Cultures in coverslips of femur bone marrows of unilateral sympathectomized rabbits were compaired with each other side on the following 3, 5, 10, 15, 20, 30 and 90 days. The results obtained were as follows: (1) The wandering velocity of neutrophils of bone marrow of the sympathectomized side is larger than the another side, especially on the 5 th day after the operation. (2) The relative growth rate is larger than the other non-operated side on the 5 th and 10 th days after the operation. (3) The cell dencity is strikingly larger in the sympathectomized side on its 3rd, 5th, 10 th and 30th day groups after the operation. (4) Each figures show the maximum on about 5th day group after the operation, and after 30 days the results did not appear to differ between both sides, and these effects are transitory. Thus the interception of the sympathetic in rabbits promotes the function of the bone marrow transitorily. In other words the sympathetic reduces the function of the bone marrow.