In order to determine whether or not depot blood cells in the bone marrow are mobilized into the circulating blood at acute hemorrhage, as does the depot blood in other blood depot organs. Acute bleeding was applied to a rabbit and the change in hemogram of V. untricia femoris was observed. Secondly, an acute bleeding was applied to a rabbit of which the reticuloendothelial system was blocked with India ink, to observe how the blood finding of V. nutricia femoris will be effected and to compare this result with that of the first experiment. The findings are as follows: 1) When the rabbit was bled to the extent of 15 to 20cc per Kgm., the rate of decrease of red blood cells in the V. nutricia femoris was much less than that in the corresponding A. femoralis. Not only the number did not decrease, but it increased, reaching the peak 1 to 2 hours after the bleeding. Following the increase, however, the number gradually decreases until it becomes almost the same as the number of blood cells in the A. femoralis. The increase of white blood cells is much more rapid and distinct than the rate of increase of the corresponding A. femoralis blood; it marks the same peak as the red blood cell system 1 to 1 and a half hour after the bleeding. Such an increase of blood cells in V. nutricia femoris is due to the mobilization of marrow depot blood cells. From this, the bone marrow may be called one of the blood cell depot organs, having much significance in supplying blood cells to the blood circulation in case of acute hemorrhage. 2) On the other hand, no such blood cell mobolization can be seen when the rabbit with its reticuloendothelial system blocked with India ink is bled. Therefore, it is concluded that the sound functioning of the reticuloendothelial system is essential for the mobilization of bone marrow blood cells. 3) A marked contraction of the nutricia vessels was observed immediately after the bleeding, for both the non-treated rabbit and the rabbit with its reticuloendothelial system blocked with India ink. Though the contraction began to recover 30 to 60 minutes after the bleeding, the blood vessel did not recover its original diameter of before the bleeding, at least until the termination of the experiment.