SPIRILLUM TYROGENUM. 



401 



faction is just beginning to be apparent, 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, caus- 

 ing at the end of twenty-four hours a cup-shaped depres- 

 sion at the top of the needle-track, the superficial area 

 of which is about half that of the gelatin in the tube. 



Fig. 80. 



a b c d 



Stab-cultare of Deaeke*s cheese spirillum 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. 



(Fig. 80, 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. 

 80, 6.) This process continues along the track of the 



