In investigating how long it takes the bone-marrow circulation to recover after the ligating of the principal nutrient vessel of a rabbit femur with Radioisotope P(32) as a tracer, the following results were obtained. 1) When the principal nutrient artery of a fully grown rabbit is ligated, the bone-marrow circulation is about 20% of control within the lapse of one day, but the recovery by the collateral circulation is by degrees seen and the complete recovery is realized in one month. But some recovers rather more quickly, the other slowly, by each individual difference. 2) When the principal nutrient artery of a young rabbit femur is ligated, the recovery of the bone-marrow circulation is rather slow than that in the case of a fully grown rabbit. That is to say, the connection of the principal nutrient artery with the other nutrient artery in a young rabbit is worse than that in the case of a fully grown rabbit. 3) When the principal nutrient vessel of a fully grown rabbit femur is ligated, the bone-marrow stagnation recovers in the early stage. This is caused by the same reason as that expressed in the 3) item of the part 2.