CHAPTER VIII. 



THE HISTORY OF BACTERIOLOGY. 



MEN justly attempt to understand what at 

 present exists by considering the manner in 

 which it has come into existence, and we are 

 hence in the habit of drawing up an historical 

 outline of any subject we may be carefully 

 considering. In bacteriology, however, we 

 have been for some time engaged in a com- 

 plete revaluation of our data. The old facts 

 remain, but new facts have been added to them 

 with the result of bringing to maturity new 

 theories. These have either not conformed at 

 all to ideas generally received or have perhaps 

 fallen in with older views which had been ap- 

 parently set aside. Under such circumstances 

 it is best first of all to learn to know the data 

 now at our disposal in order to consider as ob- 

 jectively as possible the facts and theories of 

 an earlier time. 



Knowledge of the occurrence of poisonous in- 

 sects such as mosquitos and tse-tse flies led peo- 

 ple of the older civilizations to an ontological 



conception which set up Beelzebub as the supe- 

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