176 



INFLAMMATION AND SUPPURATION 



milk, in which it readily grows. The cultures have a somewhat 

 sour odour. 



It has considerable tenacity of life outside the body, cultures 

 in gelatin often being alive after having been kept for several 

 months. It also requires a rather higher temperature to kill 

 it than most spore-free bacteria, viz. 80 C. for half an hour 

 (Liibbert). 



The staphylococcus pyogenes albus is similar in character, 

 with the exception that its growth on all the media is white. 

 The colour of the staphylococcus aureus may become less dis- 

 tinctly yellow after being kept for some time in culture, but it 

 never assumes the white colour of the staphylococcus albus, and 

 it has not been found possible to transform the one organism 

 into the other. A micrococcus called by Welch staphylococcus 

 epidermidis albus is practically always present in the skin 

 epithelium ; it is distinguished by its relatively non-pathogenic 

 properties and by liquefying gelatin somewhat slowly. It is 

 probably an attenuated variety of the staphylococcus albus. 



The staphylococcus pyogenes citreus, which is less frequently 

 met with, differs in the colour of the cultures being a lemon 



yellow, and is less virulent 

 than the other two. 



The staphylococcus 

 cereus albus and staphy- 

 lococcus cereus flavus are 

 of much less importance. 

 They produce a wax-like 

 growth on gelatin without 

 liquefaction ; hence their 

 name. 



Streptococcus pyo- 

 genes. This organism 

 is a coccus of slightly 

 larger size than the 

 staphylococcus aureus 

 about 1 /x in diameter, 



and forms chns which 



FIG. 54.-Streptococcus pyogenes, young cul- 



ture on agar, showing chains of cocci. may contain a large num- 



Stained with weak carbol-fuchsin. x 1000. ber of members, especi- 



ally when it is growing 



in fluids (Fig. 54). The chains vary somewhat in length in 

 different specimens, and on this ground varieties have been dis- 

 tinguished, e.g. the streptococcus brevis and streptococcus longus 

 (vide infra). As division may take place in many of the cocci 



