research. Previous investigators had got so far as to discover
vibratory corpuscles in the blood of the diseased worms, and with such
corpuscles Pasteur had already made himself intimately acquainted. He
was therefore to some extent at home in this new investigation. The
calamity was appalling, all the efforts made to stay the plague having
proved futile. In June 1865 Pasteur betook himself to the scene of the
epidemic, and at once commenced his observations. On the evening of
his arrival he had already discovered the corpuscles, and shown them
to others. Acquainted as he was with the work of living ferments, his
mind was prepared to see in the corpuscles the cause of the epidemic.
He followed them through all the phases of the insect's life--through
the eggs, through the worm, through the chrysalis, through the moth.
He proved that the germ of the malady might be present in the eggs
and escape detection. In the worm also it might elude microscopic
examination. But in the moth it reached a development so distinct as to
render its recognition immediate. From healthy moths healthy eggs were
sure to spring; from healthy eggs healthy worms; from healthy worms
fine cocoons: so that the problem of the restoration to France of its
silk-husbandry reduced itself to the separation of the healthy from
the unhealthy moths, the rejection of the latter, and the exclusive
employment of the eggs of the former. M. Radot describes how this is
now done on the largest scale, with the most satisfactory results.
The bearing of this investigation on the parasitic theory of
communicable diseases was thus illustrated: Worms were infected
by permitting them to feed for a single meal on leaves over which
corpusculous matter had been spread; they were infected by inoculation,
and it was shown how they infected each other by the wounds and
scratches of their own claws. By the association of healthy with
diseased worms, the infection was communicated to the former. Infection
at a distance was also produced by the wafting of the corpuscles
through the air. The various modes in which communicable diseases
are diffused among human populations were illustrated by Pasteur's
treatment of the silkworms. 'It was no hypothetical, infected
medium--no problematical pythogenic gas--that killed the worms. It
was a definite organism.'[5] The disease thus far described is that
called _pébrine_, which was the principal scourge at the time. Another
formidable malady was also prevalent, called _flacherie_, the cause
of which, and the mode of dealing with it, were also pointed out by
Pasteur.
Overstrained by years of labour in this field, Pasteur was smitten with
paralysis in October 1868. But this calamity did not prevent him from
making a journey to Alais in January 1869, for the express purpose
of combating the criticisms to which his labours had been subjected.
Pasteur is combustible, and contradiction readily stirs him into
flame. No scientific man now living has fought so many battles as he.
To enable him to render his experiments decisive, the French Emperor
placed a villa at his disposal near Trieste, where silkworm culture had
been carried on for some time at a loss. The success here is described
as marvellous; the sale of cocoons giving to the villa a net profit of
twenty-six millions of francs.[6] From the Imperial villa M. Pasteur
addressed to me a letter, a portion of which I have already published.
It may perhaps prove usefully suggestive to our Indian or Colonial
authorities if I reproduce it here:--
'Permettez-moi de terminer ces quelques lignes que je dois dicter,
vaincu que je suis par la maladie, en vous faisant observer que vous
rendriez service aux Colonies de la Grande-Bretagne en répandant la
connaissance de ce livre, et des principes que j'établis touchant la
maladie des vers à soie. Beaucoup de ces colonies pourraient cultiver
le mûrier avec succès, et, en jetant les yeux sur mon ouvrage, vous
vous convaincrez aisément qu'il est facile aujourd'hui, non-seulement
d'éloigner la maladie régnante, mais en outre de donner aux récoltes de
la soie une prospérité qu'elles n'ont jamais eue.'
