Louis Pasteur by Nicola Kingsley - National STEM Centre

Louis
Pasteur
by Nicola Kingsley
Series editor Joan Solomon
I:i1I Science Education
~ The Association for

Acknowledgements
The publishers would like to thank the following for
permission to reproduce illustrations on pages:
5, 12, 24, 36, 38 Hulton-Deutsch; 6, 8, 21, 33,41 Pasteur
Institute, Paris; 14 Biophoto Associates; 15, 25, 28, 29 Mary
Evans Picture Library; 18 Adams Picture Library; 22 The
Whitbread Archive; 23 Ann Ronan Picture Library; 27 The
Mansell Collection; 39 Popperfoto; 40 Roger-Viollet, Paris.
First published 1989by the Association for Science Education,
College Lane, Hatfield, Herts. ALI0 9AA. Telephone: 0707
267411.
© The Association for Science Education 1989
ISBN 0 86357 114 X
Illustrations by Deanna Hammond, ASE
Designed by Colin Barker MCSD
Printed by Lithmark Limited
Tel: 0438 812872
NA1\ONAL

• Louis Pasteur

Pasteur's father
and mother
painted by Louis
when he was 16
years-old
I
Cha~_t_er_l _
Louis becomes a
scientist
Louis Pasteur was born in France in 1822 and he lived
to the age of 72. Nowadays there is nothing remarkable
about anyone in Europe living that long, or even
longer, but things were different then. Plenty of
people lived, like Pasteur, to be quite old-but plenty more
died while they were still very young. Of Pasteur's five
children, three died during his lifetime, while they were
still children. That was not unusual. The average age to
which people lived then was only about 40. These days the
average is almost twice that, and Pasteur helped to make
this possible. He spent many years studying tiny living
things, too small to be seen without a microscope, called
microbes. His discoveries changed people's understanding
of disease, and it became possible to control diseases which
before had caused widespread suffering and death.
5

Pasteur's house
6
at Dole
Pasteur grew up in the small French town of Arbois where
his father, Jean-Joseph Pasteur was a tanner (someone
who turns animal skins into leather). Jean-Joseph had
been a sergeant in Napoleon's army and was very patriotic.
He taught his son to love France and to take pride in
working for the good of his country. Even as a boy Pasteur
felt he would like to do something useful when he grew up,
but he had no clear idea what it would be. Being good at
drawing pictures he thought at one stage that he might be
an artist. There was nothing about him to suggest that one
day he would become a famous scientist-in fact one
school report described his work in chemistry as
"mediocre" (average or worse!).
Pasteur's parents placed high value on education, and they
worked hard to pay for their son's schooling. Although
Pasteur was not a brilliant pupil, the headmaster of his
school believed that he showed promise and would do well
at college. He encouraged the boy's parents to consider the
idea, and they agreed, hoping that Pasteur might
eventually become a school teacher. So when he was 16 he
went to Paris, many miles away, to study; but he was so
homesick there that he returned to Arbois after a few

weeks. The following year he tried again. He enrolled at a
college nearer home, which allowed him to visit his
parents and three sisters with ease. He was happier there,
and did well at his studies. For the next few years he
studied at various colleges, becoming increasingly
interested in science, and teaching part-time to pay his
way. At the age of 20 he passed the very difficult entrance
exams for the top college of science in France, the Ecole
Normale Superieure. He decided not to go there yet,
because he had only come sixteenth in the exams. He was
developing an ambitious character, a desire to be best, that
was to be a driving force in his life. When he did enter the
Ecole Normale, a year later, it was after sitting the exams
again, competing with the best pupils from allover France,
and coming fifth.
He thought he knew, now, what he wanted: to become a
teacher. Not just a teacher, but in his own words "a
distinguished professor". At the end of his studies at the
Ecole Normale his lecturers reported that Pasteur "Will
make an excellent teacher". By then, however, this
ambitious young man was no longer interested in just
learning or handing on other people's ideas. He wanted to
make new scientific discoveries.
He began by studying crystals, a fashionable subject
amongst scientists at that time,.and did succeed in making
a new discovery. This set him firmly on the path he desired:
he had begun to make a name for himself. He was awarded
the title of Doctor, and at the age of 26 was appointed
Professor of Physics in Dijon. Two months later he moved
to Strasbourg, to be Professor of Chemistry at the
University. Here, within a fortnight of his arrival, the
usually hard-working Pasteur found himself completely
unable to concentrate on his work. Pasteur had fallen in
love.
He was not a man to waste time. He acted as he would in
any other situation, with determination and speed. He
proposed, was accepted, and just a few weeks later married
Marie, younger daughter of the Rector of Strasbourg
University. For the rest of Pasteur's life Marie was as
dedicated to him as he was to work. In the evenings, when
7

Pasteur dictating
notes on
silkworms to his
wife
8
he came home, she wrote to his dictation, copied his notes
in her clear handwriting, and talked through his ideas with
him. She bore him five children, provided the stable family
life that he valued, and patiently accepted that for Pasteur,
science would always come first. One day she would write
to her children: "Your father is absorbed in his thoughts,
talks little, sleeps little, rises at dawn, and in a word
continues the life I began with him 35 years ago."

