LUNG PLAGUE BY' MEDIATE CONTAGION’. 
27 
pest would soon burn itself out. We would find in every infected 
herd not twenty per cent., forty per cent., or sixty per cent., but 
one hundred per cent, affected. Every epizootic would be the 
counterpart of the equine influenza of 1872, and the more fatal 
epizootics would bid fair to disappear from the face of the earth. 
The escape of a certain number proves nothing, in the face of 
one well authenticated case of mediate contagion. Twenty years 
ago it w’as hard to convince the most experienced English physic¬ 
ians that tuberculosis was contagions. Men and women had 
grown old in the consumption hospitals without contracting the 
disease, and every physician of such a hospital was a living wit¬ 
ness against contagion. For a long time glanders was thought to 
be not contagious , and even in our own time this was held by 
many with regard to chronic cases. Does the escape of the 
majority of the horses in a stable, or of the one horse working 
for weeks or months in the same team with a glandered one, 
prove that glanders is not contagious? Yet this is just the kind 
of evidence that proves (?) lung plague incommunicable by mediate 
contagion. 
The potency of the infection varies greatly in different cases 
of the same disease, and this applies to infectious diseases gener¬ 
ally. Hence we have our so-called epidemics, in which the affec¬ 
tion is not only more violent but also more communicable, and 
hence more prevalent, and we have our intervals of respite, in 
which the disease smoulders with few and mild cases. 
To return to the lung plague. The process of inoculation 
determines the specific inflammation in any part of the body 
where the virus is inserted, and if made in a place where the in¬ 
flammation will not prove fatal the system is thereby fortified 
against a second attack of the plague. But in this there is no 
actual contact with the living diseased animal. I have carried 
the liquid hundreds of miles in a bottle, and by its successful 
inoculation have saved the inoculated herd. If mediate contagion 
were impossible there would be no objection to inoculation, for 
no infection could come of the presence of the lung exudate in 
the absence of the living diseased animal. But if the virus apart 
from the living animal cannot infect, what is the use of inocula¬ 
tion ? 
