INTRODUCTION Medical historians describe medical treatment in the late 18th century and in the early 19th as challenging and problematic.1 The expectations for successful results grew as the sciences progressed. In a few places, such as in post-Revolutionary Paris, there were early signs of a clinical medicine based on firmer scientific foundations. However, doctors still tended to rely on medical traditions that did not meet the challenges of the day. When, for example, cholera rolled over Europe in repeated waves in the early 19th century, most doctors were helpless. No wonder there was room for challengers, for charismatic men driven by their grand theories. Franz Mesmer was one of them. His ‘animal magnetism’ for a short time triumphed over ‘school medicine’. But with his defiance of the medical authorities, Mesmer was bound to get into trouble. His enemies were strong. He was driven away from Vienna, Austria, and then from Paris. Mesmer remained an odd parenthesis in medical history.