THE PATHOGENIC HIGHER BACTERIA 537 



at the periphery of the colony. The pus from so-called pseudo- 

 tuberculosis, streptothrix and cladothrix infections do not exhibit 

 these characteristic "drusen." 



Morphology. Actinomyces bovis is a pleiomorphic organism belong- 

 ing to that group of microorganisms intermediate between the true 

 bacteria (Schizomycetes) and the molds (Hyphomycetes) known as 

 the Trichomycetes. It is best observed in pus from active lesions, 

 in which it occurs in gray or yellowish colonies or granules (drusen), 

 frequently large enough to be visible to the naked eye. The colonies 

 vary in size but usually measure from 0.5 to 2 mm. in diameter. 

 Such a colony, crushed between two slides or a slide and cover glass, 

 appears as a rosette-shaped aggregation of densely packed filaments 



FIG. 81. Actinomyces, bouillon culture. 



which exhibit a radial arrangement. The centre is so crowded with 

 organisms that it appears opaque and usually contains many ovoid 

 bodies measuring from 1 to 1.5 microns in diameter. According to 

 Wright, 1 these ovoid or coccoid bodies are formed by the disintegration 

 of the filaments. The periphery of the colony contains many inter- 

 laced branching filaments, many of which exhibit on their distal ends, 

 an enlargement or "club" which is a hyaline layer or sheath about 

 the extremity of a filament. These filaments measure about 10 to 

 12 microns in length and the clubs 20 to 30 microns in length by 8 

 to 10 microns in diameter. Grown in artificial media club formation 

 is absent unless blood or blood serum 2 is added, but even in enriched 

 media the formation of clubbed forms is irregular. 



1 Loc. cit. 2 Wright, loc. cit., p. 336. 



