540 TRICHOMYCETES, ACTINOMYCETES, HYPHOMYCETES 



usually the mouth, although cutaneous infections have been described. 

 The mouth and adnexa and the pharynx are more commonly the site 

 of the initial localization of the organism, but the lungs or the alimen- 

 tary canal may be first involved. The earliest stage of the infection 

 is a small nodule not unlike a tubercle; microscopically it is made up 

 of small round cells, epithelioid cells and giant cells. This soon softens 

 and sinuses often are formed, through which the pus escapes. The 

 surrounding connective tissue proliferates rapidly, forming a dense 

 encapsulation through which invasion of neighboring tissue takes 

 place; often the disease spreads in one direction w r hile simultaneously 

 the older lesion becomes cicatrized. Death frequently occurs through 

 secondary invasion by adventitious bacteria. 



FIG. 84. Mucor sporangium, 



Actinomycosis is not a contagious disease and it is practically 

 impossible to infect experimental animals, as guinea-pigs and rabbits, 

 with the virus. Wright 1 has been unable to produce progressive 

 actinomycosis in these animals, although he succeeded occasionally 

 in inducing a localized purulent nodule formation in guinea-pigs, in 

 which granulation tissues and colonies of Actinomyces appeared, some 

 of which showed poorly defined clubs. 



The disease is stated to be transmitted through wounds caused by 

 certain grains, particularly those which possess barbs, but the evidence 

 is not wholly convincing. 



The diagnosis of actinomycosis is best made by microscopic exam- 

 ination of sputum, or the pus from the lesions. The demonstration 

 of the characteristic "drusen" with their club-shaped peripheral 



1 Loc. cit. 



