312 



Suppuration 



temperatures above 8°C. and below 4S°C., the most rapid develQp- 

 ment being at about 37°C. 



Colonies. — Upon the surface of gelatin plates the colonies appear 

 as small whitish points, after from twenty-four to forty-eight hours, 

 rapidly extending to the surface and causing extensive liquefaction 

 of the medium. The formation of the yellow pigment can be best 

 observed near the center of the colonies. Under the microscope the 

 colonies appear as- round disks with circumscribed, smooth 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, full of clouded liquid, at 

 the apex of which a collection of golden or 

 orange-yellow precipitate is always present in 

 Staphylococcus aureus. It is this precipitate 

 in particular that gives the orgaiiism its name, 

 " golden staphylococcus." 



Agar-Agar. — The growth of the golden 

 staphylococcus upon agar-agar is subject to 

 considerable variation in the 'quantity of pig- 

 ment produced. Sometimes, perhaps rarely, it 

 is golden; more commonly it is yellow, often 

 cream color. Along the whole line of inocula- 

 tion a moist, shining, usually well-circum- 

 scribed growth occurs. When the develop- 

 ment occurs rapidly, as in the incubator, it 

 exceeds the rapidity of color production, so 

 that the center of the growth is distinctly 

 colored, the edges remaining white. 



Potato. — Upon potato the growth is luxuriant, Staph- 

 ylococcus 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 a diffuse 

 cloudiness, with a small quantity ■ of slightly yellowish sediment. 

 The reaction of the medium becomes increasingly acid. 



Milk. — In milk, coagulation takes place in about eight days, and 

 is followed by gradual digestion of the casein. In htmus milk slow 

 acid production is observed. 



Blood-Serum.^ — Discrete and confluent yellow colonies appear on 

 the surface of the medium in twenty-four hours. Through softening 



Fig. 104.' — Staph- 

 ylococcus pyogenes 

 aureus. Puncture 

 culture three days 

 old in gelatin (Fran- 

 kel and Pfeiffer). 



