SUPPURA TION. 251 



faction in the form of a long, narrow, blunt-pointed, in- 

 verted cone (Fig. 53) full of clouded liquid, at the apex of 

 which a collection of golden or orange-yellow precipitate 

 is always present. It is this precipitate in particular that 

 gives the organism its name, "golden staphylococcus." 



The growth of the golden staphylococcus upon agar- 

 agar is subject to considerable variations in the color 

 produced. Sometimes, perhaps rarely, it is golden ; 

 more commonly it is yellow, often cream color. Aloug 

 the whole line of inoculation a moist, shining, usually 

 well-circumscribed growth occurs. When the growth 

 takes place rapidly, as in the incubator, it exceeds the 

 rapidity of color-production, so that the centre of the 

 growth is distinctly colored, the edges remaining white. 



Fig. 52. — Staphylococcus pyogenes aureus: colony two days old, seen upon an 

 agar-agar plate; X40 (Heim). 



Upon potato the growth is luxuriant, producing an 

 orange-yellow coating over a large part of the surface. 

 The potato-cultures give off a sour odor. 



When grown in bouillon the organism causes a diffuse 

 cloudiness. 



In milk coagulation takes place, and is followed by 

 gradual digestion of the casein. 



The Staphylococcus albus is exactly the same as the 

 aureus, with the exception that in all media it is con- 

 stantly colorless. 



