A method and apparatus are provided for differentiating cells in an automated particle analyzer, such as for use in hematological analysis, by measuring apparent cell size (or volume), membrane integrity and intracellular complexity ("voltaic fragility"). The cells are suspended in a selected reagent mixture including an electrolytic fluid, such as diluent, and if necessary, one or more membrane-modifying agents are selected and mixed in relative quantities in order to selectively alter the membrane structure (i.e., the membrane integrity) of certain cells and thereby enhance cell discrimination. A predetermined dc voltage is applied across a sensing orifice to thereby create a dc electric field within and around the orifice, and the reagent mixture is passed through the center of the orifice. The magnitude of the change in current flowing through dc electric field is measured in response to the passage of each of a plurality of cells therethrough, and based on the measured change, a signal is generated for each cell which is indicative of the apparent size (or volume), membrane integrity and intracellular complexity of that cell. A visual display, such as an alphanumeric and/or graphical display, is then generated based on the signals facilitating differentiation of the cells.
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