[Lazzaro Spallanzani and his refutation of the theory of spontaneous generation]

The development and refinement of microscopy in the 17th century revealed to science a whole new world of microorganisms, until then unknown, that appeared to arise spontaneously, and fuelled a controversy that had seemed definitively resolved by Francesco Redi's experiments, the question of the spontaneous generation and origin of life. At the half of the 18th century a young Italian abbot, Lazzaro Spallanzani, Professor of Physics and Mathematics at the University of Reggio Emilia, started repeating the experiments of John Turberville Needham. The English Catholic priest claimed to have demonstrated the validity of the theory of spontaneous generation after observing the growth of small organisms in some chicken broth placed in sealed flasks and heated for 30 minutes. Spallanzani found significant errors in the experiments conducted by Needham and, after trying several variations on them, disproved the theory of spontaneous generation.