[Animal regeneration experiments from 1686 to 1765. How to defend preexistence?]

This paper deals with the way in which the pre-existence of germs was defended in the face of experimental conclusions regarding animal regeneration in the period between the turn of the seventeenth century and the 1760's. From the experiments of Claude Perrault (1680), Antoine de Réaumur (1712), Abraham Trembley (1740-44) and Charles Bonnet (1740), it became clear that pre-existence delimited its objective so narrowly as to make it invulnerable to all possible experimental refutation. Moreover, we shall argue that this construction of the objective was linked with a renewed definition of the "community of Practitioners" built upon the notion of "scientific exclusion".