90 
Pasteur and his Work, 
preserving agent. In the case of the fowl-cholera germ, the- 
attenuating influence in operation was merely the oxygen of the 
air ; and the proof of this is afforded by cultivating the germ in 
a tube having only a little air. If the tube be hermetically 
sealed, the microbe soon consumes the oxygen in the air and in 
the culture-fluid, and retains its potency for evil unimpaired, for 
months, or even for years. The reason why the oxygen of the 
air has no influence upon it during the twenty-four hours' cul- 
tivation, is explained by this being required for its nourishment 
and reproduction ; after that time, the air gradually modifies or 
weakens it, until at last its power is annihilated, though the 
organism still lives. The experimentalist can in this way 
reduce, as he wills it, a virus to any degree of virulency. 
Pasteur could inoculate fowls with a cultivation too feeble to- 
protect from the deadly action of the crude virus, but effectual 
in insuring them against a stronger cultivation. A second cul- 
tivation would nullify the action of a third, and so on until the 
most deadly virus was rendered inert in the bodies of the fowls. 
The whole secret of this protective inoculation consists in 
knowing at what moment a certain degree of virus attenuation 
is a guarantee of safety against the full-power virus. 
Trials of the attenuated virus of fowl-cholera were made by 
veterinary surgeons and agriculturists, and with perfect success 
in every instance. It was found necessary to inoculate each 
fowl twice- — at first with a very weak virus, yet sufficiently strong 
to prevent dangerous consequences from a stronger ; then in ten 
or fifteen days with a less attenuated one. The preparation of 
these cultivations — or " vaccines," as Pasteur designates them,, 
in honour of Jenner, as it is obvious they have nothing to do 
with cows in this and some other animal diseases — demands 
much care in manipulation and experimentation, in order to 
arrive at the proper degree of harmlesness and potency. Species, 
and even breeds, and likewise individual peculiarities, have to- 
be tested as to receptivity, before the method can be generally 
applied. 
When Pasteur laid before the Academy of Sciences the details 
of his new discovery, the importance of its bearings on medi- 
cine — human and veterinary — as well as on medical doctrines, 
was fully recognised by those who were competent to form an 
opinion, and by no one more enthusiastically than the eminent 
veterinarian, M. Bouley, director of the French Veterinary 
Schools, and whose death last November, while President of the 
Academy of Sciences, Medicine and Agriculture must deplore. 
" This is but a beginning," he exclaimed ; " a new doctrine 
opens itself in medicine, and this doctrine appears to me power- 
ful and luminous. A great future is preparing ; I wait for it 
