Biology

Redi’s experiment

1661

Francesco Redi was an Italian physician and poet. He 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. The hypothesis of Redi we think it was:
“If maggots arise spontaneously from rotting meat, then maggots will be found on meat exposed to air, regardless of whether the meat is covered or uncovered, because the air will provide the necessary conditions for the generation of maggots.”

John Needham

1745

In 1745, an English clergyman called John Needham claimed that spontaneous generation could occur and performed what he considered the definitive experiment.
Needham briefly heated broth to its boiling point, to kill microorganisms, and poured it into flasks. Soon after the broth cooled, he sealed them.
After some time, he observed living microorganisms in the sealed broth, thus concluding that spontaneous generation was a fact and contradicting Redi’s conclusions.

Lazzaro Spallanzani

1757

Lazzaro Spallanzani was an Italian priest, who did not agree with Needham’s conclusions so he performed hundreds of carefully executed experiments using heated broth.
He first recreated Needham's experiment.
After some time, the broth did not have any trace of life. However, once he unsealed the flask, microorganisms rapidly grew in the broth.
Her concluded that spontaneous generation was false and microbes came from contaminated air.

Louis Pasteu

1850

Louis Pasteur, the notable French scientist, accepted the challenge to re-create the experiment and leave the system open to air. He repeated the experiment and concluded that the contamination came from life forms in the air, not a supposed “life force”.