26 THE MAIN CURRENTS OF ZOOLOGY 



nearly two centuries after Leeuwenhoek's discovery 

 before these organisms began seriously to be con- 

 sidered as of practical interest. 



We cannot assign a definite date as the time of the 

 beginning of bacteriology. It took form gradually. 

 The researches of Ferdinand Cohn on the bacteria, 

 published at various times between 1853 and 1872, 

 form an important preliminary preparation. This is 

 especially true of his classification of the bacteria 

 which in its larger features is essentially the one used 

 to-day. If, however, any single man is to be con- 

 sidered as the founder of bacteriology that man is 

 Louis Pasteur, while for Robert Koch we reserve the 

 distinction of having lifted it into the position of an 

 independent science. 



For convenience we may arbitrarily adopt the 

 date 1877, as being the time when bacteriology 

 sprang into general recognition. In that year both 

 Pasteur and Koch demonstrated that splenic fever, a 

 specific disease of sheep and cattle, is owing to the 

 growth within the body of a specific micro-organism 

 called the anthrax bacillus (Bacillus anthracis). 

 Previously, Pasteur had shown the nature of fer- 

 mentations (1857) and discovered the connection 

 between microscopic particles and silk-worm diseases 



