STAPHYLOCOCCUS PYOGENES AUREUS 209 



hours, as little balls somewhat granular on the surface and of 

 brownish colour. On the second day they are visible to the 

 naked eye as whitish yellow points, which afterwards become 



FIG. 49. Staphylococcus pyogenes aureus, 

 young culture on agar, showing clumps of 

 cocci. 

 Stained with weak carbol-fuchsin. x 1000. 



FIG. 50. Two stab cultures 

 of staphylococcus pyogenes 

 aureus in gelatin, (a) 10 days 

 old, (b) 3 weeks old, showing 

 liquefaction of the medium 

 and characters of growth. 

 Natural size. 



more distinctly yellow. Liquefaction 



occurs around these, and little cups 



are formed, at the bottom of which 



the colonies form little yellowish 



masses. On ayar, a stroke culture 



forms a line of abundant yellowish 



growth, with smooth, shining surface, 



well formed after twenty-four hours 



at 37 C. Later it becomes 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 potatoes 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 jn. 



14 



