With the purpose to study the toxic substance contained in the gastric juice of the patients with gastric cancer the author observed the tissue growth and pseudoeosinophil function by performing rabbit bone-marrow tissue culture and also observed the functions of the erythrocyte series in the fluid medium tissue culture; and obtained the following results: 1. The tissue growth in the rabbit bone-marrow tissue culture loaded with gastric juice from gastric cancer patients is diminished as compared with that of the control. 2. In the case loaded with the gastric juice of gastric cancer the wandering velocity of pseudoeosinophils is lower in the majority of the cases when compared with the control. 3. Pseudoeosinophils with vital staining in the case loaded with the gastric juice are stained earlier and deeper and also fade earlier than the control. This fact seems to be due to the diminution of functions of cells. 4. There is no significant trend in the fluctuations of the erythrocyte counts and Hb content in the tissue culture by fluid medium. 5. From these findings it is assumed that the toxic substance of gastric juice from gastric cancer acts directly on the bone marrow and thus decreases the leucocyte functions but for the erythrocyte series it has no direct action on the bone marrow.