DESCRIPTION OF SPECIES 



429 



with raised centres and irregularly 

 sloping edge. 



Milk — Coagulation after 2 days 

 at 22° C, the coagulationg radually 

 acquiring a faint yellow tint. At 

 times pigmentation in form of faint 

 reddish-yellow dots on surface of 

 coagulum. 



Anaerobic or aerobic — Aerobic 

 and facultative aerobic, but grows 

 more rapidly and with more pig- 

 ment formation in presence of free 

 ox)'gen. 



Vitality — Is killed by heating to 

 68" C, but readily withstands a 

 temperature of 64° C. for ten 

 minutes (Connell). 



Non-pathogenic. 



BACIIiliUS SCHAFFBRI 



(Freudenreich). 



Source and habitat — Isolated from 

 blown cheese. Judged by Freu- 

 denreich to belong to the coli 

 group, and much resembling B. 

 coli communis. 



Morphology — Rods ; motile ; 2 to 3 /t 

 long, by I M broad. Found also in 

 threads. 



Staining reaction — Does not stain by 

 Gram's method. 



Gelatine — Deep colonies small, round, 

 yellow, and granular. Superficial 

 colonies much spread out, porce- 

 lain - white and with somewhat 

 irregular edges. Cultures are 

 highly viscous, and can be drawn 

 out in long threads. In gelatine 

 stab-culture, flat-headed, nail-like 

 growth. 



Agar — Grey, and later brownish. 



Potato — A yellow growth. 



Bouillon — Becomes turbid, and if 



peptone is present there are many 



gas bubbles. 



Milk — Rarely coagulates. 

 Non-pathogenic. 



BACILIiUS SUBTTLIS. 



Source and habitat — Hay, straw, soil, 

 dust, milk, etc. 



Morphology— Short, thick rods with 

 round ends, sometimes form 

 threads. Sometimes also chains 

 of long rods, short rods, and cocci. 

 0-8 to 1-2 M broad, 1-3 to 3 m long. 

 Often united in strings and threads. 



Staining reaction—Stains by Gram's 

 method. 



Capsule; flagellaj fftotility— Bacillus 

 possesses a capsule and flagella 

 which are long and numerous ; 

 short forms actively motile ; threads 

 immotile. 



Spore formation — Oval spores formed 

 in presence of air, germinating at 

 right angles to long diameter. 

 Spores are set free in about 24 

 hours ; size i-2 by -6 m ; widely 

 distributed in nature, dust, air, 

 excreta, etc. 



Biology: cultural characters {includ- 

 ing biochemical features). 



Bouillon — Uniformly cloudy 

 growth with marked pellicle, 

 wrinkled and thick ; copious spore 

 formation. 



Gelatineplatesandtubes — Saucer- 

 like depressions ; colonies have 

 granular centres and folded mar- 

 gins. Surface gro^vth in stab- 

 cultures is whitish-grey ; colonies 

 sink on liquefaction of medium ; 

 liquefaction progresses in a cylin- 

 drical form, and a thick white 

 scum is formed. 



Agar plates and tubes— Sn\al\ 

 irregular, greyish-white colonies ; 

 moist glistening growth along 

 needle track in stab-cultures. 



Potato — Dirty white to yellowish 

 coloured growth ; elevated, dull, 

 spreading, with scolloped border ; 

 copious spore formation. 



