112 BIOLOGY OF PNEUMOCOCCUS 



to which they belonged. Armstrong regretted the use of the Ameri- 

 can designation Type IV for the unclassified strains as being too 

 narrow. Yu 1567 found Types I and III to be uniform and definite. 

 In 1921, Cooper, with Mishulow and Blane, 273 published the first 

 of a series of studies which were to bring a new order out of the 

 confusion regarding the proper serological classification of Group 

 IV pneumococci, and to establish many of the atypical subgroups 

 as separate and definite types. By the agglutination method, 

 checked by absorption tests when cross-agglutination occurred, 

 the authors placed their fifty-three cultures in six small groups 

 with thirteen unrelated strains — a total of nineteen types. 



In the next few years there were additional reports on the sero- 

 logical classification of pneumococci, but only a few were of major 

 importance. In 1921, Griffith 558 compared strains of his own isola- 

 tion with standard type strains sent him from America by Flex- 

 ner. To a 1 to 10 dilution of the monovalent type rabbit serums 

 he had prepared was added an equal amount of the supernatant 

 fluid from centrifuged peritoneal washings from mice inoculated 

 with pneumococcal strains. It was found that the agglutination 

 test was sufficient for the identification of the first three specific 

 types and the author considered that the method of absorption of 

 agglutinins was unnecessary. Group IV was separated into six 

 types, including the American Types IIA and IIB, but these did 

 not complete his classification. Griffith, by the way, like others, 

 noted that agglutinating serum from horses was less selective than 

 that of rabbits. 



Yoshioka (1922 and 1923), 15601 using strains of the American 

 Types I, II, and III from the Hospital of the Rockefeller Insti- 

 tute, and a Type I strain of German origin, was not always able 

 to obtain type-specific protection in mice actively immunized with 

 these cultures. The serum of immunized rabbits was type-specific in 

 protection experiments, but fresh normal serum in fairly high di- 

 lutions sometimes also agglutinated heterologous types. Yoshioka 



