Staphylococci Pyogenes Aureus et Albus 291 



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. 91), 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 



Fig. 91. Staphylococcus pyogenes aureus. Puncture culture three 

 days old in gelatin (Frankel and Pfeiffer). 



this precipitate in particular that gives the organism its 

 name " golden Staphylococcus." 



Agar-agar. The growth of the golden Staphylococcus 

 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 



