Experiments

Redi's experiment

1668

At that time, it was believed that maggots and other small organisms could arise spontaneously from decaying organic matter. In his most famous experiment he placed meat in two jars. One jar was left open to the air, while the other was covered with a fine mesh to prevent any flies from entering. Within a few days, maggots appeared in the open jar, while the meat in the covered jar remained free of maggots. Redi's experiment provided strong evidence against the idea of spontaneous generation.

Needham’s rebuttal

1745

John Needham was an English naturalist who conducted experiments that he believed supported the theory of spontaneous generation.He believed that microorganisms were spontaneously generated from the broth even after it had been heated, and that these organisms were able to grow and thrive in the sealed flask.

Criticism from Spallanzani

1765

Lazzaro Spallanzani did not agree with Needham’s conclusions. Spallanzani's experiment showed that no microorganisms appeared in the broth, even after several days of incubation. This led him to conclude that the microorganisms observed by Needham were not spontaneously generated from the broth, but rather were introduced from the air or from other sources. Despite these criticisms, Spallanzani's work helped to establish our understanding of the origins of life.

Louis Pasteur experiment

1861

One of his most famous experiments involved the use of a swan-necked flask to demonstrate that microorganisms do not arise spontaneously. In this experiment, Pasteur boiled a nutrient-rich liquid, such as broth, in a flask with a long, curved neck that ended in a U-shaped bend. Over time, the nutrient-rich liquid remained clear and free of microorganisms. However, if the curved neck was broken or the nutrient-rich liquid was disturbed, microorganisms from the air would enter the flask.