By adding the serum of patients with varicus blocd diseases to the medium of bone-marrow tissue culture of rabbits, the author studied mainly its influence on the vital staining of pseudoeosinophils with neutral red. At the same time the author pursued vital staining of neutrophils in the bone marrow of the sternum from the same patients with neutral red; and as for the verification of the study, the cells that had been cultured for several hours were vitally stained. As the result the author arrived at the following conclusions: 1. When the cell functions (wandering velocity and carbon-particle phagocytosis) are low during the tissue culture, vital staining by neutral red takes place fast and highly but the stained color fades quickly. 2. ...