AEROBIC SPORE-BEARING NON-PATHOGENIC BACTERIA 523 



agar they measure 0.375 to 0.5 by 2 to 3 microns. On glucose agar 

 they are more uniform and shghtly thicker and longer, measuring 

 usually 0.5 by 3 to 4 microns. (Figures 78, 79 and 80.) 



Motility. Active progressive motility in 24 hour agar cultures. 



Staining properties. Gram-negative. 



Spore formation. Spores are formed early appearing often within 

 24 hours on plain and glucose agar. They are cyUndrical, usually 

 subterminal in position, thicker than the organisms from which 

 they spring, and present a characteristic appearance. They may 

 retain spurs of protoplasm at each end or may be entirely naked. 

 They measure usually 0.75 by 1.125 to 1.5 microns. Rarely they 

 may be distinctly terminal in position. 



Agar slant. Thick moist spreading growth with a silvery sheen 

 abundant in 24 hours and becoming thick white and glistening in 

 older cultures. Easily scraped from medium. 



Agar stab. Fihform growth along line of inoculation with an 

 abundant surface growth spreading to the tube wall. 



Agar colonies. Surface colonies in 24 hours are round aiid regu- 

 lar or thin spreading translucent, under low power slightly granu- 

 lar with entire edges. Deep colonies small fine, under low power 

 irregular and pale yellow. As the superficial colonies get older 

 they become thicker and heaped up sUghtly. The deep colonies 

 may show irregular fuzzy margins under the low power. 



Glucose agar. Heaped up white moist non-spreading growth in 

 24 hours, becoming thick and raised in old cultures. Reaction 

 alkahne. 



Glucose agar colonies. Superficial colonies are shghtly thicker 

 than plain agar colonies in 24 hours and show a greater tendency 

 to spread. Under the low power they are granular with entire 

 edges. Deep colonies small and fine, under low power irregular and 

 pale yellow. Older superficial colonies are thick, irregular and 

 heaped up. Reaction of agar alkahne. 



Gelatin stab. Faint growth along hne of inoculation and at the 

 point of puncture in 3 to 4 days, with beginning hquefaction. Dis- 

 tinct cup-shaped or funnel liquefaction in two weeks. Occasionally 

 a fragile scum appears on the hquid gelatin. 



Gelatin colonies. Colonies begin to appear in 48 hours and show 



