276 



VETERINARY BACTERIOLOGY 



that meat and milk may become contaminated from these sources. 

 Milk and meat are probably the most common sources of infection, 

 although water has been clearly shown, in some instances, to be the 



source of epidemics. 



Bacillus psittacosis 



Nocard, in 1892, isolated an organism belonging to the inter- 

 mediate group from cases of psittacosis (Latin, psittacus, parrot), 

 a type of pneumonia supposed to be contracted from infected 

 parrots. The same organism has since that time been isolated 

 from other outbreaks. In cultural, morphologic, and physiologic 

 characters it is scarcely to be differentiated from the B. enteritidis. 

 Some differences have been found in agglutinating properties of 

 the specific sera, and this organism is believed, on these grounds, 

 by some authors to constitute a distinct species. The disease is 

 uncommon, and is of little importance. 



Bacillus typhi murium 



Loftier, in 1889, described an organism as the cause of an epi- 

 demic among the mice kept for experimental purposes. Danysz, 



in 1900, described a 

 similar, probably iden- 

 tical, organism, and 

 recommended its use in 

 the destruction of rats. 

 These forms have all the 

 morphologic and cultural 

 characteristics of the 

 enteritidis group, but 

 show some differences in 

 pathogenicity and in 

 formation of specific 

 agglutinins. Cultures of 

 these organisms have 

 Fig. 114. Bacillus typhi murium (Migula). been widely exploited as 



specific for mice and 



rats, producing a rapidly fatal disease, but as harmless to the 

 Higher animals. Reports as to their efficacy when fed to the 

 vermin are conflicting; the results seem in some cases to have 



