PRODUCERS OF ABSCESS, CELLULITIS, ETC. 463 



along the line of puncture, followed by liquefaction of 

 the medium, which rapidly extends to the sides of the 

 test-tube. At the end of two days the yellow pigmen- 

 tation begins to form, and this increases in intensity 

 for eight days. Finally, the gelatin is completely 

 liquefied, and the " golden staphylococci " form a 

 golden-yellow or orange-colored deposit at the bottom 

 of the tube. Under unfavorable conditions the staphyl- 

 ococcus aureus gradually loses its ability to make pig- 

 ment and to liquefy gelatin. 



Growth on Agar. In streak and stick cultures on 

 agar a whitish growth is at first produced, and this 

 at the end of a few days becomes golden-yellow on the 

 surface. The yellow pigmentation is produced only in 

 the presence of oxygen; colonies found at the bottom 

 of a stab culture or under a layer of oil remain white. 



Milk inoculated with this inicrococcus at the end of 

 from one to eight days is coagulated; bouillon and 

 peptone solutions are densely clouded by the lux- 

 uriant growth produced. 



In the three last-named culture media, as the result 

 of the growth of the staphylococcus aureus, there is a 

 production of acid in considerable quantities, these con- 

 sisting chiefly of lactic, butyric, a.nd valerianic acids. 

 These acids have been supposed to play a part in the 

 production of pus, in which, according to some ob- 

 servers, they are often present. 



The staphylococcus is distinguished from most other 

 pathogenic bacteria by its comparatively greater power 

 of resistance to outside influences, desiccation, etc., as 

 well as to chemical disinfectants. Cultures of the 

 staphylococcus pyogenes in gelatin or agar retain their 

 vitality for a year or more. Its thermal death-point is 



