322 ACTINOMYCOSIS AND ALLIED DISEASES 



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. In an organ such as the liver, multiple foci 

 of suppuration are seen at the spreading margin of the disease, 

 often presenting a honeycomb appearance, 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, 

 however, irregular abscess formation may be present. 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, 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 



