With the planimeter the author measured the area of splenic dullness in normal persons, patients with infectious hepatitis. liver cirrhosis, cholcystopathia, mechanical jaundice, endocarditis lenta and several patients with other diseases, and obtained the following results. 1. The expansion of area in the spleen can be recognized in 93 per cent of acute hepatitis and in 62.2 per cent of chronic hepatitis. Moreover, splenomegaly is marked at the initial stage of the acute case, and in most cases it disappears within about 50 days. In the chronic hepatitis generally splenomegaly disappears in about 60 days, but in some it persists for a relatively long period of time with poor prognosis. 2. Since in infectious hepatitis the low palpability and highly expanded area of dullness are the evidences of splenomegaly, an emphasis need be placed on the importance of measuring area of splenic dullness in diagnosing this disease. 3. In infectious hepatitis the swelling of the liver has a considerable correlation with the swelling of the spleen, and moreover, the greater the swelling of the liver, the correlation can be said to be that much closer. However, even in the case where the liver is unpalpable, the swelling of the spleen can be quite great, and therefore, it seems difficult to decide at once the mutual realtionship between the two. 4. As for the relationship between the area of the spleen and the liver functions examined in infectious hepatitis correlation in not necessarily clear from the relationship between the spleen and the findings of Takata reaction as the serum colloid reaction, serum proteins, especially the albumin content, albumin globulin ratio, serum bilirubin titer and the degree of bilirubinuria and urobilinogenuria, but in the results of synthetic judgment and observations carried out in the course of disease a relatively parallel relationship can be recognized. 5. That in diseases other than infectious hepatitis such as in liver cirrhosis and hemolytic jaundice, a marked splenomegaly can be recognized, and in hepatoma, cholecystopathia, and mechanical jaundice with exception of a few cases no splenomegaly can be observed offers an important clue for the differential diagnosis of these diseases. Moreover, in endocarditis lenta and Basedow's disease likewise splenomegaly can be recognized though it seems natural from the cause of disease, this is important for diagnosis in the consideration of other symptoms. Splenomegaly can not be observed in gastric ulcer, lung tuberculosis, nephritis, polyneutritis and diabetes mellitus.