Mishulow, Mowry and Scott1 demonstrated that exotoxic filtrates could be obtained from whooping cough cultures. They planted their organisms on chocolate agar over which they had poured a small amount of horse serum-beef heart broth. The small amount of diluent made the harvest of toxin necessarily small. On the other hand, Craster and Smith2 mentioned that there was a signal absence of toxin formation in planted cultures, and Riesenfeld3 stated that there was no proof that this bacillus produced a toxin in ascitic broth. Besredka4 isolated toxic substances termed endotoxins from the dried and powdered organisms.In 1928, we found that pertussis bacillus produced a substance in culture growth, the exact nature of which was problematic. With the report of Mishulow, Mowry and Scott, we felt that further work should be done along this line. Since large amounts of toxin could not be practically produced on solid preparations, various liquid media were tried. We found that Pelouze's and Viteri's gonococcous med...