256 Wound Infection; Suppuration 



edges. They are distinctly granular and dark brown. When 

 the colonies are grown upon agar-agar plates, the formation 

 of the pigment is more distinct. 



Gelatin Punctures. In gelatin the growth occurs along 

 the whole length of the puncture, causing an extensive 

 liquefaction of the medium in the form of a long, narrow, 

 blunt-pointed, inverted cone, sometimes described as being 

 like a stocking (Fig. 75), full of clouded liquid, at the 

 apex of which a collection of golden or orange-yellow pre- 

 cipitate is always present in Staphylococcus aureus. It is 

 this precipitate in particular that gives the organism its 

 name "golden Staphylococcus." 



Agar-agar. The growth of the golden Staphylococcus 



Fig. 74. Staphylococcus pyogenes aureus. Colony two days old, seen 

 upon an agar-agar plate. X 40 (Heim). 



upon agar-agar is subject to considerable variation in the 

 quantity of pigment produced. Sometimes, perhaps rarely, 

 it is golden ; more commonly it is yellow, often cream color. 

 Along the whole line of inoculation a moist, shining, usually 

 well-circumscribed growth occurs. When the development 

 occurs rapidly, as in the incubator, it exceeds the rapidity of 

 color-production, so that the center of the growth is dis- 

 tinctly colored, the edges remaining white. 



Potato. Upon potato the growth is luxuriant, Staphylo- 

 coccus aureus producing an orange-yellow coating over a 

 large part of the surface. The potato cultures may give off 

 a sour odor. 



Bouillon. When grown in bouillon, the organism causes 



