MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 779 



commonly affected, but humans, hogs, horses, sheep, and dogs are sus- 

 ceptible. Actinomyces produces a local disease which never spreads 

 widely or rapidly. 



Actinomycosis is to be considered as an infectious disease which 

 spreads by inoculation. 



The disease produced by this microorganism usually runs a chronic 

 course and is distinguished especially by enlargement of affected parts, 

 by hardening of the tongue, and by suppuration. The latter is one of 

 the most constant and conspicuous characteristics. Head parts, in- 

 cluding the facial bones, are commonly affected; lungs and various other 

 internal organs and even the vertebrae may be involved. 



The extent of injury done by this fungus depends on the location 

 and size of the involved area. Usually the most conspicuous injury is 

 impaired nutrition. 





FIG. 164. Actinomyces 



bovis. The ray-fungus from cow. (Diagrammatic.) 

 (After Williams.') 



There is probably but little risk to human health from actinomycosis 

 n cattle as parts of the carcass most commonly affected are not eaten 

 and edible parts are usually cooked. It is generally considered that 

 sound portions of carcasses which do not show generalized disease are 

 fit for human food purposes. 



There are apparently several varieties of Actinomyces all of which 

 are recognized for the present as Actinomyces boms. 



The varieties of Actinomyces are to be regarded as members of a very 

 complicated group of microorganisms higher than bacteria and are 

 generallv spoken of as fungi. Actinomyces bovis is commonly known 