I
Cha~ter 2
Fermentations
A
few years later Pasteur moved to Lille, w.here his
job as Professor of Chemistry required him to give
just one lecture a week, leaving plenty of time for
his scientific interests. One day he was visited by
the father of one of his students, a Monsieur Bigot. Like
many of the people in that area Monsieur Bigot made his
living manufacturing vinegar. He had come to ask Professor
Pasteur for his help with a problem. A lot of the
vinegar was turning out to be bad, and nobody knew why.
They were losing money.
Pasteur was interested in the problem. The vinegar was
produced from beet juice by a process called fermentation,
and scientists disagreed about what this process really
was. The accepted view was that it was a purely chemical
reaction in which some chemicals changed into new ones.
What interested Pasteur was that some scientists had
looked at fermenting juice through a microscope and found
there a tiny microbe called yeast, which they thought
played a part in fermentation. Four scientists had
published writings claiming that the yeast somehow made
the vinegar, but a well known scientist called Liebig said
this could not be true. How.could anything so tiny that you
could not even see it without a microscope be making all
that vinegar? The idea was ridiculous. Liebig was very
important, and when he said something people were
willing to believe him.
Pasteur visited the vats in which Monsieur Bigot made his
vinegar. He took samples from them, and examined them
under a microscope. In the samples from the vats producing
good vinegar he could see tiny cells of yeast, which
were sprouting new buds and seemed to be growing. In the
9

Budding in yeast
cells
10
bad vinegar there were only little shimmering rod-shaped
microbes, which looked very different from yeast.
"Louis", wrote Madame Pasteur, "is now up to his neck in
beet juice. He spends all his days in the distillery".
Pasteur studied everything he could find on the subj ect.
Then he thought about what he had seen and tried to
imagine what was happening. Everything that is alive
needs energy to keep living, and one way of getting energy
is to eat food, digest it, and release the energy stored in the
food. What cannot be digested is passed out of the body.
Pasteur's theory was that the yeast actually fed on the beet
juice. When it had digested the juice what was left was
vInegar.
Pasteur thought that the reason why some of the vinegar
was going bad was that the rod-shaped microbes he had
seen under his microscope were killing the yeast. These
microbes were also feeding on the beet juice-but they left
no vinegar behind. The rod-shaped microbes were
producing something that spoiled the vinegar.
Four earlier scientists had said something like this, but
nobody had listened. Pasteur knew that if he wanted
people to take his theory seriously he would have to collect

more evidence. Developing a theory was like building a
model in his head. The model showed how he thought
things worked. Anything that happened must be explained
by his model. Nothing could happen in the model which did
not fit in with the results of his experiments. Pasteur could
also use his model to predict what might happen in new
experiments. If the results turned out to be as he predicted
that would show that his model worked. Pasteur predicted
that beet juice would only turn into vinegar when there
was live yeast present. His experiments showed again and
again that this was true.
Experiments can be explained by different people in different
ways.
- The older scientists thought that all the yeast did was to
start the beet juice going bad. Then it turned sour and
made vinegar.
-Pasteur thought the yeast was alive and feeding on the
beet juice. He thought that the digested stuffwas vinegar.
-Nowadays scientists still believe that the yeast is alive
and feeding, but they think it turns sugar from the beet
juice into alcohol. Another microbe turns the alcohol into
vinegar.
Sometimes it takes many different experiments to make
people change their minds. Pasteur went on to show that
other microbes make other foodschange. He found a microbe
which makes milk go sour by turning it into lactic
acid.
Pasteur's thorough experimental approach was not the
only thing that won him the argument. There was also his
fighting spirit. When he believed he was right, he refused
to back down. He was never frightened by the fact that the
people he argued with might be more powerful or
influential, or older. In fact, he enjoyed arguing, and would
carryon until he won. He claimed there were three steps in
getting evidence accepted-"to convince oneself ... then to
convince others ... the third, probably less useful, but very
enjoyable, convincing the people who are against you".
Sometimes this attitude made him very unpopular, but it
ensured that his discoveries and ideas were heard and
taken seriously.
11

Pasteur in his
laboratory
12
Pasteur's model of fermentation began to change scientific
understanding of the part microbes play in the world. It
also helped to solve the problems of the local vinegar
industry. Now they were able to detect the microbe that
spoiled the vinegar and get rid of it before it did any more
damage. In addition, Pasteur worked out all the conditions
that the yeast needed to thrive and make good vinegar: the
right food, right amount of oxygen, and the best
temperature. As a result of this the manufacturers were
able to control the process much better than before. Seeing
the practical results of Pasteur's work made people much
more inclined to listen to his theories.
Pasteur liked knowledge for its own sake. He enjoyed the
voyages of discovery that lead to new ideas. Equally, he
was delighted when a new theory produced practical
results which helped people. His investigation of vinegar
fermentation ,was one link in a chain of ideas and
experiments which would produce practical results of
great importance to the whole world.

