UPON VIRULENT DISEASES-CHICKEN CHOLERA. 
47 
isms develop themselves to such an extent that fiscal excrements 
of chickens thus effected, will kill animals inoculated with them. 
In this manner one can easily understand the manner of propaga¬ 
tion of the disease in chicken yards. Evidently the manure of 
diseased animals plays the greatest part in the contagion. And 
then nothing will be easier than to stop it by isolating the animals 
for a few days only, by washing the yard well with water, or water 
acidulated with sulphuric acid, which easily destroys the microbe 
and prevents its development, in proportion of 1 gramme of the 
acid to one litre of water, and by removal of the manure. All 
causes of contagion would be disposed of, as, during the isola¬ 
tion, animals already diseased would have died, so rapid is the ac¬ 
tion of the disease. 
In passing always from one culture to another by the sowing of 
a quantity comparatively very small, for instance, by what may 
he carried on the point of a needle just dipped in the fluid, the 
repeated culture of the infectious microbe in chicken bouillon 
does not weaken the virulent power of the microscopical organ¬ 
ism, nor, what is about the same, the power of its multiplication 
in the body of the gallinaceous. This virulency is so great, that 
by the inoculation of a small fraction of one drop of a culture, 
twenty times out of twenty death will take place in two or three 
days, and often in twenty-four hours. 
These generalities being known, I now come to the most im 
portant facts. 
By some change in the culture, the virulency of the infectious 
microbe can be diminished. This is the important point of this 
paper. I nevertheless ask the Society the liberty not to trust for 
the present, too far in my faith in the means which may tend to 
the diminution I am speaking of, so far as to reserve for a short 
time the independence of my investigations as well as to insure 
their progress. 
The diminution in the virulency is manifested in the subject by 
a small stoppage in the development of the microbe; but at the 
same time the identity remains of the two varieties of virus. 
In the first state, that where it is very infectious, the microbe 
will kill twenty times out of twenty cases ; under the second it 
