ABSTRACT
Although the explantation of cells from a multicellular organism into an extraorganismal environment, that is, tissue culture, had been known since the beginning of this century, it was not until the early 1940s that Earle and associates (cf. Earle and Nettleship, 1943) attempted to induce the neoplastic transformation in cultured mammalian cells. These now classic experiments, which were carried out by the addition of polycyclic hydrocarbons to cultures of mouse fibroblasts, were monitored by the inoculation of treated and untreated cell cultures into host animals. Unfortunately the results of these experiments were ambiguous, since neoplasms arose in the test animals whether treated or control cultured cells were inoculated. As a result, the question of the feasibility of carcinogenesis in vitro lay dormant for almost two decades. However, the cells from these experiments have been maintained, even up to the present day, as the L cell line (cf. Jackson, 1991).
