A History of Science, vol 4 by Henry Smith Williams (best novels to read for beginners txt) 📖

years,

which has been the longest period devoted to these trials; and

the liquid, if it were naturally limpid, will not be in the least

polluted neither on its surface nor in its mass, although the

outside of the flask may become thickly coated with dust. This is

a most irrefutable proof of the impossibility of dust getting

inside the flask.

 

“The wort thus prepared remains uncontaminated indefinitely, in

spite of its susceptibility to change when exposed to the air

under conditions which allow it to gather the dusty particles

which float in the atmosphere. It is the same in the case of

urine, beef-tea, and grape-must, and generally with all those

putrefactable and fermentable liquids which have the property

when heated to boiling-point of destroying the vitality of dust

germs.”[7]

 

There was nothing in these studies bearing directly upon the

question of animal diseases, yet before they were finished they

had stimulated progress in more than one field of pathology. At

the very outset they sufficed to start afresh the inquiry as to

the role played by micro-organisms in disease. In particular they

led the French physician Devaine to return to some interrupted

studies which he had made ten years before in reference to the

animal disease called anthrax, or splenic fever, a disease that

cost the farmers of Europe millions of francs annually through

loss of sheep and cattle. In 1850 Devaine had seen multitudes of

bacteria in the blood of animals who had died of anthrax, but he

did not at that time think of them as having a causal relation to

the disease. Now, however, in 1863, stimulated by Pasteur’s new

revelations regarding the power of bacteria, he returned to the

subject, and soon became convinced, through experiments by means

of inoculation, that the microscopic organisms he had discovered

were the veritable and the sole cause of the infectious disease

anthrax.

 

The publication of this belief in 1863 aroused a furor of

controversy. That a microscopic vegetable could cause a virulent

systemic disease was an idea altogether too startling to be

accepted in a day, and the generality of biologists and

physicians demanded more convincing proofs than Devaine as yet

was able to offer.

 

Naturally a host of other investigators all over the world

entered the field. Foremost among these was the German Dr. Robert

Koch, who soon corroborated all that Devaine had observed, and

carried the experiments further in the direction of the

cultivation of successive generations of the bacteria in

artificial media, inoculations being made from such pure cultures

of the eighth generation, with the astonishing result that

animals thus inoculated succumbed to the disease.

 

Such experiments seem demonstrative, yet the world was

unconvinced, and in 1876, while the controversy was still at its

height, Pasteur was prevailed upon to take the matter in hand.

The great chemist was becoming more and more exclusively a

biologist as the years passed, and in recent years his famous

studies of the silk-worm diseases, which he proved due to

bacterial infection, and of the question of spontaneous

generation, had given him unequalled resources in microscopical

technique. And so when, with the aid of his laboratory associates

Duclaux and Chamberland and Roux, he took up the mooted anthrax

question the scientific world awaited the issue with bated

breath. And when, in 1877, Pasteur was ready to report on his

studies of anthrax, he came forward with such a wealth of

demonstrative experiments—experiments the rigid accuracy of

which no one would for a moment think of questioning—going to

prove the bacterial origin of anthrax, that scepticism was at

last quieted for all time to come.

 

Henceforth no one could doubt that the contagious disease anthrax

is due exclusively to the introduction into an animal’s system of

a specific germ—a microscopic plant—which develops there. And

no logical mind could have a reasonable doubt that what is proved

true of one infectious disease would some day be proved true also

of other, perhaps of all, forms of infectious maladies.

 

Hitherto the cause of contagion, by which certain maladies spread

from individual to individual, had been a total mystery, quite

unillumined by the vague terms “miasm,” “humor,” “virus,” and the

like cloaks of ignorance. Here and there a prophet of science,

as Schwann and Henle, had guessed the secret; but guessing, in

science, is far enough from knowing. Now, for the first time, the

world KNEW, and medicine had taken another gigantic stride

towards the heights of exact science.

LISTER AND ANTISEPTIC SURGERY

Meantime, in a different though allied field of medicine there

had been a complementary growth that led to immediate results of

even more practical importance. I mean the theory and practice

of antisepsis in surgery. This advance, like the other, came as

a direct outgrowth of Pasteur’s fermentation studies of alcoholic

beverages, though not at the hands of Pasteur himself. Struck by

the boundless implications of Pasteur’s revelations regarding the

bacteria, Dr. Joseph Lister (the present Lord Lister), then of

Glasgow, set about as early as 1860 to make a wonderful

application of these ideas. If putrefaction is always due to

bacterial development, he argued, this must apply as well to

living as to dead tissues; hence the putrefactive changes which

occur in wounds and after operations on the human subject, from

which blood-poisoning so often follows, might be absolutely

prevented if the injured surfaces could be kept free from access

of the germs of decay.

