The life of "8K", a vagrant microscope objective.

The aim of this article is to suggest that some scientific instruments may be considered worthy of their own biographies and that such a genre may have its own merits and charms. The instrument chosen to exemplify this point is a Hartnack microscope objective lens of about 1860 which served, in turn, the histologist and anatomist Albert von Kölliker, the comparative anatomist Robert Wiedersheim, the surgeon Frederic Kammerer, and the embryologist Edmund Beecher Wilson, and which travelled from Paris to New York by way of Würzburg, Genoa, and Freiburg. Despite a fairly discouraging archival situation, the search for the circumstances surrounding the various employers of "8K" allows us to view the role of microscopes in nineteenth-century biology from a new angle. In addition, the fate of "8K" itself endows this objective with a symbolical significance which transcends its specific functions.