342 
D. E. SALMON. 
before, is now unable to cause the least sign of disease. The 
liquid is no longer capable of producing the affection. 
Still, our opponents may maintain the demonstration more or 
less imperfect—the activity of the virus'is destroyed at this low 
temperature, it is true, but what evidence have we that the bac- 
teiia were destroyed rather than the other agents which we have 
supposed might constitute the active principle. Some bacteria 
resist a boiling temperature for a longer time than this ; others 
multiply rapidly, and seem to enjoy a temperature nearly thirty 
degrees above that to which we have subjected our virus. Is it 
not impossible that the micrococci under consideration were killed 
at so low a point ? 
The fact that this virus is destroyed so easily, and that bac- 
teiia often resist so high degrees of heat, certainly makes our evi¬ 
dence so much the stronger if we can prove that the micrococci 
which we have cultivated are actually destroyed at this point; for 
it would be extremely improbable that an accidentally introduced 
organism would be destroyed at exactly the same temperature as 
some unknown agent which was present, and upon which the ac< 
tivity of the liquid depended. 
Let us take two sets of the cultivation-apparatus containing 
sterilized liquids of the proper kind, and to each of these add, 
with suitable precautions, a minute quantity of a pure cultivation 
of the micrococci. The one we heat for fifteen minutes to 131 
deg. Fahr., the other to 132, and place both in the incubator to 
await developments. In twenty-four hours the former is turbid 
with micrococci, but the latter is as limpid as at first; we wait 
for two or three days,* but there is no change in our results. We 
now inoculate a number of fowls from each apparatus, and find 
that in those cases where the liquid containing the micrococci is 
used the birds contract the disease, while those inoculated with the 
clear liquid are not affected in the least. 
Oui demonstration is now complete—we have started with the 
micrococcus and tested each hypothesis without other result than 
to show that they are both untenable, and after traversing the 
whole ciicle of investigation we are led back to the organism as 
the pathogenic agent without which in a living condition there is 
no virulence. 
