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A CONTRIBUTION. 
inner infection, a tolerably coevial eruption of the exanthema. 
By vaccination of man we observe—as a whole, seldom, however— 
occasionally an uneven development of the vaccine pustule, as 
well as the eruption of secondary pustules, by which perhaps like 
factors come into play as by variola vaccina. Again, if a gen 
erally acting cause constituted the original development of vac¬ 
cina, all the animals in the stable would be liable to be attacked 
at about the same time ; whereas, we know, that the disease very 
gradually extends over the members of a stable or herd. 
Our considerations over the origin of variola vaccina lead us 
to the following conclusions : 
There is no such thing as a so-called genuine , original “ bovine 
variolavariola vaccina . Variola vaccina always owes its gene¬ 
sis to external infection , and indeed either from variola humana 
vera , or , which is at present the most f requent , by interposition 
of the hands of milkers , from humanized vaccine , which is dis¬ 
tributed on all sides ; according to its origin , the latter is always 
a variola vaccine. The vaccinated or re-vaccinated human being 
is, therefore, not so harmless a creature as is generally assumed ; 
he is in condition to cause the development of variola vaccina. 
When the process is once present by a cow, it extends itself from 
the same by mediate infection to others of the same stable or 
herd, and often enough back to the milkers. 
According to all which has been said, we must say we hold 
the careful search for original bovine variola as unnecessary and 
unjustified, as we can immediately produce it by inoculation of 
cattle with humanized vaccine—retro-vaccination—the product 
being throughout identical and homologous with the so-called 
“ original,” “ genuine ” bovine variola. 
The question, Which is the better and most active for the 
protective inoculation of man—the employment of the humanized 
lymph or the original vaccine ? seems to be solved by our pre¬ 
vious considerations, as both appear of equal value, both having 
originally sprung from variola vaccine. I would formulate the 
question as follows: Which is preferable for the purpose of 
human vaccination, humanized vaccine which has been passed 
through numerous generations of man, or animal vaccine which 
