412 PATHOGENIC MICROORGANISMS 



hemolytic streptococci by means of complement fixation. In this 

 work they used a number of strains and a large number of organisms, 

 and found that the group was very heterogeneous. They developed 

 in their work an interesting theory as to the inter-relationship of 

 these heterologous groups. This is not sufficiently well founded to 

 permit our going into it. It is, however, certain from their work, 

 and from that of others, that the group of viridans is probably as 

 antigenically heterologous as are the so-called Type IV pneumococci. 

 When we turn to the hemolytic group we find that a more hopeful 

 state of affairs seems to be developing. There seemed to be from 

 the beginning a certain amount of immunological grouping in organ- 

 isms of this type. Baginsky and Sommerfeld 33 found that agglu- 

 tinins were present in scarlet fever serum which seemed to be specific 

 for other strains isolated from the throats of scarlet fever patients, 

 and this observation was confirmed by Moser and Von Pirquet. 34 

 A similar apparent similarity between strains isolated from the 

 blood of smallpox cases was found by De Waele and Sugg. 35 

 Neufeld 36 suggested that there was a relationship between agglu- 

 tinability and virulence. Kinsella and Swift 37 studying this problem 

 in 1918 came to the conclusion that with complement fixation 

 methods, at least, the hemolytic variety of streptococcus is homo- 

 geneous, consisting of members that are almost identical. More 

 recent work, however, by Dochez, Avery and Lancefield 38 seems to 

 have shown that by means of agglutination it may be possible to 

 classify the hemolytic streptococci into immunological sub-groups. 

 They define four biological types which check up both by agglutina- 

 tion reactions and by protection experiments. They encountered at 

 least two other types, and indications that more existed. Their 

 work seems well founded on experimental fact, and has been recently 

 confirmed to this extent that Bliss, working with the streptococci 

 obtained from the throats of scarlet fever cases found that the 

 organisms from such sources seemed to fall" into a single group. 

 The specificity of streptococci has also been recently studied by 



33 Baginsky and Sommerfeld, Berl. klin. Woeh., 37, 1900, 588. 

 "Moser and Von Pirquet, Cent. f. Bakt., I, 1903, 34, 560. 



35 De Waele and Sugg, Arch. Internal, pharm. et therap., 12, 1904, 205. 



36 Neufeld, Zeit. f . Hyg., 40, 1902, 54. 



37 Kinsella and Swift, Jour. Exper. Med., 28, 1918, 877. 



38 Doches, Avery and Lancefield, Jour. Exper. Med., 30, 1919, 179. 



