Louis Pasteur, ForMemRS

The Father of Germ Theory

Pasteur won his doctorate of philosophy degree.

He wrote and defended two essays, one in physics and one in chemistry.

In 1860, the French Academy of Sciences had issued a challenge to French scientists: they should try to shed light on the concept of spontaneous generation. Spontaneous generation is the idea, which still persisted in the 1860s, that life can arise from nonliving materials, such as mud or water.

Louis Pasteur took on the challenge, using a precise series of experiments to show that flasks of broth and water did not spoil when he prevented organisms from entering the flasks. The Academy awarded him the prize on December 1, 1862, though other scientists continued to object to Pasteur’s findings and methods.

The Academy elected Pasteur to its membership on December 8.

Louis Pasteur produced the first laboratory-developed vaccine: the vaccine for chicken cholera (Pasteurella multocida).

Pasteur attenuated, or weakened, the bacteria for use in the vaccine. He happened upon the method of attenuation by accident: in his lab, he was studying fowl cholera by injecting chickens with the live bacteria and recording the fatal progression of the illness. He had instructed an assistant to inject the chickens with a fresh culture of the bacteria before a holiday. The assistant, however, forgot. When the assistant returned a month later, he carried out Pasteur’s wishes. The chickens, while showing mild signs of the disease, survived. When they were healthy again, Pasteur injected them with fresh bacteria. The chickens did not become ill. Pasteur eventually reasoned the factor that made the bacteria less deadly was exposure to oxygen.

Pasteur presented a paper describing results of using his new rabies vaccine in 350 people. He recorded one fatality, and reasoned that this was the result of vaccination begun too late to prevent the disease.

Louis Pasteur died in Marnes-la-Coquette, outside Paris, France, at age 72.