Letter from James B. Conant, Office of Scientific Research and Development to Michael Heidelberger

During World War II, Heidelberger conducted classified immunological research under grants from the Office of Scientific Research and Development, trying--unsuccessfully--to find a vaccine for malaria, a major health problem among U.S. troops fighting in the South Pacific. He also worked on a vaccine against ricin, research prompted by reports that the Japanese government had asked every household in Japan to grow castor beans, the source of the potent toxin. U.S. military authorities feared that Japan might try to aerosolize ricin and release it over the American mainland. It became clear only later that the Japanese military had instead sought castor bean oil as a lubricant for aircraft engines.