110 THE PATHOGENIC BACTERIA. 



Principal Biologic Characters. The Staphylococcus pyogenes 

 aureus is a facultative anaerobe. It is .non-motile and pos- 

 sesses no flagella. It clouds bouillon in twenty-four hours at 

 37 C., and shows from the second day a yellowish precipi- 

 tate, which gradually increases in color and at the bottom of 

 the tube appears of a golden yellow. It liquefies gelatin. 

 Stab-cultures on this media at 20 C. on the second or third 

 day have the appearance of a funnel, at the bottom of which 

 is an orange-yellow deposit. At the end of three days the 

 gelatin in the tube is completely liquefied. On gelatin plates 



FIG. 47. 



i 



. :.vw ^ 



l.;i / "it^-A 



/ 



Preparation from pus, showing pus-cells, A, and staphylococci, C. (Abbott.) 



colonies of a dark-yellowish color are observed with a centre 

 of more or less intense orange color. 



On agar-agar the colonies appear small, regularly spherical, 

 and of an orange-yellow. Plates made from this medium 

 have the same characteristics as on gelatin, being more or less 

 pigmented yellow. It does not liquefy agar. The cultures 

 on blood-serum have the same characteristics as on agar. 

 Staphylococcus pyogenes aureus has a reducing action in cul- 

 tures, reducing nitrates to nitrites. It decolorizes litmus. The 

 Staphylococcus pyogenes aureus stains with all the anilin dyes, 

 and also by Gram's method. 



Pathogenesis. When inoculated into the blood of an animal, 



