THE SEPARATION OF TYPES AMONG THE PNEUMOCOCCI HITHERTO CALLED GROUP IV AND THE DEVELOPMENT OF THERAPEUTIC ANTISERUMS FOR THESE TYPES.

The pneumococci hitherto known as Group IV have been separated into ten types which have been designated by Roman numerals from IV to XIII. These have been correlated as far as possible with the types described by others. The prevalence and mortality of cases due to each type have been estimated in the limited number of cases studied. Laboratory tests indicated that therapeutic antiserums for Types I, II and III have very little protective power against the recently separated types. Monovalent antiserums of high agglutinative and protective power were prepared in rabbits for each type. Several monovalent antiserums each specific for a type, which are suitable for agglutination and experimental therapeutic use, have been obtained by immunizing horses. An antiserum prepared for one type had very little cross-protective power against other types.