176 PRACTICAL BACTERIOLOGY. 



its manner of slowly liquefying the gelatine, and in 

 its development generally on plates and on agar-agar 

 it exactly resembles the aureus. Even microscopically 

 no difference can be observed, except that here again 

 the cells are not so frequently arranged in groups. 

 Lately some other very rare staphylococci have been 

 found in pus ; these also show distinct colorations, 

 by means of which they may be distinguished from 

 the others, but on account of the rarity of their 

 occurrence they are practically of small importance. 

 Whether all these species are really distinct, or 

 whether they are only various forms of the Staphy- 

 lococcus pyogenes aureus itself, has not been yet 

 decided ; for the present, until sufficient reasons have 

 been given for classing them together, it is best to 

 consider them as distinct. 



2. Streptococcus pyogenes. 



Another organism, which occurs with equal fre- 

 quency as the exciting cause of suppuration, and 

 which frequently extends itself along the lymph 

 ducts, is the Streptococcus pyogenes, so-called, from 

 its great tendency to form chains resembling strings 

 of pearls. There are also a great number of other 

 diseases caused by this organism, which are called 

 by various names, and which are frequently marked 

 by their very malignant course. Progressive gan- 

 grene, puerperal fever, and pyemia, are very fre- 

 quently, even if not invariably, caused by the Strepto- 



