64 
Pasteur and his Work, 
them, since they are surrounded with air. Deeper in the fluid 
they would perish, and they only linger at the sides of the barrel 
until they get an opportunity to again contend with their vege- 
table enemy. Pasteur's intervention removed the evil : the vats 
are thoroughly and frequently cleaned, so that the organisms 
have no time to do any harm. 
Guided by his studies on vinegar, Pasteur has been able to 
effect great improvements in the manufacture of beer and wine, 
by which production is cheapened, and the keeping properties 
of the liquids much enhanced. 
These improvements are founded upon the observed injurious 
effects of the organisms which give rise to the acetic, lactic, and 
butyric fermentations ; and the measures adopted to prevent them 
are most simple and effective — the process now being known as 
" Pasteurisation." With regard to beer, he recommended that 
it should be bottled when fermentation is nearly completed, and 
the bottles then subjected to a temperature of between 122^ and 
131° Fahr., so as to destroy all injurious germs. The wort, 
while cooling, was also to be guarded against all atmospheric 
germs, and the leaven employed for making it was likewise to 
be free from them. Wine has its own peculiar micro-organism — 
the Mycoderma vini — which feeds on new wine, but dies as this 
becomes old. The vinegar ferment cannot live upon new wine, 
but as soon as the Mycoderma vini perishes and decays, the 
M. aceti attacks it and grows rapidly, so that the wine becomes 
sour. " Flat " wine, and " greasy " wine (peculiar to the white 
wines of the Loire basin), as well as the " bitterness " of Bur- 
gundy wines, are also due to particular microscopical organisms. 
The ageing of wine mainly depends on its oxidation, the oxygen 
which was previously mixed in a mechanical manner with it 
becoming chemically incorporated in it ; for new wine, when 
destitute of air, does not age, and the difficulty in managing 
wine is to permit a certain amount of air to be present wil^hout 
any deteriorating germs. M. Radot, in alluding to this subject, 
says : — " In short, according to Pasteur's observations, the dete- 
rioration of wines should not in any case be attributed to a 
natural working of the constituents of the wine, proceeding 
from a sort of interior spontaneous movement, which would 
only be affected by variations of temperature or atmospheric 
pressure ; they are, on the contrary, exclusively dependent on 
microscopic organisms, the germs of which exist in the wine 
from the moment of the original fermentation which gave it 
birth. What vast multitudes of germs of every kind must there 
not be introduced into every vintage-tub ! What modifications 
do we not meet with in the leaves and in the fruit of each indi- 
vidual spoilt vine! How numerous are the varieties of organic 
