Brown Institution on Pleura-Pneumonia. 
159 
mode of action of inoculation is equally unfounded, viz. : that 
although inoculation never produces actual pleuro-pneumonia, 
yet, that it gives rise, at the place where the morbid material is 
introduced beneath the skin, to a local disease which is of the 
same kind as the real disease of the lungs, and that consequently 
the effect of the inoculation is to produce a sort of pleuro- 
pneumonia of the skin ! Now it is quite true that there is a 
great resemblance between them — a likeness sufficiently striking 
to have impressed some very well informed persons — but very 
little stress ought to be placed on it. All inflammatory exuda- 
tions, whether specific or not, are very like each other as regards 
their chemical and anatomical characteristics ; so much so that 
it is not possible to distinguish them from each other excepting 
by their disease-producing properties. In other words, the only 
way in which it would be possible to prove that any diseased 
material derived from the skin of the inoculated animal was 
pleuro-pneumonic would be by showing experimentally that 
when introduced into another animal it produced pleuro-pneu- 
monia. If this proof were given we should have a right to 
conclude from analogy with similar cases, that in all probability 
immunity would be conferred on the infected animal ; but in 
the absence of such proof, the only way in which the protective 
power of inoculation can be settled for practical purposes, is by 
observing whether inoculated animals can get pleuro-pneumonia 
by exposure. 
The experiments which had previously been made for this 
purpose Avere unquestionably in favour of the protective power 
of inoculation. The inquiries of the French Commission, 
carried out in 1851, in which fifty-four animals were experi- 
mented upon at an expense of 2400/., led to the conclusion 
that " inoculation possesses a preservative power conferring on 
the inoculated animal an immunity which protects it from the 
contagion of the disease for a time which remained undeter- 
mined," inasmuch as the experiments could not be continued 
for more than six months. This conclusion, founded on experi- 
ments which were evidently conducted with the utmost care and 
impartiality, has been largely confirmed by the trials which 
have been made of the practice by owners of stock in this and 
other countries, and particularly in our Australian colonies. It 
appears from a recent Government Report, that in the colony of 
New South Wales the practice of inoculation has been so suc- 
cessful as a preventive that it has become general ; so much so, 
that the chief inspector of the colony was prepared in 1876, to 
recommend to the colonial government that it should be made 
compulsory. 
But the proof of the protective power of inoculation, even if 
it were much stronger than it is, would afford an insufficient 
