The conditions responsible for the preparation of crude, activated and purified toxins of Clostridium botulinum Type E and the antigenic properties of toxoids prepared from these toxins, are described. Optimum toxin production and toxin activation are seen to be critically dependent on conditions such as hydrogen-ion concentration, and incubation time and temperature. Immunization of human volunteers with the formolized toxoids demonstrated that the highest level of immunity occurred in those individuals who received the crude toxoids. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate