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400 BCE
Aristotle's theory
Aristotle was the first to believe in spontanious generation. He expanded the work of scientist and philospher's who believed in it. -
Francesco Redi's experiment
Francesco Redi, didn't believe in spontaneous generation and decided to prove that it could not exist with an experiment. It consisted in having 3 flasks, one opened, the other totally closed and the last one with a kind of filter and seeing if worms appeared. It resulted in the appearance of worms only in the opened flask, which proved they weren’t spontaneously created, but came from elsewhere. -
Needham's rebuttal
John Needham believed in spontaneous generation and proved through an experiment that it existed. He boiled chicken broth and then put it in a closed jar. He proved and saw a few days later that microorganisms actually grew from inside of it. -
Lazzaro Spallazani's experiment
Lazzaro Spallazani didn’t believe John Needham’s theory and decided to prove he was wrong. He changed some important features in his experiment. Firstly, differing from Needham, he vacuumed the air before sealing the chicken broth and boiling it. In his experiment, during the whole process, the flasks remained sealed. During his experiment, no microorganisms grew inside the broath. -
Louis Pasteur's experiment
Louis Pasteur proved that the theory of spontaneous generation was wrong by doing an experiment which mixed Needham’s and Spallazani’s. Pasteur boiled firstly meat in a sort of flask and heated it. Then he bent it like an S shape. No microorganisms grew. This is because the S shape permits that the air goes into the flask but not the microorganisms enter on it as they stay in the S shape.This proved the microorganism didn't grew from inside, but they came from outside in previous experiments.