, DE DUVE and WATTIAUX 1966; , September 1975 E. Perspectives 1 1. Definitions . General Functional Categories 2 1. Outline of Lysosome Functioning in Phagocytes 3 1. Characterization of Lysosomes . . . . . . . . . . The Lysosomal Enzymes . Cytochemical Methods . . . . . . . . . . Cytochemical Studies of Exogenous Tracers .