Louis Pasteur by Nicola Kingsley - National STEM Centre

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