NATURE AND CAUSE OF HOG CHOLERA 11 



Putrefaction is the only natural influence 

 which operates to destroy the virus rapidly. Ac- 

 cording to Uhlenhuth it will live in putrefying car- 

 casses for about eight days, but undoubtedly the 

 many influences which govern putrefactive proc- 

 esses render data of this kind of value merely in 

 establishing tendencies. It is certain that decom- 

 posing carcasses do not harbor the virus regu- 

 larly, and likewise it is true that virus kept in bot- 

 tles in the laboratory often is killed when putre- 

 faction develops. When sufficient preservative is 

 added to prevent the growth of putrefactive or- 

 ganisms, the virus regularly lives several months, 

 and may even exist for years. 



Moderate degrees of heat attenuate or destroy 

 the virus, and under no circumstances has it been 

 found to survive temperatures near the boiling 

 point. The following rather incomplete table pre- 

 pared by the German Imperial Board of Health 

 laboratories gives a fair idea of the effects pro- 

 duced by various degrees of heat. 



Degrees 



Material Centigrade Time Results 



Liquid serum 

 filtrate 45 24 hours Not killed or 



weakened 

 Liquid serum 

 filtrate 46.5 24 hours Not killed or 



weakened 



