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Redi's experiment
Redi tested the theory of spontaneous generation by placing meat in three jars: one open to the air, one sealed, and one covered with cloth. Maggots appeared only in the open jar, showing that flies laid eggs on the meat, not that maggots were created spontaneously. This demonstrated that life didn’t arise from rotting meat if not, from living organisms, challenging the idea of spontaneous generation. -
Needham’s rebuttal
John Needham, an English clergyman, believed in spontaneous generation and conducted an experiment with broth. He heated the broth to kill existing microorganisms, then sealed it in flasks. To his surprise, microorganisms appeared in the sealed flasks, concluding that spontaneous generation was real. However, the experiment had flaws: the flasks may not have been sealed properly, or the broth wasn’t boiled long enough to kill all microorganisms. These issues cast doubt on Needham’s conclusions. -
Criticism from Spallanzani
In 1745, John Needham, an English clergyman, supported spontaneous generation. He heated broth to kill microorganisms, poured it into sealed flasks, and observed microorganisms growing inside. This led him to conclude that spontaneous generation occurred, contrary to Redi’s findings. However, flaws in his experiment, such as insufficient boiling time or improper sealing, likely allowed contamination. His results were not convincing, as they failed to fully rule out outside contamination. -
Pasteur puts spontaneous generation to rest
Lazzaro Spallanzani, an Italian priest, disagreed with Needham’s conclusion. He boiled broth in sealed flasks for longer, ensuring no contamination. His results showed no microorganisms in the sealed flasks. Once opened, microorganisms grew rapidly, supporting the idea that life came from the air. Spallanzani’s method addressed potential flaws in Needham’s experiment, confirming that life did not arise spontaneously.