The author studied various conventional methods of bone marrow tissue culture in fluid medium and its history, and compared these methods with a modified form of own design, and obtained the following results: 1. With this modified method a series of rabbit bone marrow tissue culture in fluid medium has been performed and studied hematopoietic effects of inorganic ferrous and ferric compounds and organic ferric compounds by adding each of these compounds to the medium. As the results it has been found that ferric gluconate proves to be the most effective hematopoietic, moreover, when this compound is added to the medium along with serum, Hb content increases strikingly, thus indicating that serum is an indispensable factor Hem synthesis. 2. Among iron compounds other than ferric gluconate no appreciable difference can be found in their hematolwietic effectiveness, at least from the standpoint of its direct action in bone marrow, it is not the valency of iron itself nor organic or inorganic nature, but rather the form of the compounds, that will have any bearing on the utilization of iron for the production of Hb.