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Francesco Redi was an Italian physician and poet. He is known for being the first to question the theory of Spontaneous generation by performing an experiment that would revolutionize the thinking of that time. The greatest discovery he made was to encourage other scientists to question things. -
It was believed that worms arose in rotten meat as spontaneous generation, but Redi disproved this through an experiment. It had three phases, the first demonstrated that worms come from the eggs of flies and not from the meat itself. In the second he continued to demonstrate that without flies worms do not form. And in the final of the experiments, he concluded that flies form the worms and do not come from the meat. With the experiment he questioned spontaneous generation. -
John Needham un clergue anglès que defensava la generació espontània, va afirmar que es podia produir sobretot en microorganismes, i va realitzar el que ell considerava l'experiment definitiu.
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Italian priest and scientist who refuted Needham's conclusions since he did not agree with spontaneous generation, and proposed more rigorous experiments with heated broth. -
Needham's experiment involved briefly heating a broth to kill microorganisms, allowing it to cool, and sealing it in jars. He observed that the microorganisms reappeared, but they reappeared because his experiment was obviously flawed. Either because he did not boil the broth long enough to kill all the microorganisms, or because he did not seal the jars. Needham's conclusions stated that spontaneous generation was real because microorganisms arose spontaneously.
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Spallanzani's experiment involved boiling the broth for a much longer time and sealing the jars before boiling it. He observed that no microorganisms appeared as long as the jars were sealed. When he opened the jars, microorganisms began to appear. The conclusions were that the microorganisms came from the air, not the broth. This showed that spontaneous generation was not possible, at least under controlled conditions.
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Louis Pasteur, the remarkable French scientist, known for his seminal experiments that ended the theory of spontaneous generation, took on the challenge of recreating the experiment and leaving the system open to the air. -
Louis Pasteur used flasks with swan-shaped necks, which allowed air to pass through but prevented dust and microorganisms from entering. After sterilizing the broth by boiling it, no microorganisms appeared as long as the flasks remained intact. However, when he broke the neck or tilted the flask, the broth became contaminated and microorganisms emerged. Microorganisms come from the air, not from a “life force.” Pasteur declared: “Life comes only from life.”