STREPTOCOCCUS PYOGENES 51 



the individual cells, length of chains, and variability 

 in the spaces between the cells the streptococcus 

 shows much variety ; many species have been de- 

 scribed and named — e.g., Strept. Longus, Brevis, 

 &c. Streptococcus Erysipelatosus appears to be one 

 of the varieties of this organism, and great differ- 

 ences in virulence are noted in cultures from 

 various sources. From such pus as that described 

 cultures of the organism — which grows between the 

 temperatures of 18° C. and 42° C, with an optimum 

 of 37° C. — can be obtained on gelatine or agar or in 

 bouillon. The organism is a facultative anaerobe. 

 The growth on gelatine (Fig. 44) forms a series 

 of small discrete, semitransparent, dewdrop-like 

 circular colonies, and produces no liquefaction of the 

 gelatine. 



On agar the growth closely resembles that on 

 gelatine, and there is often a very free growth in the 

 fluid of condensation which collects at the bottom 

 of the tube. 



As in the morphological, so in the cultural 

 characteristics, considerable variation is met with, 

 affecting the freedom of the growth and the size 

 and density of the colonies. In all cases, however, 

 the colonies tend to keep separate and never reach 

 any large size, while their vitality is not lasting, 



