TISSUE LESIONS. 287 



mediate staining 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 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. This is to 

 be associated with abundant growth of the parasite in the 

 filamentous form. 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 some- 

 what characteristic, whilst the colonies of the parasite may 

 be seen in the pus with the naked eye. In the older parts 

 the abscesses have become confluent, and formed large 

 areas of suppuration. The pus is usually of greenish- 

 yellow colour, and of somewhat slimy character. 



In cattle the tissue reaction is more of a formative type, 

 there being abundant growth of granulation tissue, which 

 may result in large tumour-like masses, usually of more or 

 less nodulated character. The cells immediately around the 

 colonies are usually irregularly rounded, or may even be 

 somewhat columnar in shape, whilst farther out they 

 become spindle-shaped and concentrically arranged. It is 

 not uncommon to find leucocytes or granulation tissue 

 invading the substance of the colonies, and portions of the 

 parasite, etc., may be contained within leucocytes or within 

 small giant cells which are sometimes present. A similar 

 invasion of old colonies by leucocytes is sometimes seen in 

 human actinomycosis. 



Origin and Distribution of Lesions. The lesions in the 

 human subject may occur in almost any part of the body, 



