STAPHYLOCOCCnS PYOGENES AUREUS 203 



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 



Ki(i. r>0.- Staphylococeoa pyogenes auveus, 

 young culture on agar, showing clumps 

 of cocci. 



Stained with weak carbol-fuchsin. x 1000. 



more distinctly yellow. Liquefac- 

 tion occurs around these, and little 

 -ii] is are formed, at the bottom 

 <>t 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 

 ;i -tivjik 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 tin- various media it renders the reaction acid, and it 

 n tabulates milk, in which it readily grows. The cultures have 

 a siiiiii-wliat sour odour. It lia< <-<>nsi<lrral>lr tenacity of life 



FKI. :")!. 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. 



