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Redi’s experiment
Want to demonstrate that dead maggots or flies would not generate new flies when placed on rotting meat in a sealed jar, whereas live maggots or flies would. Redi's experiment simply but effectively demonstrates that life is necessary to produce life. -
Needham’s rebuttal
Needham thought Redi was wrong.
He covered a flask with a cork and heated it up, reasoning that he would've killed all the microbes like that. He waited, and when he observed the flask: microbes were there. -
Criticism from spallanzani
He did not agree with Needham’s conclusions, however,
and performed hundreds of carefully executed 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 spontaneous generation to rest
Louis Pasteur, accepted the challenge to re-create the experiment and leave the system open to air. He subsequently 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, and observed no life in for one year. He then broke off the top of the bottle, exposing it more directly to the air, and noted life forms in days. He say that the contamination came from life forms in the air,