Pathogenicity. Natural Infection. 63 



of the skin as well as subcutaneous injection produces a typical 

 affection of erysipelas which terminates fatally in 6 to 9 days 

 (Preisz). The feeding of cultures also makes hogs ill (Corne- 

 vin, Kitt), but this mode of infection is not always successful. 

 Other animals cannot be infected. Repeated passage of the 

 bacilli through the body of liogs increases their virulence for 

 hogs (Schiitz), and passage through pigeons results simiUirly 

 for mice (Stickdorn), while the virulence is gradually dimin- 

 ished by continued cultivation. 



Natural infection usually occurs through the intestinal 

 canal, more rarely through injuries to the skin. The greater 

 frequency of the infection per os is proven by the presence of 

 the bacilli in the intestinal contents of affected hogs, also by the 

 numerous affections which occur in a herd. The infection may 

 also occur through the uninjured intestinal mucous membrane. 

 Injuries such as those from the echinorhynchus, however, facili- 

 tate infection. 



Food and drinking water are usually the carriers of the 

 infective agent, and become readily contaminated througli feces 

 or excrement, urine and other offal of affected animals. The 

 infection may also occur through the ingestion of blood and 

 meat of dead or slaughtered hogs. 



The disease is introduced into territories which have been 

 free from the infection, and is thus spread mostly by animals 

 sick or dead of tlie disease, or by their products. The bacilli 

 are present both in the blood and the excrement of the affected 

 animals, of which the infectivity has been established by the 

 experimental work of Cornevin and Kitt. The infection is 

 present in the excrement even when the hogs are infected 

 tlirough the skin. Therefore the bacilli reach the lumen of 

 the intestines through the blood. The urine of affected animals 

 may also contain erysipelas bacilli. Therefore pastures in 

 which affected animals have been kept or fields which have been 

 fertilized with the manure of such hogs are particularly dan- 

 gerous. The annual occurrence of erysipelas in herds which 

 have been exposed to such pastures or fields is thus readily 

 explained. On the other hand, pastures are frequently con- 

 taminated by improperly buried carcasses, especially since the 

 carcasses of such animals are frequently dug up by dogs and 

 hogs which scatter the infection over the pastures. If dead ani- 

 mals are thrown into flowing water the infection is transmitted 

 to herds of hogs which are pastured along the banks of the 

 streanj. 



Peddling of hogs and hog markets greatly aid in the dis- 

 semination of the disease, inasmuch as affected animals driven 

 over the roads contaminate the roads and the halting places 

 with their manure. 



The infection is further spread througli the meat of hogs 

 slaughtered in emergency, particularly when healthy animals 



