132 BACTERIOLOGY 



or orange-coloured growth develops, with an iridescent 

 margin. 



Bacillus violaceus. — In water of a violet tint, in that from 

 rivers and water-works — in the Thames and the Spree, for in- 

 stance — there are found motile rods with rounded ends, whose 

 colonies on the gelatine plate are at first small, resembling 

 air-bubbles enclosed in the gelatine, but later on liquefy 

 it and form granular islets of a bluish-violet colour, which 

 are distinctly visible as early as the fourth or fifth day. In 

 the thrust-culture a funnel-shaped area is formed by the 

 liquefaction, 'to the bottom of which the blue-coloured 

 masses of bacilli sink. A dark blue coating develops on 

 agar, and the bacillus grows very well on potato, spreading 

 out radially from the place of inoculation until the disc is 

 nearly covered. Blood serum and plovers' egg albumen 

 are liquefied with the formation of a violet colour. 



Bacillus gasoformans. — The gas-forming bacillus consists 

 of small highly motile rods, and forms islets on the gelatine 

 plate, which, though at first small, rapidly liquefy the 

 medium and spread into its substance as well as over the 

 surface. In this way a capsule-like figure is formed, in 

 which bubbles of gas are visible ; but the formation of these 

 bubbles is especially characteristic in the clear gelatine along 

 a thrust-canal. The gelatine is speedily liquefied. Growth 

 only takes place at the temperature of an ordinary room. 



Bacillus phosphorescens. — Fischer found the Bacillus 

 phosphorescens indigenus, or native luminous bacillus, in 

 phosphorescent water from Kiel harbour. Its rods are 

 short, rounded at the ends, and actively motile, and will 

 not grow on serum nor on potato. Small round colonies form 

 on the gelatine plate, which liquefy rapidly, and in about 

 eight days present the appearance of holes cut with a 

 punch in the gelatine, and evidently containing air. The 

 young colonies are sea-green, the older of a dirty greyish- 



