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F. S. BILLINGS. 
of variola originally proceeded from one primeval form, yet it 
cannot be denied, that the contagimn of variola humanavera , as well 
as that of variola ovina , possesses especial affinities, the first to the 
organismus of man, the latter to that of sheep, and that both 
diseases present themselves as well characterized forms in a 
natural historical sense, which may be perhaps related to each 
other; even homologous, but in no ways identical. And even 
though we may succeed, by inoculation of variola humana vera, or 
of vaccina upon sheep, in generating a disease by the latter, the 
phenomena of which strongly resemble those of variola ovina, yet 
we have by no means proven thereby, that variola humana, vac¬ 
cina (bovina) and ovina are identical diseases. 
From these general remarks, we will now give our attention 
more especially to our tliema; and we find variola appearing as a 
severe and general infection by man and sheep , as a general, but 
weakened form again by man (variolois) and by swine; as a light 
and local process by cattle and horses , while the goat possesses a 
susceptibility as well for the general variola of sheep, as for the 
localized form of cattle. 
In general we may consider the following as axiomatic, viz: 
the domestic animals have either none or a very insignificant dis¬ 
position to accidental infection from the contagium of variola 
humana vera. This is amply proven by the history of every 
variolic epidemic, by which occasions enough are given to the in¬ 
fection of the domestic animals. I shall have occasion to notice 
the isolated observations of Ceely, Dinter and others, which make 
it .probable, that a spontaneous, accidental, (not experimental) 
transmission of human variola to cattle is possible. Accidental 
transmission of human variola to monkeys has also been reported; 
also to swine, and lately it is reported to foals (Scholz.) During 
1871 and 1872, a severe variolic epidemic was raging, and Scholz 
observed a pustulous exanthema by foals, at the same time and on 
the same farms where human variola prevailed, which continued 
and took a similar course with the latter, and which failed on 
farms in the same district where the same did not come to erup¬ 
tion. The exanthema was distributed over the entire surface of 
the body, and only in isolated cases was its eruptions anticipated 
