STREPTOCOCCUS PYOGENES. 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 pneumococeus. 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. 
Fie. 61, Fie. 62, 
Streptococci in peritoneal fluid, x 
partly enclosed in leucocytes. x Streptococci in throat exudate smeared 
1000 diameters. on cover-glass. X 1000 diameters. 
Morphology. Spherical cocci, when fully developed, 
having no independent movements, from 0.4 to ly 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- 
