330 
W. SILBERSCHMIDT. 
2. The mobility of the hog cholera may, according to Smith 
himself, disappear. 
3. The generally more active growth of the hog cholera 
diminishes when the microbe becomes more virulent. 
4. Salmon and Smith are obliged to distinguish varieties 
of hog cholera , some more saprophyte than others. 
To the point of view of the morbid symptoms, the con¬ 
fusion is still greater. Animals dying of hog cholera have 
often, by the deductions of the American authors, pulmonary 
lesions, and swine plague which was localized to the lungs 
generally occasions also troubles and lesions in the digestive 
canal. 
The fact that the two microbes are often met m a same 
epidemy is, to say the least, strange. It was necessary, to 
solve the question, to have recourse to another process of com¬ 
parison. At present, now that vaccination has entered upon the 
period of success, it is of high interest to know if animals j 
vaccinated against one of the two diseases were also possessed 
of immunity towards the other. Von Schweinitz is the only 
author who, to our knowledge, has experimented in that 
direction; as we have seen, he differentiates the swine * plague 
from hog cholera because guinea pigs vaccinated against the 
first disease did not show themselves refractory to the other. 
The experiments reported are not very numerous, and, besides, 
the contrary proof not having been made, it is admissible that 
the second virus was more active than the first. 
On a proposition of Mr. Roux, thanks to the kindness of 
Mr. Metchnikoff, who gave me cultures of hog cholera and of 
swine plague sent by Mr. Smith at the Pasteur Institute, with 
a number of tubes containing the blood of rabbits dead by 
the microbe obtained from the epidemy of Gentilly, I under¬ 
took to compare these three specific agents. 
Before relating my experiments, I desire to express my 
gratitude to Mr. Roux for the constant interest he has taken 
in my researches and for his precious advice. 1 also address 
my thanks to Mr. Metchnikoff for his numerous indications 
and his great amiability toward me. I shall begin by the com¬ 
parative study of the microbes of swi?ie plague and of hog 
