Morphology 805 



tangled mass of mycelial threads. In an outer zone these 

 threads are seen to terminate in conspicuous, club-shaped, 

 radiating forms which give the colonies their rosette-like 

 appearance. The clubs are inconspicuous in the human 

 lesions of the disease. 



The pleomorphism of the organism and the branched 

 network it forms class it among the higher bacteria in the 

 genus Actinomyces. When the clumps formed in artificial 

 cultivations of the parasite are properly crushed, spread 



Fig. 264. Actinomyces granule crushed beneath a cover-glass, 

 showing radial striations in the hyaline masses. Preparation not 

 stained; low magnifying power (Wright and Brown). 



out, and stained, the long mycelial threads, 0.3-0.5 p. in 

 thickness, frequently show flask- or bottle-like expansions 

 the clubs at the ends. These probably depend upon 

 gelatinization of the cell-membrane of the degenerating 

 parasite. The club is one of the chief characteristics of the 

 organism. In sections of tissue the radiating filaments are 

 very distinct, and the terminal clubs are all directed outward, 

 closely packed together, and making the whole mass form 

 a rounded little body often spoken of as an "actinomyces 

 grain." When tissues are stained first with carmin and then 

 by Gram's method, the fungous threads appear blue-black, 

 the clubs red. The cells of the tissues affected and a larger 

 or smaller collection of leukocytes form the surrounding 

 resisting tissue-zone. 



