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Francesco Redi
Francesco Redi, an Italian physician and poet, made the first serious attack on the idea of spontaneous generation in 1668. At that time, it was widely held that maggots arose spontaneously in rotting meat. To achieve his goal of proving spontaneous generation to be wrong, he set out a controlled experiment such as the one described in this figure: -
Franceso Redi
Francesco Redi, an Italian physician and poet, made the first serious attack on the idea of spontaneous generation in 1668. At that time, it was widely held that maggots arose spontaneously in rotting meat. To achieve his goal of proving spontaneous generation to be wrong, he set out a controlled experiment such as the one described in this figure: -
Lazzaro Spallanzani
Lazzaro Spallanzani disagreed with Needham's conclusions and performed hundreds of carefully executed experiments using hot broth.
Spallanzani poured broth into flasks and sealed them. He then boiled the jars for a long time, to kill any microorganisms present.
After a while, the broth had no trace of life. However, once the flask was opened, the microorganisms grew rapidly in the broth.
Spallanzani concluded that the spontaneous generation was false and that the microbes came from polluted air. -
John Needham
In 1745, an English clergyman called John Needham claimed that spontaneous generation could occur and performed what he considered the definitive experiment.
Needham briefly heated broth to its boiling point, to kill microorganisms, and poured it into flasks. Soon after the broth cooled, he sealed them.
After some time, he observed living microorganisms in the sealed broth, thus concluding that spontaneous generation was a fact and contradicting Redi’s conclusions. -
Louis Pasteur
Louis Pasteur, accepted the challenge to recreate the experiment and leave the system in the air. Later he designed several bottles with downward-facing S-shaped necks. Put a nutrient-enriched broth in one of the gooseneck bottles, boiled the broth inside the bottle. He then broke the top of the bottle, exposing it more directly to air and trapped particles, and he noticed life forms. He reasoned that the pollution came from life forms in the air