The pathogenicity of E. coli was analyzed from 2 factors; multiplication in vivo and disease-producing activity, as the pathogenicity is thought to consist of these two factors according to the author.
A) Multiplication activity was investigated by culturing the human stools after the oral administration of pathogenic E. coli as well as nonpathogenic E. coli as contrast.
1) From stools of 15 adults who had swallowed nonpathogenic E. coli, O-16, this strain was recovered only in 12 cases in small amounts and for a short period of time. And the remaining 3 cases, O-16 was not recovered at all.
rom stools of 5 newborns given O-16 orally, this strain was recovered in all the cases.
A marked multiplication was recognized as well in 19 out of 20 adults given orally SM and SM-resistant O-16 simultaneously.
2) Out of 20 cases of human adults having swallowed pathogenic E. coli O-111: B4, 17 cases (85%) presented a marked multiplication.
3) Swallowed strains of E. coli were not recovered in 5 (71%) out of 7 cases with gastric hyperacidity, suggesting multiplication-inhibiting activity of gastric acid against exogenic E. coli. On the contrary, exogenic E. coli was isolated from stools of 17 (89.5%) out of 19 cases with gastric hypoacidity or anacidity.
B) Secondly, the disease-producing activity was studied through the De's experiment using rabbit's intestine coupled with the human experiments swallowing pathogenic E. coli.
1) Ten (50%) out of 20 adults who had swallowed 1 billion of O-1114-B4, suffered from diarrhea accompanied with slight abdominal pain and peristaltic sounds. One of them showed even an elevated temperature.
2) Out of 36 known strains of pathogenic E. coli, 26 strains (ca. 72%) caused macroscopic changes in the ligated loop of rabbit's bowel and 31 strains (ca. 86%) microscopic changes. Out of 40 strains of nonpathogenic E. coli as contrast, only 7 strains (17.5%) evoked macroscopic changes in the ligated loop of rabbit's bowel and 6 strains microscopic changes.
In addition, 4 pathogenic strains (3 strains of salmonella and 1 of Shigella) induced conspicuous macroscopic and microscopic changes.

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The antigenic material (0-antigen) of E. coli O-111 was isolated in a relatively pure condition by the modified method of diethyleneglycol extraction described by Morgan (1940), and by ultracentrifugation (SPINCO).
This study was undertaken to investigate the biological toxicity, especially, pathogenic effects on the intestine of mice and erythrocyte sensitizing activity of this purified antigen. On lesions in the intestine of mice produced by this antigen, the following experiments were carried out. This antigen was decomposed by etherethanol and acetic acid to determine which fraction produces the lesions in the intestine of mice. And these decomposed products were tested in mice to determine whether the products possess harmful action on the intestine of mice or not. Next, the effects of chlorpromazine, tetraethylammonium bromide, prednisolone acetate and hexamethylene-1: 6bistrimethyl-ammonium bromide on this injurious action were observed in order to gain an insight of the mechanism responsible for the lesions.
Furthermore, the physical nature of this antigen were investigated.
The results were as follows:
1) LD₅₀ of this purified 0-antigen prepared from E. coli O-111 was 25.0 mg per kg for mice of the ddN strain and 31.5 mg per kg for mice of the SM strain. By the injection of this antigen into mice, it caused a relatively localized lesion in the intestine. Erythrocytes are sensitized by this antigen, in different ways according

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The Prontosil synthetized in 1935 brought a epoche-making progress in the therapy as well as in the prophylaxis of plague. Particularly the sulfadiazine proved effective not only against all formes of plague except pneumonic plague but also for the prophylaxis of them including the pneumonic form.
After the discovery in 1944, streptomycin was applied by Meyer and Herbert to the therapy of the disease, and it's excellent effectiveness was reexamined by the author, too. The prophylactic value, however, has not been yet, experimentally testified. It was reported in the previous papers by the author that a large dosis therapy of this agent inhibited the disease in 100% of the experimental cases. Applying this result, further experimental studies on the prophylactic effectiveness of the drug were carried out and reported in this paper.

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Serum specimens of 120 patients of Tsutsugamusi disease group including Ezo fever were tested in order to elucidate their antibody response in Weil-Felix reaction and rickettsiaspecific complement fixation tests. The reliability of these tests were thought to be questionable by some investigators, but the improved CFT antigens (by Kawamura) and OXK antigen (by Hazato et al.) have made it possible to compare the results of serological tests in man and laboratory animals. The following conclusions were obtained from the present investigations.
1) With patient sera from Niigata, Akita, Shichito Islands and Pescadores, agglutinin titers against improved OXK antigen cultivated on the synthetic medium giving higher titer for rabbit sera, fell almost within the same range as against the ordinary OXK antigen.
In Ezo fever, the causative agent of which was named R. Tamiyai, n. sp. by Dr. Kawamura, the infected human serum agglutinated the ordinary OXK antigen but not the improved antigen.
2) CFT antigen of Ozeki strain (R. orientalis) made by the Amberlite process by Kawamura showed no nonspecific reaction with control sera, all the patient sera except for those taken within 3 days after the onset of fever showed a significant rise in their specific CFT antibody titer, and the results were not influenced by the strain specificity.
3) In the case of rabbit sera, rise of CFT antibody titer preceeded that of WFR agglutinintiter. This tendency was also found in the patient sera but was less marked than in the case of rabbit sera. Similarly the therapy with antibiotics suppressed the WFR antibody formation, but did not influence the rise of CFT antibody.
These results were discussed from the viewpoint of antigenic constitution of rickettsia and the necessity of its more detailed analysis was emphasized.

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Landis-method, though under a new interpretation by the author, was applied in order to clarify the pathogenesis of “ekiri”. The pressure 60 mmHg for 15 min. was found to be optimum.
The results were as follows:
1) Two sorts of changes were observed in the peripheral stagnant blood at the height of “ekiri”. First, the erythrocyte component was more diluted than in the circulating blood, whereas the plasma was more concentrated, which is characteristic at the height of “ekiri”. Second, the erythrocyte as well as plasma component were more concentrated as compared with those in the circulating blood. But, the concentration of plasma was higher than that of the erythrocyte component. This sort of change was, however, more frequently observed in the acute stage of dysentery.
2) In the relaxing stage, the erythrocyte as well as the plasma component were mostly more concentrated than those in the circulating blood. But, the concentration of erythrocyte component was more marked than that of the other.
3) In dysentery as contrast, though the concentration of both erythrocyte and plasma component was elevated, the concentration of the latter was more so as compared with the former, as was mentioned above. The findings in the convalescent stage were almost the same as those in the same stage of “ekiri”.
4) The characteristic blood findings at the height of “ekiri”, i.e. elevation of plasma concentration accompanied with the diluted blood concentration was presumably caused by the spasm of capillaries which hindered erythrocytes to flow through the capillaries and brought the tissue fluid rich in protein into them.
5) According to the author's investigations of erythrocyte condition carried out simultaneously, the erythrocytes were thought to be contracted at the height of “ekiri” and swollen in the relaxing stage, whereas they seemed to be in the condition of microcytemia vera in the acute stage of dysentery. The condition in the convalescent stage of the latter, however, could not be clarified yet.
Consequently, it might be concluded that these data constitute a strong support to the theory that the spasm of peripheral blood vessels account for the great part of the severe symptoms at the height of “ekiri”.

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