New toxic substances in certain tuberculin, O.T., and B. typhosus culture filtrates are described. These substances are capable of eliciting the hemorrhagic necrosis characteristic of the phenomenon of local skin reactivity provided heterologous bacterial filtrates of high potency are used either for the intradermal or the intravenous injection. The toxic substances apparently have no relationship to the tuberculin substances proper.
The experiments with inactive preparations also demonstrate in rabbits a state of hypersensitiveness to tuberculin, O.T., and bacteria-free culture filtrates in the absence of tuberculous foci. The reactions are elicited provided the tissues are rendered vulnerable through contact with certain soluble bacterial factors capable of eliciting the phenomenon of local skin reactivity to bacterial filtrates, and provided the tuberculin or the tuberculous culture filtrates are injected intravenously into immunized rabbits.