Antonio Vallisneri e la questione dei vermicelli spermatici: un’indagine storico-naturalistica

This paper deals with the identification of the microscope used by the Italian physician and naturalist Antonio Vallisneri (1661-1730) during his experimental research activity. The investigation was structured in three phases: a) a first text analysis on published and manuscript sources, looking for information about the microscope(s) used by Vallisneri; b) an hypothesis was put forward based on the chronological and descriptive compliance between the examined writings and the technological level achieved by eighteenth- and seventeenth-century microscopy; c) there was an experimental verification of the hypothesis, through the reproduction of observations reported by Vallisneri, using similar material and instrument. The letters written by Vallisneri to Louis Bourguet and Jacopo Riccati between 1713 and 1721 were the most important documents for the purpose of this research. They concern the observation of spermatozoa in rabbit semen. In these letters Vallisneri mentioned some «English microscopes with eight lens orders» that fitted the description of the screw-barrel microscope by the English craftsman James Wilson in three pamphlets issued between 1702 and 1711. Original copies of Wilson-type microscopes are preserved at the Muse´e d’Histoire des Sciences of Geneva, where the possibility of manipulating them allowed the experimental observation of the rabbit semen. Among the instruments preserved there, inventory no. 466 was mainly considered: a Wilson-type microscope on a brass stand – a change introduced by John Cuff in the early 1740s. The spermatic cells were clearly observed through three lenses, with magnifications ranging from 120 X to 300 X. Though it must be pointed out that these lenses were not standardised, this result reasonably confirmed the hypothesis, e.g. the microscope used by Vallisneri for the observation of spermatozoa was a screw-barrel instrument made by James Wilson, probably in the first decade of the eighteenth century. In the conclusion I discuss the role played by single lens microscopes in Vallisneri’s activity and in the development of early eighteenth-century scientific research and markets in northern Italy.