INFECTIOUS DISEASES 



277 



pi'oducts of the carcasses of swine that were infected with the filtrable 

 \drus when killed or in which death resulted from cholera. 



From the foregoing the ease with which infection is transmitted 

 may readily be comprehended. The virus is transmitted from an 

 infected swine on non-infected premises to other swine, or to soil, 

 food, water, bedding, and general surrovindings, thus practically in- 

 suring infection of exposed swine on the same premises and other 

 premises as well. Serious outbreaks of cholera are sometimes trace- 

 able to the introduction of a new boar, or other animal, that is 

 infected. 



If the carcass of a swine dead of cholera is permitted to remain 



A B 



Pig. 72. Lymph-Nodes. A, normal; b, hyperemic due to hog cholera. 



in the hog lot, other swine will become infected by eating the flesh, 

 and the soil and surroundings will be contaminated with the virus. 

 Some men have shown their faith in the protection of swine against 

 cholera with serum by putting the carcass of a swine dead of cholera 

 in their pens and thus infecting their premises. 



From the lack of care in the use of virus in producing a perman- 

 ent immunity there is little doubt but that farms have become in- 

 fected. Food hauled in wagons or other vehicles that have been 

 previously used in transporting cholera-infected swine may become 



