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Francesco Redi
Francesco Redi, was an Italian physician, naturalist, biologist and poet.
He is referred to as the "founder of experimental biology" and the "father of modern parasitology".
He was the first person to challange the theory of spontaneous generation, with his experiment in 1668. -
Redi's experiment
At the time, it was believed that maggots arose spontaneously in rotting meat.
To test the hypothesis, Redi placed meat in various jars. He left 2 open, as expected the meat attracted flies and was soon swarming with maggots. He sealed 2 tightly,so that flies could not get in,and no maggots arose. And covered 2 jars with gauze to let air in,and flies clustered on the gauze, which was soon full of maggots, but the meat remained intact.
He thus concluded that spontaneous generation does not exist. -
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John Needham
John Needham was a clergyman in the Roman Catholic Church, a teacher and a scientist. He was an avid defender of the notion of spontaneous generation. -
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Lazzaro Spallanzani
Lazzaro Spallanzani was an Italian Catholic priest, biologist and physiologist. His extensive reserch and careful experiments on biogenesis helped with the downfall of the theory of spontaneous generation. He also made important contributions to the experimental study of bodily functions, animal reproduction, and animal echolocation. -
Needham's rebuttal
In spite of Redi's experiment, the belief in spontaneous generation continued. John Needham claimed it could occur and performed what he considered the definitive experiment.
He heated broth to its boiling point, to kill microorganisms, and poured it into flasks. Soon after the broth cooled, he sealed them.
After some time, he observed living microorganisms in the sealed broth, thus concluding that spontaneous generation was a fact and contradicting Redi’s conclusions. -
Critisism from Spallanzani
Lazzaro Spallanzani did not agree with Needham's conclusions, and performed carefully executed experiments with heated broth that proved them wrong.
He sealed flasks with broth inside, then boiled them for a long time, to kill present microbes. After some time, the broth did not have any trace of life. However, once he unsealed the flask, microorganisms rapidly grew in the broth.
Spallanzani thus concluded that spontaneous generation was false, and microbes came from contaminated air. -
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Louis Pasteur
Louis Pasteur was a French chemist and microbiologist and one of the most important founders of medical microbiology. Pasteur’s contributions to science, technology, and medicine have led to remarkable breakthroughs in understanding causes and preventions of dieases which laid down the foundations of hygiene, public health and much of modern medicine. He is responsible for the final disproving of the theory of spontaneous generation. -
Pasteur puts spontaneous generation to rest
Pasteur's experiment finally disproved spontaneous generation.
He boiled a broth in a flask that had a S-curved neck orientated downward. The idea was that the bend in the neck prevented particles from reaching the broth, while still allowing the flow of air. He observed no life for a year. He then broke off the top of the bottle exposing it more directly, and noted life in the broth within days. He thus concluded the contamination came from life forms in the air, not a supposed “life force”.