Redi experiment

Redi experiment (1665)

   As late as the 17th century, some biologists thought that some simpler forms of life were generated by spontaneous generation from inanimate matter. Although this was rejected for more complex forms such as mice, which were observed to be born from mother mice after they copulated with father mice, there remained doubt for such things as insects whose reproductive cycle was unknown. [An important step was the documentation by Maria Sibylla Merian (1647 - 1717) of the stages of metamorphosis in butterflies].

    To test the hypothesis, Francesco Redi placed fresh meat in open containers [left, above]. As expected, the rotting meat attracted flies, and the meat was soon swarming with maggots, which hatched into flies [left, below]. When the jars were tightly covered so that flies could not get in [middle, above], no maggots were produced [middle, below]. To answer the objection that the cover cut off fresh air necessary for spontaneous generation, Redi covered the jars with several layers of porous gauze [right, above] instead of an air-tight cover. Flies were attracted to the smell of the rotting meat, clustered on the gauze, which was soon swarming with maggots, but the meat itself remained free of maggots [right, below]. Thus flies are necessary to produce flies: they do not arise spontaneously from rotting meat.

    Redi went on to demonstrate that dead maggots or flies would not generate new flies when placed on rotting meat in a sealed jar, whereas live maggots or flies would. This disproved both the existence of some essential component in once-living organisms, and the necessity of fresh air to generate life.

    Note that is unnecessary to observe or even imagine that are such things as fly eggs, nor does the experiment prove that such exist. Redi's experiment simply but effectively demonstrates that life is necessary to produce life. Redi expressed this in his famous dictum as "
Omne vivum ex vivo" ("All life comes from life").

All text material © 2022 by Steven M. Carr