A History of Science, vol 4 - Henry Smith Williams (epub e ink reader .txt) 📗

of their original spores. There exist

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-THERAPY

In 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