THE GENUS STREPTOCOCCUS 153 



Ruediger (1906, a), still more recently, has shown that this 

 green coloration is due to the action of the cocci upon the 

 muscle-sugar present. In sugar-free media the action dis- 

 appears ; and, on the other hand, in glucose blood-agar he 

 found that Str. pyogenes produces a green coloration. 

 Which type of colony will appear depends then on the 

 relative amount of action v on sugar and blood cells respec- 

 tively. Kerner (1905) in his investigations found that 

 the hemolytic power was strong in streptococci freshly 

 isolated from the body, but decreased rapidly on artificial 

 media. 



On the whole, the much debated question of the " Viel- 

 heit" or "Einheit" of the streptococci received no satis- 

 factory solution from the methods of experimental immu- 

 nity. These organisms remained as before, — a more or 

 less closely related group made up of an indefinite number 

 of varieties. 



Two recent revisions of the genus have been made by 

 Le Gros (1902) and v. Lingelsheim (1903). Le Gros, 

 after reviewing the evidence from morphology and the 

 biochemical tests, recognized ten groups. Group (1) 

 included streptococci showing typical chains, long or 

 short, producing or failing to produce turbidity in broth, 

 and non-pathogenic; group (2) differed in having patho- 

 genic power; group (3) included motile; and group (4) 

 non-motile streptococci; group (5) was defined by nega- 

 tive reaction to the Gram stain; group (6) by abundant 

 growth on potato; group (7) included liquefying forms; 



