A CONTRIBUTION. 
195 
rewarding them in every case where the information proves on 
inspection to be correct. 
With regard to the period (season) in which the eruption most 
frequently takes place, the observation of Jenner’s that variolse 
vaccina comes to pass most frequently in spring and early sum¬ 
mer, has been completely confirmed by Reiters and Hering; 
although no season of the year is entirely free from the same. 
Authors have sought to explain this in many ways, for instance: by 
assuming a certain inclination to prevail at such times to critical 
eruptions ; that at this time the change from dry to green food 
takes place, and that the cause or a collateral cause to the erup¬ 
tion of variola must be sought in the increased How of fluids to 
the udder, as well as in the increased lactation. 
That an individual or better sexual disposition took part in the 
pathogenesis of the disease, was concluded, from the fact, that the 
disease is almost exclusively limited to cows, and, indeed, especially 
during the period of lactation, that § of the complicated cows 
were found to be in the primary stages of milking, while the 
other J were old milkers. When the disease is found by non¬ 
milking heifers, a very seldom occurrence, we are in general able 
to prove, that a short time previously other animals—milk-cows— 
had been diseased with variola in the stable in question ; that the 
disease can only take place by infection. The case is the same 
when variolae are observed by young animals, and by bulls (upon 
the scrotum) when the disease is prevailing in a large stable ; in 
both cases it is not the hand of the milkers, but in all probability 
the straw has been the intermediator or vehicle of the con- 
tagium. 
What is then the genesis of variola vaccina ? 
When I again reopen this frequently ventilated and as fre¬ 
quently unanswered question, it is with the hope of presenting 
some new points to the consideration of observers, which have to 
this time received but little attention, and which are yet of im¬ 
portance in investigating for the origin of the bovine variola. 
When a so manifestly contagious disease as variola vaccina 
appears so seldom, and then only in a sporadic form, and as sud¬ 
denly disappears, it is certainly natural that we should desire to 
