I40 PERIOD V. 



The career of Pasteur exhibits a striking unity. His 

 first research, which dealt with a subject so remote from 

 the ordinary studies of the biologist as the crystalline 

 forms of tartrates, made him acquainted with activities, 

 hitherto unsuspected, of minute forms of life. The hope 

 of aiding the industries of Lille, Orleans, and France 

 kept him long engaged upon ferments. If he turned 

 aside to examine the superstition of spontaneous genera- 

 tion, it was to protect his methods from misconstruction. 

 An apparent break in his programme of work was forced 

 upon him by the silkworm pestilence. It proved to be 

 no real break, for pebrine and flacherie were both bac- 

 terial diseases. At a comparatively early date (1863) 

 he wrote that his chief ambition was to throw light on 

 the spread of contagious diseases ; he could not then 

 foresee that he was destined, not only to elucidate, but 

 in a measure to control them. Around his tomb are 

 inscribed words, each of which commemorates a signal 

 service to his fellow-men : " 1848, Molecular dissymetry. 

 1857, Fermentations. 1862, Spontaneous generation. 

 1863, Studies of wine. 1865, Silkworm diseases. 1871, 

 Studies on beer. 1877, Contagious diseases of animals. 

 1880, Vaccination against contagious diseases. 1885, 

 Prevention of hydrophobia." These manifold researches 

 form a continuous chain, each being linked to what 

 precedes and follows. The devotion by which all were 

 inspired, beginning with devotion to science and the 

 fatherland, ended by embracing all mankind. 



Biology, which in the sixteenth century sent out only 

 a few feeble shoots, has now become a mighty tree with 

 innumerable fruit-laden branches. The vigour of its 

 latest outgrowths encourages confident hopes of future 

 expansion. 



