A CT1NOMYCETES. 36 9 



central masses and the filamentous threads making up 

 the mass of the mycelium are stained blue ; the club- 

 like extremities of the thread are red. Often the red- 

 stained hyaline material is seen to be penetrated to its 

 extremity by a sharply defined blue thread. 



Cultivation of the fungus from the actinomycotic pus 

 presents difficulties for the following reasons : Not all 

 the mycelia seen by microscopic examination are living ; 

 as a rule they grow slowly even under the best of cir- 

 cumstances ; and generally there are many other, more 

 rapidly growing, living organisms in the pus. When 

 pure cultures are obtained, it grows (according to Bos- 

 trom) on all the ordinary artificial media. It develops 

 at room-temperature, but better at that of the body. 



It grows both with and without oxygen. 



The young colonies appear as grayish points com- 

 posed of a felt- work of fine threads. As the colonies 

 become older they become denser and more opaque. 

 Very old colonies are almost leathery in consistency. 

 On blood-serum the growth after a time assumes a 

 salmon, an orange, or a yellowish-red color. Growth 

 on gelatin is accompanied by slow liquefaction. 



A yellowish-red growth, limited in extent, occurs on 

 potato. It causes no clouding of bouillon, but grows as 

 cottony clumps that sink to the bottom. 



The bulbous extremities seen upon the mycelial 

 threads fresh from the pus are not usually seen under 

 conditions of artificial cultivation. They are sometimes 

 observed in colonies located in the depths of solid media. 

 The white, powdery coating seen on old colonies repre- 

 sents the so-called l< spores." They are not, however, 

 resistant to heat, being destroyed, according to Domec, 

 by 75 C. in five minutes. 