I
ChoQter 3
Crocodiles and bad
soup
Having begun to discover the part that microbes
played in life, Pasteur took up a question that had
been bothering scientists for a long time: where did
microbes come from?
It was easy for people to see that cows gave birth to new
cows, and dogs to new dogs, but for a long time it seemed to
most people that some living things just appeared, as if
from nowhere. They felt it was possible for living things to
arise from dead matter-that maggots, for instance, came
from dead meat. Crocodiles were said to be created from
the mud of river banks-someone even published a recipe
giving the exact quantities of flour, dust, sacking and other
bits and pieces found on the floor of a mill that were
needed to make mice! This idea that living things could
arise out of dead things, without the need of a living parent
to produce them, was called the Theory of Spontaneous
Generation.
Back in 1668, an Italian biologist called Francesco Redi
had wondered if the maggots which appeared in decaying
meat had anything to do with the flies he noticed buzzing
around the meat. So he experimented. He put pieces of
meat in several little pots, and over the top of half of the
pots he stretched gauze, to keep the flies out. The rest of
the pots he left uncovered. All the meat decayed, but
maggots appeared only in the meat left in open pots-the
meat on which flies could land. Redi decided that flies must
lay eggs on decaying meat which hatched into maggots,
and that the maggots fed on the meat and eventually
changed into flies, rather like caterpillars turned into
13

A drop of pond
water magnified
to show various
micro-organisms
14
butterflies. Using a magnifying glass he looked for, and
found, the eggs.
A few years later, in 1677,a shopkeeper in the Netherlands,
Anton van Leeuwenhoek looked through a microscope,
which he had made in his spare time, at a drop of pond
water. He discovered lots of tiny living things, which
nobody had suspected. A few years later he made a better
microscope that allowed him to just make out even tinier
dots and rods, which he thought might also be alive. He
had found the type of microbe that was later given the
name "bacteria".
Biologists wondered if the microbes van Leeuwenhoek had
found arose, like maggots, from something else that was
alive, or if they appeared by spontaneous generation. They
discussed the matter for years. Then in 1748 an English
biologist, John Needham, set up an experiment which he
hoped would provide an answer. He took some mutton soup
and boiled it for a few minutes to kill any microbes in it.
Then he put the soup in a container which he sealed
tightly to stop any fresh microbes getting in. After a few
days he opened the container and found the soup swarming
with microbes. He decided they must have arisen from the
soup by spontaneous generation.

Paris at the time
of Pasteur
An Italian biologist, Lazzaro Spallanzi, thought this was a
poor experiment. He said Needham might not have boiled
the soup for long enough to kill all the microbes in it. If
this were the case, the microbes Needham found when he
unsealed the container could have been in the soup all
along, multiplying in number while the soup stood. In 1768
Spallanzi began to test how long it took to kill microbes by
boiling. He found that some were quite hard to kill, and
that it was not safe to assume they were all dead until the
soup had been boiled for at least half an hour. When he
repeated Needham's experiment with soup that had been
boiled for this long, no microbes at all appeared. He
realised that microbes must develop from other microbes,
and not by spontaneous generation.
Some biologists argued that Spallanzi's experiment proved
nothing. They pointed out that as soon as you left the
boiled soup to stand around in cool fresh air, microbes did
appear. Perhaps there was a chemical in fresh air which
helped spontaneous generation happen. By boiling the
soup, Spallanzi might have destroyed that chemical. That,
they said, would explain why no microbes had appeared.
15

16
By 1859 no one had come any closer to resolving the
argument, and Pasteur decided that he would be the one to
do it. Some of his friends tried to persuade him not to waste
his time getting involved in a dispute which they were sure
could not be settled. Pasteur admitted that he would not be
able to prove that spontaneous generation never happened.
Somewhere in the universe life might be creating itself, but
he intended to show that there was no evidence for this.
He set·to work in his new laboratory, five small rooms in
an outbuilding at the Ecole Normale. He had persuaded
the authorities to let him have these when the two little
attic rooms he had been using became too cramped.
Scientists in those days were expected to make do with
very little and Pasteur was short of money and space for
his experimental work. He needed an incubator
(somewhere warm where microbes could be grown) and the
only place he could find to build it was the space under the
stairs. There, in a little room that was reached by crawling
on hands and knees, he spent hours every day, observing
the flasks used in his experiments.
He began by investigating the claim that fresh ~ir started
spontaneous generation. He boiled some guncotton in
water until both cotton and water were sterile (had
nothing alive in them). Then he forced fresh air through
the sterile cotton. When he put the cottorl back in sterile
water, he found microbes appeared in the water. He
dissolved the cotton in alcohol, and looked at what was
left. It turned out that the cotton had filtered dust out from
the fresh air, and the dust contained all the microbes.
Pasteur then experimented to see if'microbes could have
developed in the cotton by spontaneous generation. He
filtered air through a sterile cotton plug, and then through
a second sterile plug. When he put the second plug in
water, there were no microbes, and none developed later.
They had all been filtered out by the first plug. He
concluded that microbes could be carried in the air, but
fresh air in itself could not actually give rise to microbes.
To further prove the point he put soup in glass flasks and
then melted the top of each flask and shaped it into a long
tube that curved down and then up again, like the neck of

Pasteur's swannecked
flask
a swan. When he boiled the soup, steam rushed out
through the swan-neck, which was very narrow, sterilising
the flask and the swan-neck. Then he let the flasks cool and
stand. Air could get in and out of the flasks, but any dust in
the air was trapped in the lower curve of the swan-neck.
He let the soup stand for months, and no microbes grew in
it, in any of the flasks.
He announced his findings. Other scientists repeated his
experiments and got the same results. There were plenty of
people who liked the notion of spontaneous generation and
did not want to give it up, but they no longer had a
scientific leg to stand on. There was now good reason to
believe that just as giraffes come from other giraffes, so
microbes come from other microbes.
Nevertheless, some supporters of spontaneous generation
tried to pour scorn on Pasteur's theory. One of them, a
certain Monsieur Pouchet, said that if Pasteur were right
about there being enough microbes in fresh air to account
for all the soup and everything else that went bad and
decayed, the air would be so thick with microbes that we
would not be able to walk through it. There was no need
for Pasteur to take this remark seriously, but he saw an
opportunity for an argument, which he always liked, and a
chance to give his findings even more publicity. In
response to Pouchet, he went to the lengths of travelling
17

