The greatest biologist
of the nineteenth century was (1822-1895). His work had both practical
use and profound theoretical significance. On the practical side, what
discovery in the history of mankind is more important than the germ
theory of disease? As for theoretical significance, Pasteur disproved
the widely held belief in the spontaneous generation of life. In a simple
experiment using a sterilized flask with a bent neck, he showed that
plain air cannot initiate the growth of microorganisms. A culture can
grow in the flask only if germs enter it. "There is no known circumstance
in which it can be confirmed that microscopic beings came into the world
without germs, without parents similar to themselves," he concluded,
in 1864 (3).
demonstrated that life comes only from life. One can only wonder what
the history of biological science would be if this principle had been
taken as fundamental. Perhaps today we would still be unsure how life
on Earth began. But if so, we would approach the question differently.
We would assume that life here had to be seeded somehow. We would investigate
possible mechanisms for this seeding. We would look for evidence that
bacteria, the simplest known form of life, can survive in space, for
example. We would look for means by which they could travel across interstellar
space and for survive for the millions of years such trips might take.
For the suggestion that life can assemble itself from nonliving chemicals,
we would have the utmost scepticism. "Extraordinary claims require
extraordinary evidence," we would say (4). Such extraordinary evidence
in the laboratory of any kind of life simpler than a cell. (Nothing
• Evidence in nature of any kind of life simpler than a cell.
(Viruses and prions are not alive. However, newly topical nanobacteria
look too small to contain the lowest amount of DNA previously believed
necessary for a bacterium. Yet most neo-Darwinists doubt that they are
even biological. Additional research on them will be interesting.)
• Fossil evidence of a long period during which evolution of precellular
life was underway on Earth. (The fossil record indicates that there
were whole cells on Earth in a geological instant.)
• Evidence that any highly organized structure specifiable only
with lengthy encoded instructions can emerge with its instructions from
a closed system containing only unorganized, simple components, over
any period of time, by any natural means whatsoever. (The emergence
of life on Earth cannot serve as evidence; how life on Earth emerged
is the question.)
But history went a different way. People in the late nineteenth centory
believed that Earth was biologically isolated from the rest of the Universe.
Therefore, the spontaneous generation of life by natural means from
nonliving chemicals was considered the only scientific alternative for
explaining the origin of life on Earth. It is still the consensus, accepted
with little questioning, even though the process has never been observed
or even described in plausible detail. That life could have come to
Earth from elsewhere is considered to be the extraordinary claim. But
the situation may be changing.
When asked by a wine company to explain why some wine turned sour whilst
it was being made, the French chemist, , discovered that there were
germs in the air that caused liquids to go off.
He went on to develop a process which he called 'pasteurisation', killing
the germs by boiling and then cooling the wine. Pasteur then set about
proving that the germs came from the air and could therefore be prevented
from entering the liquid in the first place. He demonstrated this by
sealing a quantity of a liquid in an airtight jar and leaving another
quantity exposed to the air.
He used this discovery to help treat diseases and with the British doctor
Edward Jenner he developed a process of vaccination against the killer
disease, smallpox. Pasteur believed that his germ theory could be used
to explain how vaccination worked. He examined the blood of healthy
people and compared it with the blood of people with various diseases.
He observed that when people were infected with disease their blood
contained lots of germs.
The process of boiling a liquid to destroy germs is still used today;
most dairy products are pasteurised. Pasteur went on to discover vaccinations
for chicken pox, cholera, diphtheria, anthrax and rabies. However, not
all of Pasteur's ideas were accepted. He recommended that surgical instruments
be boiled before an operation to kill any germs on them, but most surgeons
ignored this advice. This had to wait until aseptic surgery developed
in the 20th century.
Pasteur's work was revolutionary and led the way for further research
into type of germs causing specific diseases.
born on December 27, 1822 in Dole, in the region of Jura, France. His
discovery that most infectious diseases are caused by germs, known as
the "germ theory of disease", is one of the most important
in medical history. His work became the foundation for the science of
microbiology, and a cornerstone of modern medicine.
Pasteur's phenomenal contributions to microbiology and medicine can
be summarized as follows. First, he championed changes in hospital practices
to minimize the spread of disease by microbes. Second, he discovered
that weakened forms of a microbe could be used as an immunization against
more virulent forms of the microbe. Third, Pasteur found that rabies
was transmitted by agents so small they could not be seen under a microscope,
thus revealing the world of viruses. As a result he developed techniques
to vaccinate dogs against rabies, and to treat humans bitten by rabid
dogs. And fourth, Pasteur developed "pasteurization", a process
by which harmful microbes in perishable food products are destroyed
using heat, without destroying the food.
Each discovery in the body of Pasteur's work represents a link in an
uninterrupted chain, beginning with molecular asymmetry and ending with
his rabies prophylaxis, by way of his research in fermentation, silkworm,
wine and beer diseases, asepsis and vaccines.
From Crystallography to Molecular Asymmetry
In 1847 at the age of 26, Pasteur did his first work on molecular asymmetry,
bringing together the principles of crystallography, chemistry and optics.
