292 ACTINOMYCOSIS AND ALLIED DISEASES. 



condition is sometimes found in the subcutaneous tissue, espe- 

 cially when the disease has not advanced far, and also in dense 

 fibrous tissue. In most cases, however, and especially in inter- 

 nal organs, suppuration is the outstanding feature. This is to 

 be associated with abundant growth of the parasite in the fila- 

 mentous 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 somewhat charac- 

 teristic, 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 immediately around the 

 colonies are usually irregularly rounded, or may even be some- 

 what 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. Swell- 

 ing 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 intes- 

 tine, generally of the large intestine. The parasite penetrates 



