Urodele limb and tail regeneration in early biological thought: an essay on scientific controversy and social change.

Lazzaro Spallanzani (1729-1799) announced his discoveries of salamander tail and limb regeneration to Charles Bonnet (1729-1793) in the 1760's. The phenomenon soon became embroiled with the ongoing epigenesis/preformation controversy over the fundamental nature of generation. The concept of animal regeneration as a process linked to reproduction had emerged in 1740 with Abraham Trembley's (1710-1783) demonstration that a bisected hydra gives rise to two new, completely formed individuals. The discovery of urodele appendage regeneration revealed for the first time that a quadruped could regenerate and restore complex form, lizard tail regenerates having been recognized as only substitute structures. Moreover, regeneration of a quadruped appendage became problematic because it was not supposed to be possible and because it conflicted with prevailing opinion about the nature of higher organisms. Why animal regeneration in general engendered conflict transcends biological concerns and touches on personal philosophical commitments. Preformation had been adopted into orthodox theology as a validation of predestination and of the hierarchical structuring of man's relationships to nature and within society. Epigenetic interpretations of regeneration represented challenges to certain aspects of the extant social and political fabric in their extrapolation to ideas of what constituted natural order. Urodele regeneration as an integral part of the epigenesis/preformation debate therefore constituted a formative component of eighteenth century thought in a period of social and intellectual revolution.