1. 120 strains of Group A Coxsackie viruses isolated in Tokyo were typed by means of neutralization reaction. Of these strains 7 was isolated in 1951-52, 24 in 1953-54, 71 from herpangina patients and the remaining 18 in 1955.
2. As the results of typing 1 strain falls in A1, 33 in A2, 27 in A4, 28 in A5, 20 in A6, 2 in A8 and 9 in A10 types of Dalldorf's classification. Of 71 strains isolated from herpangina patients 26 belonged to A2, 10 to A4, 25 to A5 and 10 to A6 types.
3. In three herpangina patients two serological types were isolated at the same time from their stools.
4. Some discussions are made on the type distribution of Group A Coxsackie viruses in Japan in comparison with that of some other countries. Some considerations are also made on the relationship between the serological types of viruses and the clinical features caused by them, especially from the viewpoint of herpangina.

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The pathogenic organism of the Hyuganetsu disease, regarded as infectious mononucleosis, was isolated in Japan. However, many doubts remain in that the pathogenic organism is the causative agent of real infectious mononucleosis. On the other hand, the Tsutsugamushi disease seems to be included in the Hyuganetsu disease. The present authors have made investigations concerning the cultivation of the Nakazaki strain, which was isolated as the causative agent of the Hyuganetsu disease, in yolk sacs and the cultivation in tissues of whole embryonic mice. These results are obtained as follows:
1) The Nakazaki strain was successfully cultivated in yolk sacs only up to the 4th passage. 2) Cultivation in tissues of whole embryonic mice was successfully conducted. The infectivity of tissues increased to approximately 100-1000 times after 15 days of cultivation and the cultivation in vitro was successfully continued during at least 30 days by two passages.
3) At this time, the addition of hyaluronidase in the materials for inoculation promoted the establishment of infection and the cultivation was accelerated by this addition. 4) The pathogenic organisms propagated in the cytoplasma of cultivated tissues were either coccoid or oval in shape, approximately 0.3-0.4μ in diameter, under the photomicroscope. There was no remarkable variation compared with that of prepared from the living body.

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Electron micrograph of the pathogenic organism of the Hyuganetsu disease (Nakazaki strain) was made clear by the material which was obtained from the infected mouse brain by means of elution and differential centrifugation method. (Details of this method was shown as a table.)
This microorganism was either coccoid or oval in shape and approximately 0.3-0.4μ in diameter, but there is marked variation in size and shape. With the electron microscope one sees a distinct limiting membrane from which a central irregular plasmic mass has retracted, just like a rickettsia. On the other hand, some of them, in fact, resemble closely to the elementary bodies of psittacosis or lymphogranuloma venereum and the mean form between the above two forms was also observed.

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For the purpose to establish the method to classify the Rickettsia orientalis serologically, the possibility to produce OXK antibody in mice infected or immunized with it was tested.
After it was found to be possible to produce OXK antibody in mice by immunization with the killed vaccine of Proteus OXK, the following methods were tested to detect OXK antibody in mice. i) Mice were infected with the infective organ emulsion (spleen and liver of mice) through subcutaneus route with and without Freund-type adjuvant. Almost all mice infected could survive during the observed periods of 3 or more weeks, although the control mice died within 2 weeks after the infection of intraperitoneal route with it. ii) Mice were immunized with the killed vaccine made from the infective organ with and without adjuvant.
Two strains of R. orientalis, Kato (Niigata, Japan) and Karp (New Guinea), were used in these experiments. These strains had already identified as R. orientalis serologically.
By the infection through subcutaneus route, antibody could be detected in mice sera remarkably following inoculation of vaccine combined with adjuvant, but not so remarkably without adjuvant. On the other hand, by the immunization with the killed vaccine, it was found that antibody formation in mice was easy with adjuvant, but very difficult without adjuvant.
From these results, it was suggested that it is possible to produce OXK antibody in mice by the immunization of the killed vaccine of R. orientalis with adjuvant, and this method may be applicable to the serological classification of it.

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From the previous experiments, the author found that the killed vaccine of R. orientalis combined with adjuvant could produce OXK antibody in mice.
Following these experiments, eight strains, which were identified as R. orientalis by the morphological observation and animal patterns, were tested if it could produce OXK antibody in mice by this method. These strains were recently isolated from the field rats which were trapped in the various areas of Japan, in some of which tsutsugamushi disease is common, but in others that disease is not known.
Out of eight strains, two strains, Kumamoto 4, and Oshima 1, were proved to be positive in producing OXK antibody in mice by this method, but in others it could not succeed to detect OXK antibody.
The reason why all of the tested strains could not show positive by this method were discussed.