He formulated a fundamental law: asymmetry differentiates the organic
world from the mineral world. In other words, asymmetric molecules are
always the product of life forces. His work became the basis of a new
science -- stereochemistry.
Research on Fermentation and Spontaneous Generation
At the request of a distiller named Bigo from the north of France, Pasteur
began to examine why alcohol becomes contaminated with undesirable substances
during fermentation. He soon demonstrated that each sort of fermentation
is linked to the existence of a specific microorganism or ferment --
a living being that one can study by cultivation in an appropriate,
sterile medium. This insight is the basis of microbiology.
Pasteur delivered the fatal blow to the doctrine of spontaneous generation,
the theory held for 20 centuries that life could arise spontaneously
in organic materials. He also developed a germ theory. At the same time,
he discovered the existence of life without oxygen: "Fermentation
is the consequence of life without air". The discovery of anaerobic
life paved the way for the study of germs that cause septicemia and
gangrene, among other infections. Thanks to Pasteur, it became possible
to devise techniques to kill microbes and to control contamination.
Technique of "Pasteurization"
Emperor Napoleon III asked Pasteur to investigate the diseases afflicting
wine which were causing considerable economic losses to the wine industry.
Pasteur went to a vineyard in Arbois in 1864 to study this problem.
He demonstrated that wine diseases are caused by microorganisms that
can be killed by heating the wine to 55deg.C for several minutes. Applied
to beer and milk, this process, called "pasteurization", soon
came into use throughout the world.
Research on Infectious Diseases Afflicting Man and Animal
In 1865, Pasteur began to study the silkworm diseases that were crippling
the silk industry in France. He discovered the infectious agents and
revealed the manner in which these agents are transmitted--by contagion
and hereditary principle -- and how to prevent them. Elaborating on
his study of fermentation, he could now confirm that each disease is
caused by a specific microbe and that these microbes are foreign elements.
With this knowledge, Pasteur was able to establish the basic rules of
sterilization or asepsis. Preventing contagion and infection, his method
of sterilization revolutionized surgery and obstetrics.
From 1877 to 1887, Pasteur employed these fundamentals of microbiology
in the battle against infectious diseases. He went on to discover three
bacteria responsible for human illnesses : staphylococcus, streptococcus
Treatment and Prevention of Rabies
discovered the method for the attenuation of virulent microorganisms
that is the basis of vaccination. He developed vaccines against chicken
cholera, anthrax and swine erysipelas. After mastering his method of
vaccination, he applied this concept to rabies. On July 6, 1885, Pasteur
tested his pioneering rabies treatment on man for the first time : the
young Joseph Meister was saved.
The Creation of the Pasteur Institute
On March 1, 1886, Pasteur presented the results of his rabies treatment
to the Academy of Sciences and called for the creation of a rabies vaccine
center. An extensive, international public drive for funds financed
the construction of the Pasteur Institute, a private, state-approved
institute recognized by the President of France, Jules Grévy,
in 1887 and inaugurated by his successor Sadi Carnot in 1888. In accordance
with Pasteur's wishes, the Institute was founded as a clinic for rabies
treatment, a research center for infectious disease and a teaching center.
The 66-year-old scientist went on to dedicate the last seven years of
his life to the Institute that still bears his name. During this period,
Pasteur also came to know the joys of fame and was honored throughout
the world with prestigious decorations.
His work was continued and amplified throughout the world by his disciples,
A Man of Freedom and Rigor
Pasteur's work is not simply the sum of his discoveries. It also represents
the revolution of scientific methodology. Pasteur superimposed two indisputable
rules of modern research: the freedom of creative imagination necessarily
subjected to rigorous experimentation. He would teach his disciples
"Do not put forward anything that you cannot prove by experimentation"
was a humanist, always working towards the improvement of the human
condition. He was a free man who never hesitated to take issue with
the prevailing yet false ideas of his time.
He ascribed particular importance to the spread of knowledge and the
applications of research. In the scientist's lifetime, Pasteurien theory
and method were put into use well beyond the borders of France.
Fully aware of the international importance of his work, Pasteur's disciples
dispersed themselves wherever their assistance was needed. In 1891,
the first Foreign Institut Pasteur was founded in Saigon (today Ho Chi
Minh City, Vietnam) launching what was to become a vast international
network of Instituts Pasteur.
Because he changed the world forever, his homeland and the world have
long considered him a benefactor of humanity.
The Progress of Humanity
"I beseech you to take interest in these sacred domains so expressively
called laboratories. Ask that there be more and that they be adorned
for these are the temples of the future, wealth and well-being. It is
here that humanity will grow, strengthen and improve. Here, humanity
will learn to read progress and individual harmony in the works of nature,
while humanity's own works are all too often those of barbarism, fanaticism
and destruction." --
French microbiologist and chemist Born December 27, 1822
Dole, Jura, France Died September 28, 1895
Saint-Cloud, Hauts-de-Seine, France ( December 27 1822 – September
28 1895) was a French microbiologist and chemist who advocated the germ
theory of disease and developed techniques of inoculation.
was born in Dole, Jura départementThe departements (or departments)
are administrative units of France, roughly analogous to British counties
and are now grouped into 22 metropolitan and four overseas regions''.
