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Jan 1, 1000
Aristotle
At the time (322BCE), people believed in the 4 elements. Aristotle thought that living being had a mixture of the different elements, and that was what gave things life. In his writings, he mentions that inanimate objects can directly generate some animals. -
Francesco Redi
In an effort to disprove spontaneous generation, he published a set of experiments in 1668 that falsified spontaneous generation. He placed raw meat into different jars. Some of the jars were covered with gauze and some were left uncovered. Days later, he observed that maggots had infested the meat in the uncovered jars. However in the gauze-covered jars, maggots were only found on the gauze but not in the meat itself. This experiment proved that maggots did not spontaneously appear. -
John Needham
Working in England, John Needham was not convinced by Redi’s experiments. He said that although complicated organisms like maggots might not be able to be spontaneously created, but simpler organisms like bacteria could in fact be spontaneously generated. In 1745, he proved his thinking by boiling nutrient broth in a flask, letting the flasks cool, and then sealing them. Days later, the broth contained significant numbers of mold and bacteria. -
Lazzaro Spallanzani
Lazzaro Spallanzani argued that Needham did not heat the flask long enough, and that new bacteria were introduced since the broth was allowed to cool uncovered. Spallanzani repeated Needham’s experiment in 1768, except this time he allowed the flasks to boil for an extended time, and sealed one of the flasks immediately after boiling. Using his modified procedures, he found that the sealed flask remained microorganisms free, while the open flask had developed a lot of bacteria. -
Louis Pasteur
Some people said that spontaneous generation needed air. Pasteur faced the challenge of having a flask open to the air while at the same time preventing contaminants from falling in. The swan neck flask had a long bent neck allowing air to enter but prevented bacteria from falling into the solution. He boiled the broth in the flask and let the flask stand for over a year and no life was found in the flask. After Pasteur broke off the neck of the flask, the broth spoiled, thus proving his point.
