BACTERIA AND DISEASE 317 



been mistaken for other diseases or have received popular 

 names. 



Here we can only mention the most outstanding facts 

 concerning the disease. It is caused by the " ray fungus," 

 or Streptothrix actinomyces, which, growing on certain 

 cereals, often gains entrance to the tissues of man and beast 

 by lacerations of the mucous membrane of the mouth, by 

 wounds, or by decayed teeth. Barley has been the cereal 

 in question in some cases. The result of the introduction 

 of the parasite is what is termed an " infective granuloma. " 

 This is, generally speaking, of the nature of an inflammatory 

 tumour composed of round cells, epithelioid cells, giant 

 cells, and fibrous tissue, forming nodules of varying sizes. 

 In some cases they develop to large tumours, in others they 

 soon break down. Actinomycosis in some ways closely 

 resembles tuberculosis in its tissue characters. 



In the discharge or pus from human cases of the disease 

 small sulphur-yellow bodies may be detected, and these are 

 tufts of " clubs " which are the broken-down rays of the 

 parasite; for in the tissues which are affected the parasite 

 arranges itself in a radiate manner, growing and extending 

 at its outer margin and degenerating behind. In cattle the 

 centre of the old ray becomes caseated, like cheese, or even 

 calcified, like a stone. In the human disease abundant 

 " threads " are formed as a tangled mass in the middle of 

 the colony. As clubs characterise the bovine actinomy- 

 cosis, so threads are a feature of the human form of the 

 disease. But in both there is a third element, namely, 

 small round cells, called by some spores, by others simply 

 cocci. Authorities are not yet agreed as to the precise 

 significance and role of these round cells. The life-history 

 of the micro-organism may be summed up thus : 



" The spores sprout into excessively fine, straight or sinuous, 

 and sometimes distinctly spirilliform threads, which branch irreg- 