They are subdivided into 342 arrondissements''. Departements are also
found i, France, the son of a tanner. He was admitted in 1843 at the
École Normale Supérieure in Paris and got a doctoral degree
in 1846. He studied chemistry, but showed little promise at first (one
of his professors described him as "mediocre"). Nevertheless,
he became a scientist.
In his early work as a chemist he resolved a problem concerning the
nature of tartaric acid ( 1849). A solution of this compound derived
from living things (specifically, wine lees) rotated the plane of polarization
of light passing through it. The mystery was that tartaric acid derived
by chemical synthesis had no such effect, even though its reactions
were identical and its elemental composition was the same.
Pasteur noticed, upon examination of the tiny crystals of tartaric acid,
that the crystals came in two asymmetric forms that were mirror iimages
of one another. Tediously sorting the crystals by hand gave two forms
of tartaric acid: solutions of one form rotated polarised light clockwise,
while the other form rotated light anticlockwise. An equal mix of the
two had no effect on polarized light. Pasteur correctly deduced that
the tartaric acid molecule was asymmetric and could exist in two different
forms that resemble one another as a left- and right-hand glove resemble
one another. As the first demonstration of chiral molecules, it was
quite an achievement, but Pasteur then went on to his more famous work
in the field of biology/medicine.
His doctoral thesis on crystallography got him a position of professor
of chemistry at the Faculté (College) of Strasbourg.
In 1854, he was named Dean of the new College of Science in Lille. In
1857, he was made administrator and director of scientific studies of
the École Normale Supérieure.
He demonstrated that fermentation was caused by the growth of microorganisms,
and that the growth of microorganisms in nutrient broths was not due
to spontaneous generation. He exposed freshly boiled broths to air in
vessels that contained a filter to prevent all particles from passing
through to the growth medium and even in vessels with no filter at all,
with air being admitted via a long tortuous tube that would not allow
dust particles to pass. Nothing grew in the broths; therefore, the living
organisms that grew in such broths came from outside, as spores on dust,
rather than being spontaneously generated within the broth. Thus, Pasteur
dealt the death blow to the theory of spontaneous generation and supported
did not develop germ theory; Girolamo Fracastoro, Friedrich Henle and
others suggested it earlier. Pasteur conducted experiments that clearly
indicated its correctness and managed to convince most of Europe that
it was true.
Pasteur's research also showed that some microorganisms contaminated
the fermenting beverages. With this established, he invented a process
in which liquids such as milk were heated to kill all bacteria and molds
already present within them. He and Claude Bernard completed the first
test on April 20, 1862. This process was soon afterwards known as pasteurization.
Beverage contamination led Pasteur to conclude that microorganisms infected
animals and humans as well. He proposed preventing the entry of microorganisms
into the human body, leading Joseph Lister to develop antiseptic methods
In 1865, Pasteur set out to help the silk industry. A disease called
pebrine was killing great numbers of silkworms. He worked several years
to prove that a microbe that attacks silkworm eggs causes the disease,
and that eliminating this microbe in silkworm nurseries would wipe out
His later work on diseases included work on chicken cholera. During
this work, a culture of the responsible bacteria had spoiled and failed
to induce the disease in some chickens he was infecting with the disease.
Upon reusing these healthy chickens, Pasteur discovered that he could
not infect them, even with fresh bacteria: the weakened bacteria had
caused the chickens to become immune to the disease, although they had
not actually caused the disease. In the 1870s he applied this immunization
method to anthrax, which affected cattle, and aroused interest in combating
The notion of a weak form of a disease causing immunity to the virulent
version was not new: this had been known for a long time for smallpox.
Inoculation with smallpox was known to result in far less scarring and
greatly reduced mortality than with the naturally acquired disease.
Edward Jenner had also discovered vaccination, using cowpox to give
cross-immunity to smallpox, and by Pasteur's time this had generally
replaced the use of actual smallpox material in inoculation. The difference
with chicken cholera and anthrax was that the weakened form of the disease
organism had been generated artificially, and so a naturally weak form
of the disease organism did not need to be found.
This discovery revolutionised work in infectious diseases, and Pasteur
gave these artificially weakened diseases the generic name of vaccines,
to honour Jenner's discovery. Pasteur produced the first vaccine for
rabies, which was first used on 9-year old Joseph Meister on July 6,
1885 after the boy was badly mauled by a rabid dog. This was done at
some personal risk for Pasteur, since he was not a licensed physician
and could have faced prosecution for treating the boy. Fortunately,
the treatment proved to be a spectacular success, with Meister avoiding
the disease. So Pasteur was hailed as a hero and the legal matter was
not pursued. The treatment's success laid the foundations for the manufacture
of many other vaccines. The first of the Pasteur Institutes was also
built on the basis of this achievement.
Pasteur also discovered anaerobiosis - that some microorganisms can
develop and live without air or oxygen.
He won the Leeuwenhoek medal, microbiology's highest honor, in 1895.
