CHICKEN-CHOLERA. 327 



white, shining, rather luxuriant, and devoid of charac- 

 teristics. 



Upon potato no growth occurs except at the incubation- 

 temperature. It is a very insignificant, yellowish-gray, 

 translucent film. 



The introduction of pure cultures of this bacillus into 

 the tissues of chickens, geese, pigeons, sparrows, mice, 

 and rabbits is sufficient to produce the disease. Feed- 

 ing chickens, pigeons, and rabbits with material in- 

 fected with the bacillus is also sufficient to produce the 

 disease with pronounced intestinal lesions. Guinea-pigs 

 usually seem immune, though they succumb to very 

 large doses, especially when given intraperitoneally. 



The autopsy shows that when the bacilli are intro- 

 duced subcutaneously a true septicemia results, with the 

 addition of a hemorrhagic exudate and gelatinous infil- 

 tration at the seat of inoculation. The liver and spleen 

 are enlarged, circumscribed, hemorrhagic, and infiltrated 

 areas occur in the lungs ; the intestine shows an in- 

 tense inflammation with red and swollen mucosa, and 

 occasional ulcers following small hemorrhagic spots. 

 The bacilli are found in all the organs. If, on the other 

 hand, the disease has been produced by feeding, the 

 bacilli are chiefly to be found in the intestine. Pasteur 

 found that when pigeons were inoculated into the pectoral 

 muscles, if death did not come on rapidly, portions of the 

 muscle (sequestra) underwent degeneration and appeared 

 anemic, indurated, and of a yellowish color. 



The bacillus of chicken-cholera is one whose peculiar- 

 ities can be made use of for protective vaccination. 

 Pasteur discovered that when cultures are allowed to 

 remain undisturbed for several months, their virulence 

 is greatly lessened, and new cultures planted from these 

 are also attenuated. When chickens are inoculated with 

 such cultures, no other change occurs than a local in- 

 flammatory reaction by which the birds are protected 

 against virulent bacilli. From this observation Pasteur 

 worked out a system of protective vaccination in which 



