By determining periodically the O(2)-consumption and the anaerobic glycolysis in the bone marrow of the rabbits depleted successively 4 times the rate of 10 c.c. /kg., with the slicing and the homogenate methods mentioned in the previous report, and by tracing the effects of the sera of these depleted rabbits on the O(2)-consumption in the bone marrow of normal rabbits, the authors have obtained the following results: 1. As regards the rate of O2-consumption in the case where the slicing method had been used or that in the homogenate method, the rates in both cases tended to increase 24 hours after a single depletion, and it later showed a continuous rise. Whereas in those rabbits subjected to four successive depletions, the O(2)-consumption reached the highest point 24 hours afterwards, and on cessation of depletion and following the gradual recovery of anemia, the O(2)-consumption decreased concomitantly; and 9 days after the cessation of depletion the rate returned more or less to normal. 2. The rate of O(2)-consumption paralleled with the percentage of immature cells of the erythroblastic system as well as of erythroblasts in the bone marrow and with the increase of mitotic figures. 3. A slight increase of the anaerobic glycolysis Q(M)(N(2)) could be observed only during the depleting periods in the case where either of the two methods had been employed; and the periodic fluctuations of Q(M)(N(2)) tended to be similar to those of the O(2)-consumption. The rate, however, returned to normal 3 days after the cessation of depletion; and later lowering slightly, it finally returned to normal. 4. A parallel relationship existed between the lowering of respiratory and glycolytic ration (Q(M)(N(2))/Q(O(2))) and the percentage of the myeloid cells in the bone marrow. 5. Some substances promoting the O(2)-consumption of the bone marrow of normal rabbits were found to exist in the serum of the depleted rabbits previously mentioned; and the time of the appearance or the disappearance of these substances as well as their effects seemed to coincide with the amounts of O(2)-consumption of the bone marrow itself. 6. These substances found in the above-mentioned serum were found to be so heatresistant that they could not be destroyed even when heated at the temperature of 100°C for 30 minutes.