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Louis Pasteur
By Vesna Bos
The theory of spontaneous generation of life was universally accepted
up until the seventeenth century. It supported the possibility of living
creatures arising out of seemingly inanimate substrates. Louis Pasteur,
a scientist who lived in the years of 1822-1895, was convinced that microbiology
and medicine could only progress when the idea of spontaneous generation
was vanquished. Using proper scientific method, he was able to disprove
spontaneous generation and change the study of medicine to one, which
we can still appreciate today.
At a young age, Pasteur knew what he wanted to do with his life. Although
his family, friends and teachers recognized him as an individual with
incredible artistic talent, Pasteur chose to give up this loved hobby
to commit to another area of interest: science. When Pasteur decided to
give up art for science, many of his teachers were disappointed. Some
of his science teachers told him that he was only mediocre in science
and would be more successful advancing his artistic ability. However,
Pasteur was a strong individual. He did not stop until his goals were
accomplished. With his goal-orientated drive and curious young mind, Pasteur
set off to pursue his interests. Pasteur underwent competitive examination
for admission to the Ecole Normale Superieure. In 1842 he was declared
admissible, sixteenth in rank. Through Pasteurs eyes this was insufficient
so he gave up his admissions to take up his studies again and better prepare
himself. He succeeded and in 1843 entered the school being fifth in rank.
At the age of twenty-five and working in a laboratory for only two years,
Pasteur made his first discovery. By studying crystals, he found that
asymmetric molecules are always the product of life forces. Soon Pasteur
was able to disprove the widely held belief that life occurred through
spontaneous generation. Pasteur’s’ long time friend Jean Biot warned Pasteur
to put aside the topic of spontaneous generation. Both Biot and Pasteur
knew that attempting to prove a universal negative is logically absurd
and thus neither scientifically or philosophically a rewarding position.
Nonetheless, Pasteur continued his work. He designed a number of experiments
to rule out spontaneous generation, for example, ‘the Swan-neck Flask’.
The ‘Swan-neck Flask’ was a flask designed with a neck the shape of a
swan so that when the fluid in the flask was boiled, the vapor created
forced the air out of the bottle. In his experiment he used meat broth
as the fluid in the flask. When the broth was cooled, because the way
that the neck of the flask was shaped the moisture got trapped in the
neck and as air seeped back into the flask it got washed in the moisture.
Air particles could enter the flask, but airborne microorganisms could
not because they would settle by gravity in the neck. When the flask was
left for several days no organisms grew. This meant that spontaneous generation
did not occur and that living things came from living things. This did
not lead to the discovery of the origin of life but had shown that life
would not appear on an organic medium that had been sterilized (protected
from the dust and particles from the air).
With that Pasteur was able to disprove spontaneous generation and at the
same time invented ‘the germ theory’. With the ability to connect ideas
and the need to prove hypothesis, Louis’ discovery led to numerous important
discoveries. First, he developed practices to minimize the spread of disease
by microbes. Second, he discovered that weakened forms of microbes could
be used as an immunization against more virulent forms of the microbe.
Third, he revealed the world of viruses. Finally, he developed a
process by which harmful microbes in perishable food products are destroyed
using heat, without destroying the food. This is otherwise known as "pasteurization".
Today Louis Pasteur is known as one of the greatest biologist of the nineteenth
century.
Questions for Discussion
1. Why was Louis Pasteur known as the greatest biologist of the nineteenth
century?
2. What characteristics did Pasteur have that made him a good scientist?
3. Would Pasteur’s argument about spontaneous generation be as successful
if it were not for the experiments like the ‘Swan-neck Flask’?
4. Like Louis Pasteur, there have been other scientists who worked to
disprove universally accepted beliefs. Give one example and explain what
would of happened if they had not taken the risk to challenge these beliefs?
5. Pasteur once said, "Do not put forward anything that you can not prove
by experimentation". What do you think he meant? Do you agree?
References
Burton, Mary Jane (1963). Louis Pasteur: Founder of Microbiology. New
York: Franklin Watts, Inc.
Dubos, Rene (1960). Pasteur and Modern Science. New York: Doubleday &
Company, Inc.
Dubos, Rene (1976). Louis Pasteur: Free Lance of Science. New York: Charles
Scribner’s Sons
Lois, N. Magner (1994). A History of the Life Sciences: 2nd Ed. New York:
Marcel Dekkler, Inc.
http://www.accessexcellence.org/AB/BC/Spontaneous_Generation.html
http://www.panspermia.org/pasteur.htm
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