52 STREPTOCOCCUS PYOGENES 



and unless frequently transplanted sub-cultures often 

 fail. The media most suited to secure the continued 

 vitality of the organism, and also to preserve its 

 pathogenicity, are those consisting of admixtures of 

 blood serum or ascitic fluid with bouillon (Mar- 

 morek, &c.). 



Cover-glass preparations made from such cultures 

 present the appearance shown in Fig. 45. The 

 length of the chains of cells depends in part on the 

 humidity of the medium ; the longer ones are found 

 in bouillon cultures or in the condensation fluids of 

 agar. 



In fresh preparations from these fluids the organism 

 is seen to form very long intertwisted and convoluted 

 chains, which are generally much broken up in cover- 

 glass preparations. It is probably due to this inter- 

 twisting that the microscopic characters of the cul- 

 tures in bouillon are to be referred viz., a primary 

 turbidity with a subsequent rapid clearing of the 

 fluid and deposit of flocculi at the bottom of the 

 tube. 



In cultures the same varieties are met with as 

 have been described as occurring in pus, and are 

 perhaps even more marked. The pathogenic affec- 

 tions produced by inoculations of the pure cultures 

 vary greatly with the changing virulence of the 



