TISSUE LESIONS 291 



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 associated with abundant growth of the parasite 

 in the filamentous form presenting a honeycomb appearance. 

 In an organ such as the liver, multiple foci of suppuration are 

 seen at the spreading margin of the disease, 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, and often consisting of well-developed 

 fibrous tissue containing areas of younger formation in which 

 irregular abscess formation is usually present. The cells immedi- 

 ately 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, the 

 paths of entrance being very various. In many cases the 

 entrance takes place in the region of the mouth probably 

 around a decayed tooth by the crypts of the tonsil, or by some 

 abrasion. Swelling and suppuration may then follow in the 

 vicinity and may spread in various directions. The periosteum 

 of the jaw or the vertebrae may thus become affected, caries or 

 necrosis resulting, or the pus may spread deeply in the tissues of 

 the neck, and may even pass into the mediastinum. Occasionally 

 the parasite may enter the tissues from the oesophagus, and in a 

 considerable number of cases the primary lesion is in some part 

 of the intestine, generally of the large intestine. The parasite 

 penetrates the wall of the bowel, and may be found deeply 

 between the coats, surrounded by purulent material. Thence it 

 may spread to the peritoneum or to the extraperitoneal tissue, 



