An electrical counter for cell population studies.

T H E R E are on the market automatic counters which can rapidly assess the percentage of cells in a population which have a single simple characteristic. An excellent example is the Coulter counter which can assess the size distribution of the cells in a suspension by means of the change in electrical properties that they cause in the surrounding fluid. Another is the scanning microscope which can count dark points (e.g. stained cell nuclei) or changes in optical density (e.g. grain boundaries in metal specimens). There appears to be no apparatus commercially available to ease the labour of assessing the frequency of several cell characteristics at the same time, where these characteristics are complex enough to require to be recognized by the human brain rather than denoted by simple physical properties. For instance, it would be difficult and expensive to devise a computer capable of recognizing the different stages of mitosis.