TISSUE LESIONS 321 



much older colonies, the clubs constitute the most prominent 

 feature, whilst in most colonies the filaments are more or less 

 degenerated, and it may sometimes be imi>ossible to find any. 

 They often form a dense fringe around the colony, and when 

 stained by Gram's method retain the violet stain. They have, 

 in fact, undergone some further chemical change which produces 

 the altered staining reaction. Occasionally in very chronic 



FIG. 93. Colonies of actinomyces, showing general structural 

 arrangement and clubs at periphery. From pus in human subject. 

 Stained Gram and safranin. x 60. 



lesions in the human subject the clubs stain with Gram's 

 method. Clubs showing intermediate staining reaction have 

 been described in the ox by McFadyean. The club-formation 

 probably represents a means of defence on the part of the 

 parasite against the phagocytes of the tissue ; the view, formerly 

 held, that the clubs are organs of fructification has now been 

 generally abandoned. 



Tissue Lesions. In the human subject the parasite produces 

 by its growth a chronic inflammatory change, usually ending 

 in a suppuration which slowly spreads. In some cases there 

 21 



