PARASITES AND DISEASE (VEGETABLE PARASITES) 177 



upon the physiologic processes is not well understood. 

 No toxin has been demonstrated, though an attack con- 

 fers immunity, and the symptoms of the intestinal 

 form diarrhea, vomiting, fever, and rapid pulse 

 resemble a toxemia. In view of the fact that immunity 

 may be produced by vaccination, both with attenuated 

 and dead cultures, it would seem that the immunity was 

 a result of phagocytosis. The opsonic index is high in 

 immune animals and low in susceptible ones, which 

 would also support the phagocytic theory of the im- 

 munity. 



ACTINOMYCOSIS 



Definition. A chronic infectious disease of cattle, 

 occurring occasionally in man, caused by Actinomyces 

 bovis and characterized by the formation of lumpy 

 tumors. 



Etiology. The disease is due to a peculiar vegetable 

 organism termed the ray fungus. It occurs chiefly in 

 cattle, but occasionally in man, the horse, pig, sheep, 

 dog, cat, and elephant. The mode of infection is still 

 in question, instances occurring in individuals having 

 no association with cattle. Nor has there been any 

 observation of instances of direct contagion among 

 cattle. Because of the frequency of infection in the 

 jaw and about the throat it is supposed to occur through 

 carious teeth. 



Morbid Anatomy. This organism produces a granu- 

 lation tumor consisting of proliferating connective-tissue 

 12 



