22 ON BOVINE PLEURO PNEUMONIA ; 
means of inoculation the disease has been completely stamped 
out in New Zealand, that statement may yet prove to be premature, 
or else the disease could never have been very virulent or have had 
the footing there that it had in Queensland herds. The disease 
is so insiduous and developes itself in so many different forms 
and under such varying circumstances, and after such extraordinary 
lapses of time, that no one can say that the disease is definitely 
stamped out as long as any cattle are living during whose life the 
disease was prevalent. Inoculation being admitted to be a 
preventive, the great drawback is, it cannot be carried out only 
when the disease is raging among the herd. 
All the cattle in Australia may be said to be saturated with the 
seed of pleuro-pneumonia, and under fostering circumstances 
those seeds germinate, and although no symptons may discover 
themselves for years, even without any fresh infection the germs 
of the disease are present and await development. The circum- 
stances under which the disease is most likely to develope itself 
are well known to bushmen and drovers ; such as over driving or 
even ordinary droving, wet weather and exposure in wet dirty yards, 
bad tailing or herding, or other causes which tend to lower or 
depress the vital system. The only method for a thorough eradi- 
cation of this scourge is to adopt the plan successfully followed in 
the human species in the case of inoculating for smallpox, where 
children of tender years are made the vehicle for reducing the 
attacks of the disease. With this difference, that the virus of 
cowpox, which is a distinct complaint from smallpox, is found to 
be effectual in preventing an attack of the latter. 
The vitality of the virus, or contagium of pleuro, has been well 
ascertained, it has been known to retain its activity for many 
months up to six months, even without any preparation. Hay 
soiled by sick cattle has induced the disease after even a longer 
period. Healthy cattle lodged in stables occupied three or four 
months previously by diseased ones have become contaminated ; 
it is even recorded that cattle buried in the ground infected 
others sixty feet distant. There is no proof yet, that any other 
than horned cattle will receive the infection of this lung plague. 
But the infecting principle of the disease exists even after con- 
valescence ; and may be transmitted months after recovery, and 
exists in its greatest intensity in the air expired by a sick animal. 
But whenever the virus can be so cultivated and preserved as 
to be available at all times, and under all circumstances, the 
remedy then will only be a matter of time. 
