148 SUPPURATION AND ALLIED CONDITIONS. 



out to the wall of the tube (Fig. 41). In gelatine plates 

 colonies may be seen with the low power of the microscope 



in twenty-four 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 

 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 culture forms a line 

 of abundant opaque 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 yellow oil paint. 

 Single colonies on the surface 

 of agar are circular discs of 

 similar appearance, which 

 FIG. 4 i. -Two stab cultures of may reach 2 mm. or more in 



staphylococcus pyogenes aureus in,. ^ , , , 



gelatine, (a) 10 days old, (b) 3 weeks dimeter. On/tfAl/towitgTOWS 

 old. Showing liquefaction of the well at ordinary temperature, 

 medium and characters of growth, forming a somewhat abund- 

 Natural size. L , l c 



ant layer of orange colour. 



In bouillon it produces a uniform turbidity, which afterwards 

 settles to the bottom as an abundant layer which 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 gelatine often being alive after having been kept 



