552 BACTERIOLOGY. 



When distributed through a deep layer of liquefied 

 gelatin that is subsequently solidified colonies develop 

 at only the lower portions of the tube. The single 

 colonies appear as discrete globules that cause rapid 

 liquefaction of the gelatin, and ultimately coalesce 

 into irregular, tabulated liquid areas. In some of the 

 larger colonies an ill-defined, concentric arrangement 

 of alternate clear and cloudy zones can be made out. 

 (Fig. 91.) 



In deep stab-cultures in gelatin growth begins after 

 about two or three days at 20 to 25 C. It begins 

 usually at about one or two centimetres below the sur- 

 face, and causes slow liquefaction at and around the 

 track of its development. During its growth gas- 

 bubbles are produced. 



In deep stab-cultures in agar-agar at 37 to 38 C. 

 growth begins in from twenty-four to forty-eight hours, 

 also at about one or two centimetres below the surface, 

 and is accompanied by the production of gas-bubbles. 

 There is produced at the same time a peculiar, pene- 

 trating odor somewhat suggestive of that of rancid 

 butter. Under these conditions spores are formed after 

 about thirty hours. 



It grows well in bouillon of very slightly acid reac- 

 tion under hydrogen, but does not retain its virulence 

 for so long a time as when cultivated upon solid media. 

 In this medium it develops in the form of white flocculi 

 that sink ultimately to the bottom of the glass and leave 

 the supernatant fluid quite clear. If the vessel be now 

 gently shaken, these delicate flakes are distributed homo- 

 geneously through it. In bouillon cultures there is 

 often seen a delicate ring of gas-bubbles round the 

 point of contact of the tube and the surface of the 



