Infectious Diseases of Animals. 
499 
duced into premises where the disease had previously existed. These animals 
were seen by Mr. Cope during his final inspection some time after these two 
districts had been declared free, and were found to be perfectly healthy. 
This circumstance was satisfactory, as it indicated that the measures which 
had been taken to disinfect the premises had been effectual. 
During the recent investigation of the disease in Yorkshire it was com- 
monly remarked that the infection spread very slowly among the animals 
which had been exposed to it ; that in many cases the period of incubation 
was unusually long, and that only in one or two instances did the disease 
manifest an excessive virulence. The apparent peculiarities, however, were 
referable to the conditions which obtained during the time that the disease 
existed. In the former outbreak in 1865 precautionary measures were at first 
generally neglected ; animals were allowed to remain together in masses, and 
were subjected to various forms of medical treatment. Under these circum- 
stances the infection spread with rapidity, and the diseased animals being 
allowed to live, the affection was permitted to manifest itself in its most 
virulent form. 
In various parts of the country, however, where animals were pastured in 
the open air, instead of being confined in a shed, it was observed that the 
virulent type of the malady was considerably modified. The period of incuba- 
tion appeared to be considerably prolonged, and cattle resisted the effects of 
the disease for a long time before they succumbed. In the last outbreak in 
Yorkshire all the conditions were opposed to the rapid progress of the disease. 
As soon as its true character was ascertained, animals affected with illness of 
any kind became subjects of suspicion, and isolation was carefully enforced. 
When cattle-plague appeared in a herd, the sick animals and those herded with 
them were generally slaughtered and buried, and in the few instances where 
these measures were not adopted the affected animals were at once removed 
from contact with the healthy. This precaution, in two instances, secured the 
safety of the rest of the herd ; but in other parts of the same district, in which 
the same course was adopted, disease extended to the other animals, and it 
ultimately became necessary to destroy the whole of them. 
It is further to be remarked, in reference to the apparent extension of the 
period of incubation when animals are placed under favourable sanitary con- 
ditions, that the date of discovery of the indications of disease is by no means 
to be accepted as the time of their appearance. It occurred to me on several 
occasions to examine animals which gave positive evidence of being affected 
with cattle-plague in the third or fourth day of its progress, notwithstanding 
that these animals, according to the statement of the owner or the attendants, 
had remained apparently healthy up to the evening before the day of my 
inspection. There can be no question that in all these cases a professional 
examiner would have observed positive symptoms of the presence of the 
disease some days before it was actually detected. The facts referred to, 
namely, the perfectly sanitary condition of the districts in which the cattle- 
plague occurred, the immediate isolation of sick animals, and general adoption 
of the system of slaughter both of the sick and of the healthy which had been 
herded together, sufficiently account for the absence of any extreme virulence 
in the type of the malady, for its slow progress, and the apparent extension of 
the period of incubation. In the two or three instances in which the disease 
was concealed, or when it was not recognised for some time after its appear- 
ance in the herd, it was found to spread with its usual rapidity, and to present 
characteristic indications of mahgnancy. 
Notwithstanding the experience which was gained in the districts recently 
infected with cattle-plague during the outbreak of 1865-7, there was consider- 
able opposition on the part of the owners of cattle to the adoption of the 
stamping-out system. It was commonly pleaded that compensation very 
VOL. IX. — S. S. 2 L 
