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Francesco Redi
Francesco Redi, an Italian physician and poet, 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. -
Redi's expermient
Redi theory was: “If I put fresh meat in a jar and leave it open flies will be attracted to the smell and maggots will appear, if I put it in a closed jar no maggots will appear and if I cover it just with a cloth so that air can get in no maggots will appear.” The conclusion is that maggots didn’t appear spontaneously from rotten meat, but flies created them, laying their eggs on the meat. Without flights maggots didn’t appear so it wasn’t the rotten meat the creator. -
Needham's rebuttal
Microscopy revealed a new world of microorganisms that appeared to arise spontaneously. In 1745,John Needham claimed that spontaneous generation could occur and performed what he considered the definitive experiment. Needham heated broth to its boiling point, to kill microorganisms, and poured it into flasks. After the broth cooled, he sealed them. Then, he observed living microorganisms in the sealed broth, concluding that spontaneous generation was a fact and contradicting Redi’s conclusions. -
Criticism from Spallanzani
Lazzaro Spallanzani, did not agree with Needham’s conclusions, so he performed hundreds of experiments using heated broth. 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. -
Pasteur puts spontaneus generation to rest
Louis Pasteur, re-created the experiment and let the system open to air. 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, exposing it directly to the air and noted life forms in the broth within days. He concluded that contamination came from life forms in the air.