Mer de Glace on
Mont Blanc
where Pasteur
carried out some
of his
experiments
18
over 200 miles and heading up into the Jura mountains
with his assistants and a large supply of sealed flasks
containing a sterile mixture of sugar, water and yeast
extract-good food for microbes. At different heights up
the mountains he carefully broke the necks of the flasks to
admit fresh air, and then resealed them using a flame. The
higher they went up the mountains, the fewer of the flasks
exposed to air in this way grew any microbes. Because the
air was so clean, especially right at the top among the
glaciers, some developed no microbes at all. Once again
Pasteur showed that fresh air alone was unable to give rise
to microbes.
Pouchet, too, was a fighter. He set off up another range of
mountains, the Alps, to try the experiment, and he came
back saying he had got different results. Every single flask
he had opened developed microbes.
Pasteur demanded that the Academy of Sciences repeat his
experiments. He was completely sure his own results were
correct, and he wanted Pouchet to be shown, in public, to
be wrong. The experiments were done again, and the
Academy announced their decision: Pasteur was right.

Why did Pouchet say his results were different? It turned
out that he was being honest: his results were different.
There really were microbes in all of his flasks. What he did
not realise was that they had been there all along, even
before the flasks were opened. While Pasteur had used
sugar, yeast and water, Pouchet had put into his flasks
water in which some hay had been boiled. In the hay lived
some particularly tough little microbes, which survived
the boiling and went on to thrive and multiply.
Pasteur had shown that there are microbes in the air
which can multiply and produce more microbes.
Furthermore, he had demonstrated that the conditions
which supporters of the Theory of Spontaneous Generation
claimed were sufficient for microbes to appear, without
other microbes being there first, simply were not sufficient.
Cool fresh air was not enough to produce microbes. Now
the people who argued for spontaneous generation had a
theory, but no evidence to support it. Pasteur, on the other
hand, had a theory that microbes come from other
microbes, and evidence to back it up.
It makes no sense to favour a theory for which there is no
evidence, rather than one for which there is evidence.
Pasteur had cast doubt on the Theory of Spontaneous
Generation: and he had set out to do this for a particular
reason. He wanted to clear the way for another theory
which was taking shape in his mind: a theory about
disease.
19

20
I
ChaQter 4
A theory of disease
t can take a long time, often years, to collect the
I
experimental evidence needed to support a scientific
theory. Pasteur was usually working on several different
projects side by side. He worked very hard,
sometimes resenting the fact that he had to stop to sleep. "I
would consider it a bad deed", he said, "to let one day go
without working".
By now he had several assistants working with him. He did
not make life easy for them. He never told them what he
was thinking and why he wanted an experiment done. He
just gave them their tasks, and expected them to get on
with it-in silence. Pasteur needed silence to work. He
could not bear to have anyone in the laboratory who was
not involved in the work he was doing. He had a particular
way of working on a new theory. He began by spending
days in isolation, reading. Then he would pace up and
down silently for days; at these times he was so wrapped up
in his thoughts that he did not notice anyone else. If
someone needed to talk to him, it took a while to attract
his attention. Then he would start suddenly and pass his
hand several times in front of his face, as if waking himself
from a dream. "Dreamy" was a word his colleagues often
used to describe him. He allowed his imagination and
intuition to work. Some of the ideas he considered were
very strange, but once a theory had taken shape in his
mind, he would put it to the test. He would make
predictions from it and tryout experiments. If the
predictions were wrong, out went the theory.
In the years following his work on the Theory of
Spontaneous Generation he was very busy. He was a
professor, teaching science. In addition to this he was
asked to help his country by solving problems that were

Drawing of a
healthy silkworm
from Pasteur's
book 'Diseases
of Silkworms'
costing various industries a great deal of money. He spent
five years finding out what was killing the silkworms upon
which the silk industry relied, and finding ways of
preventing the spread of the disease responsible. This
taught him a lot about how disease spreads. During this
time he suffered a haemorrhage (severe bleeding) in the
brain, and for a while it seemed likely that he would die.
Friends and colleagues waited anxiously. The Emperor of
France himself sent a messenger every day' for news of
Pasteur's progress. He survived, but the illness left him
partly paralysed on one side of his body. From then on he
was unable to handle some of the equipment he needed in
his work, and had to rely on his assistants. His
determination, however, was unshaken. Within a few
weeks, against the advice of his doctors, he was travelling
across France to get back to work on the silkworms.
The wine growers, who were very important to the French
economy, also brought their problems to him. After the
grapes have been fermented to alcohol, wine has to stand
for a long time maturing. During this time a lot of it was
going bad. Once again, it was microbes at work. Pasteur
found two microbes. One was responsible for the fermentation,
and one was responsible for the wine being spoiled
after fermentation. Then he worked out a way of heating
21

