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Francesco Redi challenges spontaneous generation
Francesco Redi, an Italian physician, conducted an experiment to test whether maggots arose spontaneously from rotting meat. He placed meat in three types of jars: open, sealed, and covered with gauze. Maggots only appeared in the open jars where flies had direct access, while no maggots developed in the sealed or gauze-covered jars. His work showed that maggots were the offspring of flies, not spontaneously generated, though it didn’t address microorganisms. -
John Needham supports spontaneous generation
John Needham, an English clergyman, aimed to prove spontaneous generation by boiling broth and sealing it in flasks. Microbial growth appeared after a few days, leading Needham to claim life arose spontaneously. However, his method had flaws: boiling was insufficient to kill all microorganisms, and sealing the flasks after boiling allowed contamination. His experiment was seen as evidence for spontaneous generation, despite its shortcomings. -
Lazzaro Spallanzani refutes Needham
Italian scientist Lazzaro Spallanzani improved on Needham’s work by sealing flasks before boiling and boiling for longer. His results showed no microbial growth unless the flasks were unsealed, proving contamination from the air. Spallanzani concluded that microorganisms did not arise spontaneously but came from preexisting microbes. Critics argued that sealing the flasks excluded a "vital force" needed for life, leaving the debate unresolved for the time. -
Louis Pasteur ends the debate
Louis Pasteur designed swan-neck flasks to address the issue of air access while preventing contamination. These flasks allowed air to flow but trapped airborne particles in their curves. Pasteur boiled broth inside the flasks, which remained sterile for over a year. Only when the flasks were tilted or broken did microbial growth occur. This experiment conclusively disproved spontaneous generation, proving that life arises from existing life, and solidified germ theory.