In recent years outbreaks of dysentery and enteritis have been found, on occasion, to be due to late lactose fermenting organisms allied to the Flexner dysentery group. Sonne (1915) found that the main cause of dysentery in Copenhagen was a late lactose fermenting bacillus. D'Herelle (1916) in France and Øhnell (1918) in Sweden also found this atypical organism to be associated with cases of dysentery. Andrewes (1918) suggested the nameB. disparfor lactose fermenting members of the dysentery group, which he obtained from cases of suspected dysentery and from convalescents. Thjøtta (1919) in Norway while investigating cases of dysentery obtained 40 strains of Flexner dysentery bacilli (Thjøtta group II) and 25 strains of the Sonne type (Thjøtta group III). He explained that the less frequent finding of the Sonne type was due to the fact that this organism often caused a mild diarrhoea that was not sufficiently serious to necessitate the services of a physician, with the result that the cases were not subjected to bacteriological investigation. He showed that the Sonne bacilli had the following characteristics, viz.: Large irregular crenated colonies grew on litmus lactose agar plates; acid was produced in maltose and glucose, and occasionally in lactose; no indol was produced; and serologically the group showed no relationship to the other groups of dysentery bacilli (Flexner and Shiga).