The microscope
used by Pasteur
at Whitbreads
when he was
called to England
to investigate
. some brewing
problems
22
the wine, after fermentation was completed, to kill off the
second lot of microbes. Now the wine would be able to
mature without going bad. This treatment by gentle
heating became known as "pasteurization", and is the
same process used to make sure the milk we drink is free
from harmful microbes.
At first the wine growers were horrified. They were sure it
would ruin the flavour of the wine. Pasteur was able to
show them that it did not, but it took a long time to
convince everyone. He kept a cellar full of pasteurized and
unpasteurized wines, and at regular intervals official
parties of wine tasters would sample them and publish
reports saying that the treated wine was better. He even
publicized his method by getting the French navy to take
pasteurized wine on long voyages, to show how well it
travelled. Having worked hard to develop a good idea, he
made sure that everyone was convinced by it. He also
worked out how to apply it on a large scale, making sure it
did not cost too much, and how to preserve other drinks
and foods by the 'same method. As a result of this work, he
was then asked to help the 'beer brewing industry to
improve its production methods.
Pasteur could have made a lot of money from his
discoveries, but he refused to profit from them in this way.
He took no interest in money in case it might distract him
from science. His salary was paid directly to his wife, and
he left the financial side of running his laboratory to others.

Joseph Lister
All these investigations, as well as helpin'g the country's
economy, were giving more evidence about how different
microbes behaved. For a while Pasteur had been convinced
that there was a link between fermentation, putrefaction
(rotting) and some diseases. He believed they all involved
microbes.
Pasteur said that microbes caused disease when they
entered the body. He published a paper outlining the
theory, which was read by an English doctor called Joseph
Lister. Lister decided to put the theory to practical use. In
those days a major operation such as the removal of a
tumour, the amputation of a limb, or the treatment of a
compound fracture in which a broken bone was sticking
out through the surrounding flesh, was highly dangerous.
Even if patients survived the shock and loss of blood, they
had a one in three chance of dying from infections like
gangrene and blood poisoning which set in after the
operation. The air of hospitals was thick with horrible
smells of putrefying human flesh and cries of pain. Lister
decided that after he operated he would apply to the wound
a dressing soaked in carbolic acid which kills microbes. If
Pasteur was right, and the infections killing his patients
were the result of microbes getting into the wounds, this
might prevent infection. So he tried this idea on eleven
patients. Nine of them survived, and their wounds healed.
This was a much higher survival rate than Lister could
23

Lister greets
Pasteur at the
Sorbonne
24
normally expect. Encouraged by the result, he expanded
this new principle of "antisepsis" (which means "against
rotting") and began washing his hands and medical
instruments in weak carbolic acid to sterilise them before
examining patients or performing operations. The effect
was a remarkable decrease in infections. These simple
practices began a revolution in hospitals which eventually
saved millions of lives.
As soon as he was sure his antiseptic methods worked,
Lister published his findings, and wrote to Pasteur, telling
him what he had achieved. Pasteur was delighted. Not only
were lives being saved, but Lister's results were also
evidence that supported the germ theory of disease.
Shortly after this the Franco-Prussian war began. Patriotic
Pasteur tried to join the army. The army would not have
him. Quite apart from his paralysis, he was an important
scientist and too useful to be wasted in battle. So Pasteur
spent the war putting his germ theory to use, travelling
round military hospitals insisting that bandages and
instruments be boiled to prevent infection.
It is hard for us, living today, to imagine what life was like
in Pasteur's time. The average length of life was half what

French hospital
ward in 1885
it is today, largely because so many people died from
serious infectious diseases that spread from person to
person. For centuries people had tried to explain what
caused disease. Some said it was God's punishment for
human sinfulness, others that it resulted from demons or
evil spirits invading the body. A common belief was that it
was caused by "bad air"-the disease malaria got its name
from the Italian "mal aria", which means "bad air".
During the great plague which swept seventeenth century
England, people used to carry around posies of flowers and
oranges with cloves stuck in them; these were intended to
do more than just mask the foul smells of sickness and
death. People hoped that by sweetening the air they could
protect themselves against the disease.
Pasteur's idea, that microbes could cause disease, was not
entirely new. The notion that living things too small to be
seen existed and could pass from one person to another
through the air, on clothing, or by touch, causing disease,
is recorded far back in history, before the time of Christ.
But there was no convincing evidence for that idea until
microbes were discovered. Just knowing that microbes
existed was not enough. It still remained to show that they
caused disease. Lister's work was a step in the right
direction, but Pasteur still needed more evidence to
support the germ theory.
25

26
I
Cha~ter 5
Farmyard microbes
Without a clear idea of what caused diseases,
people could not control them or treat them
effectively. Some things, however, were well
known. One was that disease could spread
between people or animals. Another was that if you
survived certain diseases, such as chicken pox or measles,
you were unlikely to have them again. By having it once,
you developed immunity (protection against catching that
disease).
At the end of the 1700s, an English doctor, Edward Jenner,
had developed a way of giving people immunity to a
disease called smallpox. It was a very widespread and
terrible disease, which killed many of its victims. Those
who survived were often left covered in pockmarks-deep
scars on their faces and bodies left by the septic blisters
that were one symptom of smallpox. Many also lost their
eyesight.
It was common knowledge among country people that if
you caught cowpox, a disease which normally afflicted
cattle, you would not catch smallpox. Cowpox was not a
particularly dangerous disease for people to have, so
Jenner tried deliberately infecting people with it, in order
to save them from getting smallpox. He did this by
injecting them with infected matter taken from the sores of
people who already had cowpox. He called his method
"vaccination"-from the Latin word for a cow, "vacca". It
worked, but Jenner had no idea why.
Pasteur wondered if vaccination could only be used to
prevent smallpox, or if it might work with other diseases.
An accident answered his question. In 1879 he was

