Relative to the determination of O(2)-consumption and glycolysis with the use of Warburg's apparatus, as one of the methods in tracing bone marrow functions, the authors have carried out comparative studies on the following three methods by using the same normal domestic rabbits. METHODS 1. Slicing method is a method in which two Graefe's knife are used as to obtain the slices of bone marrow in the thickness, the socalled limit slice. 2. Homogenate method is a method in which the precipitate of bone marrow is obtained after homogenization and centrifugation. 3. Boring method is a method in which punctuate is obtained from a given portion of the tibia by aspirating it as rapidly as possible at the pressure of -10 mg. Hg. RESULTS 1. The bone marrow pictures observed both in the slicing and in the homogenate methods presented rather similar findings, while in the case of the boring method it revealed the increases of the pseudo-eosinophiles, the mononuclear, and the polymorphonuclear leucocytes as well as a marked proliferation of lymphocytes, mixed with some peripheral blood. 2. The impairment of cells has been found least in the case of the slicing, followed by tho homogenate method, and the geatest in the boring. The boring method, however, has advantages of making over-all course observations of the same individual possible and it is simpler to manipulate, but it also has disadvantages of giving lower values of O(2)-consumption and glycolysis, and a greater error in the evaluation. As for the determination of O(2)-consumption values in the slicing method, the values yielded are highest and the lowering rate of value during the observation period is least. For the determination of anaerobic glycolysis, the values obtained by the homogenate method have been found to be highest; while in the case of the slicing method, more constant values with respect to the elapse of time during observation has been obtainable. From these results I have reached a conclusion that the slicing method is the best of the three methods for the determination of O(2)-consumption and glycolysis in the rabbit bone marrow.