A method is described for demonstrating leukocyte peroxidase activity in which benzidine dihydrochloride is used as the indicator compound instead of the more commonly used but potentially more hazardous benzidine base. The method is highly sensitive and rapid and permits the use of fixed blood smears and organ imprints. The incubation mixture, which incorporates safranin as a counterstain, may be used over and over again, for as long as 6 months. The method is also applicable to fresh frozen tissue sections.

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A rapid and simple method is described for demonstrating the presence of alkaline phosphatase activity in cells of blood and bone marrow. Smears were fixed with 10 per cent formalin in methanol at 0 ± 5 C. for 30 seconds and stained by the azo dye procedure, using propanediol buffer at a pH of 9.6. A "scoring" technic is outlined, which permits the comparison of alkaline phosphatase activities of blood leukocytes of different individuals. Alkaline phosphatase activity was found only in neutrophilic granulocytes and was localized exclusively in the cytoplasm of these cells. In normal adults, 43 to 95 per cent (mean of 78%) of all neutrophils were unstained. Staining was up to ten times more intense in smears from patients with a variety of pathologic disorders.