Microbic Diseases Individually Considered. 179 



of duck cholera are a little larger than those of 

 chicken cholera. Like the latter they do not admit 

 of double staining. 



Their culture on the different solid media is richer 

 than that of chicken cholera. This peculiarity is es- 

 pecially noticeable upon potato, which is a very bad 

 field for the growth of the organism of chicken 

 cholera, whilst that of duck cholera grows very well 

 on this medium. 



Whilst chicken cholera is pathogenic for ducks, 

 duck cholera is inoffensive for chickens and pigeons. 

 The latter disease does not even kill all ducks with 

 the same rapidity ; some species resist for a longer 

 time than others. 



The rabbit succumbs to duck cholera as well as to 

 chicken cholera, but requires a larger dose of the 

 former than of the latter. 



It might be thought that the virus of duck cholera 

 was an attenuated form of that of chicken cholera. 

 But inoculation of the former to the chicken ought 

 then to vaccinate against the latter disease, which is 

 not the case. 



The penetration of the germs, in the case of spon- 

 taneous contamination, takes place by the digestive 

 canal ; this mode of infection has also been demon- 

 strated experimentally. The experimental disease 

 can also be communicated by hypodermic injection.* 



* [Several other microbic diseases of fowls have been described : 

 Vibrio-cholera of chickens ( Vibrio MeUchnikovi, Gameleia) in 

 Russia, — caused by an organism presenting morphological and 

 cultural resemblances with that of Asiatic cholera ; septicaemia 

 in geese {Spirochete anserina, Sakharoff) in swampy regions of 

 Transcaucasia — a spiral microbe resembling that of relapsing fever 



