The cellular morphological description was attempted by the investigation of myelogram in 20 of normal mice and the hemogram and myelogram were also observed on the mice with the intraperitoneal inoculation of liver emulsion of ectromelia virus 10(9) LD(50) in the dilution of 10(2) and 10(7) under the control of myelogram in normal mice, and then the mode of bone marrow in the infection of hepatitis virus was observed. comparing the above results with the myelogram of epidemic hepatitis in human and analysing the origin of the significant changes shown on the hemogram. And the results wene as follows. 1. Signifcant change was not observed on the erythroblast system. 2. The myelogram showed a parallel change to the peripheral hemogram in severe cases with remarkable leukocytosis and neutrocytosis on the peripheral blood picture. 3. The monocytosis and the appearance of plasma cells and plasmoid cells in mild cases had no direct relation to the bone marrow and it was thought that the origin of this reaction should be searched on other system, except bone marrow. 4. The myelogram in this experiment was relatively agreed with that of epidemic hepatitis in human, and it was thought that the main change was on the neutrocyte system.