366 



BAC1ER10LOGY. 



size, about which liquefaction is just beginning to be ap- 

 parent, show a dense granular centre, the colony itself, 

 and round about it a delicate, granular developmental 

 zone. 



In stab cultures in gelatin liquefaction is rapid, 

 causing at the end of twenty-four hours a cup-shaped 



FIG. 73. 



\ 



a b c d 



Stab culture of Deneke's cheese spirillum in gelatin, at 18 to 20 C. 



a. After twenty-four hours. &. After forty-eight hours, c. After seventy-two 



hours, d. After ninety-six hours. 



depression at the top of the needle-track, the superficial 

 area of which is about half that of the gelatin in the 

 tube. (Fig. 73, a.) The liquefying process spreads 

 laterally and at the end of forty-eight hours the whole 

 upper portion of the gelatin may have become liquid. 



