multiplied experiments of Pasteur. But before occupying himself with
further discoveries, although it had been irrefutably proved that the
microscopic parasite was the true contagium, it was necessary to throw
light upon the facts, mainly accurate, which had been announced by
Jaillard and Leplat, and to bring them into harmony with the facts, not
less certain, which had been advanced by Davaine. The rabbits which
Jaillard and Leplat had inoculated with a drop of the blood of a cow or
sheep stricken with splenic fever, died rapidly, and the blood of these
rabbits was shown to be also virulent. It was sufficient to inoculate
other rabbits with a very minute quantity to cause their death. But
Jaillard and Leplat affirmed that the examination of that blood did not
reveal the existence of any microscopic organisms. Paul Bert, on his
part, had succeeded in destroying the bacteria by compressed oxygen,
and yet the virulence had continued.
Were there, then, two kinds of virus? What escape was there from this
darkness? A new light suddenly began to dawn. Pasteur had already some
years previously demonstrated that the animal body is sealed against
the introduction of lower organisms--that in the blood, the urine, the
muscles, the liver, the spleen, the kidneys, the brain, the marrow,
and the nerves, in a normal state, no germ is found, or particle of
any kind, known or unknown, which could be transformed into bacteria,
vibrios, monads, or microbes. The intestinal canal alone is filled
with matters associated with a host of germs and living products in
process of development, and in divers states of physiological action.
Not only is its temperature favourable to the life of infusoria,
but it receives incessantly matters charged with the germs of these
microscopic organisms. To the upper portions of the canal the air
still has access, so that even in the stomach aerobic microbes may be
found, but in the lower parts of the intestinal canal oxygen is absent,
and only anaerobic microbes can be developed there. Although the life
exerted in the mucous surface of the intestines opposes itself to the
passage of those little organisms into the interior of the body, this
ceases to be the case after death. There is no longer any obstacle to
arrest or prevent them from acting according to the respective laws of
their evolution and of the decomposing influence which belongs to them.
It is by anaerobic organisms, in fact, that the putrefaction of dead
bodies is begun. They penetrate into the organs and into the blood as
soon as this liquid is deprived of oxygen; and it is not long before
this happens, the oxygen fixed in the globules being soon consumed. In
the body of an animal which has died of splenic fever, putrefaction is
still more rapid, because, through the action of the disease, the blood
is already in a great degree deprived of oxygen at the time of death.
Nothing is more striking than the rapid inflation and almost immediate
putrefaction of animals which have succumbed to splenic fever. Of all
the vibrios ready to pass from the intestinal canal into the network
of mesenteric veins which surround the canal those which seem to take
the foremost place are the septic vibrios. These specially merit the
name of vibrios of putrefaction, from the very putrid gases which
result from their action upon nitrogenous and sulphurous substances.
The others diffuse themselves more or less slowly in the blood, but
the septic vibrio takes almost immediate possession of the dead body.
Already after twelve or fifteen hours, the blood of the diseased
animal, which at the time of its death and during the first following
hours contained exclusively the parasite of splenic fever, harbours
at one and the same time both the bacillus of splenic fever and the
septic vibrio. Then occur the very curious effects arising from the
anaerobic nature of these vibrios, and their opposition to the bacillus
of splenic fever, which is exclusively aerobic. Diffused in blood
deprived of oxygen gas, the splenic bacillus soon perishes. In its
place are to be found amorphous granulations deprived of all virulence.
The septic anaerobic vibrio, on the contrary, finds itself after death
in the most favourable conditions for its life and development. Not
only does it penetrate into the blood by the deep mesenteric veins, but
also into the liquids which ooze out of the abdomen and muscles.
