348 PATHOGENIC MICROORGANISMS 



Precipitins have been found by Aronson ' in streptococcus immune 

 horse serimi. Special methods of extracting the bacteria were em- 

 ployed. 



Classification. — Frequently observed differences in the minor cul- 

 tural characteristics and in the virulence of streptococci obtained from 

 various sources have given rise to much discussion as to the identity of 

 all races of streptococci. The earliest observers were forced to abandon 

 their separation of the streptococci of erysipelas from other streptococci 

 because of the work of Marbaix ^ and others, who produced erysipelas 

 in rabbits with streptococci from non-erysipelatous lesions, after en- 

 hancement of their virulence. V. Lingelsheim ' has proposed a purely 

 morphological differentiation of "longus" and "brevis"; the former 

 class including the streptococci most usually found in pyogenic le- 

 sions and having a tendency to form chains of six or more links, the 

 latter designating the short-chained varieties, including, as a rule, 

 the less virulent streptococci. This classification, however, is not 

 scientifically tenable because of the considerable dependence of chain 

 formation upon reaction, consistency, and nutritive qualities of the 

 media employed for cultivation, and upon the influence of animal fluids 

 if the microorganisms are taken direct from lesions. Schottmiiller,* 

 who has made a careful study of streptococci, in 1903 proposed a classi- 

 fication based both upon morphology and the appearance of cultures 

 upon human blood agar. By this method he divided streptococci into 

 two main groups as follows: I. Streptococcus longus seu erysipelatos, 

 consisting of the most virulent varieties, having a tendency to form long 

 chains, and regularly producing hemolysis upon blood media. II. 

 Streptococcus mitior seu viridans, including less virulent strains, with 

 usually shorter chain-formation, and producing green, non-hemolyzing 

 colonies upon blood media. These are the streptococci which he 

 usually obtained from milder or more chronic lesions. A third group 

 which he adds, Streptococcus mucosus, will receive special considera- 

 tion in a separate section, and is probably more closely related to the 

 pneumococci than to the streptococcus groups. 



Attempts to separate the streptococci into subdivisions by their 

 powers to ferment various carbohydrates have been made by Hiss, 

 Gordon, and others. These attempts have, so far, been without practical 



1 Aronson, Deut. med. Wooh., 25, 1903. 



2 Marbaix, loc. cit. 



"v. Lingelsheim, "Aetiol. u. Therap. d. Streptokok. Krankh.,'' etc., Berlin, 1899. 

 ' Schottmiilkr, Miinch. med. Woch., 1903. 



