QUALITATIVE BACTERIOLOGICAL ANALYSIS. 65 



extensions into the gelatine ; about the fourth day there is a cup- 

 shaped liquefaction at the surface containing a golden-yellow 

 slimy deposit. On agar there is a straw-coloured growth. On 

 potato there is a coffee-coloured layer. It is a short, thin, non- 

 motile bacillus, occurring usually in long spiral or bent threads 

 containing many individual bacilli. 



B. Helvolus. 



Described by Zimmermann. The colonies in the depth of 

 gelatine plates are small, circular, bright yellow dots ; on the 

 surface there is a pale yellow expansion with an irregular margin 

 which in a short time rests in a depression of liquefied gelatine. 

 In gelatine-slab it forms a button-like growth of a Naples-yellow 

 colour ; the growth extends to the margin of the tube and a 

 saucer-like depression is produced ; there is very little growth 

 along the stab. On agar it produces a thick Naples-yellow 

 growth. On potato there is an abundant yellow expansion. It 

 is a thin bacillus with only rotatory movement. It stains with 

 Gram. 



The following organisms do not liquefy gelatine : 



B. Aureus. 



Found in water by Adametz. In gelatine plates the surface 

 colonies have a golden yellow centre, the margin, however, is 

 lighter in colour and crinkled ; growth is slow and the gelatine 

 is not liquefied. In gelatine-stab the growth on the surface 

 resembles a colony ; along the stab there is a fine growth of a 

 golden-yellow colour. On potato a golden-yellow, raised, 

 coarsely granular growth appears. In broth there is a diffused 

 growth with a formation of the same golden-yellow pigment. 

 There is no gas formation in glucose gelatine. Nitrates are 

 reduced to ammonia. It is a fine bacillus of variable length. 

 Movement is feeble, and no spores have been observed. 



B. Aurantiacus. 



This bacillus was isolated by Frankland from deep wells in the 

 chalk. On gelatine plates it produces bright orange pin-heads. 

 Under the microscope the colonies in the depth are seen to be 

 smooth-rimmed. Growth is slow, and no liquefaction of the 



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