From the antagonism existing between the physiological peculiarities of
the splenic bacilli and the septic vibrio, it results that if, in order
to inoculate an animal capable of contracting the fever, a drop of
blood be taken from one that has just died of it, and if the operation
is performed during the first few hours after death, it is certain to
communicate to that animal splenic fever, and splenic fever only. If,
on the other hand, the operation is performed after a greater number
of hours--say, between twelve and twenty, according to the season of
the year--then the inoculation of the blood will communicate, at one
and the same time, splenic fever and septicæmia--acute septicæmia, as
it may be called, because of the rapid inflammatory disorders that the
septic vibrio causes in the inoculated animal. The two diseases may be
developed simultaneously in the inoculated animal, but generally one
precedes the other. The septic contagium is the quickest in its action;
it generally causes death before the splenic fever has had time to
develop itself and to produce appreciable effects.
We are now in a position to explain all the contradictory results
obtained by MM. Jaillard and Leplat on one side, and by Davaine on
the other. In a country which splenic fever had made famous, the
Département d'Eure-et-Loir, they had asked for a little splenic fever
blood. Now, what takes place in a farm where an animal has died of
this disease? The dead body is thrown upon a dungheap, or into some
shed or stall, until the knacker's cart happens to pass. The knacker
takes his own time, and the body often remains there twenty-four or
forty-eight hours. The blood taken from this animal is more or less
invaded by putrefaction, and vibrios are mingled with the bacteria of
splenic fever, the development of which is arrested the moment the
animal dies. In short, it may be easily conceived that an experimenter
writing to Chartres to procure some splenic fever blood might, without
his knowledge, or the knowledge of his correspondent, receive blood at
the same time both splenic and septic. And this septicæmia is sometimes
manifold, for a special septicæmia may be said to correspond to every
sort of vibrio of putrefaction.
Such were the circumstances which, without their being aware of
it, accompanied Jaillard and Leplat's researches upon splenic fever
infection. This impression will be derived from reading the successive
notes laid by them before the Academy of Sciences. The blood of the cow
which had died of splenic fever, sent from the knacker's establishment
of Sours, and the blood of the sheep sent by M. Boutet, must both have
been taken from the bodies of animals which had been dead a sufficient
number of hours to render their blood both splenic and septic; and it
was septicæmia, so prompt in its action, that had killed the rabbits
of Jaillard and Leplat. As the examination of the blood of these
animals showed no signs of bacteria, they had concluded, with great
apparent truth, that the inoculation of splenic blood could cause death
without any appearance of these organisms, even while the blood used
for inoculation was full of them. The presence of _septic_ vibrios in
the blood of the inoculated rabbits escaped their notice. When Davaine
replied that Jaillard and Leplat had not worked with pure splenic blood
he had hit upon the truth, but he could not give plausible reasons for
it. The contest was carried on by experiments in which, on both sides,
truth and error were closely blended.
The work of M. Paul Bert, at the close of 1876, was surrounded with
circumstances no less complex. To thoroughly understand them we must
call to mind Pasteur's discovery as to the mode of reproducing the
anaerobic germs of putrefaction. These vibrios reproduce themselves
by spores. In the vibrio of acute septicæmia this is the mode of
generation. Short or long jointed filaments show themselves studded
with brilliant points, which are precisely the spores of which we
speak. Experience proves that these spores resist perfectly the
poisonous action of compressed oxygen. Inoculating an animal with blood
which is at the same time septic and splenic, after the blood has been
compressed, the septic germs, remaining alive, produce death, although
neither bacteria nor filaments may be perceptible in its blood at
the moment of death. It was likewise from Chartres that M. Paul Bert
obtained his supply of splenic fever blood. The blood he had received
was without doubt not only splenic but also septic. The filaments of
bacteria and the filaments of septic vibrios had perished under the
influence of the compressed oxygen; but the spores were there, and the
great pressure of oxygen gas had not affected them. The new contagium
which had appeared, and which had killed the inoculated animals, was
due to these spores.
As regards the proof that this virulence in the blood of the body of
an animal which has died of splenic fever is really the effect of
the septic vibrio, Pasteur, assisted by Joubert and a new assistant,
M. Chamberland, has given that proof, as he did in the case of the
bacterium of splenic fever, by resorting to the method of successive
cultivations in an artificial medium. These cultivations, however, of
the septic vibrio require very special precautions and conditions.
