[Chromosome study in leukemic C57Bl mice].

Whereas the incidence of spontaneous leukemias is extremely low in the C57Bl mice, the exposure of young animals to fractionnated X-ray doses can induce up to 85% of lymphosarcomas. The i.p. injection to isologous mice of acellular extract of spleen or lymphnodes from such leukemic animals results in the apparition of reticulosarcoma in the treated animals. Most of them die within three to four months. Our cytological observations performed at different intervals of time after i.p. of RadLV failed to demonstrate the presence of numerical or structural chromosome aberration in the leukemic animals.