A CONTRIBUTION. 
97 
perfect. However, I am convinced that from this comparative 
study of the variolae, we shall gain a general idea, which will offer 
much of importance for the pathology of the same, as well as 
much of great practical value. 
Before we undertake to consider the different form of variola 
in special, it may be well to consider some general principles, 
which may serve to guide us in our comparative consideration of 
the variolse of man and animals. The previous plan, of looking 
upon the variolse as they come to pass bv the different species of 
animals and man, as of equal importance “ auf gleiche Linie zu 
stellen,” appears to me entirely unjustifiable. When for instance 
authors speak of and consider variola humana, ovina, caprica and 
canina as the same, and throughout analogous processes, they 
completely overlook the fact that the two first—those of man and 
sheep—represent well characterised pests, the continuity and de¬ 
scent of which in concrete cases is in general clearly manifest, 
because “variola humana vera ” always generates from pock 
diseased men , and u variola ovina ” always proceeds from variolic 
diseased sheep. As a rule we find but little difficulty in proving 
infection in these cases. The question is quite different with 
regard to variola caprina, canina, equina, and vaccina (bovina); 
they scarcely ever assume a pest-like form, they appear here and 
there in a form much more resembling sporadic diseases, they are 
limited to individuals, or at the most to single herds; they are infre¬ 
quent occurrances. In my opinion it is not difficult to explain this 
fundamental differance in the eruption of the individual form of 
variola. After the eminent transmissability of the variolic contagii 
to other species has been confirmed, the most important question 
which then springs up in the consideration of the single forms, is 
what cause or causes lead to their generation? We have ever to 
decide, if we have before us a variolic form peculiar to the animal 
species in question , or one which has only been transmitted acci¬ 
dentally to the same, as it were , a ivandered form of disease. 
In the last case it would perhaps deport itself when a com¬ 
parison is allowable—in a similar manner, as cysticercus cellulo" 
sae when present by man or dog, or when we meet with malleus 
or autlirax by man. We may assume or not, that the contagium 
