PART III. METHODS USED IN 

 THE STUDY OF BACTERIA 



CHAPTER VI 

 CULTURE MEDIA 



Introduction. Very little can be determined about the 

 bacteria by microscopical examination alone. It is necessary 

 to cultivate them artificially in order to study them satis- 

 factorily. The reason for this will be seen when one realizes 

 that upwards of two thousand different species of bacteria have 

 been described, some of them man's worst enemies, and all 

 of them belonging to the three simple form types which have 

 been previously described. By microscopical examination we 

 can learn something of their distribution, something of their 

 form and structure, and something of their relation to, or at 

 least their association with, diseases, and such natural processes 

 as fermentation, putrefaction, etc., but nothing more. 



The artificial cultivation of bacteria has been developed 

 entirely within the last half century. The first attempts were 

 crude and unsatisfactory, as viewed from our present stand- 

 point, but since the time of Pasteur and Koch great progress 

 has been made. The science of bacteriology begins with this 

 work. The underlying principles of the artificial cultivation 



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