INDIVIDUAL FEATURES OF PYOGENIC BACTERIA. 103 



chain are equal ; in older cultures they vary very much even 

 in the same chain. 



Biologic Characters. The streptococcus is aerobic and fac- 

 ultative anaerobic. At 37 C. it clouds bouillon in twenty- 

 four hours, and this becomes again clear at the end of three 

 or four days, when small spherical bodies may be seen at the 

 bottom of the tube. The bouillon becomes acid. On gelatin 

 it forms small spherical opaque colonies about the size of a 

 pin-head, which cease to increase after the third or fourth 

 day. It does not liquefy gelatin. On agar-agar also it forms 

 spherical colonies of the size of a pin-head, semitransparent 

 and of a grayish- white appearance, shaped somewhat like a 

 bead. It does not develop on potato. The streptococcus does 

 not live longer than three weeks in cultures. It stains by the 

 Gram method, and also by the other anilin dyes. 



Pathogenesis. Intravenous inoculations in animals produce 

 variable effects. The germ usually kills the animal, causing 

 a rapid general septicaemia ; at other times the animal reacts 

 only slightly. Subcutaneously it causes erysipelas and the 

 formation of abscesses. All laboratory animals are susceptible 

 to infection by means of the streptococcus pyogenes. 



V. The Micrococcus Cereus Albus. 



VI. The Micrococcus Cereus Flavus. 



These were found in pus by Passet associated with other 

 organisms. Their pathogenesis has not been fully established. 

 They differ from the other groups of cocci just described by 

 the shiny, waxy appearance of their growth. 



VII. The Micrococcus Pyogenes Tenuis. 



This was found in pus by Rosenbach, is very irregular in 

 size and somewhat larger than the Staphylococcus albus. On 

 agar-agar its biology presents a thin opaque streak along the 

 line of inoculation, resembling a thin layer of varnish. Its 

 pathogenic properties have never been fully determined. 