 

In the hope of accomplishing this result, Lister began

experimenting with drugs that might kill the bacteria without

injury to the patient, and with means to prevent further access

of germs once a wound was freed from them. How well he succeeded

all the world knows; how bitterly he was antagonized for about a

score of years, most of the world has already forgotten. As early

as 1867 Lister was able to publish results pointing towards

success in his great project; yet so incredulous were surgeons in

general that even some years later the leading surgeons on the

Continent had not so much as heard of his efforts. In 1870 the

soldiers of Paris died, as of old, of hospital gangrene; and

when, in 1871, the French surgeon Alphonse Guerin, stimulated by

Pasteur’s studies, conceived the idea of dressing wounds with

cotton in the hope of keeping germs from entering them, he was

quite unaware that a British contemporary had preceded him by a

full decade in this effort at prevention and had made long

strides towards complete success. Lister’s priority, however, and

the superiority of his method, were freely admitted by the French

Academy of Sciences, which in 1881 officially crowned his

achievement, as the Royal Society of London had done the year

before.

 

By this time, to be sure, as everybody knows, Lister’s new

methods had made their way everywhere, revolutionizing the

practice of surgery and practically banishing from the earth

maladies that hitherto had been the terror of the surgeon and the

opprobrium of his art. And these bedside studies, conducted in

the end by thousands of men who had no knowledge of microscopy,

had a large share in establishing the general belief in the

causal relation that micro-organisms bear to disease, which by

about the year 1880 had taken possession of the medical world.

But they did more; they brought into equal prominence the idea

that, the cause of a diseased condition being known, it maybe

possible as never before to grapple with and eradicate that

condition.

PREVENTIVE INOCULATION

The controversy over spontaneous generation, which, thanks to

Pasteur and Tyndall, had just been brought to a termination, made

it clear that no bacterium need be feared where an antecedent

bacterium had not found lodgment; Listerism in surgery had now

shown how much might be accomplished towards preventing the

access of germs to abraded surfaces of the body and destroying

those that already had found lodgment there. As yet, however,

there was no inkling of a way in which a corresponding onslaught

might be made upon those other germs which find their way into

the animal organism by way of the mouth and the nostrils, and

which, as was now clear, are the cause of those contagious

diseases which, first and last, claim so large a proportion of

mankind for their victims. How such means might be found now

became the anxious thought of every imaginative physician, of

every working microbiologist.

 

As it happened, the world was not kept long in suspense. Almost

before the proposition had taken shape in the minds of the other

leaders, Pasteur had found a solution. Guided by the empirical

success of Jenner, he, like many others, had long practised

inoculation experiments, and on February 9, 1880, he announced to

the French Academy of Sciences that he had found a method of so

reducing the virulence of a disease germ that when introduced

into the system of a susceptible animal it produced only a mild

form of the disease, which, however, sufficed to protect against

the usual virulent form exactly as vaccinia protects against

smallpox. The particular disease experimented with was that

infectious malady of poultry known familiarly as “chicken

cholera.” In October of the same year Pasteur announced the

method by which this “attenuation of the virus,” as he termed it,

had been brought about—by cultivation of the disease germs in

artificial media, exposed to the air, and he did not hesitate to

assert his belief that the method would prove “susceptible of

generalization”—that is to say, of application to other diseases

than the particular one in question.

 

Within a few months he made good this prophecy, for in February,

1881, he announced to the Academy that with the aid, as before,

of his associates MM. Chamberland and Roux, he had produced an

attenuated virus of the anthrax microbe by the use of which, as

he affirmed with great confidence, he could protect sheep, and

presumably cattle, against that fatal malady. “In some recent

publications,” said Pasteur, “I announced the first case of the

attenuation of a virus by experimental methods only. Formed of a

special microbe of an extreme minuteness, this virus may be

multiplied by artificial culture outside the animal body. These

cultures, left alone without any possible external contamination,

undergo, in the course of time, modifications of their virulency

to a greater or less extent. The oxygen of the atmosphere is

said to be the chief cause of these attenuations—that is, this

lessening of the facilities of multiplication of the microbe; for

it is evident that the difference of virulence is in some way

associated with differences of development in the parasitic

economy.

 

“There is no need to insist upon the interesting character of

these results and the deductions to be made therefrom. To seek to

lessen the virulence by rational means would be to establish,

upon an experimental basis, the hope of preparing from an active

virus, easily cultivated either in the human or animal body, a

vaccine-virus of restrained development capable of preventing the

fatal effects of the former. Therefore, we have applied all our

energies to investigate the possible generalizing action of

atmospheric oxygen in the attenuation of virus.

 

“The anthrax virus, being one that has been most carefully

studied, seemed to be the first that should attract our

attention. Every time, however, we encountered a difficulty.

Between the microbe of chicken cholera and the microbe of anthrax

there exists an essential difference which does not allow the new

experiment to be verified by the old. The microbes of chicken

cholera do not, in effect, seem to resolve themselves, in their

culture, into veritable germs. The latter are merely cells, or

articulations always ready to multiply by division, except when

the particular conditions in which they become true germs are

known.

 

“The yeast of beer is a striking example of these cellular

productions, being able to multiply themselves indefinitely

without the apparition