Pasteur died in 1895 near Paris from complications caused by a series
of strokes that had begun plaguing him as far back as 1868. He was buried
in the Cathedral of Notre Dame, but his remains were soon placed in
a crypt in the Institut Pasteur, Paris.
Pasteur's method of immunization was effective and was employed by many
other physicians, leading to the eradication of the diseases typhus
and polio as threats. Pasteurization led to the elimination of contaminated
milk and other drinks as sources of disease. In fact, Pasteur inaugurated
the modern age of medicine, leading to an increase in the human life
span in much of the (wealthy) world and a surprising population explosion.
Accordingly, he has been hailed as the "Father of Medicine"
and a "Benefactor of Humanity." Craters on Mars and the Moon
are named in his honor. In popular culture, Pasteur is the eponymous
French scientist, his name appearing in science fiction shows like Star
We need no reminder
that the foundations of our knowledge of health and disease were constructed
by scientific giants who worked decades, even centuries, ago. It is
with tributes such as the one today to that we pay homage to these great
minds -- to acknowledge their achievements and our indebtedness to them
which we can never repay.
With certainty, one hallmark of Pasteur's research was not only the
importance of his individual discoveries, but the overwhelming breadth
of his accomplishment. Pasteur's long time collaborator, Emile Duclaux,
wrote, "A mind ... of a scientific man is a bird on the wing; we
see it only when it alights or when it takes flight. ... We may by watching
closely keep it in view, and point out just where it touches the earth.
But why does it alight here and not there? Why has it taken this direction
and not that in its flight toward new discoveries?"
Pasteur, himself, provided us with an answer: He believed that his research
was "enchained" to an inescapable, forward moving logic. As
we review today Pasteur's scientific discoveries we shall see the truth
of this statement: how one discovery, one concept, led almost "inescapably"
Education and Growing Up
Pasteur was born in Ole and grew up in the nearby town of Arbois, the
only son of a poorly educated tanner, Jean Pasteur. Louis was not an
outstanding student during his years of elementary education, preferring
fishing and drawing to other subjects. In fact, young Louis drawings
suggested that he could easily have become a superior portrait Artist.
His later drawings of friends done at college were so professional that
Pasteur was listed in at least two compendia of XIX C. artists.
The Senior Pasteur, however, did not see his son ending up as an Artist,
and Louis, himself, was showing increasing interest in chemistry and
other scientific subjects. The highest wish Father Pasteur had for his
son was that he complete his education in the local schools and become
a professor in the college at Arbois. However the headmaster of the
college recognized that Louis could do much better and convinced father
and son that Louis should try for the Ecole Normale Sup rieure in Paris.
This most prestigious French University was founded specifically to
train outstanding students for University careers in science and letters.
And it was here that Pasteur entered and began his long journey of scientific
It may surprise some to learn that Pasteur, the father of microbiology
and immunology, was a chemist who launched his memorable scientific
career by studying the shapes of organic crystals. Pasteur was 26 years
old, working for his doctorate in chemistry in the laboratory of Antoine
Balard. Crystallography was just emerging as a branch of chemistry.
His project was to crystallize a number of different compounds. Happily
he started working with tartaric acid. Crystals of this organic acid
are present in large amounts in the sediments of fermenting wine. Often
one also found in the sediments in the wine barrels crystals of a second
acid called paratartaric acid or "racemic acid". A few years
earlier, the chemical compositions of these two acids, tartaric and
paratartaric, had been determined. They were identical. But in solution
there was a striking difference. Whereas tartaric acid rotated a beam
of polarized light passing through it to the right, paratartaric acid
did not rotate the light. This puzzled the young Pasteur. How could
Pasteur refused to accept the notion that two compounds that had the
same chemical composition yet acted so differently in respect to rotation
of light could be identical. He was convinced that the internal structure
of the two compounds must be different and this difference would show
itself in the crystal form. The experts in this field had looked examined
tartrate and paratartrate crystals but never saw a difference, perhaps
because, as Duclaux thought, they believed that no difference could
exist. Pasteur believed that there were differences and indeed found
Upon intense examination beneath his microscope, he saw that every crystal
of pure tartaric acid looked like every other one. When he examined
the paratartrate crystals, on the other hand, he saw two types of crystals,
nearly identical but not quite! One type was the mirror image the other
-- the way the right hand mirrors the left hand. This was the difference
he was looking for!
Pasteur then performed one of the simplest and yet most elegant experiments
in the annals of chemistry. With a dissecting needle and his microscope,
he separated the left and right crystal shapes from each other to form
two piles of crystals. He then showed that in solution one form rotated
light to the left, the other to the right. This simple experiment proved
that the organic molecules with the same chemical composition can exist
in space in unique stereospecific forms. And with this work did Pasteur
launch the new science of stereochemistry.
To Pasteur this discovery had a deeper meaning. He proposed that asymmetrical
molecules were indicative of living processes. In the broadest sense,
he was correct. We know today that all of the proteins of higher animals
are made up of only those amino acids that exist in the left-hand form.