Gilray cartoon of
inoculation
studying a disease called chicken cholera,. which was
destroying flocks of chickens. He was trying to find out
more about the part played by microbes in disease. Many
doctors believed that although microbes could be found
where there was disease, they did not actually cause it.
Their view was that disease made changes in the body
which allowed microbes to invade: in other. words, the
disease came first, and the microbes afterwards. Pasteur
himself thought there was something in this idea. After all,
when any group of people was exposed.to a disease, some
people got it and others did not, and some became more
sick than others. Perhaps some were already less healthy.
He still believed that microbes actually caused particular
illnesses, even if they were not the only factor involved.
In the bodies of chickens suffering from chicken cholera he
had found the microbe he believed to be responsible for the
disease. He had succeeded in culturing it-that is, growing
it in the laboratory instead of inside a living animal. Now
he was injecting the culture of microbes into healthy
chickens to demonstrate that the introduction into their
27

Early vaccination
for diphtheria
28
bodies, of this microbe grown outside the body, could bring
about the disease. Once injected, the chickens rapidly
became ill and died.
On the day the laboratory was due to close for the summer
holidays, one of the assistants forgot to inject a batch of
chickens with the culture of microbes that had been
prepared. It was left standing in a cupboard for several
weeks. When the holiday was over, the assistant, picking
up where he had left off, went ahead and injected the
culture. The chickens receiving it became ill-but instead
of dying, quickly recovered. The assistant fetched Pasteur,
explained what had happened, and was about to throw
away the rest of the culture when Pasteur stopped him.
"In the field of experimentation", Pasteur once said,
"Chance favours only the prepared mind." It may be that
the memory of Jenner's vaccination had prepared Pasteur's
mind for this chance occurrence. His assistant might have
been ready to dismiss it as a hiccup in the experiment, but
Pasteur was not. He told him to inject the hens again, this
time with a fresh culture capable of giving a deadly dose of
the disease. The birds remained perfectly healthy. Someone
was sent to the market to buy some more chickens.
Injected with the same culture, these hens rapidly
developed chicken cholera and died.

Inoculation for
tuberculosis
Pasteur made a guess at what had happened. The microbes
left exposed to the air over the holidays had become
somehow weakened. They were still alive, but no longer
able to produce the full-blown disease, only a mild form.
After a chicken had suffered the disease in its mild form, it
was immune to the stronger microbes which would
previously have killed it.
He made further weakened cultures, and the results were
repeated. Pasteur had discovered another case of
vaccination against disease. He was eager now to see if the
same approach would work in the case of further diseases.
Two years before he had begun investigating another
farmyard disease. Anthrax affected sheep, goats, cattle,
horses, and sometimes humans. Spreading amongst the
livestock, it could ruin a farmer's livelihood. The first
symptom was a raised temperature, followed by trembling,
gasping for breath, fits, and finally, all too often, death.
The illness caused thick black blood to ooze from any
scratch or wound-hence the name anthrax, which came
from the Greek word for coal. So powerful was the disease
that the very fields where infected animals grazed appeared
to become, as farmers put it, "cursed with anthrax". Even
years later animals put out in these fields would go down
29

Anthrax bacilli
30
with the disease. Outbreaks were particularly common in
dry weather. Some places, however, were seldom, if ever,
affected by the disease.
Pasteur found the microbe he believed to be responsible for
anthrax in the blood of animals suffering from the disease.
It produced spores (extra tough cells) which were so hardy
that they could survive outside the body for years.
Walking around the fields "cursed with anthrax" he
noticed many worm casts, the little piles of earth that
earthworms brought to the surface. When he looked at the
worm casts under a microscope, he found anthrax spores.
He collected earthworms and cut them up. In the soil in
their intestines were the same spores. Livestock which had
died of anthrax was buried by farmers, often many feet
deep, in the fields where it died. What was happening, he
reasoned, was that worms were carrying the spores from
the diseased carcasses buried below to the surface of the
fields. During dry weather the worm casts dried out and
the wind blew about the fine particles of soil bearing the
spores. Some landed on plants and were eaten by grazing
beasts. The reason why anthrax occurred in some places
but not others was that some places had soil so sandy or
chalky that there were very few earthworms to spread the
disease.

Cartoon of
Pasteur
vaccinating
himself
Pasteur designed an experiment to show farmers how the
disease entered the bloodstream of their animals. He mixed
anthrax spores with alfalfa, fed it to the animals, and
waited to see what would happen. The number of animals
that died was no greater than the farmers would have
expected to lose during that time under normal
circumstances. When they were fed with the same sporeinfested
alfalfa mixed with thistles, many more animals fell
ill and died. The thistles had punctured the animals'
mouths, creating wounds which allowed the anthrax to
invade the blood stream.
The results of Pasteur's demonstration impressed the
farmers, and they followed his instructions for preventing
the spread of the disease. He told them to burn the bodies
of animals which died of anthrax, instead of burying them.
Also they were to avoid using prickly foodstuffs which
could puncture the animals' mouths. These measures
helped to limit the spread of anthrax, but they could
neither prevent it completely, nor cure it. It continued to
be an unpleasant and costly problem.
31

