THE STREPTOCOCCUS GROUP 303 
media, the individuals occurring; typically in pairs. The organism 
is closely related to the pneumococcus, and Dochez and Gillespie^ 
have named it Pneumococcus mucosus-. It is probable that Strepto- 
coccus mucosus is a distinct entity, however, differinj^: from Pneumococ- 
cus mucosus both in being insoluble in bile, and in not fermenting 
inulin. It is usually less pathogenic for white mice than the Pneumo- 
coccus mucosus, and it produces a narrow, clear zone of hemolysis 
upon blood-agar plates. 
Streptococcus pyogenes stains readily with ordinary anilin dyes. 
It is typically Gram-positive, although old cultures may fail to retain 
the (iram stain. The saprophytic types frequently are Gram-negative. 
Isolation and Culture. ^Streptococci may be isolated directly from 
inflamed areas and from pus upon agar plates, better upon glucose- 
agar plates. The typical colonies are minute, gray and transparent, 
and maybe readily overlooked; if they occur in association with sta- 
phylococci or other rapidly growing organisms, they are readily over- 
grown. The more virulent varieties develop less readily, and require 
the addition of blood or ascitic fluid to ordinary media for their initial 
growth outside the body. On blood-agar plates (1 part human blood, 
2 parts of nutrient, svc/ar-free agar) the majority of \'irulent stre])tococci 
produce a wide, clear zone of hemolysis 4 to 8 mm. in diameter around 
each colony. This medium is particularly valuable for the isolation 
of streptococci from lesions.'' On Loffler's blood serum growth is 
moderately luxuriant; typical chains are found in the condensation 
water of solid media, but not, as a rule, upon the surface. The organ- 
isms grow feebly in gelatin stab cultures producing a few small discrete 
gray colonies along the line of inoculation. Little or no growth is 
found on the surface of the medium. Liquefaction does not take place. 
A slightly alkaline reaction (neutral to phenolphthalein) is most 
favorable for the growth of streptococci; the addition of sugars, par- 
ticularly glucose, to ordinary media (but not blood-agar) increases 
the rate and extent of development, which, however, are soon limited 
by the accumulation of acid products of fermentation. The addition 
of solid calcium carbonate (marble) to sugar media is important; 
it neutralizes the excess of acid, and also appears to add somewhat to 
the nutritive value of the medium.'^ 
Streptococci grow slowly in plain broth, producing a sediment after 
twenty-four to forty-eight hours' incubation. A flocculent sediment 
1 Jour. Am. Med. Assn., 1913, 61, 727. 
2 Schottmiiller (Miinchen. med. Wchnschr., 1903, 50, 849) has classified streptococci 
according to the changes they produce in blood-agar as follows: 
I. Streptococcus longus pyogenes seu erysipelatis (Streptococcus pyogenes) produces 
a wide, clear zone of hemolysis around the colony ; in blood broth the color changes to a 
Burgundy red. Long-chained streptococci. 
II. Streptococcus mitior seu viridans (Streptococcus viridans) produces a greenish 
area around the colony; a brownish color in blood broth. Short-chained streptococci. 
III. Streptococcus mucosus. Hemolysis on blood-agar slight. Colonies viscid. 
Organisms distinctly encapsulated. 
3 Bolduan: New York Med. Jour., 1905, 81, 956. 
