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Redi's Experiment
“If I put fresh meat in a jar and leave it open flies will be attracted to the smell and maggots will appear, if I put it in a closed jar no maggots will appear and if I cover it just with a cloth so that air can get in no maggots will appear.” It was the Theory of Francesco Redi. The conclusion is that maggots didn’t appear spontaneously from rotten meat, but flies created them, laying their eggs on the meat. Without flights, maggots didn’t appear, so it wasn’t the rotten meat of the creator. -
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. -
John Needha
John Needha was an English scientist and Catholic priest, defender of the theory of spontaneous generation. Needham carried out numerous experiments in which he prepared meat and vegetable broths. -
Spallanzani
Lazzaro Spallanzani was an Italian Catholic priest, biologist and physiologist who made important contributions to the experimental study of bodily functions, animal reproduction, and animal echolocation. -
Needham's rebuttal
Microscopy uncovered a new world of microorganisms that seemed to pop up spontaneously. In 1745, John Needham asserted that the spontaneous generation could occur and execute what he regarded as the definitive experience. Needham stock heated to its boiling point, to kill microorganisms, and poured in bottles. After the broth cooled, he sealed them. Then, he observed living microorganisms in the sealed broth, concluding that spontaneous generation was a fact and contradicting Redi’s conclusions. -
Criticism from Spallanzani
Spallanzani, didn't agree with Needham’s conclusions, so he performed hundreds of experiments using heated broth. Spallanzani poured broth into flasks and sealed them. Next, he boiled the flasks for a long time, to kill present microorganisms. After some time, the broth didn't have any trace of life. However, once he unsealed the flask, microorganisms rapidly grew in the broth. Spallanzani concluded that spontaneous generation was false and microbes came from contaminated air. -
Louis Pasteur
Louis Pasteur was a French microbiologist and chemist. He was known to the public for his demonstration of the germ theory of a disease and its development and inoculation techniques. -
Pasteur put spontaneus generation to rest
Louis Pasteur recreated the experiment and opened the system to air. He designed several S-shaped bottles with the neck facing down. He put a nutrient-rich broth in one of the gooseneck flasks, boiled the broth in the bottle, and observed that there was no life in the jar for a year. He then uncapped the bottle, exposing it directly to the air, and within a few days noticed life in the broth. He concluded that the pollution originated from life forms in the air.