The mirror image right-hand amino acids are not used by human or animal
cells. Likewise, our cells burn only the right-handed form of sugar,
not the left-handed form that can be made in the test tube. It was the
discovery of asymmetry of organic molecules that provided Pasteur with
the "inescapable forward moving logic" that enchained him
as he began his studies on alcoholic fermentation.
Pasteur served on the faculty of science of Dijon for a brief period
and then was transferred to Strasbourg University where he continued
his studies on molecular asymmetry. In Strasbourg, Pasteur had the immense
good fortune to meet and marry the University Rector's daughter Marie
Laurent, who was to be his devoted wife, mother and scientific helpmate
through the remainder of his life.
In 1854 Pasteur was appointed Dean and professor of chemistry at the
Faculty of Sciences in Lille, France. Lille was an industrial town with
a number of distilleries and factories. The Minister of Public Instruction
was not completely sold on "science for science's sake". He
reminded university faculty that (and here I quote the Minister's words)
"whilst keeping up with scientific theory, you should, in order
to produce useful and far reaching results, appropriate to yourselves
the special applications suitable to the real wants of the surrounding
Pasteur, in contrast to other faculty, needed no prodding. He enjoyed
taking his students on tours of the factories and was quick to advise
the managers that he was available to help solve their problems. In
the summer of 1856, M. Bigot, father of one of his students in chemistry,
called upon Pasteur to help him overcome difficulties he was having
manufacturing alcohol by fermentation of beetroot. Often, instead of
alcohol, Bigot's fermentations yielded lactic acid.
To better appreciate the discoveries to follow, we should understand
what was believed at that time about alcoholic fermentation. Chemistry
was emerging as a true science, freed from the pseudoscience of the
alchemist. The mysterious chemical processes of living animals were
slowly being unraveled in strictly chemical terms. Lavoisier had shown
that chemical combustion in living animals was quantitatively identical
to that occurring in a furnace. Lavoisier also showed that sugar, the
starting product of fermentation, could be broken down to alcohol, CO2
and H2O by simply dropping a sugar solution on heated platinum. Woehler
startled the scientific world by sythesizing the organic compound urea,
showing for the first time that organic compounds, believed up to then
as capable of synthesis only by living animals could be made in a test
tube. And due, in no small part to Pasteur's work on crystals, internal
structure and analysis of complex organic compounds was becoming routine.
In this light, fermentation leading to production of wine, beer and
vinegar was believed to be a straightforward chemical breakdown of sugar
to the desired molecules. The chemical experts of the day proclaimed
that the breakdown of sugar into alcohol during fermentation of sugar
to wine and beer was due to the presence of inherent unstabilizing vibrations.
One could transfer these unstabilizing vibrations from a vat of finished
wine to new grape pressings to start fermentation anew.
Yeast cells were found in the fermenting vats of wine, and were recognized
as being live organisms, but they were believed simply to be either
a product of fermentation or catalytic agents that provided useful ingredients
for fermentation to proceed. Those few biologists who earlier concluded
that yeast was the cause of, and not the product of, fermentation were
ridiculed by the scientific experts: The deep conviction of the scientific
establishment was that chemistry had come too far to allow a vitalistic
life force theory to challenge pure chemical explanations of molecular
reaction. To attribute such chemical changes to mysterious life forces
would represent a major backward step in science!.
Unfortunately, the "scientific establishment" was not providing
much help to the brewers of wine, beer and vinegar. These manufacturers
were plagued by serious economic problems related to their fermentations.
Yields of alcohol might suddenly fall off; wine might unexpectedly grow
ropy or sour or turn to vinegar; vinegar, when desired, might not be
formed and lactic acid might appear in its place; the quality and taste
of beer might unexpectedly change making quality control a nightmare!
All too often the producers would be forced to throw out the resultant
batches, start anew, and sadly have no better luck!
Into M. Bigot's factory, microscope in hand, came Pasteur. He quickly
found three clues that allowed him to solve the puzzle of alcoholic
fermentation. First, when alcohol was produced normally, the yeast cells
were plump and budding. But when lactic acid would form instead of alcohol,
small rod like microbes were always mixed with the yeast cells. Second,
analysis of the batches of alcohol showed that amyl alcohol and other
complex organic compounds were being formed during the fermentation.
This could not be explained by the simple catalytic breakdown of sugar
shown by Lavoisier. Some additional processes must be involved. Third,
and this may have been the critical clue to Pasteur, some of these compounds
rotated light, that is they were asymmetric. As we said earlier, Pasteur
suspected that only living cells produced asymmetrical compounds. He
concluded and was able to prove that living cells, the yeast, were responsible
for forming alcohol from sugar, and that contaminating microorganisms
turned the fermentations sour!
