Summary
Temporary ischemia of the rat’s hind paw induces severe thrombohemorrhagic lesions following sensitization by the intravenous injections of ferric dextrin and agar I. Other substances such as India ink and saccharated ferric oxide, which exhibit no thrombohemorrhagic sensitizing properties when a tourniquet, epinephrine or 5-HT are used separately as challengers, prove extremely effective upon application of the tourniquet if epinephrine is also injected into the contralateral paw. Scandium chloride, given intravenously, sensitizes the rat for the production of thrombohemorrhagic lesions by temporary ischemia of the dorsal skin but fails to induce similar changes after an equally severe ischemia of the paw. It is concluded that, following sensitization, two in themselves ineffective agents, can become active thrombohemorrhagic challengers upon conjoint application.