In skin tests with killed cultures of the green-producing diplococcus from measles, Tunnicliff1 obtained positive reactions in 100 per cent of persons who had not had measles, and in only 4 per cent of those with a history of measles. This intracellular toxin was neutralized in persons with a negative history of measles by convalescent human measles serum, but not by the serum of a person who had not had measles. The toxin was neutralized in rabbits by convalescent human measles serum and by the serum of goats convalescing from the reaction produced by measles diplococci, but not by normal goat serum. The measles toxin produced reactions in normal rabbits, but not in rabbits immunized against measles. Berkefeld W filtrates of cultures of measles diplococci failed to produce any reactions.
Recently, Ferry and Fisher2 have demonstrated an extracellular toxin in filtered cultures of green-producing streptococci from measles with