The transplantation of small numbers of tumor cells.

inoculum containing 80 cells. Over 5 million cells were needed to give 100 per cent takes. With mouse adenocarcinoma db & B, the smallest num ber of cells necessary to induce tumors was eight een (three takes out of 57 mice). For 50 per cent takes, 300 cells were necessary; for 100 per cent takes, 2,590 cells were required (4). Hewitt (1), working with a cell suspension of a spindle-cell carcinoma in C3H mice, found that 80-90 per cent