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 0/ a temperature considerably below boilmg 

 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 tbe south of France to the value of some millions sterling 

 annually, was threatened with extinction, in consequence of the 

 isilk 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 domaiu 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 



