The author studied the virological characters of the virus isolated by the Chick-embryo technic, and obtained the following results: Inoculation of the virus into the chorio-allantoic cavity of the 7 day old chick-embryo killed the chick-embryo on the 5th to 7th day after inoculation. The serial passage could be carried out by inoculation of the chorio-allantoic fluid or the chick-embryo liver, of which the latter gave a better result. The amniotic inoculation could kill the chick-embryo on the 4th to 5th day after inoculation, but LD(50) was lower than that by the chorio-allantoic route. The yalk sack inoculation could not give a good result. As for the distribution of the virus by chorio-allantoic inoculation, the virus could be best proved in the chick-embryo, particularly in the liver, the next in the chorio-allantoic fluid and very few in the other parts. The isolated virus easily passed Seitz E. K., Berkefeld N. and also Berkefeld W., though somewhat difficult through the last one; this fact suggests that the isolated virus is pretty small one. Though the infectious index of the virus to the chick-embryo varied with the generations of the passage, the average for 10 to 20 generations was 8.0. The isolated virus could be well preserved in the glycerin-salt solution.