On the basis of the results obtained in Parts 1 and 2 the author studied the erythropoietic and leucopoietic functions in cancer patients by means of bone-marrow tissue culture and also observed the wandering velocity, vital staining and carbon-particle phagocytosis of neutrophils appearing in the growth area; and obtained the following results: 1. The tissue growth in cancer patients is diminished fiarly markedly as compared with that in normal persons, the control. 2. Although there are cases showing the wandering velocity of neutrophils almost at the normal level, in more than one half of them the wandering velocity seems to be slightly lower than that in the control. 3. By the vital staining of neutrophils the function of the cells is likewise diminished as compared with the control. 4. The carbon-particle phagocytotic ability of neutrophils is also diminished when compared with the control. 5. By the bone-marrow tissue culture in a fluid medium it has been observed that on the whole erythropoiesis tends to show a slight decrease while Hb content a slight increase as copared with the control. 6. From these the leucopoietic function of the bone marrow in various cancer patients is somewhat diminished, and also judging from the wandering ability, finding of vital staining and carbon-particl phagocytosis, function of neutrophil is similarly decreased, but the erythropoietic function of the bone marrow can not necessarily be judged as to have declined.