Means for counting particles suspended in a fluid by Wallace H. Coulter (1953)

Original patent US2656508A, filed 27 August 1949, granted 20 October 1953. Description of Figs.1–4 and 6–7: conductive suspension, constricted current path, individual-particle pulses, measured sample volume and dilution; masking when particles coincide. Primary scan linked from record.