Over the next several years Pasteur identified and isolated the specific
microorganisms responsible for normal and abnormal fermentations in
production of wine, beer, vinegar. He showed that if he heated wine,
beer, milk to moderately high temperatures for a few minutes, he could
kill living microorganism and thereby sterilize (pasteurize), the batches
and prevent their degradation. If pure cultures of microbes and yeasts
were added to sterile mashes uniform, predictable fermentations would
In the midst of the great excitement and controversy created by Pasteur's
research on fermentation, a debate was ongoing in the scientific world
on the theory of "spontaneous generation". The idea that beetles,
eels, maggots and now microbes could arise spontaneously' from putrefying
matter was speculated on from Greek and Roman times. And in the 1860's
spontaneous generation was still a subject of debate in the exalted
French Academy of Sciences. Against the advice of his colleagues, who
saw dabbling in this field as thankless and unrewarding, Pasteur entered
the fray. Based on his work on fermentation it seemed obvious to him
that the sources of yeasts and other microorganisms that were found
during fermentation and putrefaction entered from the outside, for example,
on the dust of the air. Pasteur conducted a series of ingenious experiments
that destroyed every argument supporting "spontaneous generation".
He showed that the skin of grapes towards the beginning of grape harvest
was the source of the yeast. Drawing grape juice from under the skin
with sterile needles gave juice that would not ferment. Covering the
grape arbors with fine cloth or wrapping the grapes with cotton to keep
off contaminating dust, gave grapes that would not produce wine. In
order to show that dust of the air was the carrier of contamination,
he allowed air collected at different altitudes, from sea level to mountain
tops, to enter sterilized vessels containing fermentable solutions.
The higher the altitude the less the dust in the air and the fewer flasks
The experimental design that clinched the argument was the use of the
swan-neck flask. In this experiment, fermentable juice was placed in
a flask and after sterilization the neck was heated and drawn out as
a thin tube taking a gentle downward then upward arc -- resembling the
neck of a swan. The end of neck was then sealed. As long as it was sealed,
the contents remained unchanged. If the the flask was opened by nipping
off the end of the neck, air entered but dust was trapped on the wet
walls of the neck. Under this condition, the fluid would remain forever
sterile, showing that air alone could not trigger growth of microorganisms.
If, however, the flask was tipped to allow the sterile liquid to touch
the contaminated walls and this liquid was then returned to the broth,
growth of microorganisms immediately began.
In the words of Pasteur "Never will the doctrine of spontaneous
generation recover from the mortal blow of this simple experiment. No,
there is now no circumstance known in which it can be affirmed that
microscopic beings came into the world without germs, without parents
similar to themselves."
As if Pasteur was not busy enough with his studies on fermentation and
spontaneous generation, hE was asked by the Department of Agriculture
to head a commission to see what could be learned about a devastating
disease of silkworks that was destroying the French silk industry. Even
though Pasteur knew nothing of silkworms and had no idea that they suffered
from disease, his research on silkworms forged another link in his "inevitable"
chain of discovery.
Now there were at least two different types of silkworm diseases that
Pasteur came to grips with: Pebrine, in which black spots and corpuscles
are generally, but not always, present on the worm. In such cases the
worms often die within the cocoons . In the second type of disease,
flacherie, the worms exhibit no corpuscles or spots but fail to spin
cocoons. Pasteur suspected, but was not sure, that pebrine corpuscles
were associated with the failure of the worms. Nonetheless, by examining
the worms under the microscope he was able to identify those free of
pebrine and used only their eggs for breeding. Next he excluded from
breeding eggs from worms with flacherie whom he identified by their
sluggish behavior in climbing leaves when about to construct cocoons.
He instructed the silkworm farmers on these methods of selection and
how to use the microscope to detect sickness in the worms. Soon the
silk industry in France, Italy and other European countries returned
Pasteur considered these studies important landmarks in his investigations
on infection and infectious disease. As he expanded his research, he
found that healthy worms became infected when allowed to nest on leaves
used by infected worms. He also noted that the susceptibility of the
worms varied widely, some worms dying shortly after infection, some
weeks later, some not at all. He determined that temperature, humidity,
ventilation, quality of the food, sanitation and adequate separation
of the broods of newly hatched worms each played a role in susceptibility
to the disease. So here from Pasteur's research we see the emergence
of his future concepts of the influence of environment on contagion.
Germ Theory of Disease
The crowning achievements of Pasteur's career were development of the
germ theory of disease and the use of vaccines to prevent these diseases.
Pasteur's studies on contamination of wine and beer by airborne yeast
clearly stimulated certain investigators to recognize that these "diseases"
were due to entry of foreign microorganisms. Lister in England was so
impressed by Pasteur's work that he began to systematically sterilize
his instruments, bandages and sprayed phenol solutions in his operatories
thus reducing infections following surgery to incredibly low numbers.
By 1875 many physicians recognized that some diseases were accompanied
by specific microorganisms, but the body of medical opinion was unwilling
to concede that important diseases --cholera, diptheria, scarlet fever,
childbirth fever, syphilis, smallpox - could ever be caused by these
agents. To give you an idea of the magnitude of the problem, according
to Pasteur's biographer son-in-law Vallery-Radot between April 1 and
May 10, 1856, in the Paris Maternity Hospital there were 64 fatalities
due to childbirth fever out of 347 confinements. The hospital was closed
and the patients were transferred to a different hospital. Sadly, the
contagion followed these women and nearly all of them died!