* * * * *
The studies on wine prepare us for the 'Studies on Beer,' which
followed the investigation of silkworm diseases. The sourness,
putridity, and other maladies of beer Pasteur traced to special
'ferments of disease,' of a totally different form, and therefore
easily distinguished from the true _torula_ or yeast-plant. Many
mysteries of our breweries were cleared up by this inquiry. Without
knowing the cause, the brewer not unfrequently incurred heavy losses
through the use of bad yeast. Five minutes' examination with the
microscope would have revealed to him the cause of the badness, and
prevented him from using the yeast. He would have seen the true
_torula_ overpowered by foreign intruders. The microscope is, I
believe, now everywhere in use. At Burton-on-Trent its aid was very
soon invoked. At the conclusion of his studies on beer M. Pasteur came
to London, where I had the pleasure of conversing with him. Crippled by
paralysis, bowed down by the sufferings of France, and anxious about
his family at a troubled and an uncertain time, he appeared low in
health and depressed in spirits. His robust appearance when he visited
London, on the occasion of the Edinburgh Anniversary, was in marked and
pleasing contrast with my memory of his aspect at the time to which I
have referred.
* * * * *
While these researches were going on, the Germ Theory of infectious
disease was noised abroad. The researches of Pasteur were frequently
referred to as bearing upon the subject, though Pasteur himself
kept clear for a long time of this special field of inquiry. He was
not a physician, and he did not feel called upon to trench upon the
physician's domain. And now I would beg of him to correct me if, at
this point of the Introduction, I should be betrayed into any statement
that is not strictly correct.
In 1876 the eminent microscopist, Professor Cohn of Breslau, was in
London, and he then handed me a number of his 'Beiträge,' containing a
memoir by Dr. Koch on Splenic Fever (_Milzbrand_, _Charbon_, Malignant
Pustule), which seemed to me to mark an epoch in the history of this
formidable disease. With admirable patience, skill, and penetration,
Koch followed up the life history of _bacillus anthracis_, the
contagium of this fever. At the time here referred to he was a young
physician holding a small appointment in the neighbourhood of Breslau,
and it was easy to predict, as I predicted at the time, that he would
soon find himself in a higher position. When I next heard of him he
was head of the Imperial Sanitary Institute of Berlin. Koch's recent
history is pretty well known in England, while his appreciation by the
German Government is shown by the rewards and honours lately conferred
upon him.
Koch was not the discoverer of the parasite of splenic fever. Davaine
and Rayer, in 1850, had observed the little microscopic rods in the
blood of animals which had died of splenic fever. But they were
quite unconscious of the significance of their observation, and for
thirteen years, as M. Radot informs us, strangely let the matter drop.
In 1863 Davaine's attention was again directed to the subject by the
researches of Pasteur, and he then pronounced the parasite to be the
cause of the fever. He was opposed by some of his fellow-countrymen;
long discussions followed, and a second period of thirteen years,
ending with the publication of Koch's paper, elapsed, before M. Pasteur
took up the question. I always, indeed, assumed that from the paper
of the learned German came the impulse towards a line of inquiry in
which M. Pasteur has achieved such splendid results. Things presenting
themselves thus to my mind, M. Radot will, I trust, forgive me if I
say that it was with very great regret that I perused the disparaging
references to Dr. Koch which occur in the chapter on splenic fever.
After Koch's investigation, no doubt could be entertained of the
parasitic origin of this disease. It completely cleared up the
perplexity previously existing as to the two forms--the one fugitive,
the other permanent--in which the contagium presented itself. I may
say that it was on the conversion of the permanent hardy form into
the fugitive and sensitive one, in the case of _bacillus subtilis_
and other organisms, that the method of sterilising by 'discontinuous
heating' introduced by me in February 1877 was founded. The difference
between an organism and its spores, in point of durability, had not
escaped the penetration of Pasteur. This difference Koch showed to be
of paramount importance in splenic fever. He, moreover, proved that
while mice and guinea-pigs were infallibly killed by the parasite,
birds were able to defy it.
And here we come upon what may be called a hand-specimen of the genius
of Pasteur, which strikingly illustrates its quality. Why should birds
enjoy the immunity established by the experiments of Koch? Here is the
answer. The temperature which prohibits the multiplication of _bacillus
anthracis_ in infusions is 44° Cent. (111° Fahr.). The temperature of
the blood of birds is from 41° to 42°. It is therefore close to the
prohibitory temperature. But then the blood globules of a living fowl
are sure to offer a certain resistance to any attempt to deprive them
of their oxygen--a resistance not experienced in an infusion. May not
this resistance, added to the high temperature of the fowl, suffice
to place it beyond the power of the parasite? Experiment alone could
answer this question, and Pasteur made the experiment. By placing its
feet in cold water he lowered the temperature of a fowl to 37° or 38°.
