FOWL CHOLEKA. 215 



fowl is the only medium which really suits the mi- 

 crobe of fowl cholera. It suffices to inoculate the fowl 

 with the hundredth, even the thousandth, part of a 

 drop of this mixture, to produce the disease and cause 

 death. But here is a strange peculiarity. If guinea- 

 pigs are inoculated with this little parasite they are 

 hardly ever killed by it. Guinea-pigs of a certain age 

 generally exhibit only a local lesion at the point of 

 inoculation, which ends in an abscess more or less 

 prominent. After opening spontaneously, the abscess 

 closes again and heals, while the animal preserves its 

 appetite and its appearance of health. These abscesses 

 sometimes last several weeks. They are surrounded 

 by a pyogenic membrane and filled with a creamy 

 pus, in which the microbe swarms side by side with the 

 pus globules. It is the life of the microbe inoculated 

 under the skin which causes the abscess. The abscess, 

 with the membrane which surrounds it, becomes for 

 the little organism a sort of closed vessel, which it is 

 even easy to tap without sacrificing the guinea-pig. 

 The organism is mixed with the pus in a state of great 

 purity, and although it is localised its virulence is ex- 

 treme. When fowls are inoculated with the contents 

 of the abscess they die rapidly, while the guinea-pig, 

 which has furnished the virus, gets well without the 

 least suffering. A curious instance this is of the 

 local evolution of a very virulent microscopic organism, 

 which produces neither internal disorders nor the 



