200 



INFLAMMATION AND SUPPURATION 



naked eye as whitish yellow points, which in typical strains 

 afterwards become more distinctly yellow. Liquefaction occurs 

 around these, and little cups are formed, at the bottom of which 

 the colonies form little yellowish masses. On agar, a stroke 



FlG. 44. — Staphylococcus pyogenes aureus, 

 young culture on agar, showing clumps 

 of cocci. 



Stained with weak carbol-fuchsin. x 1000. 



culture forms a line of abundant 

 yellowish growth, with smooth, shin- 

 ing surface, well formed after twenty- 

 four hours at 37° C. Later it be- 

 comes bright orange in colour, and 

 resembles a streak of oil paint. 

 Single colonies on the surface of 

 agar are circular discs of similar 

 appearance, which may reach 2 mm. 

 or more in diameter. On potato it 

 grows well at ordinary temperature, 

 forming a somewhat abundant layer 

 of orange colour. In bouillon it produces a uniform turbidity, 

 which afterwards settles to the bottom as an abundant layer 

 and assumes a brownish-yellow tint. In the various media it 

 renders the reaction acid, and it coagulates 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. 



Fig. 45. — Two stab cultures 

 of staphylococcus pyogenes 

 aureus in gelatin, (a) 10 days 

 old, (6) 3 weeks old, showing 

 liquefaction of the medium 

 and characters of growth. 

 Natural size. 



