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many mucedines (Mucedinae?) of tubular mushrooms, which in
certain conditions of culture produce a chain of more or less
spherical cells called Conidae. The latter, detached from their
branches, are able to reproduce themselves in the form of cells,
without the appearance, at least with a change in the conditions
of culture, of the spores of their respective mucedines. These
vegetable organisms can be compared to plants which are
cultivated by slipping, and to produce which it is not necessary
to have the fruits or the seeds of the mother plant.
The anthrax bacterium, in its artificial cultivation, behaves
very differently. Its mycelian filaments, if one may so describe
them, have been produced scarcely for twenty-four or forty-eight
hours when they are seen to transform themselves, those
especially which are in free contact with the air, into very
refringent corpuscles, capable of gradually isolating themselves
into true germs of slight organization. Moreover, observation
shows that these germs, formed so quickly in the culture, do not
undergo, after exposure for a time to atmospheric air, any change
either in their vitality or their virulence. I was able to
present to the Academy a tube containing some spores of anthrax
bacteria produced four years ago, on March 21, 1887. Each year
the germination of these little corpuscles has been tried, and
each year the germination has been accomplished with the same
facility and the same rapidity as at first. Each year also the
virulence of the new cultures has been tested, and they have not
shown any visible falling off. Therefore, how can we experiment
with the action of the air upon the anthrax virus with any
expectation of making it less virulent?
“The crucial difficulty lies perhaps entirely in this rapid
reproduction of the bacteria germs which we have just related. In
its form of a filament, and in its multiplication by division, is
not this organism at all points comparable with the microbe of
the chicken cholera?
“That a germ, properly so called, that a seed, does not suffer
any modification on account of the air is easily conceived; but
it is conceivable not less easily that if there should be any
change it would occur by preference in the case of a mycelian
fragment. It is thus that a slip which may have been abandoned in
the soil in contact with the air does not take long to lose all
vitality, while under similar conditions a seed is preserved in
readiness to reproduce the plant. If these views have any
foundation, we are led to think that in order to prove the action
of the air upon the anthrax bacteria it will be indispensable to
submit to this action the mycelian development of the minute
organism under conditions where there cannot be the least
admixture of corpuscular germs. Hence the problem of submitting
the bacteria to the action of oxygen comes back to the question
of presenting entirely the formation of spores. The question
being put in this way, we are beginning to recognize that it is
capable of being solved.
“We can, in fact, prevent the appearance of spores in the
artificial cultures of the anthrax parasite by various artifices.
At the lowest temperature at which this parasite can be
cultivated—that is to say, about +16 degrees Centigrade—the
bacterium does not produce germs—at any rate, for a very long
time. The shapes of the minute microbe at this lowest limit of
its development are irregular, in the form of balls and pears—in
a word, they are monstrosities—but they are without spores. In
the last regard also it is the same at the highest temperatures
at which the parasite can be cultivated, temperatures which vary
slightly according to the means employed. In neutral chicken
bouillon the bacteria cannot be cultivated above 45 degrees.
Culture, however, is easy and abundant at 42 to 43 degrees, but
equally without any formation of spores. Consequently a culture
of mycelian bacteria can be kept entirely free from germs while
in contact with the open air at a temperature of from 42 to 43
degrees Centigrade. Now appear the three remarkable results.
After about one month of waiting the culture dies—that is to
say, if put into a fresh bouillon it becomes absolutely sterile.
“So much for the life and nutrition of this organism. In respect
to its virulence, it is an extraordinary fact that it disappears
entirely after eight days’ culture at 42 to 43 degrees
Centigrade, or, at any rate, the cultures are innocuous for the
guinea-pig, the rabbit, and the sheep, the three kinds of animals
most apt to contract anthrax. We are thus able to obtain, not
only the attenuation of the virulence, but also its complete
suppression by a simple method of cultivation. Moreover, we see
also the possibility of preserving and cultivating the terrible
microbe in an inoffensive state. What is it that happens in these
eight days at 43 degrees that suffices to take away the virulence
of the bacteria? Let us remember that the microbe of chicken
cholera dies in contact with the air, in a period somewhat
protracted, it is true, but after successive attenuations. Are
we justified in thinking that it ought to be the same in regard
to the microbe of anthrax? This hypothesis is confirmed by
experiment. Before the disappearance of its virulence the anthrax
microbe passes through various degrees of attenuation, and,
moreover, as is also the case with the microbe of chicken
cholera, each of these attenuated states of virulence can be
obtained by cultivation. Moreover, since, according to one of our
recent Communications, anthrax is not recurrent, each of our
attenuated anthrax microbes is, for the better-developed microbe,
a vaccine—that is to say, a virus producing a less-malignant
malady. What, therefore, is easier than to find in these a virus
that will infect with anthrax sheep, cows, and horses, without
killing them, and ultimately capable of warding off the mortal
malady? We have practised this experiment with great success upon
sheep, and when the season comes for the assembling of the flocks
at Beauce we shall try the experiment on a larger scale.
