The Germ Theory
Louis Pasteur finally figures out
how diseases are spread
Existing Theories
• Miasma & Spontaneous Generation
– Disease carried by foul air
– Micro-organisms are the result of the
process of decay
• Pus and gangrene mutates into Germs
– Flies and Maggots provided evidence
• Non-life creates living organisms
Micro-Organisms
• Leeuwenhoek
– Dutch clockmaker
– Built an early powerful microscope
– Examined everything he could
• He kept on noticing small living organisms in
everything he examined
– In food, water, excreta, plaque
• He did not know what function they
played
Improved Microscopes
• Joseph Lister in the 1830s
– Improved lens production
allowed Joseph Lister to
produce microscopes that
could magnify 1,000 times
– Any scientist could buy this
microscope
– Micro-organisms could be
studied in more detail
Pasteur’s Germ Theory
• Pasteur
– A Scientist (not a doctor)
• Brewery in France
– Asked Pasteur to investigate why
some vats of alcohol would go bad
• His theory
– Germ = Germination
• A growing, living organism caused the
problem
• His solution to the problem was
to boil the liquid to kill the germs
– Pasteurisation
• Applied to milk, beer, wine, vinegar
Pasteur battles Spontaneous
Generation Theory
• French Academy
launches competition
to prove or disprove
Spontaneous
Generation in 1860
• Pasteur devises
experiments to show
that microbes existed
in the air
• Copy source 2 page
129
Linking Germs to Disease
• “If wine and beer are
changed by germs, then
the same can and must
happen sometimes in men
and animals”
• French Silk Industry
– Asked Pasteur to investigate
why their silkworms kept
dying.
– He discovered that a certain
germ was responsible for
•
•
Homework Task
Step
Brief
Description
Why was it
Important?
Factors that
helped
development
•
•
Task page 129
Draw a flow chart to
show how germs
were linked to
disease
Explain why each
step was important
What factors helped
the scientists at each
step.
Suitable
Image