Abstract
Cell free filtrates from the liver and spleen of MR leukemia rats, induced by exogenous carcinogens, were injected into newborn and 4-week-old rats. Myelogenous leukemia developed in 24% of the newborn group after a latent period of 520 days, and in 30% of the 4 week old group after 570 days. The induced leukemias were transplantable. Many of the injected animals which did not develop leukemia died of hepatic cirrhosis.