■94 
Pasteur and his Work, 
the operation at a period before anthrax is usually developed — 
in March and April ; for it is recognised that such inoculation 
is powerless against the disease in a state of incubation — this 
is, when the poison is developing in the system. 
If we consider that France was estimated to lose, annually, 
from this disease alone, animals valued at twenty millions of 
francs (800,000/.), w"e need not wonder at the anxiety of agricul- 
turists to avail themselves of any measure which offered a 
prospect of diminishing such a serious drain upon their re- 
sources — not to mention the risk they and their labourers 
incurred from such a dangerous contagion, as well as the trouble 
of burial of carcasses, and other disadvantages which cannot be 
directly estimated. 
A few words may now be employed in describing, in outline, 
the method of enfeebling or attenuating the virus of this and some 
other virulent diseases, in order to procure protective material, or 
" vaccines," for inoculation, as well as in sketching the manner 
of performing inoculation. 
The crude virus of the disease is first sown, in minute quan- 
tity, in what is termed cultivation liquid. But in order to 
exclude all other germs, except those which are to be culti- 
vated, the greatest care is necessary in order to completely " ste- 
rilise" this liquid, previous to the sowing; and everything 
relating to the operation — cotton-wool, filters, culture-tubes, 
flasks, and all implements — has to be rendered thoroughly free 
from germs, or sterile, by exposure to a high temperature, 
such as will certainly destroy all organisms (298^ to 334° 
Fahr.). The seed-bed, or cultivation liquid itself, which is 
some simple infusion or decoction of suitable organic matter, 
is boiled for an hour at a time on two consecutive days, 
in glass vessels with a narrow neck, which is then plugged 
with baked cotton-wool ; this wool intercepts the entrancfe of 
germs by filtering the air, while allowing the latter to pass 
through. And to make certain that all spores which may have 
been in the fluid at the first boiling are killed, it is main- 
tained at a temperature varying between 89^ and 90° Fahr., 
which will induce any that may have escaped to advance to 
that stage of germination at which destruction would be certain 
at the second boiling. After this it is kept for some weeks 
again at the medium temperature, still secluded by the cotton- 
wool ; if it remains clear and limpid for that time, it is fit for 
sowing, but if it becomes turbid, it shows that it has been im- 
perfectly sterilised, and is unfit for use. If every precaution 
has been taken, the fluid will remain perfectly limpid for 
months, though the cultivation-tubes which contain it are only 
closed by some loose cotton-wool. Instead of cotton-wool, the 
