MICROSCOPICAL CHARACTERS. 



291 



running for a distance in the centre, and may have a knob-like 

 extremity. In many of the colonies in the human subject the 

 clubs are absent. In the ox, on the other hand, where there are 

 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 impossible 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 



*^ 



FIG. 103. Colonies of actinomycosis, showing general structural arrangement and 

 clubs at periphery. From pus in human subject. 

 Stained by Gram and safranin. x 60. 



the altered staining reaction. Clubs showing intermediate stain- 

 ing reaction have been described by M'Fadyean. The view 

 that the clubs are organs of fructification has been abandoned 

 by most authorities, and there appears to us little evidence in 

 support of it. 



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 is a 

 comparatively large production of granulation tissue, with only a 

 little softening in the centre, so that the mass feels solid. This 



