1. A new histochemical method is described for arylsulfatase activity (ASA) in hemic cells and organ imprints. Some common limitations in histochemical technics have been tested and appear to be minimized in this method.
2. With the present method, a wide series of hemic cells may be identified, and their ASA separately graded from 0-4.
3. A study has been made of normal ASA values in all series of human hematopoietic cells and of neutrophilic granulocyte ASA in common laboratory animals. Eosinophils, megakaryocytes, and neutrophils have the highest ASA. Increases in ASA occur early during cell maturation in neutrophils and eosinophils.
4. Humans have a higher ASA than the laboratory animals tested. Within certain species, there is some general correlation between neutrophilic granulocyte ASA and ASA of other organs. Under these conditions, leukocyte ASA is a potentially useful general screening method for ASA.
5. Some factors which enhance or inhibit leukocyte ASA have been tested.