SO
WHAT DID PASTEUR ACTUALLY DO?
Pasteur
founded the science of microbiology and proved that most infectious diseases
are caused by micro-organisms. This became known as the "germ theory"
of disease. He was the inventor of the process of pasteurisation and also
developed vaccines for several diseases including rabies. The discovery of the
vaccine for rabies led to the founding of the Pasteur Institute in Paris in
1888.
SO
HOW DID PASTEUR MAKE HIS DISCOVERIES?
When he was
only twenty-six years old Pasteur solved a problem that had been puzzling the
great chemists of the day. He found that when light was passed through tartaric
acid - this was found in wine dregs, it produced a strange effect. Pasteur
proved that this was because the acid is actually not one acid but a mixture of
different acids. This find impressed the scientists of influence and
established Pasteur's reputation.
While at the
University of Strasbourg he became interested in fermentation and this interest
continued when he moved to the University of Lille. The faculty had been
established partly to serve as a means of applying science to the problems of
the industries of the region, especially the production of alcoholic drinks.
This work in fermentation enabled Pasteur to identify that the changes brought
about when beer or wine ferments, milk turns sour or meat decays, occur when
special micro-organisms are present.
As a result
of these findings Pasteur was asked to help the local breweries where the beer
had turned bad. The souring of wine and beer was a major economic problem in
France. Pasteur looked at some droplets of bad beer through a microscope and
observed that the beer contained small rod shaped bacteria, instead of round
yeast cells. Although micro-organisms are essential in fermentation they must
be the right ones. This was a major discovery. Pasteur made brewing a more
scientific procedure and showed brewers how to culture the right organisms for
good beer. He also demonstrated to the wine industry that if wine is gently
heated to sixty degrees celsius for a short time, the growth of harmful
bacteria is prevented and the wine does not go sour in bottles or barrels.
Pasteur then
extended this to other problems such as the souring of milk. He proposed
heating the milk to a high temperature and pressure before bottling. The
process is now in widespread use and is called pasteurisation.
WHAT
OTHER DISCOVERIES DID PASTEUR MAKE?
By 1857
Pasteur had become world famous and took up an appointment as director of
scientific studies at the Ecole Normale in Paris. He was asked to help to
investigate a serious disease that was ruining the silk industry in southern
France. The disease known as pebrine attacked the silk worms. The signs of the
disease were that the eggs did not hatch or the worms would die before making
their silk cocoons. It had now reached epidemic proportions and even disease
free worms brought in from Spain and Italy had been contaminated. By 1864 there
were no uncontaminated eggs left, except for those brought in from Japan.
Pasteur
observed through his microscope that the diseased caterpillars and eggs all
contained tiny organisms. He identified these as disease producing organisms.
He managed to obtain some healthy worms and he divided them into two lots. He
fed one lot with mulberry leaves smeared with the remains of diseased worms and
fed the others with mulberry leaves smeared with the remains of healthy worms.
Pasteur was able to show that the worms fed on diseased smeared leaves got the
disease, whereas those fed on uncontaminated leaves remained disease free. He
then worked with the silk industry to devise a simple way of keeping silk worms
under healthy conditions and therefore disease free.
Not only had
Pasteur rescued the French silk industry but he had established the connection
between bacteria and disease. The connection had not been fully understood
before.
This was a major discovery.
Pasteur's work on the link between bacteria and disease came
to the attention of the famous Edinburgh surgeon Lord Lister. Lord Lister was
concerned with the number of people who died after having operations in
hospital. To combat infection, Lister introduced disinfectant sprays during
operations, these prevented bacteria from entering a wound. He also introduced
the use of dressings soaked in carbolic acid and strict hygiene rules to combat
sepsis. The sterile methods introduced by Lister, drastically reduced the
number of hospital deaths.
In France at that time many cattle suffered from anthrax, a
serious disease from which many of them died. Pasteur made a careful study of
anthrax and noticed that some cows developed the disease more severely than
others. So he decided to inject two cows with a strong dose of the anthrax
bacteria, fully expecting them to die. To Pasteur's amazement neither of them
developed the disease. Later, he found that both animals had already suffered
from anthrax. Could they be immune to it? Could they be protected in some other
way? Pasteur believed that if it were possible to give an animal a mild attack,
this might be sufficient to prevent it from getting the disease later on.
Eventually, after many experiments Pasteur succeeded in
producing a weakened and harmless culture of anthrax bacteria. He inoculated
cattle and sheep with this giving them a mild form from which they recovered.
When these animals were put with others who had a severe form they remained
unaffected. They were immune.
Pasteur worked throughout the rest of his life on the
various causes of diseases and how these could be prevented by vaccination.
PASTEUR AND RABIES
Pasteur is particularly renowned for his work on the vaccine
for rabies, a highly contagious infection which attacks the central nervous
system. It enters the body through the bite of an infected animal or through
infected saliva entering an existing wound. After experimenting with the saliva
of animals suffering from the disease, Pasteur concluded that the disease rests
in the central nervous system of the body. When an extract from the spinal
column of an rabid dog was injected into healthy animals symptoms of rabies
were produced. By studying the tissues of infected animals- rabbits, Pasteur
was able to produce an attenuated form of the virus. This could be used for
inoculation.
On July 6 1885, Pasteur tested his pioneering rabies vaccine
on man for the first time. He saved the life of a young man called Joseph
Meister who had been bitten by a rabid dog. Pasteur was urged to treat him with
his new method. The treatment lasted 10 days and at the end he recovered and
remained healthy. Since then thousands have been saved by this treatment.
On March 1886, Pasteur was invited to present his results to
the Academy of Sciences and in 1888 went on to found the Pasteur Institute in
Paris. This was a pioneering clinic for the study of infectious diseases, the
treatment of rabies and a centre for teaching. Pasteur directed the Institute
personally until he died. The Pasteur Institute is still one of the most
important centres in the world.
Pasteur became a national hero and was honoured in many
ways. He died at Saint-Cloud on 28 September 1895 and was given a state funeral
at the Cathedral of Notre Dame and his body placed in a permanent crypt at the
Pasteur Institute.
Modifications of the Pasteur method are still used in rabies
therapy today. The traditional vaccine contains inactivated rabies virus grown
in duck eggs. A newer vaccine which contains virus prepared from human cells
grown in the laboratory is safer and requires a shorter course of injections.
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