72 
D. E. SALMON. 
killed for examination one of the four was found seriously 
diseased, the three others were either slightly or not at all 
affected. 
Still later four Nebraska inoculated hogs and two other 
hogs which had not been inoculated were fed upon the vis¬ 
cera of hogs which had died of hog cholera. Two of the in¬ 
oculated hogs and the two that had not been inoculated con¬ 
tracted hog cholera and died. Two of the inoculated hogs 
remained well. 
/ / ^ 
As a last test, the remaining six animals from Nebraska 
were inoculated by intravenous injection of the cultivated 
virus of hog cholera. Of these, three had been inoculated 
with hog cholera virus, and had been inoculated with 
the sterilized liquids in which hog cholera germs had 
grown, and two had recovered from an attack of hog cholera. 
The four hogs which had received the protective inoculation 
all died. One of the recovered hogs died and the other re¬ 
sisted the virus and remained well. 
It is quite evident from these experiments that the ani¬ 
mals inoculated in Nebraska were fully as susceptible to hog 
cholera after the operation as were those which had been 
inoculated in the experiments of this Bureau in Washington. 
The conclusion that inoculation is not a satisfactory pre¬ 
ventive for hog cholera is by no means inconsistent with the 
results obtained in investigating other diseases. Various ex¬ 
periments have shown that the protection which follows one 
attack of a disease or which is produced artificially by inocu¬ 
lation or vaccination is by no means absolute. It is simply 
an increased power to resist that particular contagion, and it 
may be sufficient to guard against the small doses of the virus 
which with most diseases are all that an animal is exposed to 
under ordinary conditions. But if from any cause a larger 
quantity of the contagion finds its way into the animal’s body, 
it will contract the disease in a fatal form in spite of the im¬ 
munity derived from a previous attack or from inoculation. 
This was strikingly shown in the writer’s experiments with 
fowl cholera (Report Department of Agriculture, i88i-’ 82, p. 
289) and by the researches of Professor Chauveau with an- 
