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Francesco Redi
Francesco Redi (18 February 1626 - 1 march 1697) was an Italian scientist and physician who worked as a naturalist, doctor and poetist. He is known for his experiments of rebuttal the spontaneous generation theory. The principle experiment he did was in 1668. At that time it was believed that maggots grew spontaneously from rotting meat. With this theory, Redi did the first serious experiment to prove that spontaneous generation was not a true fact. -
Redi's experiment
He placed flesh meat into three jars: the first one was uncovered, the second one was tightly sealed, the final one was a jar covered with cloth netting. If maggots arise spontaneously from meat maggots would appear in all of the jars, the uncovered and the covered ones, because the air can reach the meat and carry the eggs of the maggots. He controlled loads of variables, this way he could ensure that the only variable possible was that some jars were covered and some others no. -
Redi's concluisons
The results of this experiment were: in the uncovered jar, maggots appeared, that means that spontaneous generation was a true fact. In the tightly sealed jar, maggots did not appear, that means that spontaneous generation was not a true fact. Finally, in the covered one, maggots did not appear, that means it also refutes this idea.
In conclusion, Redi confirmed that spontaneous generation did not exist. -
John Needham
John Needham (10 September 1713 - 30 December 1781) was an English biologist. He is known for his experiment of rebuttal to Redi’s observations. He first did other experiments but that one was the most remarkable. -
Needham’s rebuttal
In 1745 he did an experiment that consisted of heating broth until it boiled, to kill microorganisms. He poured that into flasks. Then, when they cooled, Needham sealed them. After a few minutes, Needham observed that in the sealed flasks were alive microorganisms. That conclusion was a rebuttal to Redi’s one because he said spontaneous generation was not a true fact, but Needham proved that spontaneous generation existed. -
Lazzaro Spallanzani
Lazzaro Spallanzani (1729–1799) was an Italian biologist and priest. He didn’t agree with Needham’s conclusions so he did loads of experiments to prove that spontaneous generation wasn’t a true fact. -
Criticism from Spallanzani
One of those experiments consisted of putting broth into flasks and sealing them. After boiling these flasks for a long time to kill the microorganisms, the broth did not have a trail of alive organisms. However, when he opened the flask, microorganisms grew rapidly. With this experiment Spallanzani could see that microorganisms came from contaminated air and that meant that spontaneous generation was not a true fact. -
Louis Pasteur
Louis Pasteur (27 December 1822 - 28 September 1895) was a French microbiologist and chemist. He is considered a pioneer of modern microbiology. -
Pasteur puts spontaneous generation to rest
He boiled a meat broth in a flask that had a neck with a particular design, whcih prevented oxygen and particles from getting in contact with the broth while they were still in contact with free air. The broth had a filter to prevent all types of particles from going to it. At that time, it did not grow anything in the flask. After one year, Pasteur opened the flask and immediately they grew microorganisms. That proves that what makes microorganisms grow is the contaminated air.