A sheep being
vaccinated
32
When he discovered that he could vaccinate against
chicken cholera, Pasteur turned his attentions back to
anthrax. Could he develop a vaccine for this disease too?
Both anthrax and chicken cholera were caused by rodshaped
microbes; this type of microbe was called a bacillus.
The chicken cholera bacillus was weakened by exposure to
air, but the anthrax bacillus was not. It just produced
spores which survived and later grew into more microbes.
Eventually Pasteur's assistants discovered that it was
affected by temperature. If kept at 42-43°C it stopped
producing spores, and after eight days at this temperature
it lost its virulence (its ability to produce disease). Using
this weakened bacillus, Pasteur successfully vaccinated
guinea pigs, rabbits, and sheep.
As usual, he wanted to give his discovery as much
publicity as possible. He seized upon an article which had
been written a month before he developed the new vaccine.
In the article, which appeared in a veterinary journal, a
Monsieur Rossignol had tried to turn all the new
discoveries being made about microbes into a big joke.
Obviously he thought that some scientists, Pasteur in
particular, exaggerated the power of such tiny creatures.
He ended the article by suggesting that the claims of the
microbiologists be put to the test in public.

Pasteur and his
wife in 1884
It was just the opportunity Pasteur wanted. He
volunteered to give a public display of the anthrax vaccine.
The terms agreed upon were these: the trial would take
place on Monsieur Rossignol's farm at Pouilly Ie Fort.
Sixty sheep were to be provided. Twenty-four would be
vaccinated with two doses of weakened vaccine given
twelve to fifteen days apart. A few days later these
twenty-five and a further twenty-five which had not been
vaccinated would be injected with virulent anthrax
bacillus. The remaining ten sheep would be kept apart to
be compared with the injected animals.
The date fixed for the start of the experiment was May 5th,
1882. Crowds of farmers, vets, doctors and newspaper
reporters flocked to Pouilly Ie Fort. Pasteur supervised the
vaccinations with an air of calm confidence. When the time
came to inject the virulent bacillus he even gave the
vaccinated animals a triple dose. Then everyone waited to
see what would happen. Many were hoping that Pasteur's
experiment would fail. His argumentative self-publicizing
had won him enemies as well as admirers.
33

34
His assistants brought the news to Pasteur-all the
unvaccinated sheep were ill, but so were several which had
been vaccinated. Pasteur, less calm than he had appeared
in public, lost his temper and began shouting at his
assistants, saying they had made a mess of the experiment
and a fool of him. He spent a sleepless night working
himself up into a state, but the next day brought better
news. The vaccinated animals were recovering.
He returned to Pouilly Ie Fort on June 2nd, the date set for
judging the experiment. As he walked towards the farm the
crowd began to applaud, and as he got closer, to cheer.
Twenty-two of the unvaccinated sheep lay dead, and a
further two died as the spectators looked on. Meanwhile,
every single one of the vaccinated animals was grazing
contentedly, in a state of perfect health. Pasteur was
triumphant, and soon all Europe knew about his success.

A rabid dog
One final success was to crown Pasteur's achievements.
The year before the public trial of the
anthrax vaccine, Pasteur had begun studying
rabies. Although it was a relatively rare disease
people were very frightened of it. A dog suffering from
rabies would go mad, foaming at the mouth and ferociously
biting people. Someone who was bitten might not develop
the disease, but if they did they would die a horrible
agonizing death. The only known way of preventing the
disease after biting was immediately to cauterize the
wound-to burn it with hot metal. This was terribly
painful, and it did not always work.
In order to study rabies, Pasteur and his assistants had to
collect saliva from mad dogs. An accident at any stage of
handling the material they were investigating could have
resulted in a terrible death.
35

Pasteur
experimenting on
a chloroformed
36
rabbit
They found that if the saliva was injected into rabbits, the
rabbits developed rabies. There was still a problem: they
were unable to find the microbe responsible, although
Pasteur was sure it must be there. The microbe is a virus,
too small to be seen through any microscope available in
Pasteur's time.
A further problem was that the incubation period for
rabies-the time it took for symptoms to appear-was quite
lengthy. A person bitten by a rabid animal would take at
least two weeks to show signs of the disease. Having to
wait a long. time for signs of infection slowed the
experiments down. Pasteur thought that as the symptoms
included madness and convulsions, the brain and nervous
system might be affected. Perhaps it would be better to
introduce infected tissue directly into the nervous system.
To do this he drilled a hole in the skull of the rabbit which
he wanted to infect with rabies. The method proved
successful; the incubation period became both shorter and
more certain.
Having decided that the microbe was in nervous tissue, he
set about finding a method of weakening it. The most
successful approach proved to be by drying out of lengths

