The contagion

Extract from A. Vallisneri, Miglioramenti e correzioni d’alcune sperienze ed osservazioni del Signor Redi, edited by Ivano Dal Prete, Biological notes by Andrea Castellani; C.F. Cogrossi – A. Vallisneri, Nuova Idea del male contagioso de’ buoi, edited by Mauro De Zan, Edizione Nazionale delle Opere di Antonio Vallisneri, Opere edite (Serie II), Sec. I, Vol. 5, Florence, Olschki, 2005.


The Miglioramenti e correzioni d’alcune sperienze ed osservazioni del Signor Redi came out in 1712 at the end of the first volume of Redi’s Opere, but took up materials from the Quaderni di osservazioni written between 1694 and 1701. The main methodological reference was Redi’s observation model and the main purpose was to refute the thesis of spontaneous generation and, with it, biological Aristotelianism.

With the Nuova idea del male contagioso de’ Buoi in 1714, Carlo Francesco Cogrossi and Antonio Vallisneri took part in the debate on the causes of the 1711 epidemic of epizootic disease. The most widespread thesis at the time among physicians belonging to the Galilean and mechanistic area was that of a disease produced by a poisonous effluvium of an inorganic nature, which would be passed from one animal to another. On the contrary, Cogrossi and Vallisneri supported the microbial origin of contagion, imagining that submicroscopic pestilential ‘worms’ passed from animal to animal.

The hypothesis of live contagion was supported mainly by theoretical arguments. Vallisneri invoked Malpighi’s (but also Redi’s) model of the analogy of nature, widely shared by the mechanistic life science of the time. On the basis of this principle and the assertion of the existence of the infinitely small, he also made an analogical extension of the causes of parasitoses caused by visible agents, such as flies and worms, to those of epidemic contagions, assuming similar morphological characteristics, albeit miniaturised, to those of the parasitic worms already studied.

In the Nuova idea Vallisneri did not abandon the empirical model of naturalistic research, but allowed the rationalistic and interpretative dimension to emerge more clearly.