SPIRILLUM TYROQENUM. 



347 



to be apparent, show a dense granular centre, the col- 

 ony itself, and about it a delicate, granular develop- 

 mental zone. 



In stab cultures in gelatin liquefaction is rapid, 

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



Fio. 69. 



ij^s^ 



r/ 



a, b c d 



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

 a. After twenty-four hours. 6. After forty-eight hours, u. 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. 69, 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. 

 (Fig. 69, b.) This process continues along the 



