Methods of Studying Bacteria. 



A culture thus obtained is called a pure culture since 

 it contains but a single kind of an organism, as the 

 colony is the result of the growth of a single cell. These 

 cultures then serve as a basis for continued study, and 

 must be planted and grown upon the different kinds 

 of media that are obtainable. In this way the slightest 



FIG. 5. DIFFERENT KINDS OF BACTERIA GKOWING IN GELATIN. 

 A, meager growth, no liquefaction or surface growth; B, pro- 

 fuse surface growth, radiating filaments from the growth be- 

 low the surface; C, a rapid liquefying form; D, a gas pro- 

 ducer that grows equally well in the presence or absence of 

 air; E, form that grows only in the absence of air, an ana- 

 erob. 



variations in the growth of different forms are detected, 

 and the peculiar characteristics are determined, so that 

 the student is able to recognize this form when he meets 

 it again. 



These culture methods are of essential importance in 



