304 BACTERIOLOGY. 



formation present in the rods. On plate cultiva- 

 tions the colonies occur as circumscribed liquefied 

 areas, in the centre of which is a collection of the 

 coloured growth. In test-tubes a funnel-shaped 

 liquefaction takes place, while a granular-looking 

 violet mass subsides to the bottom. On agar-agar 

 and potatoes a beautiful violet growth rapidly 

 develops. They were observed on pieces of pigs' 

 bladder floating on the surface of water rich in 

 bacteria. They occurred only on the surface of 

 the bladder exposed to the air, and never on the 

 part under water. They occasionally occur in 

 common tap water. The colouring matter is 

 soluble in alcohol. 



Bacillus cyanogenus, Fuchs. (Bacterium 

 syncyanum. Bacillus of Blue Milk}. Motile rods, 

 2-5 3*5 p in length, and "4 ^ wide (Fig. 119). 

 The rods after division may remain linked 

 together, and form chains. Non-motile rods 

 enveloped in a gelatinous capsule, and involution- 

 forms, have also been described. Spore-formation 

 present. 



Cultivated in a test-tube of nutrient gelatine, the 

 bacilli grow principally upon the free surface, in 

 the form of a white layer. The surface of the 

 gelatine becomes cupped, and a peculiar greenish - 

 brown colour develops in the medium, especially 

 in proximity to the growth. 



On a sloping surface of nutrient agar-agar, 

 they grow as a white layer, and colour the 



