Although several noteworthy data have been obtained by clinical application of bonemarrow tissue culture, in view of the complexity of its procedures we have devised a simple method of bone-marrow tissue culture modified from the cover-slip method for the purpose of a still wider clincal application. By observing the bone marrow of the sternum of healthy persons by means of this method, the following results were obtained: 1. The medium was consisted of a drop each of normal human serum and vitamin B(12) solution placed on a tissue culture plate of our own device, and the best results were obtained by the vitamin B(12) solution (containing 100 r/cc) to be added to the serum; and the most suitable space-distance between the surface of the slideglass and the coverglass was in the range of 150-200 μ. 2. In the determination of the relative growth rate, cell-density index and the wandering velocity of mature neutrophils in the bonemarrow tissue culture of the sternum of healthy persons, within 24 hours of the culture the results obtained resemble quite closely to those obtained by the conventional method of tissue culture, proving that this method is sufficiently worthy of clinical application even though the shortening in the duration of arresttime in all cells can be observed.