In order to cause chronic infection, each virus of Ishihara, Kanamitsu and Noda strains was inoculated into 37 canaries (Serinus canaria), 33 siskins (Chloris sinica minor T. & S.) and 20 love-birds (Uroloncha domestica). During this chronic infection course of about 6 months, the author studied the interrelation between the pathologic changes of the liver and lung and the white cell count and blood picture. By the intrapectoral inoculation of the emulsion of virus-inoculated mouse liver or embryonated egg, though a few lethal cases were observed, in most cases there was established the so-called inapparent infection which showed clearly the tendency of chronic infection. Remarkable leucopenia was observed at high percentage in the early stage of infection. Severe increase of atypical leucocytes, which happened in the same stage as that of leucopenia, was a characteristic change together with the appearance of the vacuole-degenerated leucocytes. In the liver, various remarkable changes resembling to thoes in the hepatitis liver of human being appeared: round cell infiltration in the periportal connective tissue, liver cell degeneration full of varieties such as nodules and necrotic changes and the localized necrosis scattered in the intermediate parts of acini. Especially in the lethal cases of siskins (Chloris sinica minor T. & S.) which showed many lethal cases, very severe necrosis and cell infiltration were observed. This fact seems to suggest that chloris sinica minor T. & S. is the most susceptible of all kinds of tested fowls. On the other hand, in the lung there were observed the mesodermal cell infiltration, interalveolitis, hemorrhage around bronchi, alveoli and blood vessels. These changes in the lung appeared later than those in liver, and persisted for 6 months.