It is now fifty-four years since Gottstein1 discovered that some bacteria are able to decompose hydrogen peroxide with evolution of gaseous oxygen, an activity he attributed to their possessing an intracellular enzyme which later came to be called ‘catalase’. Since then much work has been done on bacterial catalase; but none of it has been directed towards elucidating the chemical nature of the enzyme and no attempts have been made to isolate it in a pure state from any micro-organism. A similar state of affairs exists in regard to the majority of the intracellular enzymes of bacteria, which have been little studied in comparison with their counterparts in animal tissues. One reason for this is undoubtedly the technical difficulty of liberating such enzymes from the bacterial cell. Most of the techniques hitherto used for destroying the cell wall and liberating intracellular enzymes (for example, autolysis, drying, shaking with glass beads or grinding with powdered glass, the roller-crushing mill, ultrasonic disintegration) either tend to be destructive of labile enzymes, are difficult to employ on a large scale, or require specialized apparatus.