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Spontaneous generation
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Redi’s experiment
In 1668, Francesco Redi put meat in three jars, one open, one sealed and one closed with cloth. Flies laid their eggs on the meat in the open jar. Unable to reach the meat, flies laid their eggs on the cloth of the second jar and the maggots hatched on the cloth, not on the meat.. No eggs were laid on the sealed jar, so it remained free of maggots. With this repeatable experiment, Redi proved scientifically that life, the maggots, comes from life, the flies, and not from non life, the dead meat. -
Needham’s rebuttal
In 1745, John Needham challenged Redi's findings by conducting an experiment in which he placed a broth into a bottle, heated the bottle to kill anything inside, then sealed it. Days later, he reported the presence of life in the broth and announced that life had been created from nonlife. -
Criticism from Spallanzani
Lazzaro Spallanzani, also an Italian scientist, reviewed
both Redi's and Needham's data and experimental
design and concluded that perhaps Needham's did something wrong during his experiment. He constructed his own experiment by placing broth in each of two separate bottles, boiling the broth in both bottles, then sealing one bottle and leaving the other open. Days later, the unsealed bottle was teeming with small living things. The sealed bottle showed no signs of life. -
Pasteur puts spontaneous generation to rest
subsequently designed several bottles with Scurved necks that were oriented downward so gravity would prevent access by airborne foreign materials. He placed a nutrientenriched broth in one of the gooseneck bottles, boiled the broth inside the bottle, and observed no life in the jar for one year. He then tipped the bottle, exposing it more directly to the air and to the trap, and noted life-forms in the broth within days.
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