As Pasteur wandered through hospital wards he became increasingly aware
that infection was spread by physicians and hospital attendants from
sick to healthy patients. Pasteur impressed on his physician colleagues
that avoidance of microbes meant avoidance of infection. In a famous
speech before the august Academy of Medicine in Paris he stated, "This
water, this sponge, this lint with which you wash or cover a wound,
may deposit germs which have the power of multiplying rapidly within
the tissue....If I had the honor of being a surgeon....not only would
I use none but perfectly clean instruments, but I would clean my hands
with the greatest care...I would us only lint, bandages and sponges
previously exposed to a temperature of 1300 to 1500 degrees. Slowly,
but surely, through the preachings of Pasteur, Lister and other physicians
antiseptic medicine and surgery became the rule.
At this time, anthrax, a fatal disease of sheep and cattle, was decimating
the sheep industry and the economy of France. Important strides in identifying
the causative agent of anthrax had been made by the time Pasteur entered
the arena. The great German physician/scientist Robert Koch, isolated
the anthrax bacillus, previously identified by the French physician
Davain, from infected spleens and showed that under resting conditions
the bacillus formed long-lived spores.
Definitive proof was still lacking that the cultured bacillus, itself,
and not something carried along in Koch's culture medium was responsible
to giving injected animals anthrax. Pasteur provided this proof. As
described by Dubos, Pasteur placed one drop of blood from a sheep dying
of anthrax into 50 ml of sterile culture, grew up the bacterium, and
then repeated this process 100 times. This represented a huge dilution
of the original culture so that not a single molecule of the original
culture remained in the final culture. Yet, the last culture was as
active as the first in producing anthrax. As only the bacillus, itself,
by growing up each time in the new culture, could escape dilution, it
proved beyond all doubt that the anthrax bacillus and nothing else could
be responsible for the disease. Thus was the germ theory of disease
But how did the disease spread? Why was one field deadly to sheep, another
harmless? Here Pasteur's studies on silkworm contagion provided the
clue. During one of Pasteur's excursions to a field where sheep were
grazing he noted that the ground in one part of the field was differently
colored than the rest. There it was that the farmer had buried some
sheep dead of anthrax. The color of the soil was due to earth worm casts.
He realized that earth worms were feeding on the carcasses of the buried
sheep and bringing the anthrax spores to the surface where other sheep
could graze on the contaminated soil. Although containment of the animals
on uncontaminated fields would help control the spread of anthrax, more
Interestingly, Pasteur's studies on chicken cholera going on at this
time provided the breakthrough that led to development of specific vaccines
to fight disease. Cholera was a serious problem for farmers. Chicken
cholera would spread through a barnyard rapidly and wipe out the entire
flock in as little as 3 days. Spread could be by contaminated food or
animal excrements. Pasteur had identified the cholera bacillus and was
growing it in pure culture. When injected, chicken invariably died in
Then luck intervened. During the heat of the summer, Pasteur returned
to Paris leaving the cholera cultures used for infection stored on the
shelves of the Arbois laboratory. Upon return, Pasteur's collaborators
were disappointed to find that these stored cultures no longer killed
injected chickens, nor even made them sick. The group set to work to
make new cultures of the bacillus and tested these batches on new birds
and those healthy previously treated birds. The results were astonishing:
The previously injected birds were unaffected by the bacillus, while
the new birds all died. When Pasteur saw these results he immediately
realized that in a sense he was repeating the studies of Jenner 80 years
earlier who had conferred on humans immunity to smallpox by vaccinating
individuals with a mild form of cowpox. Pasteur then reproducibly manufactured
attenuated cultures of chicken cholera vaccines and could routinely
prevent cholera in the vaccinated chickens.
If attenuated cholera bacillus could render chickens resistant to the
disease, would not an attenuated anthrax bacillus render sheep immune
to anthrax? By various techniques involving oxidation and aging, anthrax
vaccines indeed prevented anthrax in laboratory trials. Pasteur's reports
on preventing sheep anthrax were so exciting to some and unbelievable
to many, that he was challenged by the well-known veterinarian Rossignol
to conduct a carefully controlled public test of his anthrax vaccine.
This was to take place at Pouilly le Fort, a farm in the town of Melun
south of Paris. Twenty-five sheep were to be controls, the other twenty-five
were to be vaccinated by Pasteur and then all animals would receive
a lethal dose of anthrax. All of the control sheep must die and the
vaccinated sheep must live. When Pasteur's colleagues learned that he
had agreed to the test they were concerned. The challenge was severe
and there was no room for error. The vaccines were still in the developmental
stage. "What succeeded with 14 sheep in our laboratory will succeed
with 50 at Melun", said Pasteur.
The publicity was intense. A reporter from the London Times sent back
daily dispatches. Newspapers in France followed the events with daily
bulletins. There were crowds of onlookers, farmers, engineers, veterinarians,
physicians, scientists and a carnival atmosphere. Would Pasteur's claims
of vaccination hold up? Even Pasteur was privately concerned that he
had acted impetuously in accepting the challenge. Happily, the trial
was a complete success -- indeed, a triumph! Two days after final inoculation
(May 5, 1882), every one of 25 control sheep was dead and every one
of the 25 vaccinated sheep was alive and healthy. The fame of Pasteur
and these experiments spread throughout France, Europe and beyond. It
was, says Duclaux, "the anthrax vaccine that spread through the
public mind faith in the science of microbes". Within 10 years
a total of 3.5 M sheep and a half M cattle had been vaccinated with
a mortality of less than 1%. The immediate savings to the French economy
were enormous, at least 7 M francs, estimated to be enough to cover
the reparations that France was required to pay to Prussia for the loss
of the Franco-Prussian War in 1880.
