The critique to spontaneous generation

Excerpt from Ex ovo omnia. Parasitology and the origin of epidemics in the research and work of Antonio Vallisneri,
edited by Dario Generali, Florence, Olschki, 2019.

From Redi to Spallanzani, one of the most debated scientific topics in Italy was that of the spontaneous generation of the so-called imperfect organisms. The main exponents of the Galilean medical school, such as Redi, Malpighi and Vallisneri, took sides against this thesis.

After Redi’s experiments, the Aristotelian front found arguments in support of spontaneous generation by referring to organisms with a less easily investigated life cycle, such as parasites of plants and animals, for which Redi himself had admitted a non-parental origin, produced by the zoogenetic potential of the beings that host them.

Vallisneri played a primary role in this debate, concentrating his efforts on filling the gap that had opened in the theory of the parental generation of every living thing. With a series of studies, exemplary for methodological rigour and technical expertise, he came to illustrate the hitherto completely unknown origin of many parasites, thus reaffirming the image of uniformity and necessity of the laws of nature and the universality of the theory of parental generation as species-specific to each organism.

On the basis of his parasitological studies, Vallisneri was able to ascertain on several occasions how insects could cause widespread pathologies, even lethal for large animals, and to elaborate the theory of live contagion, determined by submicroscopic pestilential worms, in his opinion at the origin of both animal and human epidemics, in opposition to the dominant theory of venomous effluvia.

[online 17/04/20]