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Francesco Redi
Francesco was born in Italy, he was a naturalist, physician and poet. He carried out experiments in Florence considered very relevant in the refutation of the theory of spontaneous generation. He did an experiment on 1668 to achieve his goal of proving spontaneous generation wrong. At that time, it was widely held that maggots arose spontaneously in rotting meat and he did an experiment to find out if that was correct. -
Redi's Experiment
In this experiment, Redi demonstrated that dead maggots or flies would not generate new flies when placed on rotting meat in a sealed jar, whereas live maggots or flies would. To do this experiment he used different variables:- The independent (the jar cover)
- The dependent (the magots)
- And a third one which was the jar and the meat (this variable does'nt affect the final result).
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John Needham
He was an English biologist and he was ordained a Catholic priest in 1738. He began to expound on "natural philosophy" in a seminar at school and later in a published article. This article was mainly in the field of geology but it also described the mechanics of pollen and with its dissemination it gained recognition within the botanical community. He did an experiment in 1745 and he claimed that spontaneous generation could occur and performed what he considered the definitive experiment. -
Needham’s rebuttal
In this experiment, Needham briefly heated the broth to its boiling point, to kill the microorganisms, and then poured it into flasks. Shortly after the broth cooled, he closed them. After a while, he observed living microorganisms in the sealed broth, so his conclusion was that spontaneous generation was a fact and that life can arise from dead matter. With that, he proved Redi's conclusions wrong. -
Spallanzani's experiment
Spallanzani poured broth into flasks and sealed them. Then boiled the flasks to get rid of microorganisms already present. After some time, the broth did not have any trace of life. However, once he unsealed the flask, microorganism grew in the broth.
Conclusion: - spontaneous generation was false and microbes came from contaminated air. Needham and others, argued that he had not disproved it, he proved that spontaneous generation could not occur without the “life force” contained in air. -
Lazzaro Spallanzani
He was an an Italian priest and he was born in 1729 and died in 1799. He was a professor of physics and mathematics at the University of Reggio Emilia, in 1757. He didn't agree with Needham’s conclusions and to prove hime wrong, he performed hundreds of carefully executed experiments using heated broth just like Needham did. He proved that living organisms can't live without air. -
Louis Pasteur
He was a notable French microbiologist and chemist. He accepted the challenge to re-create the experiment and leave the system open to air. In a lecture in 1864, Pasteur articulated “Omne vivum ex vivo” which means “Life only comes from life”. In this lecture, Pasteur recounted his famous swan-neck flask experiment stating: “life is a germ and a germ is life. Never will the beliefes of spontaneous generation recover from the mortal blow of this simple experiment”. -
Pasteur's experiment
He designed several bottles with S-curved necks. He placed a nutrient-enriched broth in one of the swan-neck bottles, boiled the broth inside the bottle, and observed no life in the jar for one year. He then broke off the top of the bottle or tilted the flask, exposing it to the air and trapped particles, and noted life forms in the broth within days. He reasoned that the contamination came from life forms in the air. This experiment falsified the spontaneous generation.