148 BACTERIOLOGICAL EXAMINATION OF WATER. 



Agar-plate Cultures. The colonies are white and more or less 

 circular in shape ; the growth is not characteristic. 



Potato Cultures. A porcelain-white growth slowly develops, 

 afterwards the colour becomes dirty yellowish -white, and the 

 bacterial layer becomes unequally thickened. 



Broth Cultures. The growth is scanty and not characteristic. 



Litmus-milk Cultures. No clotting occurs ; after sixteen days 

 very feeble acidity is produced. 



Indol Reaction. No indol reaction is obtained in broth 

 cultures. 



Reduction of Nitrates. No reduction after twelve days at 20C. 



Microscopical Characters. Large motile bacillus, with rounded 

 ends ; solitary, in pairs, and in chains. It forms large spindle- 

 shaped spores. 



Remarks. This micro-organism has a somewhat negative 

 character in all the media ordinarily in use. It has been called 

 B. fusiformis, owing to the spores being spindle shaped. 



Bacillus Subtilissimus. 



Isolated from crude sewage. 



Gelatine-plate Cultures. The surface colonies are very cha- 

 racteristic, and grow so quickly that a single colony may cover 

 nearly a whole plate in two days. The growth is film-like, 

 exceedingly thin and transparent, dull grey in colour, and very 

 faintly granular. Under a low power the colony resembles 

 B. coli, but the growth is so delicate that it is difficult to see 

 the delicate veining of the bacterial film. The surface colonies 

 are more or less circular in shape, but the spreading margin is 

 nearly always irregular. 



Gelatine-streak. The growth is like an elongated surface 

 colony. In less than twenty-four hours a delicate film has 

 spread nearly to the walls of the tube. The spreading edge is 

 very irregular, and in older cultures may present a terraced 

 appearance. 



Gelatine-shake Culture. No gas bubbles are formed in the 

 gelatine. 



Agar-streak. A white film is formed on the surface, having 

 a markedly irregular edge. The lateral expansion is less than 

 in the case of gelatine cultures. 



