“…Initially consid ered to be a reticulum cell sarcoma (17,18) associated with a reactive erythroblastosis (19), it was suggested in 1962 by Zajdela (20), on the basis of both pathological studies and radio-iron uptake, that the primary disease initiated by Friend virus complex was a neoplastic proliferation of ery thropoietic elements. With both the Friend and the Mirand variants, the daily output of young red blood cells in infected animals is significantly augmented (24), and is associated with considerable ineffective erythropoie sis, a term for premature death of young nucleated erythroid cells (25,26). With both the Friend and the Mirand variants, the daily output of young red blood cells in infected animals is significantly augmented (24), and is associated with considerable ineffective erythropoie sis, a term for premature death of young nucleated erythroid cells (25,26).…”