ABSTRACT
Other experiments3 ,4 have demonstrated that for many {Tetrahymena) cells suspended in shallow culture dishes, the cells rapidly ( 2 0 s) aggregate to give a characteristic signature pattern (polygonal net). The honeycombed patterns change repeatedly when chemicals alter the culture media (water), and using image analysis of the aggregation patterns, chemical toxicity could be scored accordingly. This advance took away the capital investment in microscopes and technician time required by Silverman’s test, 1 but nevertheless demanded an extended time for culturing cells to high enough densities (million cells/ml). The assay’s aim was to make the advantages of
the single-cell method more widely accessible to smaller labs or for field tests where microscopic observation and individual cell counting might prove impractical.
