By means of bone marrow tissue culture method deviced by Hiraki, the author investigated the effects cytochrome C on the thrombopoietic function in bone marrow and obtained the following results. 1) Cytochrome C diluted in several concentrations was added to the bone marrow tissue culture of normal guinea pigs, normal persons and patients with various diseases. Average number of megakaryocytes in the growth zone and its thrombopoietic function were examined. As a result, it has been seen that the thrombopoietic functions of normal bone marrow added with an optimal amount of cytochrome C were moderately accelerated both in guinea pigs and human beings as compared with that of control added with saline. 2) The cytochrome C and each of three kinds of carcinostatic substances; mitomycin C,
trenimon, and carzinophyllin were added to the bone marrow tissue culture of normal persons the effects of these drugs on the thrombopoietic functions in the bone marrow were investigated. On the other hand, the bone marrow of guinea pigs of which bone marrow had been rendered to hypoplastic by repeated administration of the above described carcinostatic substances and then treated with repeated administration of cytochrome C were cultured. The thrombopoietic functions of megakaryocytes in these bone marrow tissue culture treated with cytochrome C were maintained moderately high as compared with the control treated with carcinostatic substances and saline only. From these results it could be concluded that cytochrome C has the accelerating effects on the thrombopoietic function of normal bone marrow as well as the protecting effects on the thrombopoiesis from the myelodegenerative especially thrombopoiesisinhibiting action of several carcinostatic substances.