The transplantation kinetics of tumour cells.

The data from a dilution assay can be used not only to form an estimate of the TD50 (or log TD50), but also to throw light on the transplantation kinetics of tumours. Transplantation "by single cells" is the simplest sort of kinetics, and some tumours, of which we have given two examples, will transplant by single cells. Other tumours consistently transplant with anomalous kinetics-i.e. non-single-cell. A sensitive statistical test for single-cell behaviour has been developed, and we give three examples of tumours that clearly fail the test. The mechanism by which these anomalous tumours depart from single-cell behaviour is unknown, but we suggest an approximate statistical analysis for their assay.