STREPTOCOCCUS PTOGENES. 



477 



species which has been appropriately termed the "strep- 

 tococcus pathogenes longus." Some of the streptococci, 

 at least in so far as their specific products and their 

 reaction in the presence of a curative serum is con- 

 cerned, belong to a species as distinct from the strepto- 

 coccus pyogenes as the pneumococcus. This question 

 has a very practical side, for upon its decision rests our 

 ability to choose a suitable protective serum in cases of 

 streptococcus infection. 



FIG. 61. 



FIG. 62. 



Streptococci in peritoneal fluid, 

 partly enclosed in leucocytes. X 

 1000 diameters. 



Streptococci in throat exudate smeared 

 on cover-glass. X 1000 diameters. 



Morphology. Spherical cocci, when fully developed, 

 having no independent movements, from 0.4// to I/* in 

 diameter, usually larger than the staphylococci, but 

 varying in dimensions in different cultures and even in 

 different parts of a single colony. They multiply by 

 binary division in one direction only, forming chains of 

 eight, ten, twenty, and more elements, being, however, 

 often associated distinctly in pairs. On certain media 

 the cocci occur mostly in diplococci, but usually they 

 grow in longer or shorter chains. Certain cocci fre- 



