Needham (1748) and Spallanzani (1765): infusions, boiling and sealed flasks
A dispute of the mid-eighteenth century: do microscopic beings arise by themselves in heated and closed infusions.
The English priest John Needham reported in 1748 to the Royal Society that 'animalcules' still appeared in heated and closed infusions, and together with Buffon interpreted this as spontaneous generation of microscopic life. The Italian Lazzaro Spallanzani in 1765 repeated the experiments with prolonged boiling and hermetic sealing and showed that microorganisms do not appear.
Needham objected that heat and the absence of air destroyed the very capacity of the infusion to generate life (its 'vegetative force'; after Roe, 1983). The dispute remained methodologically unresolved: the parties disagreed about what counted as a correct experimental setup.
Why this date
high for both publication dates: 1748 (Needham), 1765 (Spallanzani); the axis follows Spallanzani. Needham's objection about the "vegetative force" is given after Roe (Isis, 1983), whose text is behind a paywall and has not been checked verbatim
What grew out of it
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Pasteur: swan-neck flasks and the memoir on organized corpuscles in the atmosphere
influenced · Confidence: medium
Pasteur continued Spallanzani's line (boiling in flasks), adding protection from dust with free access of air, which removes Needham's main objection about the "spoiled" air in sealed flasks.
Dispute: Parke describes Pasteur's experiments directly as a continuation of Spallanzani's line ("continued along these lines"). What remains unsourced is only the methodological detail that the purpose of the curved neck was precisely to remove Needham's objection about spoiled air.
Link sources
- Parke E. C. «Flies from meat and wasps from trees: Reevaluating Francesco Redi's spontaneous generation experiments», Studies in History and Philosophy of Biological and Biomedical Sciences 45, 34-42 (2014) Verified 25 Sep 2026
In the eighteenth century, Lazzaro Spallanzani did experiments demonstrating that infusoria do not grow in sterilized flasks. In the nineteenth century Pasteur continued along these lines, showing that microscopic life forms are not spontaneously generated in vessels of sterilized liquid, but rather get there by contamination through exposure to microbes in the surrounding air (Pasteur, 1864).
"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.
- Parke E. C. «Flies from meat and wasps from trees: Reevaluating Francesco Redi's spontaneous generation experiments», Studies in History and Philosophy of Biological and Biomedical Sciences 45, 34-42 (2014) Verified 25 Sep 2026
Node sources
- Sunderland M.E. Lazzaro Spallanzani (1729-1799). Embryo Project Encyclopedia (2007) Verified 20 Sep 2026
Unconvinced by Needham and Buffon's description of the genesis of animalcules in plant and animal infusions, Spallanzani carefully replicated their study and showed their techniques were inadequate and therefore that their conclusions about the existence of spontaneous generation were unwarranted. He published his results refuting spontaneous generation in 1765
- Britannica, «Lazzaro Spallanzani» Verified 20 Sep 2026
In a series of experiments he showed that gravy, when boiled, did not produce these forms if placed in phials that were immediately sealed by fusing the glass. As a result of this work, he concluded that the objects in pond water and other preparations were living organisms introduced from the air and that Buffon's views were without foundation.
"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.
Further reading
Not evidence: these carry no quotation and support nothing we wrote. They are books and scans to read next.
- Needham T. A Summary of Some Late Observations upon the Generation, Composition, and Decomposition of Animal and Vegetable Substances. Phil. Trans. 45 (JSTOR 104587) (1748)
- Spallanzani L. Saggio di osservazioni microscopiche concernenti il sistema della generazione de' signori di Needham e Buffon (OU History of Science Collections) (1765)
- Roe S.A. John Turberville Needham and the Generation of Living Organisms. Isis 74(2) (1983)