PATHOGENIC BACTERIA. 121 



wounds are made clean and kept without suppurating. Vari- 

 ous forms of bacteria have been found in septic processes, and 

 the formation of pits cannot be ascribed to any particular one 

 alone ; some, more common than others, are found in nearly all 

 forms of suppuration ; others give rise to special types. 



Wounds are often irritated by foreign bodies and chemicals, 

 and a discharge occurs in them even when every aseptic and 

 antiseptic precaution has been taken ; but such a discharge is 

 free from bacteria, and no more like pus than a benign growth 

 is like a malignant one. 



Streptococcus Pyogenes. (Rosenbach.) Streptococcus erysipe- 

 latis. (Fehleisen. ) 



, Origin. Fehleisen discovered this microbe in the lymphatics 

 of the skin in erysipelas, and he thought it the cause of the 

 same. Under the name streptococcus pyogenes, Rosenbach 



FIG. 67. 



Streptococcus pyogenes in pus 1000 X- (Frankel and Pfeiffer.) 



described an identical coccus which has been found in nearly 

 all suppurative conditions. 



Form. Small cocci singly and in chain-like groups. Spores 

 have not been found, though it is supposed because of their 

 permanency that spores are present. 



Properties. They are im motile, do not liquefy gelatine. 



Growth. They grow slowly, usually on the surface, and best 

 at higher temperatures. 



Colonies. In three days a very small" grayish speck, which 

 hardly ever becomes much larger than a pin-head ; under micro- 

 scope, looking yellowish, finely granular, the edges quite defined. 



