234 



BACTERIOLOGY. 



atively rapid, it is quickly entirely liquefied, and one 

 often sees the colonies floating about in the pale-green 

 fluid. 



Fig. 49. 



Colony of b. pyocyanus after twenty-four 

 hours on gelatin at 20°-22° C. 



Fig. 60. 



Stab culture of b. 

 pyocyanus in gel- 

 atin after twenty- 

 eight hours at 22° C. 



Colony of b. pyocyanus after forty-two hours 

 on gelatin at 20°-22° C. 



On agar-agar the growth is dry, sometimes with a 

 slight metallic lustre, and is of a whitish or greenish- 

 white color, while the surrounding agar is bright green. 

 With time this bright green becomes darker, passing to 

 blue-green, and finally turns almost black. 



On potato the growth is brownish, dry, and slightly 

 elevated above the surface. With some cultures the 

 potato about the growth becomes green; with others 

 this change is not so noticeable. With many cul- 