of spinal column taken from rabbits with rabies. After
fourteen days of exposure to air the microbe seemed to be
no longer virulent. By giving an injection of spinal column
dried for fourteen days, followed the next day by some
dried for thirteen, the following day by some dried for
twelve, and so on, he could produce complete immunity in
two weeks. A final injection of virulent material would fail
to produce the disease.
Actually, drying the spinal column did not weaken the
virus, it just decreased the number of virus particles-but
being unable to see the virus, Pasteur could not know that.
His model of vaccination involved using weakened
microbes, and that was what he thought he was doing.
Pasteur tried the course of vaccination on fifty dogs, with
complete success. He did not like to see suffering and
always tried to make sure that the animals used in his
experiments experienced as little pain as possible.
Nonetheless his work brought him into conflict with
anti-vivisectionists, people who believed that he was being
cruel to animals and had no right to experiment on them.
Having succeeded in vaccinating the dogs, Pasteur of
course wanted to know if it would work with people. At
first he did not dare to find out. It would be terrible if the
vaccine failed, and someone died of rabies given to them
during the experiment. It would amount to murder-and
Pasteur's reputation would be ruined.
He was, by now, a famous man, and many people took an
·interest in what he was doing. He lived ata time when
railways were built allover Europe. Suddenly travel had
become easier and faster, not only for people but also for
letters, newspapers, books. At the same time, high-speed
printing was being perfected. News and new ideas were
travelling much faster than ever before in history. The
news that Pasteur was working on rabies had reached the
remote French region of Alsace, and when, in July 1885,a
nine-year-old boy called Joseph Meister was bitten
fourteen times by a mad dog, his mother rushed with him to
Paris as fast as she could. She brought Joseph to Pasteur,
and begged the scientist to help her son.
37

Statue at the
Pasteur Institute
of a shepherd boy
killing a rabid dog
38
Everyone in the laboratory was in a terrible state. They did
not know what to do. Should they try the vaccine, and risk
Joseph's life and Pasteur's reputation? Pasteur called in
two doctors to examine the boy. They looked at the deep
bites in his hands and said Joseph was very likely to die if
not treated. So they made their decision. Under the
supervision of Dr. Graucher they began the course of
injections. For a few days everything went well. Then
Joseph began to develop symptoms of rabies~ which grew
worse with each new injection. After ten days everyone
was in a state of great anxiety. Pasteur was sleeping badly
and having nightmares. Then something terrible happened.
Carrying a syringe full of virulent rabies microbes with
which he was going to inject the boy, Dr. Graucher slipped
and accidently jabbed it into his own leg. Now he would
have to have the same treatment he was giving Joseph'.
Two of the laboratory assistants begged him not to take
the treatment; nobody knew yet if it worked. "Do you
think that I would do this job every morning", Graucher
replied calmly, "if I wasn't absolutely sure of the method?"
In the argument that followed, Graucher was so persuasive
that the two assistants ended up volunteering themselves
as guinea-pigs for the trial of the vaccine. Pasteur then

Pasteur with a
group of English
children who had
been bi"en by
dogs and sent to
him for
inoculation
insisted that he too be vaccinated, but nobody would hear
of it. In the end Graucher and the two assistants
underwent the fourteen-day course of injections, giving
them to each other.
Joseph Meister, Graucher and the assistants all survived.
The news of the success with the boy was announced to the
public-but the story of Dr. Graucher's accident and the
trial of the vaccine on the two healthy assistants was kept
secret for a long time.
People who were bitten by rabid animals began arriving in
Paris, asking for treatment. They came not only from
France but from other countries too. Pasteur was hailed as
a hero, but not everyone was convinced that the treatment
was safe. As usual, there were some people waiting to see
him proved wrong. Their chance came, only four months
after the success with Joseph Meister. A ten-year-old girl,
Louise Pelletier, was brought to Pasteur by her parents
thirty-seven days after being bitten. Pasteur knew it was
probably too late for the treatment to work, but Louise's
parents pleaded and wept. So, in the end, he went ahead
and treated her. She returned home after the treatment,
went back to school-and after only a few days showed
signs of rabies, went into convulsions and died.
39

The Pasteur
Institute
40
The news of this failure spread as fast as the previous news
of success. The newspapers no longer called Pasteur a life
saver; now he was a murderer. A fierce argument followed.
Some political and medical journals set up a campaign
against Pasteur, and the anti-vivisectionists joined in.
Pasteur and his assistants were worked off their feet
running a clinic for the people who were still arriving in
large numbers for treatment. In the 15months after Joseph
Meister was treated, 2,490people received the vaccine. At
the same time Pasteur had to respond to the critics and
their accusations. He pointed to the statistics-out of 350
people treated, only 1 had died. By July he reported only 10
failures out of the 1,726 French people treated. The
expected death-rate from bites by rabid dogs was 16 out of
every 100 people bitten. Still his opponents were not
satisfied. They argued that most people who were bitten
never developed rabies anyway, and that Pasteur's
treatment involved the risk of giving rabies to people who
might never have got it at all. They accused him of not
giving the treatment an adequate trial before using it on
people. To make matters worse, there was no other
laboratory in Europe equipped to repeat Pasteur's
experiments and judge how well they worked.

Pasteur's tomb at
the Pasteur
Institute
Finally, in 1887, the English Commission on Rabies
published their report, confirming Pasteur's findings and
the effectiveness of his treatment.
The fuss died down. Public confidence in Pasteur's work
was such that money began pouring in, making it possible
to set up an institute for the treatment of rabies and
investigations into other diseases. In 1888 the Pasteur
Institute opened in Paris. Later it was to expand, opening
branches in many parts of the world.
Pasteur had always been a fighter, but he was in his sixties
now, and this last, fierce battle had worn him out. He no
longer had the energy to push forward to new ideas. In
1887he suffered another attack of paralysis. He lived for a
few years more, but his years of great scientific creativity
were over.
41

42
Before his success with rabies, Pasteur had made a second
attempt to find the microbe that causes cholera, and again
failed. It was left to others to succeed. In the twenty years
following his discovery of the anthrax bacillus many other
microbes causing disease were identified, by people using
Pasteur's theories. Much remains still to be learned.