162 ACTINOMYCETES 



Colonies exhibit a considerable degree of polymorphism, but no stable 

 variants have been established. Tougher in texture than those of Actino- 

 myces bovis. Old colonies warted in appearance. Adherent to the medium. 



Gelatin: Occasionally scant, flaky growth. No liquef action. 



Liquid media: Usually clear. 



Pigments: No soluble pigments on protein media. No insoluble pig- 

 ments produced by growth. 



Egg or serum media: No proteolytic action. 



Milk: Becomes acid but usually does not clot. No peptonization. Fre- 

 quently no growth. 



Temperature: Optimum 37°C. 



Source: From 2 cases of human actinomycosis: (1) a retromaxillary 

 tumor, (2) actinomycosis of lung and breast (Wolff and Israel). 



Remarks: Anaerobic to microaerophilic. No hemolysis. 



