Among about dozen islets, dotted off Shima Peninsula, three islets, all relatively small but densely populated, had sufferred dysentery epidemics at three different periods within recent five years between 1963 and 1968.
These epidemics are briefly outlined as follows: In Toshijima; with 7.8 Km² area, 401 houses and 2898 population; a period from August 8 to September 5, 1963; 137 persons sufferred dysentery; positive cultures were DI (113 cases) B2a (4) B3a (3.) B I b (3) B6 (3); strains of DI are all sensitive to CP, SM & TC, resistant to SA. In Sakatejima; 0.51 Km², 113 houses and 1717 population; a period from January 8 to February 11, 1966; 163 sufferred; positive cultures were DI (140) B3a (1) B3b (5); D1 are resistant to CP, SM & TC, sensitive to KM and PF-S, and show colicine type 6. In Kamishima; 0.85 Km², 240 houses and 1088 population; a period from September 5 to October 18, 1968; 78 sufferred; positive cultures were B2a (67) D1 (11); B2a are resistant to CP, SM & TC, and show colicine type O.
Judging from such elements as bacillus types, its drug-resistant patterns, and chronology of the epidemics, these three occasions are considered to be each independent. Furthermore, through these investigationson each islet, it came out that there are several epidemiologically unfavorable aspects in natural and socio-hygienic conditions, some of which are characteristic to the life of small islets dependent on small scale agriculture and fishery.
The followings are the points, and reforms should be undertaken along these lines without delay.
1) There are a lot of human excretas depots in the field which are used by farmers as natural fertilizer. By the heavy rain, they used to be easily overflown, among which those placed in hill-side stairlike paddy-fields (seen in Fig. 2) are especially risky to the sanitation of small scale tap water reservoirs.
2) The total amount of the water the reservoirs can afford to supply is definitely insufficient; only 5 m³per day for 2898 population in Toshijima, for example. Therefore, every houshold life is apt to be unclean and insanitary.

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Bezjak established in 1954 the classification of Corynebacterium (Cory.) belfanti, giving a name as such, by clarifying its biological property not reducing nitrate. Nothing but this property can be usable identifying it from Cory. diphtheriae type mitis, as of the present time. The author adopted this criterion in this paper.
So far, in this country, few attempts have been made to distinguish Cory. belfanti in the case of diphtheria. Therefore, there would have been mixing-up of this type of Corynebacterium in the outcome of surveys of diphtheria epidemics conducted in this country.
In this respect, the author restudied bacteriological properties of 88 strains isolated in other institutes and put under the classification of Cory. diphtheriae. Three standard strains of Cory. belfanti were used contrast. The results were summed up as follows:
Of these 88 strains, 38 turned out to be Cory. diphtheriae type gravis, 45, type mitis and 5, Cory. belfanti. These identifications were done mainly by observing the colonies on Clauberg media, hemolytic property, starch dissolution and nitrate reducing property.
Between Cory. diphtheriae type mitis and cory. belfanti, properties such as diphtheria toxin productivity, drugsensitivity, DNase activities and nitrate reducing activities were compared. No significant differences other than nitrate reducing property were demonstrated between the two.
It is another point of noteworthy that there found one sttain of Cory. diphtheriae type gravis that proved not to reduce nitrate.

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