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Francesco Redi
Francesco Redi (1629-1697), an Italian physician and poet, demonstrated that the presence of maggots in putrefying meat does not result from spontaneous generation but from eggs laid on the meat by flies. -
Redi's experiment
Francesco Redi, made the first serious attack on the idea of spontaneous generation in 1668. At that time, it was widely held that maggots arose spontaneously in rotting meat. To achieve his goal of proving spontaneous generation to be wrong, he set out a controlled experiment. Francisco hypotesisi was that, if the jar is covered with cloth netting or tightly sealed and there is one piece of meat inside then there don’t appear any flies, because spontaneous generation doesn’t exist. -
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John Needham
John Needham (1713 -1781), a microscopist, was a staunch supporter of the aforementioned theory of spontaneous generation, which was the idea that living organisms can develop from non-living matter. Needham's most important experiment claimed that microorganisms in broth developed independently of other cells. -
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Lazzaro Spallanzani
Lazzaro Spallanzani (1729–1799), an Italian priest, did not agree with Needham’s conclusions, however, and performed hundreds of carefully executed experiments using heated broth. -
Needham’s rebuttal
John Needham claimed that spontaneous generation could occur and performed what he considered the definitive experiment.
Needham briefly 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. -
Criticism from Spallanzani
Spallanzani poured broth into flasks and sealed them. Next, he boiled the flasks for a long time, to kill present microorganisms.
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 concluded that spontaneous generation was false and microbes came from contaminated air. -
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Louis Pasteur
Louis Pasteur (1822 -1895), the notable French scientist, accepted the challenge to re-create the experiment and leave the system open to air. -
Pasteur puts spontaneous generation to rest
He designed several bottles with S-curved necks that were oriented downward. He placed a nutrient-enriched broth in one of the swan-neck bottles, boiled the broth inside the bottle, and observed no life in the jar for one year. He then broke off the top of the bottle or tilted the flask, exposing it more directly to the air and trapped particles, and noted life forms in the broth within days. He reasoned that the contamination came from life forms in the air, not a supposed “life force”.