66 
D. E. SALMON AND THEOBALD SMITH. 
very ill and died before the next day. The other pigeons we! 
perfectly well. The effect of this dose of strong virus, so h 
markable on the unprotected pigeons, was even more evanescet 
than that of the heated virus in which all life had been destroy el 
There can be no doubt, therefore, from this very positi 
result, that the pigeons had acquired an immunity through the effe 
upon the tissues of the chemical products formed by the bacteriu 
in the culture liquid. 
A table giving the dates of the injection and the quantity i 
troduced into each animal is below: 
Pigeons. 
1885. 
18S6. 
Total 
of Heated 
Virus. 
Remarks, j 
Dec. 24. 
Jan. 21. 
Jan. 29. 
Feb. 6. 
Feb. 13. 
Heated 
Virus. 
Heated 
Virus. 
Heated 
Virus. 
Heated 
Virus. 
Strong 
Virus. 
CC. 
CC. 
CC. 
CC. 
CC. 
CC. 
No. 8_ 
.8 
.75 
.8 
Died in 48 hoi 
after injecti 
of strong virii 
“ 10.... 
.4 
1.5 
1.5 
1.5 
.75 
4.9 
Well Feb. 20. t 
“ ll.... 
1 5 
1.5 
1.5 
75 
4.5 
Same. 
“ 12.... 
1.5 
1.5 
1 5 
4 5 
Same 
“ 13.... 
1.5 
1.5 
75 
3.0 
Same. 
“ 14.... 
.75 
Died in 24 boii 
after injecti 
of strong viri 
In the birds that died, (Nos. 8 and 14), the pectoral muscll 
at the place of injection were pale and friable. Necrosis w:| 
already at hand. The internal organs were not macroscopieall 
altered, excepting the spleen of No. 8, which was enlarged at 
dark. The presence of the bacterium of swine plague in the bloc 
from the heart was demonstrated by liquid cultures, which, inoc 
lated with a minimum quantity of blood, were turbid with till 
specific microbe on the following day. 
The conclusions to be drawn from this experiment we believ 
are of superlative importance to a correct understanding of til 
phenomena of contagious diseases, and the methods by whit! 
these diseases are to be combatted. They probably apply to af 
bacterial plagues of men and animals in which one attack confei 
immunity from the effects of that particular virus in the futur. 
