Abstract
Certain problems in erythrocytogenesis have been studied by means of the in vitro culture of bone marrow. A few conclusions have been reached by this method:
1. Liver extract stimulates production of mature erythrocytes.
2. Plasma contains substances which stimulate the production of mature erythrocytes.
3. Plasma in anemic individuals (anemia of bleeding) probably contains substances which stimulate the production of mature erythrocytes; and the greater the anemia, the greater the stimulation.
4. Mitoses do not account for the production of mature erythrocytes from erythroblasts. Erythropoiesis rather occurs in two stages, in the first of which mitosis is of prime importance, and in the second of which gemmation of erythroblasts is the main mechanism.