An automatic recording cell counter for monitoring growing populations of unicellular micro-organisms.

Modifications and readily assembled accessories are described for converting the manually operated photoelectric Fisher Autocytometer blood cell counter into a versatile automatic sampling and recording monitor for following growth curves in axenic unicell populations. Three versions of this equipment have been developed, between them covering a wide range of cell densities extending from a few dozen to 500 000 cells per ml. A batch sampling system is used for handling very low cell densities, continuous sampling with autodilution is used for high cell densities, and a recently developed model, in which the sample is pumped continuously through a sterile counting loop and returned to the parent culture, is suitable for use with very small culture cuvettes.