SPIBILLVM TYROGENVM. 479 



rough and broken, and the body of the colony is fre- 

 quently marked by creases or ridges that give it a 

 lobulated appearance. The larger colonies under the 



Fig. 82. 



,1 , — -r-~~ "S i\ 





i III ' /, I , ^^ "» 



Deneke's cheese spirillum, spirillum tyrogenum. From agar-agar culture 

 twenty-four hours old. 



same lens appear as granular patches, a little denser at 

 the periphery and centre than at the intermediate por- 

 tions. The periphery gradually fades away and no 



Fig. 83. 





\ 





Colony of spirillum tyrogenum on gelatin, twenty-four hours old. 



distinct circumference can be made out. (See Fig. 83.) 

 The colonies of an intermediate size, about which lique- 

 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 



