ABSTRACT
This chapter considers the hypothesization and discovery of the toxins of diphtheria, tetanus and botulism. There are two types of bacterial toxins, exotoxins and endotoxins, so named originally because it was believed that, respectively, they were secreted by Gram-positive organisms into the culture medium, or contained within the cell substance of Gram-negative organisms. Diphtheria is an acute infectious disease caused by the Gram-positive Corynebacterium diphtheriae. Tetanus is an ancient disease resulting from infection by the Grampositive Clostridium tetani of wounds that are often so slight as to be undetectable post mortem. People who survive diphtheria are generally immune to it, or at least to its worst effects, for life, largely because they have gained immunity to the toxin. The lesions in animals succumbing to diphtheria toxin were the same as those observed in the natural disease and in animals inoculated with the bacillus.
