Abstract
All extract of polymorphonuclear leucocytes of the rat, prepared by means of ultrasonic vibration, was found to be bactericidal against M. aureus. The bactericidal activity was primarily confined to the mitochondrial fraction of the leucocytes. The rat leucocyte mitochondrial extract was bactericidal against both Gram-positive (M. aureus, beta-Streptococci, Diplococcus pneumoniae, Corynebacterium diphtheriae) and Gram-negative (Shigella dysenteriae, Salmonella enteritidis, Pasteurella pestis) bacteria. The Gram-positive organisms were more susceptible to the bactericidal activity of the mitochondrial extracts.