TISSUE LESIONS. 265 



colonies are usually found to be in an old and somewhat 

 degenerated condition. 



In the human subject, the colony is generally a ball of 

 interlacing filaments, whilst clubs may be present at the 

 periphery, or may be absent. There is often at one side a 

 part which is so dense that its structure cannot be made 

 out, and this dense part may grow round the colony so as 

 to form a sort of hollow sphere, from the outer surface of 

 which filaments radiate outward for a short distance. In 

 the dense parts many cocci and bacillary forms are often 

 present. Between the filaments there is a homogeneous or 

 slightly granular ground substance, and this may form a 

 narrow zone around the colony, especially when it is 

 growing quickly. The older colonies show irregularity of 

 structure, and the filaments may be much broken up. 



In the ox the clubs are usually the most prominent 

 feature ; in most of the colonies the filaments have dis- 

 appeared in part, and in some it may be impossible to find 

 any. Even the clubs may be partly broken down. This 

 condition is also sometimes found in old colonies in the 

 human subject. In the ox the colonies may have under- 

 gone calcification. The growth of the parasite and progress 

 of the disease are,, therefore slower than in man, and it is 

 only in parts where the disease has recently appeared that 

 filamentous forms are well seen. 



Tissue Lesions. In the human subject the parasite pro- 

 duces by its growth a chronic inflammatory change, which 

 usually ends 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 condition is sometimes 

 found in the subcutaneous tissue, especially when the 

 disease has not advanced far, and also in dense fibrous 

 tissue. In most cases, however, and especially in internal 

 organs, suppuration is the outstanding feature. In an 

 organ such as the liver, multiple foci of suppuration are 

 seen at the spreading margin of the disease, presenting 

 a honeycomb appearance which is somewhat characteristic, 