Supported by the successes with anthrax and fowl cholera diseases, Pasteur
identified and isolated over the next 2-3 years the microbes for many
other diseases including swine erysipelas, childbirth fever and pneumonia.
The final and certainly most famous success of Pasteur's research was
the development of a vaccine against rabies or hydrophobia as it is
also known. The disease has always had a hold on the public imagination
and has been looked upon with horror. It evokes visions of "raging
victims, bound and howling, or asphyxiated between two mattresses"
(Duclaux). The treatments applied to victims were as horrible as the
supposed symptoms: this included cauterizing the bite wounds with a
red-hot poker. Actually very few persons die in any year from being
bitten by a rabid dog or wolf. The symptoms of the disease are variable:
onset may take weeks to months to develop if they develop at all. Nonetheless,
Pasteur and his colleague Roux realized that conquest of rabies would
be recognized as a great achievement to the world of science and to
the public at large.
Pasteur and Roux initially attempted to transfer infection by injecting
healthy dogs with saliva from rabid animals. The results were variable
and unpredictable. Later, recognizing that the active agent was in the
spinal cord and brain, and because they were unable to detect a specific
rabic microorganism, Pasteur and Roux applied extracts of rabid spinal
cord directly to the brain of dogs. With this technique they could reproducibly
produce rabies in the test animals in a few days.
The goal was next to develop a vaccine that would provide protection
to the subject before the rabic agent moved from the bite site to the
spinal cord to the brain. This was achieved by injecting into test animals
suspensions of spinal cord of rabid rabbits that were attenuated in
strength by air drying over a 12-day period in the now-famous Roux Bottle.
A strip of spinal cord was suspended from a hanger in the center of
the bottle containing a hole at the top of the bottle and one on the
lower side. Air entered from the bottom opening, passed over a drying
agent and exited from the top. The longer the cord was dried, the less
potent was the tissue in producing rabies.
The treatment plan used to develop immunity to rabies was to inject
under skin of a dog the least potent preparation of minced spinal cord,
followed every day for the next 12 days with a stronger and stronger
extract. At the end of this time, the animal was completely resistant
to bites of rabid dogs and failed to develop rabies if the most potent
extracts were applied directly to the brain.
Following confirmation of his reports in 1885 that he had made dogs
refractory to rabies by vaccination, Pasteur received wide acclaim and
much favorable publicity. But why not use the vaccine on humans? Frankly,
Pasteur was terribly afraid of things going wrong and he was particularly
uneasy about being unable to isolate the rabic substance. And so he
continued to insist that many years of additional research was necessary
before the treatment could be tried on humans.
But the press of events made him act sooner. On July 6, 1886, 9 year
old Joseph Meister and his mother appeared at Pasteur's laboratory.
Two days earlier the young boy had been bitten repeatedly by a rabid
dog. He was so badly mauled that he could hardly walk. His mother appealed
to Pasteur to treat her son. At the time Pasteur had treated about 40
dogs, most of whom resisted rabies. Could he risk treating this youth
who faced certain death? Pasteur, after consultation with physician
colleagues, and much trepidation treated the youth. Despite Pasteur's
fears, Meister made a perfect recovery and remained in fine health for
the remainder of his life.
A few months later a second victim turned up. He was a young shepherd
also bitten by a mad dog. Following reports of his successful treatments,
the wild acclaim for Pasteur knew no bounds! Victims of dog and wolf
bites from France, Russia, the United States poured into his laboratory
for treatment. The newspapers and public followed these treatments and
cures with intense interest. Pasteur became a hero and a legend. The
Pasteur Institute funded by public and governmental subscriptions was
built in Paris initially to treat victims of rabies who were coming
to Pasteur's laboratory in increasing numbers. Later, Pasteur Institutes
were built, including 3 in the United States, to deal with human rabies
and other diseases.
Rabies was the last major research of the master scientist. His health
was failing and a paralysis of his left side from a serious stroke he
suffered in his 46th year made his working in the laboratory increasingly
difficult. Pasteur died in 1895 after suffering additional strokes.
He was buried, a national hero, by the French Government. His funeral
was attended by thousands of people. His remains, initially interred
in the Cathedral of Notre Dame, was transferred to a permanent crypt
in the Pasteur Institute, Paris.
In a tragic footnote to history, Joseph Meister, the first person publicly
to receive the rabies vaccine, returned to the Pasteur Institute as
an employee where he served for many years as Gatekeeper. In 1940, 45
years after his treatment for rabies that made medical history, he was
ordered by the German occupiers of Paris to open Pasteur's crypt. Rather
than comply, Joseph Meister committed suicide!