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Redi's experiment
Francesco Redi made the first idea of spontaneous generation in 1668.
To prove that spontaneous generation was false, he set up an experiment that consisted of 3 jars with pieces of meat inside them, and sealed in different ways. In the jar that he left open, he found maggots in the meat. In the one that was completely sealed, there were no worms. And when it was covered by gauze, new flies appeared on the top.
He showed that the worms came from eggs laid by flies. Not by expotanian generation -
Needham’s rebuttal
In 1745, an English clergyman named John Needham claimed that spontaneous generation could occur.
Needham briefly heated the broth to its boiling point, to kill microorganisms, and poured it into flasks. Shortly after once the broth had cooled, he sealed them.
After some time, I observe live microorganisms in the sealed broth. Concluding so spontaneous generation was a fact and contradicting Redi's conclusions. -
Criticism from Spallanzani
Lazzaro Spallanzani, an Italian priest, did not agree with Needham’s conclusions.
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 did not have any trace of life.
However, once he unsealed the flask, microorganisms
rapidly grew in the broth.
Spallanzani concluded that spontaneous generation was false. -
Pasteur puts spontaneous generation to rest
Louis Pasteur, the notable French scientist, designed several bottles with S-curved necks that were oriented downward. He placed a 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 more directly to the air, and noted life forms in the broth within days. He reasoned that the contamination came from life forms in the air, not a supposed “life force”. -
Final remarks
In a lecture in 1864, Pasteur articulated “Omne vivum ex vivo”. In this lecture, Pasteur recounted his famous swan-neck flask experiment stating: “life is a germ and a germ is life. Never will the doctrine of spontaneous generation recover from the mortal blow of this experiment.