Quantitative aspects of transplantation of experimentally induced tumors of the nervous system.

Quantitative aspects of transplantation have been studied experimentally in ethylnitrosourea-induced nervous system tumors. The number of cells needed for successful transplantation, the biological behaviour-increase of malignancy-of the tumor in relation to the number of cells used during the various passages, and the relationship between number of grafted cells and induction time have been examined. A "critical" number of cells was necessary to ensure a positive result; thereafter, the induction time was directly related to the logarithm of the number of cells implanted.