The author, about the improvement of bone-marrow hematopoiesis, presumed in Part I that the blood vessel function might be one cause; in Part II, concluded that the reticuloendotherial system should be sound a prior, and as was told in the so-called "autohormone theory" it might be due to the particular hormone-like function which is proper to that extract. Accordingly, in this part, in order to exactly verify whether the bone-marrow extract would be influenced directly to the medullary parenchymal Hematopoiesis or not, the author added that extract to bone-marrow tissue culture and inspected its growth rate, wandering velosity, and changes in quantity of hemoglobin as well as in number of blood cells. First, taking observations of the growth rate of bone-marrow tissue, and the wandering velocity of intramedullary pseudoeosinocytes, under culture in cover slips, it was known that the addition of extract in a proper density improves remarkably the growth of tissue, and that the main purport of its growing process roughly coincides with non-added case as well as with controls. Also, the wandering velocity as well as time of continuance of the pseudoeosinocytes, though it was remarkably inhibited when the extract proved very dense, almost receive no other influence, and no significant differences with the controls could be discovered; i.e., the author could perceive that the increase in tissue growth rate by adding the bone-marrow extract was no result of activation of cell wandering, but it owes to the stimulation of growth in parenchymal cells themselves. Moreover, taking observation of the effect of bone marrow extract on the increase of hemoglobin as well as red blood cell number, under the culture in fluid medium, it was clarified that a certain of extract in a proper density brought about a marked increase in the amount, proving the existence of direct function by the extract. All through 3 reports the author have vindicated the fact that the improvement of medullary hematopoiesis by parenteral administration of so-called bone-marrow substances, may be caused not only by the vessel function, but also by the function of bone-marrow substance which has power to advance hematopoietic function.