Large, non-motile clostridium, and the species most frequently causing gas gangrene. Totally anaerobic and saccharolytic, 6 types (A—F) of the organism occur, differing in the toxins they produce. Alpha toxin (a lethicinase), is the most lethal of these; others are beta, epsilon, iota, gamma, delta, eta, theta, kappa, lambda, mu and nu and other toxins of enzymic nature are known. In additon to gas gangrene, septicaemia, and sometimes food poisoning in man, the organism produces a variety of infective conditions in animals, especially sheep.