278 3Iaiiual of Veterinary Microbiology. 



But penetration may also probably take place through 

 the respiratory tract, the germs being transported 

 by the air, by foreign bodies, or merely by the mu- 

 cus. 



Cutaneous wounds are also channels of introduc- 

 tion of the parasite (actinomycosis of the testicular 

 cord in the horse ; actinomycosis of the leg in the 

 same animal in consequence of a kick ; subcutaneous 

 abscesses in cattle). 



The tumors of actinomycosis {adinomycomata) re- 

 sult from the irritation excited by the actinomyces ; 

 they frequently have the structure of granulomata; 

 the parasite nearly always occupies the center of an 

 inflammatory nodule which may readily be differen- 

 tiated into two zones, an internal, formedof epithelioid 

 cells, and a peripheral, containing fusiform and lymph- 

 oid cells and indicating the transition to the con- 

 densed connective tissue which forms the frame work 

 of the tumor. The fungus may also very frequently 

 be seen surrounded by a row of giant cells. This 

 structure resembles that of the tubercle type and 

 shows that the pathogenic action of the actinomyces 

 consists in a circumscribed and chronic irritation of 

 the tissues into which it has been carried. After 

 these tumors become softened in the center they con- 

 tain a puriform yellowish or white liquid in which 

 are suspended yellow grains, most frequently hard 

 and calcified; these grains are the actinomyces. 

 When the softening is regular the tumor acquires a 

 characteristic spongy appearance. 



It may happen, and this is the rule in man, that 

 the actinomycotic tumors become complicated with 

 suppuration. It appears to be established that the 



