INTRODUCTION. XXvii 



The manufacture and maladies of wine next 

 occupied Pasteur's attention. He had, in fact, got 

 the key to this whole series of problems, and he knew 

 how to use it. Each of the disorders of wine was 

 traced to its specific organism, which, acting as a 

 ferment, produced substances the reverse of agreeable 

 to the palate. By the simplest of devices, Pasteur, at 

 a stroke, abolished the causes of wine disease. Fortu- 

 nately the foreign organisms which, if unchecked, 

 destroy the best red wines are extremely sensitive to 

 heat. A temperature of 50 Cent. (122 Fahr.) suffices 

 to kill them. Bottled wines once raised to this tem- 

 perature, for a single minute, are secured from subse- 

 quent deterioration. The wines suffer in no degree 

 from exposure to this temperature. The manner in 

 which Pasteur proved this, by invoking the judgment 

 of the wine-tasters of Paris, is as amusing as it is 

 interesting. 



Moved by the entreaty of his master, the illustrious 

 Dumas, Pasteur took up the investigation of the 

 diseases of silkworms at a time when the silk-husbandry 

 of France was in a state of ruin. In doing so he did 

 not, as might appear, entirely forsake his former line 

 of research. Previous investigators had got so far as 

 to discover vibratory corpuscles in the blood of the 

 diseased worms, and with such corpuscles Pasteur had 

 already made himself intimately acquainted. He was 