He inoculated the fowl, thus chilled, with the splenic fever parasite,
and in twenty-four hours it was dead. The argument was clinched by
inoculating a chilled fowl, permitting the fever to come to a head,
and then removing the fowl, wrapped in cotton-wool, to a chamber with a
temperature of 35°. The strength of the patient returned as the career
of the parasite was brought to an end, and in a few hours health was
restored. The sharpness of the reasoning here is only equalled by the
conclusiveness of the experiment, which is full of suggestiveness as
regards the treatment of fevers in man.
* * * * *
Pasteur had little difficulty in establishing the parasitic origin of
fowl cholera; indeed, the parasite had been observed by others before
him. But by his successive cultivations, he rendered the solution
sure. His next step will remain for ever memorable in the history of
medicine. I allude to what he calls 'virus attenuation.' And here it
may be well to throw out a few remarks in advance. When a tree, or a
bundle of wheat or barley straw, is burnt, a certain amount of mineral
matter remains in the ashes--extremely small in comparison with the
bulk of the tree or of the straw, but absolutely essential to its
growth. In a soil lacking, or exhausted of, the necessary mineral
constituents, the tree cannot live, the crop cannot grow. Now contagia
are living things, which demand certain elements of life just as
inexorably as trees, or wheat, or barley; and it is not difficult to
see that a crop of a given parasite may so far use up a constituent
existing in small quantities in the body, but essential to the growth
of the parasite, as to render the body unfit for the production of a
second crop. The soil is exhausted, and, until the lost constituent is
restored, the body is protected from any further attack of the same
disorder. Such an explanation of non-recurrent diseases naturally
presents itself to a thorough believer in the germ theory, and such
was the solution which, in reply to a question, I ventured to offer
nearly fifteen years ago to an eminent London physician. To exhaust
a soil, however, a parasite less vigorous and destructive than the
really virulent one may suffice; and if, after having by means of a
feebler organism exhausted the soil, without fatal result, the most
highly virulent parasite be introduced into the system, it will prove
powerless. This, in the language of the germ theory, is the whole
secret of vaccination.
The general problem, of which Jenner's discovery was a particular case,
has been grasped by Pasteur, in a manner, and with results, which five
short years ago were simply unimaginable. How much 'accident' had to do
with shaping the course of his enquiries I know not. A mind like his
resembles a photographic plate, which is ready to accept and develop
luminous impressions, sought and unsought. In the chapter on fowl
cholera is described how Pasteur first obtained his attenuated virus.
By successive cultivations of the parasite he showed, that after it
had been a hundred times reproduced, it continued to be as virulent
as at first. One necessary condition was, however, to be observed. It
was essential that the cultures should rapidly succeed each other--that
the organism, before its transference to a fresh cultivating liquid,
should not be left long in contact with air. When exposed to air for a
considerable time the virus becomes so enfeebled that when fowls are
inoculated with it, though they sicken for a time, they do not die.
But this 'attenuated' virus, which M. Radot justly calls 'benign,'
constitutes a sure protection against the virulent virus. It so
exhausts the soil that the really fatal contagium fails to find there
the elements necessary to its reproduction and multiplication.
Pasteur affirms that it is the oxygen of the air which, by lengthened
contact, weakens the virus and converts it into a true vaccine. He has
also weakened it by transmission through various animals. It was this
form of attenuation that was brought into play in the case of Jenner.
