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E. SALMON. 
to be stronger than the other. The first, or weaker vaccine, is 
designed to give a partial immunity from the disease, and enables 
the pig to resist the second or stronger vaccine, which wculd be 
dangerous to the life of the animal if used before the protective 
influence of the first vaccine has been acquired. The second vac¬ 
cine, while not quite so strong as the unmitigated virus of the 
disease, is near enough to this strength to increase the degree of 
immunity to such an extent as to enable the animal to resist the 
very strongest virus of the plague. In other words, this is the 
theory of Pasteur’s vaccine, but we shall soon see that the theory 
has some exceptions in practice. 
In this case the second vaccine did not appear to be as strong 
as the first; the germs did not grow so well in culture liquids, and 
they were less deadly to mice. The three pigs remaining from the 
first vaccination were given a dose of two and a half drops each, 
which is the dose prescribed by Pasteur. In addition to these two 
other pigs were given about thirty drops each, our object being to 
produce the disease if possible, that it might be compared to the 
American swine plague. Hone of these animals, however, showed 
any signs of being affected even to the slightest degree by this 
vaccination. 
The next point was to expose these vaccinated pigs to our 
American swine plague and learn if they had acquired the power 
to resist its contagion. Accordingly, one week after the second 
vaccination, the five pigs which had been operated upon were 
penned with two others that were taken from a herd affected with 
swine plague and that were undoubtedly sick with this affection. 
As a result of this exposure three of the five contracted the dis¬ 
ease and died from very acute attacks. It seems evident, there¬ 
fore, that the Pasteur vaccine cannot be relied upon as a pre¬ 
ventive of our hog cholera. To this extent our conclusion coin¬ 
cides with that reached from the Nebraska experiments. 
In another communication I will attempt to give the reason 
for this and hope to be able to show that the experiments that 
have been made by the Department of Agriculture have added 
considerably to our knowledge of the destructive malady popu¬ 
larly called hog cholera. 
