THE VITAL PHENOMENA OF BACTERIA. 1 27 



accurate knowledge have been resolved into 

 several species ; here belong for example, B. 

 termo, B. subtilis or the hay-bacillus, B. mes- 

 entericus or the potato-bacillus ; to-day such 

 names are sometimes used in a general, some- 

 times in a limited sense. 



At first stress was laid upon differences and 

 it was recognized that different genera and 

 species exist among bacteria as well as among 

 the Cyanophycea or among the moulds. These 

 discoveries, which were supported by careful 

 methods devised by J. Schroter and ingeniously 

 extended by Klebs and especially by R. Koch, 

 formed a basis for all subsequent investigation. 

 The further discoveries of J. Schroter and 

 Hueppe concerning the pigment bacteria, of 

 Pasteur, F. Cohn, Fitz, Duclaux and Hueppe re- 

 garding the processes of fermentation and decay, 

 and of Davaine, Pasteur, R. Koch, Gaffky and 

 Loffler in regard to disease-producing bacteria, 

 established bacteriology upon a firm founda- 

 tion. 



It was supposed, however, in the beginning 

 that in every typical fermentation or infectious 

 disease only one kind of micro-organism was 

 causally concerned. But Mitscherlich had 

 even then discovered that the yeasts of top and 

 bottom fermentation are of different species, 

 and I too found that not one species merely, 



