58 BACTERIOLOGICAL EXAMINATION OF WATER. 



Peptone-water. No indol reaction is obtained. 



Litmus-whey. After seven days at 22 C. the medium has a 

 markedly acid reaction. 



Microscopical Appearance. A. small non-motile bacillus, often 

 described as a micrococcus. In broth containing an acid or 

 antiseptics rods and chains are well marked ; these bacilli are 

 also motile. Scheurlen has described flagella at the sides of the 

 bacillus. It does not form spores, but resists drying for a long 

 time, when involution forms are seen. The pigment is best 

 produced at 20-24 C. When cultured continuously at 37 C., 

 forms are obtained which cannot produce the red pigment ; old 

 cultures at room temperature also lose the power of producing 

 pigment, which, however, can be restored by cultivating the 

 organism on potato. It is not stained by Gram's method. 



B. Ruber Indicus. 



Described by Koch and also found by Pasquale at Massowah. 

 It is a motile, small, thin bacillus, which does not form spores. 

 The colonies in the depth are golden-yellow with sharply-defined 

 edges ; the superficial colonies quickly liquefy the gelatine. 

 In gelatine-stab there is a stocking-shaped liquefaction ; on the 

 surface there is a brick-red membrane and a white deposit at 

 the bottom. On agar and potato at 35 C. it produces a brick- 

 red growth. 



B. Ruber Balticus. 



This organism was found by Breunig in the Kiel water. It 

 is a slender motile bacillus, which does not form spores. The 

 colonies in the depth are round and clear yellow in colour ; the 

 surface colonies are thin layers, which gradually liquefy and have 

 a rose-red colour. In stab-gelatine there is liquefaction at the 

 surface and gas development in the depth. It grows and pro- 

 duces colour at 35 C. ; at this temperature the growth on 

 potato is purple or carmine red ; at 20 C. it is orange red ; the 

 deeper layers are always reddish-violet. Milk at 20 C. is 

 coloured and eventually coagulated through acid production ; 

 at 37 C. it is quickly coagulated but there is no coloration. 



