CULTUKES 45 



Pure cultures are used for studying the morphological 

 and physiological characteristics of microorganisms. 



From mixed cultures, pure cultures may be obtained by 

 the plating method. Mixed cultures of known micro- 

 organisms may be employed in studies on symbiosis, meta- 

 biosis, or antibiosis. 



FIG. 10. Mixed Culture in Petri Dish (Plate Culture) Showing 

 Various Forms and Sizes of Colonies, (Orig, Northrup.) 



Plate cultures are cultures grown in Petri dishes contain- 

 ing a nutrient medium. 



Slant culture is the term generally applied to cultures 

 grown on the inclined surface of any medium, such as agar, 

 potato, blood serum, etc., and are designated specifically 

 as agar slant cultures, potato slant cultures, etc. They are 

 generally prepared by drawing a contaminated needle in 

 a straight line along the surface of the medium. Cul- 



