154 



PATHOGENIC BACTERIA. 



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

 inverted cone (Fig. 46) full of clouded liquid, at the apex 





FIG. 46. Staphylococcus pyogenes aureus : puncture-culture three days old 

 in gelatin (Frankel and Pfeiffer). 



of which a collection of golden or orange-yellow precipi- 

 tate is always present. It is this precipitate in particu- 

 lar that gives the organism its name, "golden staphylo- 

 coccus." 



The most characteristic growth is upon agar-agar. 

 Along the whole line of inoculation an orange-yellow, 

 moist, shining 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 golden ; the edges may be white. 



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. 



