After inducing experimental anemia in guinea pigs by the intraperitoneal injection of the anti-serum of the bone marrow and by culturing the bone marrow of these animals in a fluid medium, the author observed the changes in the number of erythrocytes and the hemoglobin (Hb) content. The results are as follows: 1. In the bone-marrow cell suspension of experimental guinea pigs erythrocytes decrease in number along with the lapse of time in all cases, while in the normal guinea pigs, the control, the number of erythrocytes increases gradually up to six hours after the initiation of the culture, and it begins to decrease only thereafter. Namely, the proliferation of erythrocytes in the test bone marrow diminishes to a greater extent than that of the control, and it further declines along with the lapse of time, clearly demonstrating the impariment of the proliferation of erythrocytes. 2. As for the rate of increase in Hb in the course of the culture no marked difference can be recognized between the test animals and normal guinea pigs.