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300
Aristotle
Claimed that there were four essencial substances: fire, water, air, and earth. He also believed that life could form spontaneously. -
Period: 300 to
Test TIme
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Jan Baptista van Helmont
Jan Baptista van Helmont discovered the recipe for making mice. To do so you had to place a dirty rag or shirt with some grains of wheat and then wait 21 days and there would be mice. -
Francisco Redi
Fancisco Redi counducted an experiment that became the first attempt at disproving spontaneous generation. To show that spontaneous generation doesn't happen Redi put dead snakes, eels, and veal in jars. He left some of the jars open, but sealed to rest. At the end of the expiriment the open jars had maggots in the meat, but the sealed jars had none. Critics said that the experiment was faulty because everything needs air, and no air went in the sealed jars, so Redi's expiriment meant nothing. -
John Needham
John Needham wanted to use the knowledge that boiling kills organisms to prove that spontaneous generation worked. To conduct his experiment he first proved the existence of micro-organisms in the broth. Then he boiled the broth and showed that all of the micro-organisms had died. He put on the stopper (but left it loose) and after a few days the micro-organisms had reappeared. -
Lazzaro Spallanzani
Spallanzani wanted to disprove John Needham with the claim that the jars were not sealed well enough, and the micro-organisms could have come from the air. So he modified Needham's experiment by: boiling the flasks for a longer period of time, and sealing some of the flasks after boiling them. After the end of the experiment the micro-organisms only reappeared in the open flasks. John Needham critisized Spallanzani's experiment saying that the longer boiling time ruined the vegetative power. -
Lazzaro Spallanzani's Modified Experiment
To prove Needham's acuzations worng, Spallanzani modified his experiment again. This time along with having some jars sealed and some jars open, he boiled the jars for different lengths of time (30, 60, 90, and 120min). After the eperiment all of the open jars had micro-organisms and none of the sealed jars did. Spallanzani concluded that the boiling length did not damage the ability to hold life, and the growth of micro-organisms only depended on the seal. -
Louis Pasteur
Louis Pasteur wanted to disprove spontaneous generation once and for all. To do this he counducted an experiment different from all of the others. Instead of sealing some of the jars and leaving some open, he used swan-neched flasks. Swan-necked flasks let in air, but kept dust and micro-organisms out. After the experiment with the dust kept out there was no growth of life. To counter critics he tipped the flask so that the liquid made contact with the dust and showed the growth that resulted. -
Thomas Huxley
Thomas Huxley may not have counducted experiment about spontaneous generation, but he played an important role in crushing the theories once and for all by giving lectures about biogenesis and abiogenesis. Biogenesis is the idea that living things only come from other living things. Abiogenesis is the term used for the theories about spontaneous generation. Huxley's lectures swayed many critics opinions in favor of Pasteur ending the belief in spontaneous generation.
