Bacillus Psittacosis 531 



kill it in from twelve to eighteen hours. Guinea-pigs are 

 more resistant. Subcutaneous injection of dogs produces a 

 hard, painful swelling, which persists for a short time and 

 then disappears without suppuration. It is also infectious 

 for man, a number of epidemics of peculiar pneumonia, char- 

 acterized by the presence of the bacillus in the blood, traceable 

 to diseased parrots, having been reported. 



Differentiation. Bacillus psittacosis can best be differ- 

 entiated from the typhoid and the colon bacilli and others 

 of the same group by its pathogenesis and by the reaction 

 of agglutination. Typhoid immune serum produces some 

 small agglutinations, but a comparison between these and 

 the agglutinations formed by cultures of the typhoid bacillus 

 shows immediately that the micro-organisms are dissimilar. 

 Differentiation is best made out when the prepared hanging- 

 drop specimens of serums and cultures are kept for some 

 hours in an incubating oven. It is not known whether the 

 bacillus is peculiar to the intestines of parrots, invading their 

 tissues when they become ill, or whether it is a purely path- 

 ogenic micro-organism found only in psittacosis. 



