CONTRIBUTION TO THE STUDY OF SWINE PLAGUE, ETC. 625 
Two animals vaccinated against pneumoenteritis died after 
:he injection of swine plague, or of hog cholera, but they pre¬ 
sented, contrary to the witness, a greater resistance; the dur¬ 
ation of the disease has lasted longer than in all of the 
fresh rabbits, and the anatomical lesions were more complica¬ 
ted. 
Before all, it was to know if the animals vaccinated against 
swine plagae, that is against the most virulent microbe, would 
possess also the immunity toward the two other viruses; this 
fact has been confirmed by my experiments, repeated several 
times upon the same animal. 
And again, it was to be presumed that vaccination against 
one microbe less virulent, as that of pneumoenteritis, would 
not be sufficient to protect altogether animals against swine 
plague and hog cholera; it only produces death at a later 
period. 
I experimented upon only one rabbit vaccinated against 
hog cholera. The results are no less conclusive. This animal, 
vaccinated with a strong dose of blood which had proved 
very virulent before sterilization, has resisted to the test of 
pneumoenteritis and to that of swine plague. 
The microbe of swine plague which was given to me was 
very virulent for the rabbit at the start; by a series of suc¬ 
cessive passages by the animal I have, not without pain, 
succeeded to render the microbe of hog cholera almost as vir¬ 
ulent ; I could probably increase that of pneumoenteritis in 
the same way. 
There was then in our three microbes but one difference 
in the intensity of the virulency, and it is probable that the 
same fact has taken place in the various epidemics already 
studied. 
Because rabbits vaccinated against pneumoenteritis have 
died with hog cholera and swine plague, we cannot, as Schwein- 
itz has done, come to the conclusion that there were different 
microbes; one must first compare their reaction to that of 
fresh rabbits, and again take account of the opposite experi¬ 
ment. 
To resume: ist, rabbits vaccinated against swine plague 
