Any discussion of the types contemplated in this paper precludes the necessity of clarifying the terminology involved. Neter's (1942) classification of shigellae has been generally accepted in America. His schema, therefore, is utilized in the present article. Neter divides shigellae found in man into three groups:
1.A mannitol-negative, lactose-negative group, which includes Sh. dysenteriae Shiga and Sh. ambigua Schmitz. Sh. newcastle Clayton-Warren is added to this group, in spite of the fact that this organism is slightly motile and, under favorable conditions, forms some gas. Both of these qualities are not observed in other shigellae.
2.A mannitol-positive, lactose-negative group, to which belong Sh. paradysenteriae Flexner and Boyd, Sh. alkalescens and Sh. gallinarum. The latter, however, is better classified as a Salmonella, due to its antigenic structure.
3.A mannitol-positive, lactose-positve group, into which Sh. sonnei and Sh. dispar are placed.
A variant of Sh. newcastle called the Manchester bacillus, is a strong gas producer. Both are antigenically but not biochemically identical with Sh. paradysenteriae VI (Boyd 88).