Indeed, injections of tuberculin could be very dangerous, as is illustrated by the example of Max Simon, a patient treated in Elberfeld in December 1890. Having just recovered from pulmonary tuberculosis, he was given what his physicians considered to be a small, diagnostic injection of 2 mg of tuberculin. What followed was a disaster:

Only three hours after the injection high fever up to 40 degrees was observed, feeble almost undetectable pulse (about 150 per minute); on top of it vomiting, unquenchable thirst. 12 hours after the injection, death came with the symptoms of paralysis of the heart4

Still, it took at least three month before it became widely accepted that tuberculin was not a cure for tuberculosis and that its use was potentially dangerous. Even then, no consensus was reached concerning this remedy, and the debate lingered on for years. This chapter focuses on the debate, allowing us to address some questions around the historicity of notions of risk in medicine. How, when and by who did tuberculin come to be considered a risky medicine, on what evidence was such knowledge based, and what role did the risk of using tuberculin play in the evaluation of the medicine? Finally, some attention will be paid to the semantics of the evaluation of risk and in particular to the

question of how the language used in this case is in any sense related to the language of health risks and their evaluation at the present day.