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become very intimately acquainted with the setiological momenta 
at the bottom of such peculiar conditions, unless we will place 
ourselves upon the very comfortable (for lazy men (b) ) and pre¬ 
viously much advocated stand-point of so-called original develop¬ 
ment, abiogenesis, (without infection), which according to the 
present views over the nature of contagii appears only suitable for 
the advocates of generatio sequivoca; or we must adopt the very 
improbable view, that the contagium of v. vaccina, which as 
known possesses an intense degree of tenacity in a desiccated con¬ 
dition, may remain latent for years in a stable, and now and again 
give occasion to an eruption of the disease. I gladly concede 
that there are certain infections and inoeulable diseases, which 
appear in a sporodic form, as for instance: Diphtheria, infectious 
wound fever, puerperal fever; but for different reasons it seems 
unjustifiable to place v. vaccina in this category. 
A nearer genesis for v. vaccina may under these conditions be 
sought. The variola? which come to pass by man and other animals, 
especially since the affinitative relations (“ verwandt-sehaflichen 
Beziehungen”) of the variola? to one another, has been repeatedly 
confirmed by means of clinical and experimental experience. The 
only variolse forms which come into consideration in considering 
the genesis of the bovine variety are: Variola ovina, v. liumana 
vera, and the variolated variola of man—humanised vaccine—for I 
believe I have sufficiently demonstrated that all the remaining so 
seldom occurring forms of variola—equina, caprina, canina and 
porcina—proceed from other primary forms, and cannot be looked 
upon as idiopathic forms. As known, Jenner credited the equine 
form as being the generator of v. vaccina, but we have, we think, 
sufficiently proven the incorrectness of this view, as by us, in Ger¬ 
many, v. equina is scarcely ever seen, and aside from this, v. vac¬ 
cina is regularly seen to develop in stables, where no horses are 
kept. 
The descent of v. vaccina from v. ovina is as improbable as 
from v. equina. We justify this conclusion from the fact that 
there are no reports in the literature of such a direct connection, 
although from the much greater frequency of the ovine variola, 
opportunity sufficient is given to the infection of cows from the 
