528 APPLICATION OF METHODS OF BACTERIOLOGY 



On plates of nutrient agar-agar the appearance of the 

 colonies is not characteristic. They appear as round or 

 oval patches of growth that are moist and moderately 

 transparent. The colonies on this medium at 37° C. natu- 

 rally grow to a larger size than do those upon gelatin at 



22° C. 



Fig. 91 



abed 

 Stab-culture of microspira comma in gelatin, at 18° to 20° C. o, after 

 twenty-four hours; b, after forty-eight hours; c, after seventy- two hours; 

 d, after ninety-six hours. 



In stab-cultures in gelatin there appears at the top of 

 of the needle-track after thirty-six to forty-eight hours 

 at 22° C. a small, funnel-shaped depression. As the growth 

 progresses liquefaction occurs about this point. In the 

 centre of the depression can be distinguished a small, dense, 



