A fluctuation of latent infection of japanese encephalitis accoring to the age was studied by means of neutralisation and complement fixation test in Tsukurimichi district of Shinminato City of Toyama Prefecture.
1) The minor age group demonstrated a lower rate of positive neutralisation test. It was the same with the mean value of neutralisation logarithm.
2) With the complement fixation test no difference regarding the age was demonstrated in the positive reaction rate as well as in the rate of positive and negative conversion rate, revealing that the incidence of latent intection is approximately the same among all age groups.
3) The annual rate of positive conversion was computed as 5.7-8.5% according to the neutralisation test and 5.2-10.3% according to the complement fixation test.
4) Among the four groups classified according to the resulfs of both tests the mean value of neutralisation logarithm were lowest in the group with negative results of both tests.
5) From the rate of positive neutralisation test, the mean value of neutralisation logarithm according to the age and the com5ihation of both tests it was concluded that the group under 15 years of age was least infected.
6) The age with 50% positive neutralisation rate lay around 13 years of age in this district.
7) Compared with the age distribution of manifest infection in three prefectures of Hokuriku during this investigation the minor age group appeared to show the highest incidence of manifest infection. This coincided well with the fact that the rate of positive neutralisation test and the value of neutralisation logarithm were low in the minor age group and high in the adult group and also with the fact that the incidence of latent infection was approximately the same with all age groups.

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In this communication a report is made on the isolation of the Behcet's disease virus. The results are summarized as follows.
(1) The new four strains of the agent of Behcet's disease were obtained from the foci (Matsumura strain: aphtha of the mouth; Fujiyama strain: ulcer of the sexual organ; Gotoh strain: ulcer of the sexual organ and the Vitreous body; Mori strain: thevitreous body) of the patients by the inoculation on chorio-allantoic membrane of developing chick embryos.
(2) The agent was inactivated at 56°C for 30 minutes.
(3) The agent passed readily through Seitz UK filter. By the routine staining and cultivating methods no other microbes have been found in the pathogenic material. This agent, therefore, is to be considered as a filtrable virus.
(4) The virus propagates in the fertile egg, especially on the chorio-allantois where it produces small pocks (pock formation form) and diffuse thickness of the membrane (diffuse form) and 10^-8.0 in chorio-allantoic fluid.
(5) Developing chick embryos yield virus titers as high as EID₅₀ 10^-9.5 to 10^-8.5 in chorio-allantoic membrane.
(6) The sera of such patients and immunized animals neutralize specifically the virus when tested by inoculation on the chorio-allantois of developing chick embryos.
(7) The neutralization tests revealed that this virus was not related to herpes simplex virus.
(8) The virus does not show positive pathogenicity to the mouse, but causes death in the guinea pig.
(9) The virus produces an iridocyclitis with hypopyon in rabbits.
(10) No characteristic inclusions have been found in the chorio-allantois infected with the virus.

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