INOCULATION AS A PREVENTIVE OE SWINE DISEASES. 
67 
For this hurried and imperfect paper I must make some 
apology, but I am so sure that I have said a few things which 
are not in accord with the views of many present, that I feel 
you will be amplv repaid by the expostulations and correc¬ 
tions of out-thinking minds. 
REPORT ON INOCULATION AS A PREVENTIVE OF SWINE 
DISEASES. 
By Dr. D. E. Salmon. v 
Inoculation with hog cholera virus was first tested as a 
preventive for this disease in the experiments of the Bureau 
of Animal Industry in the year 1886. The method of inocu¬ 
lation was discovered at that time, but the results were un¬ 
satisfactory, as the animals were not sufficiently protected, 
and the experiments have been repeated under various condi¬ 
tions from that time to the present to learn if any modification 
of the operation would make it more effectual. 
Prevention by inoculation depends on the well-known 
principle that one attack of a contagious disease generally 
protects the individual from subsequent attacks of the same 
contagion. The amount of protection received varies greatly 
with different diseases and different animals. In no case are 
all individuals protected in this way from any disease, and 
in many cases the immunity lasts only for a short period of 
time. 
Inoculation in practice consists in injecting under the skin 
as much of the strong virus of hog cholera as can be given 
without producing a fatal attack of the disease. Inoculation 
is very different from vaccination. The virus used in inocu¬ 
lation is the same in variety and strength as that found in 
animals dying with the plague, while for vaccination a 
weakened virus is used, which cannot cause a fatal disease. 
No method of vaccination has yet been introduced for the 
hog diseases of this country. Inoculation is now being ad¬ 
vocated as a preventive for hog cholera, and it should be re¬ 
membered that this means the introduction into the animal’s 
* Reprint from the advance sheets of the Annual Report, 1889. 
