Pathogenicity. 89 



cutaneous or su;b^tanet)us injection even in minimal doses. 

 The transmission may be made successfully by taking the point 

 of a needle dipped in blood and scarifying or pricking the 

 skin at any part of the body. In this manner as well as by 

 subcutaneous and intramuscular inoculations most of the dif- 

 ferent species of domestic fowl (chickens, ducks, geese, turkeys, 

 pigeons, pheasants and fancy birds) and small wild birds 

 (sparrows, finch, etc.) are easily infected. These birds also 

 become affected by the dropping of a culture into the conjunc- 

 tiva, nose or the laryngeal mucous membrane, as well as on 

 superficial wounds of the comb, wattles and feet (Hertel). 

 Further, the disease may be produced by feeding of blood, meat, 

 organs and intestinal contents of affected animals as well as 

 of pure cultures. The disease produced by inoculation usually 

 results in death in from 12 to 24 hours, while when produced 

 by feeding of the virus it terminates only after a longer period 

 (according to Semmer sometimes only after 8 to 12 days). 



Of other animals rabbits and mice are susceptible to the 

 disease, whereas in guinea pigs (Pasteur), cattle, sheep and 

 horses (Kitt) the subcutaneous inoculation produced only an 

 abscess at the point of injection (guinea pigs, however, are 

 easily infected by intraperitoneal inoculation). Intravenous 

 injections of very virulent cultures are pathogenic for domestic 

 mammals (hogs, dogs and cats), while through feeding of such 

 material infection is successful only in rabbits. Stange & 

 Persdorf observed a simultaneous infection in chickens and 

 hogs which they traced to an infection with the fowl cholera 

 virus. On the other hand, Koske has not succeeded in infecting 

 hogs artificially with the cholera virus. On man the eating of 

 affected fowl has apparently no harmful effects. 



Repeated passage of the bacteria through the bodies of 

 chickens, pigeons or sparrows increases their pathogenicity 

 which is still more increased by passage through guinea pigs 

 (intraperitoneally). In this way the virulence may be increased 

 to such an extent that intravenous injections of such virus 

 may kill domestic mammals in a few hours (Lignieres). On 

 the other tand, the air, and more so the combined action of 

 air and sunlight, attenuates the virulence of the bacteria 

 (Pasteur, see page 94). 



The bax;teria produce toxins in artificial cultures. Pasteur found 

 that the subcutaneous injections of large quantities of filtrate of bouillon 

 cultures free from bacteria cause in chickens a somnolence and stupor 

 lasting for several hours, similar to that seen in the disease. This fact 

 was later confirmed by Salmon, Stange, Kitt, as well as by Klett & 

 Braun. (See page 84.) On the other hand, Calamida obtained from 

 a 12-day old bouillon culture a hemolysin which has the strongest 

 ' action on rabbits, less on guinea pigs and still less on the red blood 

 corpuscles of chickens. 



Natural infection usually results from the ingestion of 

 droppings or saliva of affected fowls, contaminated feed, viscera 