They should be carried on in as perfect a vacuum as it is possible
to obtain, or in contact with carbonic acid gas without the presence
of air. In contact with air the cultivations of septic vibrios would
prove sterile, because the vibrio is exclusively anaerobic and air
kills it. If a spore of this organism could germinate in contact with
the air, the product of the germination would be at once arrested and
would perish by the action of the oxygen. It is exactly the contrary
with the bacilli of splenic fever, which prove sterile in a vacuum or
in presence of carbonic acid gas. If one of the spores of the splenic
fever bacillus (for it also produces spores) could germinate, the
product of the germination, deprived of free oxygen, would at once
perish. And, to mention in passing a very ingenious experiment of
Pasteur's, we thus obtain a means of separating by culture the bacillus
of splenic fever from the septic vibrio when they are temporarily
associated together. If this mixture of pathogenic organisms is
cultivated in contact with the air, the bacilli of splenic fever alone
will be developed. If this same mixture is cultivated without air,
either in a vacuum or in carbonic acid gas, the septic vibrio alone
will be developed. This device of culture is one of the best which can
be employed to demonstrate that the blood of a body dead from splenic
fever possesses immediately after death a single contagium, that of
splenic fever, and that twenty-four hours after death, on the contrary,
there are two contagia, that of splenic fever and that of septicæmia.
* * * * *
Some months ago a very hot discussion arose between Pasteur and a
commission formed principally of professors of the veterinary school
in Turin, regarding the facts above mentioned. One experiment, in
the success of which Pasteur was extremely interested, had been made
at this school. Instead of employing pure splenic fever blood, free
from all contagium, the Italian professors, whether from ignorance
of the preceding facts or from inadvertence, employed the blood of
a diseased sheep, which, from their own showing, had been dead more
than twenty-four hours. Pasteur immediately wrote, pointing out that
the commission had done wrong in using blood which must have been at
the same time splenic and septic. The Turin professors grew angry,
and affirmed that this assertion of Pasteur's was incorrect; that
this sheep's blood had been studied with care, and that no filaments
had been found in it except those of splenic fever; and it would,
moreover, be marvellous, they added ironically, that Pasteur from
the depths of his laboratory in Paris should be able to assert that
this blood was mixed with septic poison, whilst they, good observers,
armed with a microscope, had had this sheep's blood under their eyes.
Pasteur contented himself with replying that his assertion rested
upon a principle, and that he was perfectly able, without having seen
the blood of the sheep, to affirm that under the conditions in which
it had been collected that blood was septic. A public correspondence
ensued, but no understanding could be come to. Pasteur then offered to
go himself to Turin, in order to demonstrate upon as many bodies of
sheep dead of splenic fever as they would like to give him, that the
blood of these dead bodies--at the end of twenty-four hours if in the
month of March, and in twelve or fifteen hours if in the month of June,
would be found to be both splenic and septic. Pasteur also proposed,
by appropriate cultures, to withdraw at pleasure the splenic fever
poison or the septic poison, or the two together, at the choice of the
Italians. The Italians, however, shrank from Pasteur's proposal to pay
them a visit in order to convince them of their error.
The clearness and certainty of Pasteur's assertions are celebrated, but
what gives such authority to all that he advances is, as M. Paul Bert
once said, that Pasteur's boldness of assertion is only equalled by his
diffidence when he has not experiment to back him up. He never fights
except on ground with which he has made himself familiar, but then he
fights with such resolution, and sometimes with such impetuosity, that
one might say to his adversary, whoever he be, 'Je vous plains de
tomber dans ses mains redoutables.'
'Take care!' said a member of the Academy of Sciences to a member of
the Academy of Medicine, who a short time after the incident just
related was proposing scientifically to 'strangle' Pasteur, 'take care!
Pasteur is never mistaken.'
