Passage of the anemia from rat to rat was accomplished with cell-free material, and electron micrographs of the erythroblasts showed numerous C-type particles characteristic of the murine leukemia

In a recent report, we described a fulminant anemia in rats that were inoculated at birth with our stocks of Abelson virus (3). This anemia was apparent within 2 weeks, and many rats died shortly thereafter with a red cell count as low as 1 x 106 cells/cu mm. Passage of the anemia from rat to rat was accomplished with cell-free material, and electron micrographs of the erythroblasts showed numerous C-type particles characteristic of the murine leukemia sarcoma complex (2). We report now evidence that the anemia-inducing principle is separable from that inducing stem-cell leukemia, that this anemia virus is a distinct entity, and that it is a member of the leukemia-sarcoma complex of murine viruses.