THE GENUS STREPTOCOCCUS 147 



similar conditions). Each of these four groups contained 

 two subtypes, one growing at low, the other only at 

 higher temperatures. 



With the introduction of the newer methods of study- 

 ing physiological immunity, it was hoped that the relations 

 of the various pathogenic and non-pathogenic strepto- 

 cocci might at last be elucidated. The practical impor- 

 tance of a clear differentiation of these forms was greatly 

 enhanced by Marmorek's introduction (1895) into thera- 

 peutics of the anti-streptococcic serum. This investi- 

 gator, (Marmorek, 1902, a), was able to obtain a very 

 strong streptococcus toxin by first cultivating his organism 

 in serum to which the leucocytes of an immune guinea pig 

 had been added, and then growing it in broth containing 

 leucin and glycocoll, which he found favored the con- 

 tinued production of the toxin. The antitoxin corre- 

 sponding to the poison, he believed, could be used in all 

 infections in which streptococci were concerned. He 

 considered the unity of the streptococci of man to be 

 demonstrated by studies of serum reactions, of hemolytic 

 activity, and of the power to render a medium unsuitable 

 for the development of another strain (Marmorek, 1902, b). 

 In all these respects, however, his own records show marked 

 quantitative variations between different races. 



At about the same time other observers were attempting 

 to identify special strains of streptococci as the causative 

 agents of specific diseases, notably scarlet fever, small- 

 pox, and rheumatic fever. Baginsky and Sommerfeld 



