In order to observe the cell function of peripheral leucocytes of normal persons by means of tissue culture, the author studied the wandering velocity, carbon-particle phagocytosis and neutral-red vital staining of cells from various angles; and arrived at the following conclusions: 1. Neutrophils begin to wander about actively already after 3 hours' culture, and after 6 hours' their behavior becomes still more vigorous, showing the maximum wandering velocity at this stage; but thereafter it gradually decreases, and after 24 hours' the wandering becomes very sluggish. 2. In pursuing the carbon-particle phagocytosis of various leucocytes, neutrophils and monocytes reveal a marked phagocytosis; especially the phagocytosis of monocytes is highest, followed by that of neutrophils; but no phagocytosis can be recognized in eosinophils, basophilocytes, and lymphocytes. 3. The average phagocytic capacity of neutrophils after 6 hours' culture reaches its maximum, but thereafter it declines very slowly. 4. As for the degree of stain to neutral-red vital staining in various leucocytes, at first a few granules in neutrophils and monocytes are stained lightly, but with the laspe of time numbers of these granules gradually increase and these stained granules. swelling up by confluence, present a peculiar arrangement in a form of rosette. In eosinophils and lymphocytes all granules are stained light red, and in basophilocytes these are stained deep red. All these granules are stained almost simultaneously, but the confluence of stained granules are not so marked. 5. The neutral-red vital staining of neutrophils is quite high already at the early stage of culture, and reaching the maximum after 3 hours' culture, thereafter it gradually begins to fade and 9 hours' after it is about the same degree of stain as that immediately after the addition of neutral red. It is almost completely faded after 24 hours' culture.