Abstract
Lethally irradiated mice received a transfusion of normal bone marrow cells from the same strain mice. The transfused colony-forming cells (stem cells) were settled in the spleen of the recipient and proliferated in it into erythroblast colonies. Some of these mice were given chloramphenicol or thiamphenicol for 7 days after marrow cell transfusion. Annulate lamellae were frequently observed exclusively in the erythroblasts of the mice received a injection of thiamphenicol.