ACTINOMYCETES 435 



bulbous or nodular, or both, and they may show branching. 

 Sometimes the free ends of the threads are only slightly or 

 not at all swollen. 



These mycelia the actinomyces may be stained by 

 the ordinary aniline dyes, or by the Weigert or the Gram 

 method, though by either of these procedures their full struct- 

 ure is not, as a rule, brought out. The reason for this is 

 that the terminal bulbs are not due to enlargement of the 

 thread itself, but rather to a colloid degeneration of its 

 enveloping sheath. This colloid matter, having different 

 microchemical reactions from the enclosed thread, requires 

 different reagents to stain it. The entire structure may be 

 seen when the fungus is stained first by the Gram method, 

 and subsequently with eosin or saffranin. For the demon- 

 stration of the fungus in sections, the method of Mallory 

 gives satisfaction. It is as follows; Stain the section on the 

 slide with gentian- violet; clear and dehydrate with aniline 

 oil in which a little basic fuchsin has been dissolved; remove 

 the aniline oil-fuchsin with xylol, and mount in xylol balsam. 

 In sections treated in this way the coccus-like 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 circumstances; 

 and generally there are many other, more rapidly growing, 

 living organisms in the pus. When pure cultures are ob- 

 tained, it grows (according to Bostrom) on all the ordinary 



