166 



IDENTIFICATION OF BACTERIA 



at the deepest portion, it may contain flocculi, it may be uniformly 

 cloudy and turbid, and it may finally be covered by a pellicle. 



Shake Cultures. In gelatin shake cultures, gas bubbles, liquefaction, 

 or an abundant growth toward the surface are distinguished. The 

 latter indicates an aerobic development, while an abundant growth 

 in the lowest strata points to an anaerobic bacterium. 



FIG. 90 



Photographs of a large number of colonies developing in a layer of gelatin contained in a 

 Petri dish. Some colonies are only pinpoint in size; some are as large as a pencil. The colonies 

 here appear in their actual size. (Park.) 



Fio. 91 



FIG. 92 



Well-distributed colonies on agar in Petri 

 dish. (Park.) 



Irregular fringed colony (B. malignant edema). 

 (From Kolle and Wassermann.) 



Streak Cultures. In streak cultures on slanting agar or blood-serum 

 tubes, filiform, echinate, beaded, effuse, and arborescent growths are 



