INOCULATION FOR PLEURO-PNEUMONIA IN CATTLE. 467 
true. Thus many a medical student, who perchance may bid 
fair to occupy an exalted position in his profession, has fallen 
a sacrifice to a trivial wound received in the dissection of a 
diseased body, while the veterinary student, on the contrary, 
from having to dissect our ordinary domesticated animals, 
rarely suffers from such wounds. This law offers an impedi- 
ment to, but does not entirely prevent, the conveying of a 
disease, from animal to animal of a different kind, by inocula- 
tion. We have a good example in sheep not being sus- 
ceptible to the action of the smallpox virus of man, although 
remarkably so to that of their own smallpox , and also of man 
being susceptible to the virus of his smallpox , but not to that 
of sheep. 
With reference to the decrease in the number of cases of 
Pleuro-pneumonia at Ruddington since the adoption of inocu- 
lation, we should observe that great caution should be exer- 
cised in coming to an opinion of the cause of the decline of 
an epizootic, or even an ordinary contagious affection. Cir- 
cumstances about which we know but little will cause the 
outbreak of an epizootic disease, and circumstances about 
w 7 hich we probably know less will produce its removal. There 
are periods in the history of Pleuro-pneumonia on Mr. Paget’s 
premises, when the cattle have been for w r eeks as free from 
disease as since they were inoculated. The time, w r e admit, 
is longer, but the cause may be the same. 
It was acknowledged, even in Hasselt, that they had had 
as little disease in some summers, prior to the employment 
of inoculation, as during the last wdien the system had reached 
its climax. In proof that inoculation was not the sole cause 
of this freedom, is the fact that the cattle of the distillers who 
objected to have the operation performed continued as healthy 
as those of others who did not so object. What we contend 
for is, that, as there are no specific local effects produced by 
inoculation, so protection does not depend on the special action 
of a special virus on the organism, as is the case with the 
vaccine and other similar diseases. 
Protection we believe to be more apparent than real, and 
that it results mainly from simple local irritation. When this 
and the accompanying inflammation are slight, the animal is 
in constant danger of an attack of Pleuro-pneumonia, even 
whilst the local action exists : wdien greater, a simple issue is 
produced, the effects of w^hich, as a drain on the system, are 
more lasting and therefore likely to be more beneficial ; but 
when carried to the fullest extent, then the animal’s life is 
endangered from another cause, namely, from the sphacelitic 
action which ensues. With regard to the utility of simple 
