1. The greater is the amount of Extromelia virus incoculated intraperitoneally the earlier is the onset of the symptoms and death of mice, revealing a straight live rise in the erythrocyte agglutination value. In contrast to the serum affinity antigen-antibody reaction observable in the groups inoculated with a small amount of the virus, both groups inoculated with virus supernatant diluted 20-fold and 100-fold respectively show relatively or absolutely no reaction and die. 2. The toxicity of the so-called concomitant substance is trivial. 3. When the mice with incomplete immunity are reinfected with Extromelia virus, the pathological picture is controlled only by the quantity of the virus Inoculated. 4. When the mice infected with Extromelia virus are enforced to labor, these animals die at the early stage of the onset of symptoms and the recovery mechanism of pathologic changes is delayed. 5. Therefore, the principal cause of the electro-shock hepatitis lies in the toxicity of the virus and the quantity of virus inoculated and it is in no way associted with the incomplete immunity. Moreover, the enforcing labor seems only to aggravate the pathologic conditions of the animals, showing absolutely no process of recuperation and extremely little infiltration of round cells. 6. Histological changes are especially marked in the liver, spleen and bone marrow; and in the lung, hemorrhagic interalveolitis and nephro-nephritis can be recognized in the kidney. 7. Pathologic changes at the peak of the infection in the animals inoculated with a great quantity of Extromelia virus resemble closely to the histological changes of viscera in the human electro-schook hepatitis; and in the case inoculated with a relatively large amour. of the virus the changes resemble to the visceral histological changes at the peak in th. human hepatitis. Moreover, the histological picture of the liver during the period from the virus inoculation to the peak of the infection and the same in the animals escaped the death, taking the similar course as at peak of the human hepatitis observable by the biopsy, resemble the picture of the liver in the human hepatitis at the later stage of recuperation. 8. The pathological picture in the mice infected with Ectromelia virus closely resemble that in the humsn infectious hepatitis and both seem to revel mesenchymal tissue reaction as the basic histological changes.