EN
In the course of investigations on viral etiology of bovine leucoses, the necessity arose of obtaining continuous cultures of cells representing anatomo-pathological changes typical for this disease. The hitherto investigations carried out mainly by Chatziolos and Chang (2) and Dutcher et al. (1), are insufficient, as they comprised observation of too simall number of passages of such cells. Only observations of many passages of such cells can secure sufficient number of basic data for further investigations on cancerous transformation and on agents specifying the transformation processes.