The secret of attenuation had thus become an open one to Pasteur. He
laid hold of the murderous virus of splenic fever, and succeeded in
rendering it, not only harmless to life, but a sure protection against
the virus in its most concentrated form. No man, in my opinion, can
work at these subjects so rapidly as Pasteur without falling into
errors of detail. But this may occur while his main position remains
impregnable. Such a result, for example, as that obtained in presence
of so many witnesses at Melun must surely remain an ever-memorable
conquest of science. Having prepared his attenuated virus, and proved,
by laboratory experiments, its efficacy as a protective vaccine,
Pasteur accepted an invitation from the President of the Society of
Agriculture at Melun, to make a public experiment on what might be
called an agricultural scale. This act of Pasteur's is, perhaps, the
boldest thing recorded in this book. It naturally caused anxiety among
his colleagues of the Academy, who feared that he had been rash in
closing with the proposal of the President.
But the experiment was made. A flock of sheep was divided into
two groups, the members of one group being all vaccinated with
the attenuated virus, while those of the other group were left
unvaccinated. A number of cows were also subjected to a precisely
similar treatment. Fourteen days afterwards, all the sheep and all
the cows, vaccinated and unvaccinated, were inoculated with a very
virulent virus; and three days subsequently more than two hundred
persons assembled to witness the result. The 'shout of admiration,'
mentioned by M. Radot, was a natural outburst under the circumstances.
Of twenty-five sheep which had not been protected by vaccination,
twenty-one were already dead, and the remaining ones were dying. The
twenty-five vaccinated sheep, on the contrary, were 'in full health and
gaiety.' In the unvaccinated cows intense fever was produced, while
the prostration was so great that they were unable to eat. Tumours
were also formed at the points of inoculation. In the vaccinated cows
no tumours were formed; they exhibited no fever, nor even an elevation
of temperature, while their power of feeding was unimpaired. No
wonder that 'breeders of cattle overwhelmed Pasteur with applications
for vaccine.' At the end of 1881 close upon 34,000 animals had been
vaccinated, while the number rose in 1883 to nearly 500,000.
* * * * *
M. Pasteur is now exactly sixty-two years of age; but his energy is
unabated. At the end of this volume we are informed that he has already
taken up and examined with success, as far as his experiments have
reached, the terrible and mysterious disease of rabies or hydrophobia.
Those who hold all communicable diseases to be of parasitic origin,
include, of course, rabies among the number of those produced and
propagated by a living contagium. From his first contact with the
disease Pasteur showed his accustomed penetration. If we see a man mad,
we at once refer his madness to the state of his brain. It is somewhat
singular that in the face of this fact the virus of a mad dog should be
referred to the animal's saliva. The saliva is, no doubt, infected,
but Pasteur soon proved the real seat and empire of the disorder to be
the nervous system.
The parasite of rabies had not been securely isolated when M. Radot
finished his task. But last May, at the instance of M. Pasteur, a
commission was appointed by the Minister of Public Instruction in
France, to examine and report upon the results which he had up to
that time obtained. A preliminary report, issued to appease public
impatience, reached me before I quitted Switzerland this year. It
inspires the sure and certain hope that, as regards the attenuation of
the rabic virus, and the rendering of an animal, by inoculation, proof
against attack, the success of M. Pasteur is assured. The commission,
though hitherto extremely active, is far from the end of its labours;
but the results obtained so far may be thus summed up:--
Of six dogs unprotected by vaccination, three succumbed to the bites of
a dog in a furious state of madness.
Of eight unvaccinated dogs, six succumbed to the intravenous
inoculation of rabic matter.
Of five unvaccinated dogs, all succumbed to inoculation, by trepanning,
of the brain.
Finally, of three-and-twenty vaccinated dogs, not one was attacked with
the disease subsequent to inoculation with the most potent virus.
Surely results such as those recorded in this book are calculated,
not only to arouse public interest, but public hope and wonder. Never
before, during the long period of its history, did a day like the
present dawn upon the science and art of medicine. Indeed, previous
to the discoveries of recent times, medicine was not a science, but
a collection of empirical rules dependent for their interpretation
and application upon the sagacity of the physician. How does England
stand in relation to the great work now going on around her? She is,
and must be, behindhand. Scientific chauvinism is not beautiful in my
eyes. Still one can hardly see, without deprecation and protest, the
English investigator handicapped in so great a race by short-sighted
and mischievous legislation.