Swine Growers' Sessio?i. 



103 



counteracting in some way the action of the disease producing 

 germs; and, as mentioned in the case of diptheria, this substance 

 can be produced under certain conditions in one animal, and ob- 

 tained for use in protecting another animal from what might other- 

 wise prove a fatal attack. It is well known that a hog that has 

 once recovered from an attack of cholera proves very resistant 

 when exposed again to the disease. It was then reasonable to 

 suppose that the blood of the recovered hog contains an anti-toxin 

 in sufficient quantity to protect itself against future attacks ; that 

 is, to maintain its own immunity. Whether the blood of the ordi- 

 nary immune hog contains this "anti-toxin" in sufficient quantity 

 to protect another susceptible hog against the disease, by use of 

 the small quantities of serum that would be practicable to use, was 

 a matter to be decided by actual experiment. The United States 

 Bureau investigators, Drs. Dorset and Niles, found that no great 



Lot 1. Pigs 1 to 8 "vaccinated." Pigs A and B not vaccinated. Pigs A and 8 died. All 

 severely exposed to cholera. Pigs 1 to 7 all remained well. 



degree of protection was produced by this means. And in some 

 inoculations in an outbreak in Cooper county, I found that no ap- 

 preciable resistance was obtained. The Bureau workers found, 

 however, that the protective power of the blood could be greatly 

 increased by a process of "hyperimmunization," that is, by in- 

 oculating an immune hog (one that had been through an attack of 

 the disease) with large quantities of virulent blood. It was found 

 that the ordinary immune hog can resist amounts of diseased blood 

 sufficient to kill several hundred non-immune hogs ; and that after 

 this treatment the blood of these "hyperimmunized" hogs had in 

 jmany cases yvell marked protective properties, as was shown by 



