PLEtXRO-ENEtlMONtA EEYSIEELATODES. 
425 
by inflammatory phenomena, at the point of inoculation, without 
giving to the organism any protection against natural infection, 
so may also see good reasons for supposing that a genuine inoc¬ 
ulated disease may produce immunity against natural infection 
without the presence of any striking local phenomena at point of 
inoculation. If a proliferation of the specific elements at point of 
inoculation is an absolute necessity, it is very questionable. 
Chauvau has well shown that, in reference to variola, the local 
phenomena may fail and yet the organism be protected against 
natural infection for a variable length of time. 
Hence the “ ens ” of the inoculated variola, as well as of the 
disease in question, must be sought in quite different phenomena 
than local reaction at point of inoculation. As we are at present 
completely in the dark with reference to the essentiality of the 
natural disease, it is self-evident we cannot expect any more 
knowledge with reference to the artificial; so much is certain, that 
it cannot essentially differ from the natural disease, as both diseases 
owe their existence to the specific, yet unknown infectious, 
elements of pleuro-pneumonia erysipelatodes. 
As we must assume that the natural and the artificial disease 
are essentially similar, and as we know that organisms which have 
resisted the ravages of the natural disease lose their receptivity 
for the infectious elements, if exposed to the same, for the 
remainder of their lives as a rule, we cannot see why the same 
result should not follow by animals which have surely passed 
through the artificial disease. This assumption is at least justinable 
until the contrary is proved to be the case. We do not mean to 
infer that an immunity against natural infection will follow every 
case of artificial disease during the life of the questionable organism. 
Many cases are on record where animals have became the subjects 
of the natural disease in a year or less, where the inoculation had 
given every phenomena of positive affection. Such cases, how¬ 
ever, form the exception where the inoculation is performed lege 
artis, and there is no rule without exceptions. The experiments 
of Willems and others demonstrate clearly enough the specific 
action of the elements of this disease upon cattle, while negative 
results invariably followed inoculation with the same upon dogs, 