One day, in 1879, a professor attached to a faculty of medicine in
one of the provinces announced to the Academy of Sciences that he had
found, in the blood of a woman who had died in a hospital after two
weeks' illness from severe puerperal fever, a considerable number of
motionless filaments, simple or jointed, transparent, straight, or
bent, which belonged to the genus Leptothrix. Engaged in studies on
puerperal fever, and having never met with a fact of this kind in his
researches, Pasteur wrote at once to this professor to ask him for a
specimen of the infected blood. The blood arrived at the laboratory,
and some days after Pasteur wrote to the doctor, 'Your leptothrix is
nothing else than the bacterium of splenic fever.'
This answer perplexed the doctor very much. He wrote to Pasteur that he
did not dispute the affirmation, but that he proposed to control it;
that if he found he had been in error he would publish it.
Pasteur offered to send him guinea-pigs which had been inoculated with
splenic fever. 'You will receive them still living; they will die under
your eyes. You will make the autopsy and you will yourself recognise
your leptothrix.' The doctor accepted the test. Pasteur inoculated
three guinea-pigs, had them placed in a cage and sent by rail to the
professor. They arrived the following morning and died twenty-four
hours afterwards under the doctor's own eyes. The first had been
inoculated with the infectious blood of the dead woman, the second with
the bacterium of splenic fever blood from Chartres, the third with the
blood of a cow which had died of splenic fever in the Jura. At the
autopsy it was impossible to discover the slightest difference in the
blood of the three animals. Not only the blood but the internal organs,
and especially the spleen, were in exactly the same condition.
Then, in the most honourable manner, the doctor hastened to state, in a
communication to the Academy of Sciences, that he regretted doubly not
having known about splenic fever the year before, as he might have been
able, on the one hand, to diagnose the formidable complication which
had manifested itself in the woman who died on April 4, 1878, and, on
the other hand, to have traced out the mode of contamination which
now eluded him. He had, however, succeeded in learning a few details
regarding the unhappy woman. She was a charwoman, and lived in a little
room adjoining the stables of a horse-dealer. Through these stables a
large number of horses passed continually.
But to return to our septic vibrios. If air destroys them, if their
culture is impossible in contact with air, how can septicæmia exist,
since air is everywhere present? How can blood exposed to the air
become septic from particles of dust on the surface of objects or which
the air holds in suspension? Where can the septic germs be formed? The
objection seems a serious one, but it disappears before a very simple
experiment. Take some serum from the abdomen of a guinea-pig which has
died of acute septicæmia. It will be found full of septic vibrios in
process of generation by fission. Let this liquid be then exposed to
the contact of air, with the precaution of giving a certain depth to
the liquid--say, a centimeter of depth. In some hours, if examined with
the microscope, the following curious spectacle will be witnessed: In
the upper layers the oxygen of the air is absorbed, which is manifested
by the already changed colour of the liquid. There the filamentous
vibrio dies, and disappears under the form of fine amorphous
granulations deprived of virulence. At the bottom of this layer of one
centimeter in thickness, on the contrary, the vibrios, protected from
the approach of oxygen by those of their own kind which have perished
above them, continue to multiply by fission until by degrees they pass
into the state of spores; so that instead of moving threads of all
dimensions, the length of which sometimes even extends beyond the
field of the microscope, nothing is now seen but a dust of brilliant
isolated specks, upon which the oxygen of the air has no action. It
is thus that a dust of septic germs can be formed even in contact
with air. And thus it becomes possible to understand how anaerobic
organisms may be sown in putrescible liquids by the dust suspended in
the atmosphere. Thus also may be explained the permanence of putrid
diseases, even of those which are caused by anaerobic microbes, that
cannot live in the atmosphere and which escape destruction by becoming
spores.
By means of these experiments, as unexpected as they were conclusive,
Pasteur had demonstrated that Jaillard and Leplat had not really
inoculated their rabbits with an amorphous virus, liquid or solid, but
with a virus constituted of a living microscopic organism--in other
words, with a true ferment. By the side of the parasite of splenic
fever we have thus a fresh example of a living animated virus, with
germs forming dust. And the extraordinary thing is that among the
microbes of special maladies--which they produce by penetrating and
multiplying in the bodies of animals--are to be found aerobies like
the bacilli of splenic fever, and anaerobies like the vibrios of acute
septicæmia.