“Already M. Toussaint has announced that sheep can be saved by
preventive inoculations; but when this able observer shall have
published his results; on the subject of which we have made such
exhaustive studies, as yet unpublished, we shall be able to see
the whole difference which exists between the two methods—the
uncertainty of the one and the certainty of the other. That which
we announce has, moreover, the very great advantage of resting
upon the existence of a poison vaccine cultivable at will, and
which can be increased indefinitely in the space of a few hours
without having recourse to infected blood.”[8]
This announcement was immediately challenged in a way that
brought it to the attention of the entire world. The president of
an agricultural society, realizing the enormous importance of the
subject, proposed to Pasteur that his alleged discovery should be
submitted to a decisive public test. He proposed to furnish a
drove of fifty sheep half of which were to be inoculated with the
attenuated virus of Pasteur. Subsequently all the sheep were to
be inoculated with virulent virus, all being kept together in one
pen under precisely the same conditions. The “protected” sheep
were to remain healthy; the unprotected ones to die of anthrax;
so read the terms of the proposition. Pasteur accepted the
challenge; he even permitted a change in the programme by which
two goats were substituted for two of the sheep, and ten cattle
added, stipulating, however, that since his experiments had not
yet been extended to cattle these should not be regarded as
falling rigidly within the terms of the test.
It was a test to try the soul of any man, for all the world
looked on askance, prepared to deride the maker of so
preposterous a claim as soon as his claim should be proved
baseless. Not even the fame of Pasteur could make the public at
large, lay or scientific, believe in the possibility of what he
proposed to accomplish. There was time for all the world to be
informed of the procedure, for the first “preventive”
inoculation—or vaccination, as Pasteur termed it—was made on
May 5th, the second on May 17th, and another interval of two
weeks must elapse before the final inoculations with the
unattenuated virus. Twenty-four sheep, one goat, and five cattle
were submitted to the preliminary vaccinations. Then, on May 31
st, all sixty of the animals were inoculated, a protected and
unprotected one alternately, with an extremely virulent culture
of anthrax microbes that had been in Pasteur’s laboratory since
1877. This accomplished, the animals were left together in one
enclosure to await the issue.
Two days later, June 2d, at the appointed hour of rendezvous, a
vast crowd, composed of veterinary surgeons, newspaper
correspondents, and farmers from far and near, gathered to
witness the closing scenes of this scientific tourney. What they
saw was one of the most dramatic scenes in the history of
peaceful science—a scene which, as Pasteur declared afterwards,
“amazed the assembly.” Scattered about the enclosure, dead,
dying, or manifestly sick unto death, lay the unprotected
animals, one and all, while each and every “protected” animal
stalked unconcernedly about with every appearance of perfect
health. Twenty of the sheep and the one goat were already dead;
two other sheep expired under the eyes of the spectators; the
remaining victims lingered but a few hours longer. Thus in a
manner theatrical enough, not to say tragic, was proclaimed the
unequivocal victory of science. Naturally enough, the unbelievers
struck their colors and surrendered without terms; the principle
of protective vaccination, with a virus experimentally prepared
in the laboratory, was established beyond the reach of
controversy.
That memorable scientific battle marked the beginning of a new
era in medicine. It was a foregone conclusion that the principle
thus established would be still further generalized; that it
would be applied to human maladies; that in all probability it
would grapple successfully, sooner or later, with many infectious
diseases. That expectation has advanced rapidly towards
realization. Pasteur himself made the application to the human
subject in the disease hydrophobia in 1885, since which time that
hitherto most fatal of maladies has largely lost its terrors.
Thousands of persons bitten by mad dogs have been snatched from
the fatal consequences of that mishap by this method at the
Pasteur Institute in Paris, and at the similar institutes, built
on the model of this parent one, that have been established all
over the world in regions as widely separated as New York and
Nha-Trang.
SERUM-THERAPYIn the production of the rabies vaccine Pasteur and his
associates developed a method of attenuation of a virus quite
different from that which had been employed in the case of the
vaccines of chicken cholera and of anthrax. The rabies virus was
inoculated into the system of guinea-pigs or rabbits and, in
effect, cultivated in the systems of these animals. The spinal
cord of these infected animals was found to be rich in the virus,
which rapidly became attenuated when the cord was dried in the
air. The preventive virus, of varying strengths, was made by
maceration of these cords at varying stages of desiccation. This
cultivation of a virus within the animal organism suggested, no
doubt, by the familiar Jennerian method of securing smallpox
vaccine, was at the same time a step in the direction of a new
therapeutic procedure which was destined presently to become of
all-absorbing importance—the method, namely, of so-called
serum-therapy, or the treatment of a disease with the blood serum
of an animal that has been subjected to protective inoculation
against that disease.
The possibility of such a method was suggested by the familiar
observation, made by Pasteur and numerous other workers, that
animals of
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