HUMAN AND ANIMAL VARIOLAS. 
289 
any respect, and it has retained all its original infective proper¬ 
ties. Neither can the human organism transform vaccinia into 
variola, for had this been possible, surely the millions of vaccina¬ 
tions which have been made under every condition during this 
century, would have afforded us some evidence of sucli capability. 
If vaccinia cannot be transformed into variola, as little probabil¬ 
ity is there that variola can be changed into vaccinia. 
Years ago the veterinary professor, Hering, had repeatedly 
inoculated the cow with vaccine lymph, and found that this gave 
it renewed potency. The veterinarian Numann made similar ob¬ 
servations, and incidentally noticed that the bull is as susceptible 
as the cow; also that the horse and ass are, but that their vaccine, 
when re-transferred to man, is slower in its action than that from 
the cow. Besides, the transmission of vaccinia by inoculation 
from cow to cow is accomplished without any difficulty, and the 
successive transplantations of the same lymph does not appear to 
have any influence on the development of the resulting pustules. 
In the very numerous experiments of Depaul, it was found that 
the pustules of the last inoculated animal offered the same char¬ 
acters and dimensions as those of the cow first inoculated. How 
is it, then, that the vaccine virus can be transmitted for genera¬ 
tions from cow to cow, cow to horse, or horse to horse, retaining 
all its primitive potency, and even becoming revivified when car¬ 
ried from the human species; whereas the virus of human variola 
only produces a local papulation in them, quite unlike vaccinia, 
which can rarely be reproduced more than two or three times, 
and which always develops small-pox when inoculated again on 
man ? 
From all the evidence I have adduced, there is every reason 
to think that those experimenters who imagined they had pro¬ 
duced vaccinia by inoculating the cow with variolous matter, were 
in error; and if it be true that they employed the virus from the 
cow in vaccination, then if the above evidence be accepted as 
trustworthy, there is reason to believe that it was merely the 
small-pox virus returned again to the human species, just as it was 
obtained from it. There are instances on record in which the 
most serious results have followed the attempts of imitators of 
