354 EXPERIMENTS ON PLEURO-PNEUMONlA. 
carried out in 1851, in which fifty-four animals were experi¬ 
mented upon at an expense of £2400, led to the conclusion 
that “ inoculation possess 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 ex¬ 
periments 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 successful 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 govern¬ 
ment that it should be made compulsory. 
But the proof of the protective power of inoculation, even 
if it w 7 ere much stronger than it is, would afford an insufficient 
reason for recommending it as a practice, unless it can be 
shown that the third question—that which relates to the risk 
of the operation itself—admits of a satisfactory answ r er. On 
the ground of its danger the French Commission, notwith¬ 
standing their opinion as to its protective power, declined to 
recommend it as an economically advantageous practice; for 
they considered that their own experiments showed a that 
inoculation causes larger mortality than the disease which it 
is intended to prevent.” No less than 11 per cent, of their 
animals had died, w T hereas it was extremely improbable that 
so large a number would have been sacrificed had they been 
subjected without inoculation to the ordinary risk of infection. 
Notwithstanding these facts, the Commission, of which M. 
Bouley was the secretary, recommended that it ought to be 
encouraged on the ground that, its protective power having 
been demonstrated, the dangers above referred to would be 
diminished by improved methods. 
Inoculation is usually performed by inserting the liquid 
which drains from diseased lungs into the cellular tissue. The 
situation chosen for the purpose is the end of the tail. The 
reason why this part is selected is, that if, as often happens, 
the local inflammation becomes excessive, it may be limited by 
amputation. But notwithstanding this safeguard, the diseased 
action is apt to spread to the neighbouring parts, in which 
case it occasions serious illness and often death. 
The position of the question was therefore clear. The pro¬ 
tective power of inoculation, though by no means definitively 
settled, had been rendered sufficiently probable to justify a 
