DISEASES OF POULTRY. 233 



followed by the contributions of Pasteur, who, in 

 1880, cultivated the germ in chicken broth and showed 

 that its virulence might be reduced to such an extent 

 that it could safely be lised for vaccination. This is 

 the first case in which a viruleht germ was success- 

 fully modified in a laboratory and made to act as a 

 vaccine. It led to the preparation of vaccines for a 

 number of diseases, more particularly anthrax, black 

 quarter, and rabies. 



The disease was at about the same time investigated 

 by the author, who gave special attention to vaccina- 

 tion and the effect of disinfectants in destroying this 

 virus. 



General Characters. — Fowl cholera attacks 

 all varieties of domesticated poultry — chickens, ducks, 

 geese, pigeons, turkeys, and also caged birds such as 

 parrots and canaries. It also affects some species of 

 wild birds. 



The infection generally occurs by taking food or 

 drink contaminated with the excrement of sick birds. 

 It is, also, possible for birds to be infected through 

 wounds of the skin or by^ inhalation of the germs in 

 the form of dust suspended in the air. They often 

 take the germs into their bodies by consuming parti- 

 cles of flesh or blood from the carcasses of affected 

 birds that have died or have been killed. 



This disease is generally introduced upon a farm, 

 or in a locality, with new birds purchased for improv- 

 ing the flocks, or with eggs for hatching. When it 

 exists in a district it may be disseminated by wild 

 animals or wild birds. 



Fowl cholera is communicable by inoculation to 

 rabbits and mice. Guinea pigs are not very suscepti- 

 ble ; the young animals may die but the adult ones 



