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are thus often accidentally introduced into the wort, as well as the 
pure yeast ferment, and however well and scientifically the brewing 
is otherwise managed, the result is inevitably to ruin the beer. M. 
Pasteur found that heat of a temperature considerably below boiling 
point was fatal to these poisonous germs without being in any way 
injurious to the beer. Thus by a scientific microscopic test at the 
various stages of brewing, and a subsequent application of the 
requisite heat, the possibility of the beer becoming sour was re- 
duced to a minimum, if not entirely abolished, and an operation 
which was previously carried out at great risk, and with frequent 
loss of capital, was thus placed on a firm and scientific basis. A 
microscope has now become as important an item in a brewhouse 
as a thermometer. M. Pasteur’s researches were of no less value 
to wine manufacturers, for having once identified the germs which 
cause acetous fermentation, he was able to determine the exact 
degree of heat fatal to them, and was thus the means of materially 
benefiting the wine trade of the whole of France. 
M. Pasteur’s attention was next turned to a disease seriously 
affecting another, but equally important, branch of industry in his 
own country. 
Some thirty years ago, the silk weaving trade which is carried 
‘on in the south of France to the value of some millions sterling 
annually, was threatened with extinction, in consequence of the 
silk worm disease called Pebrine, from the black spots which de- 
velop on the bodies of the grubs. When at last, after much reluc- 
tance and with great modesty, M. Pasteur undertook to investigate 
the nature of this disease, many scientists openly ridiculed the idea 
-of a mere chemist venturing into the special domain of the biologist. 
Nothing daunted, however, M. Pasteur proceeded with his experi- 
ments, and in a few months formulated his theory respecting the 
disease. Other scientists had already traced micro-organisms in 
the blood and tissues of the diseased worms and moths, but they 
were unable to solve the problem why apparently healthy eggs 
developed into diseased worms, and why certain diseased worms 
yielded normal cocoons. The difficulty was solved by M. Pasteur. 
He found that moths derived from diseased worms never lay really 
healthy eggs, although in consequence of the minuteness of the 
germs they may escape detection in the eggs or in the newly 
hatched worms, the disease only developing with the growth of the 
worm, and thus rendering it incapable of spinning a cocoon. In 
this disease the microbes completely fill the silk weaving organs of 
the grub and destroy the clear, viscous fluid from which the silk is 
spun M. Pasteur found, moreover, that the disease is highly in- 
fectious as well as hereditary, and that’ worms so infected were 
capable of spinning cocoons, although they were so far impregnated 
