PATHOGENIC STREPTOTHRICES. 363 



or granules, while at the periphery the free ends of the 

 threads are more or less distinctly 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 its 

 full structure is not, as a rule, brought out. The reason 

 for this is that the terminal bulbs are not due to enlarge- 

 ment of the thread itself, but rather to a colloid degen- 

 eration of its enveloping sheath. This colloid matter, 

 having different ijaicrochemical 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 demonstration of the fungus 

 in sections, the method of Mallory gives satisfaction. 

 It is as follows : Stain the section on the side 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 : AH the 

 mycelia seen by microscopic examination are not living; 

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

 cumstances ; and generally there are many other, more 



