Louis Pasteur by Nicola Kingsley - National STEM Centre

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.