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When a broth culture of lysogenic Shigella flexneri, KA (βL) strain, was exposed to H₂O₂ at a concentration varies between 0.06 and 0.15 per cent, about 10 per cent of the culture was lysed liberating active βL phages.
The induction velocity (induced cells per unit time) was obviously depend on either temperature or H₂O₂ concentrations, but the maximum induced rate was not and kept constant at about 10 per cent.
The blocking effect of KCN (M/100) against the induction effect of H₂O₂ was tested as follows: M/100 KCN was added simultaneously with M/113 H₂O₂ to a growing KA (βL) culture and after 10 minutes exposure at 30 C the culture was diluted 1: 1, 000 into buffered saline and assays were made for induced cells as well as for colony forming living cells. The number of induced cells, then, decreased to about 20-70 per cent of the control, and surviving cells increased to about 3-17 times in number indicating that the inductive and bactericidal action of H₂O₂ is blocked in part by KCN presumably due to an inactivation of bacterial eatalase.

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An epidemic of pneumonitis in suckling children occurred in Ota from the end of December 1955. The patients died within a few days with high fever, cough, dyspnea and cyanosis.
From the clinical data an illness was indistinguishable from “Newforn Viral Pneumonitis Type Sendai”.
At autopsy consolidations were seen in the lungs and a virus was isolated from a fatal case by inoculation into the embryonate eggs.
The infected chickembryos were hyperemic and allantoic fluids were turbid. Microscopically karyorrhexis of the bronchial epithelium was seen in the chickembryo lungs.
These findings were similar to those of HVJ, but antigenically the virus was related to the current strain of influenza A.

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In this communication a report is made on the mechanism of viral hemagglutination. The results are summarized as follows. I. ELECTROSTATIC CONSIDERATION OF THE VIRAI HEMAGGLUTINATION.
The viral hemagglutination were distinguished into two processes, first, adherence of hemagglutinin to the surface of erythrocytes and, second, clot formation of those erythrocytes.
The mechanism of the first process was different from other viruses, but the mechanism of the second process was in common with other hemagglutination.
The second process was confirmed with various ionic formations of reaction medium, and then, it was nothing else but decrease of negative surface potential of erythrocytes. II. MEASUEMENT OF THE HEMAGGLUTINABILITY OF ERYTHROCYTES.
The present author has observed that the erythrocytes disclosed nonspecific hemagglutination in hypertonic concentration of NaCl solution or CaCl₂ solution. The nonspecific hemagglutination in hypertonic solution was utilized for measurement of the hemagglutinability.
Hypertonic solution (16 times of isotonic concentration) of NaCl or CaCl₂ solution was diluted serially twofold by mixing with distilled water and in each 1.0ml of this dilution was added 1 drop of 10% suspension of erythrocytes in normal saline and sedimentation was allowed to proceed at 4°C over night and the patterns were read (according to Salk).
It was concluded by the method that hemagglutinability of trypsin and tannic acid treated erythrocytes was increased.

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Amongst the various dyes tested, the thiazine dyes, oxazine dyes and acridine dyes were exceedingly active towards the photodynamic inactivation of bacteriophage (T-group).
The following hypothesis about the mechanism of photodynamic inactivation of bacteriophage has been proposed on the basis of the common structures of these active dyes. Namely, these active dyes may associate with substance-X of the phage (nucleic acid) through a bridge-like structure and a multiple electron transfer may thus occur through a single dye molecule.

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It has been found that, among the various dyes tested, triphenylmethane dyes inhibited the photodynamic inactivation of bacteriophage of active dyes.
Because, the association of active dyes with the bacteriophage was of reversibly dissociable nature, the kinetics on enzymology has been applied to the active dyephage system.
Application of the kinetcs to the inhibition of the photodynamic action has revealed that this inhibition is a competitive one analogous to that observed in the case of an enzyme-inhibitor system.

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To elucidate the role of the excited oxygen the writer have performed experiments and discussed. The inactive dyes have slight activity of photodynamic action. It may be seen that inactive dyes are only capable of exciting the oxygen, and that this excited oxygen inactivates the bacteriophage through an oxidative mechanism. From the effect of mixture of two dyes on photodynamic inactivation experiments, however, the photodynamic velocity of methylene blue remarkably increased in the presence of methyl violet than its absence. Because the amount of excited oxygen by free active dye plus inactive dye is very large in comparison with the amount of excited oxygen by only free active dye. In addition this, it is evident that molecular oxygen is essential for the photodynamic inactivation of bacteriophage, as has been found for most other photodynamic systems studied. Neverthless, the susceptibility of the T-goup of bacteriophages by hydrogen peroxide do not coincinde with the order of photodynamic susceptibility of them.
Thus, the most important factor of the susceptibility of T-group phages to photodynamic inactivation may be affinity between the dye and the strain, and these data must be reduced to that excited or molecular oxygen engage in only the intermediate step of the procss of photodynamic inactivation.

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