132 BACTERIOLOGICAL EXAMINATION OF WATER. 



Glucose-gelatine (shake). No gas formation. 



Milk. Unchanged . 



Peptone and Salt Solution. No indol reaction obtained. 



Nitrate-broth. The nitrates are not reduced. 



Broth. A diffuse growth, the broth acquires a green 

 colour. 



Potato. A yellowish-brown restricted growth, later, nut- 

 brown in colour. 



Microscopical Appearance. Thin motile bacillus, with 

 rounded ends. From two to eight spores, which have a red 

 colour, appear in each rod. The red spores are visible when 

 the bacillus has been stained with methylene blue. 



Bacillus Pyocyaneus. 



The colour of green pus is due to the products of this 

 bacillus ; it was described by Gessard and Charrin. The same 

 bacillus was found by Tils in the Freiburg water-supply. 



Gelatine Plates. The colonies develop rapidly. They are not 

 sharply circumscribed, and usually present a fringe of delicate 

 filaments, surrounding a dark granular centre ; as growth 

 advances the gelatine is liquefied, and acquires a bright green 

 colour. Lender a low power the centre of the colony appears 

 filled with dark rounded masses, and surrounded by a wide, 

 thin, filmy growth, which has an irregular margin. 



Gelatine-stab. There is rapid liquefaction of the gelatine, 

 which in the earliest stage takes the form of a long narrow 

 funnel. The gelatine assumes a bright green colour. 



Agar. There is a dry greenish- white growth ; the agar is 

 bright green. 



Potato. There is a dry brownish growth which, when touched 

 with a platinum needle, sometimes becomes green ; the colour 

 lasts about ten minutes. This is known as the chameleon phe- 

 nomenon of Ernst. 



Broth. There is a floccular growth ; a pellicle forms on the 

 surface, and the broth assumes a green colour. 



Milk. An acid reaction is produced and the milk coagulated. 



Peptone and Salt Solution. Indol is produced. 



Microscopical Appearance. It is a delicate rod with rounded 

 ends ; sometimes it is very short and resembles a coccus ; in old 



