Smithburn and others (1) have described that nine out of ten mice proved fatal showing a cerebral symptom 6-8 days after intracerebral inoculation with the serum obtained from an African native woman aged 37, having suffered from fever at Omogo, West Nile District, Uganda, in December 1937.
The virus was identified later as of a neurotropic nature and named the West Nile virus through its characteristics made clear in experiments on mice and monkeys, and the case mentioned above was in the event also ascertained to have been as such through the fact that the neutralizing antibody against the virus was proved in the serum, although no cerebral symptom were then complained of. The virus is known to have a relation to some extent to Japanese B encephalitis virus (2), as it is found neutralized more or less by the immune sera of those viruses. The same results were obtained by us as to its character and the immunological aspects having received the strain through the courtesy of Dr. Hammon. Furthermore it is of interest to make clear that mosquitoes would be also responsible for spreading the West Nile virus as in the other arthropod borne encephalitis. The most encephalitis which would break out during summer time are known to be spread by mosquitoes (Simmons (3) ), as have reported repeatedly in our previous papers (Mitamura (4) and Kitaoka (5) ) . Anyway an experimental transmission of the West Nile virus was undertaken by us. While carrying out experiment we realized that Philip and Smadel (6) reported that the West Nile virus was experimentally transmissible by Aedes albopictus and Smithburn (7) proved by means of the neutralization test that the virus was found inconceivably wide spread throughout Central Africa.

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Russian spring-summer encephalitis (RSSE), known as forest encephalitis or tick borne encephalitis, is disease Smorod.intseff and his co-workers (1) have made clear of its epidemiological aspects, causative agent, mode of infection and preventive measures during the years 1937-39. The disease prevails mainly in the Far-Eastern Russian terriory and is also reported since 1932 in European Russia and in Siberian woodlands. Kitano (2) has reported of the disease breaking out on the Manchuria-Soviet Frontiers and was successful to isolate the causative agent. Kitaoka (3) also mentioned that the disease was reported among those Japanese war prisoners engaging in wood-cutting at Sosoevka woods beyond the highlands in the north of Vladivostock in the II World War and the disease was found breaking out during the course of April 19 June 20, and about 10-16% of the total workers have contracted it, resulting in 19-50% casemortality. Symptoms, after invasion of the virus, and as far as to the studies on the neutralizing antibody in the convalescent serum are discussed about in, the report too.
The virus is spread by Ixodes persulcatus Schuize, a species of wood tick and it was also made clear by Pavlovsky (4) that Eutamia asiatica, a rodent, is known as reservoir.
Casals (5) and Hammon (6) have described that causal agent is not single and there are two types, the Far Eastern and the Western types, which Kitaoka (3) has also approved by the neutralizing test with the convalescent serum from the RSSE patient and has made clear that the former type is peculiar in the nervous disturbances and extrapyramidal symptoms, while the latter chiefly presents symptoms from irritations on meninges (Yamazaki) .
Smorod intseff (1) has mentioned of the disease being not spread by mosquitoes. But it is of interest to see if it may be transmitted by mosquitoes because the vector of the encephalitis occurring in summer season is, as Hammon (6) and Kitaoka (7) have mentioned, mainly a mosquito. The RSSE prevails most vigorously during late. spring towards the summer when mosquitoes grow thrivingly. Well an experimental study on transmission by mosquitoes of the RSSE viruses namely, the Sophy strain (Far Eastern type) and a Western type, which were given from Dr. Hammon was carried out.

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The synthetic medium for Shigella dysenteriae which has hitherto been known contains many amino acids and also niacin-amide, although the necessity of which remains obscure (5, 11, 12) . We have been examining the process of the evolution of the bacterial nutrition (or the retroevolution), especially about the nitrogen source. It is the purpose of this paper to report the nutritional nitrogen source for Shigella dysenteriae and also the significance of niacin-amide in its synthetic medium.
The strain used in this experiment is Shigella dysenteriae (Shiga type, Hanabusa) kept in N. I. H. of Japan. In the beginning Shigella dysenteriae was cultivated in the chemically defined medium as similar as possible to that of Dorfman et al (5) . One by of a amino acids were eliminated, until the minimum requirement of nitrogen source was determined as glutamic acid. Further experiments were designed to test the dispensability of niacin-amide along the growth curve in this medium. Since niacin-amide was not found always indispensable in this case, the content of niacin-amide-like substance was examined quantitatively.

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Evolutional steps of -nitrogen requirements of bacteria have been set up as follows. N₂-NO₃-NH₄-amino nitrogen-amino nitrogen+growth factor. Dysentery bacilli belong to the last step (3, 4, 6) . As shown in the preceding report (5), Shigella dysenteriae (Shiga type) belongs to the transition zone between the last two steps. We wanted to determine the nitrogen requirements of dysentery bacilli as the mother group of Shigella dysenteriae (Shiga type) and the dispensability of nicotinic acid amide in this group. We now present the results obtained concerning standard 12 strains of dysentery bacilli of Japan.

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Many antibiotic substances have been isolated in the field of streptomyces, and among them, aureomycin (1), xanthomycin (2), aureothricin (3, 4) and luteomycin (5) are yellowcolored. A strain which had been isolated about two years ago showed a new antibacterial spectrum which differed from those of streptomycin, streptothricin A (6), streptotjiricin B (7), grisein, chloromycetin and aureothricin. Further studies isolated a crystalline yellow antibiotic and another reddish brown antibiotic from the fermented broth. Comparing the former with descriptions of the above mentioned yellow crystalline antibiotics, the former is different from the latters. It seems to be a new antibiotic and the writers named it as griseolutein.
It inhibits the growth of gram-positive and negative bacteria and it is nontoxic. In the present paper, the characters of the strains and of griseolutein are described.

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This paper describes a simple and quick method for determination of free and combined cholesterol in, serum. This method requires less hours to complete the determination as compared to the older method which requires at least twenty-hours. The total choleterol is first determined by Zuckerman's method (1) . Combined and free cholesterol are determined on the chloroform extract with the aid of digitonin. Free cholesterol is in the precipitates with digitonin and the combined cholesterol remains in solution. This method is quicker and more convenient than the method of Shoenheimer (2), Sperry (3), or Pijoan (4) .

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