PATHOGENIC BACTERIA l6l 



Spores have not been found, though the cocci are very 

 resistant. 



Properties. Without movement; liquefying gelatin. It gives 

 rise to an orange-yellow pigment in the various cultures. 



Growth. It grows moderately fast at ordinary temperature, 

 and can live without air, a facultative aerobin and anaerobin. 



Colonies on Gelatin. On second day small dots on the sur- 

 face, containing in their center an orange-yellow spot. The 

 gelatin all around the colony is liquefied; the size is never much 

 greater than that attained the second day. 



Fig. 96. Staphylococcus pyogenes albus (Jakob). 



Colonies on A gar. The pigment remains for a long 

 time. 



Stab-culture. At first, gray growth along the track, which, 

 after three days, has settled at the bottom of the tube in a yel- 

 low, granular mass, the gelatin being all liquid. 



Stroke-culture on Agar. The pigment diffused over the sur- 

 face where the growth is, in moist masses. 



Potato. A thin white layer which gradually becomes yellow 

 and give out a doughy smell. 



Staining. Very readily colored with ordinary stains; also 

 with Gram's method. 