II.
In these two virulent maladies, then, splenic fever and septicæmia, the
researches of Pasteur had clearly established the parasitic theory. A
grand and novel opening was made for future studies on the origin of
diseases. Yet, judging from the surprising differences which separate
septicæmia and splenic fever, we can foresee that should the future,
copying the past, in regard to this and still more recent discoveries,
have in store, as it no doubt has, the knowledge of new microbes of
disease, the specific properties of these microscopic organisms will
demand, for each new exploration, ceaselessly repeated efforts, not
only to make the existence of these organisms evident, but also to
furnish decisive proofs of their morbific power. But the question
which may be considered as already solved is the non-spontaneity of
these infectious microbes. By what is called spontaneous disease
is meant parasitic disease. But in the present state of science
spontaneous disease has no more existence than spontaneous generation.
Such aphorisms, however, are not allowed to pass without occasional
contradictions, all the more vehement from their rarity. At the
International Medical Congress held in London, August 1881, Dr.
Bastian, who practises in one of the principal hospitals of London,
declared that though he was unable to deny the existence of parasitic
diseases, yet, in his opinion, the microbes were the effect and not the
cause of these diseases.
'Is it possible,' cried Pasteur, who was present at the meeting, 'that
at this day such a scientific heresy should be held? My answer to Dr.
Bastian will be short. Take the limb of an animal and crush it in a
mortar; let there be diffused in this limb, around these crushed bones,
as much blood, or any other normal or abnormal liquid as you please.
Take care only that the skin of the limb is neither torn nor laid open,
and I defy you to exhibit on the following day, or during all the time
the malady lasts, the least microscopic organism in the humours of this
limb.'
After the example of Liebig in 1870, Dr. Bastian did not accept the
challenge.
But if a disease like splenic fever is carried by a microbe, this
microbe is under the influence of the medium in which it finds itself.
It does not develop everywhere. Easily inoculable and fatal to the
ox, the sheep, the rabbit, and the guinea pig, splenic fever is very
rare in the dog and in the pig. These must be inoculated several times
before they contract the disease, and even then it is not always
possible to produce it. Again, there are some creatures which are never
assailable by it. It can never be taken by fowls. In vain they are
inoculated with a considerable quantity of splenic blood; it has no
effect upon them. This invulnerability had very much struck Pasteur
and his two assistants, Joubert and Chamberland. What was it in the
body of a fowl that enabled it to thus resist inoculations of which
the most infinitesimal quantity sufficed to kill an ox? They proved
by a series of experiments that the microbe of splenic fever does not
develop when subjected to a temperature of 44° Centigrade. Now, the
temperature of birds being between 41 and 42 degrees, may it not be,
said Pasteur, that the fowls are protected from the disease because
their blood is too warm--not far removed from the temperature at which
the splenic fever organism can no longer be cultivated? Might not the
vital resistance encountered in the living fowl suffice to bridge over
the small gap between 41-42, and 44-45 degrees? For we must always
allow for a certain resistance in all living creatures to disease and
death. No doubt, life to a parasite in the body of an animal would not
be as easy as in a cultivating liquid contained in a glass vessel. If
the inoculating microbe is aerobic, it can only be cultivated in blood
by taking away the oxygen from the globules, which retain it with a
certain force for their own life. Nothing was more legitimate than to
suppose that the globules of the blood of the fowl had such an avidity
for oxygen that the filaments of the splenic parasite were deprived of
it, and that their multiplication was thus rendered impossible. This
idea conducted Pasteur and his assistants to new researches. 'If the
blood of a fowl was cooled,' they asked, 'could not the splenic fever
parasite live in this blood?'
The experiment was made. A hen was taken, and, after inoculating it
with splenic fever blood, it was placed with its feet in water at 25
degrees. The temperature of the blood of the hen went down to 37 or 38
degrees. At the end of twenty-four hours the hen was dead, and all its
blood was filled with splenic fever bacteria.