128 BACTERIOLOGICAL EXAMINATION OF WATER. 



in pure supplies. Waters containing these bacteria should be 

 regarded with suspicion, and the source of the supply carefully 

 investigated. 



Bacillus Megaterium. 



This organism was first isolated by De Bary from boiled 

 cabbage leaves. It was found by Tils in the Freiburg water- 

 supply. I have also found it in a water derived from a 

 polluted upland surface. 



Gelatine Plates. The surface colonies appear as circular 

 masses with a " woolly" margin ; later they appear depressed in 

 the gelatine owing to liquefaction. Under a low power they 

 show a dark granular centre surrounded by circular lines, from 

 which fine branching processes pass off at the margin. 



Gelatine-stab. A delicate growth at first appears along the 

 needle track, from which fine hair-like processes spread out into 

 the gelatine. Liquefaction rapidly takes place, and a funnel- 

 like excavation is formed, containing an opaque yellowish-white 

 layer at the bottom. 



Agar. A thick white growth appears with a feathery 

 margin. 



Potato. A thick yellowish-white growth. 



Glucose- gelatine. No gas formation. 



Milk. Coagulated, and then partially digested. 



Peptone and Salt Solution. No indol reaction obtained. 



Nitrate-broth. Powerful reducing action, large quantities of 

 ammonia being produced. 



Microscopical Characters. A fat bacillus, often very long, but 

 by the use of dehydrating agents, separate divisions can be seen, 

 so that the bacillus then appears to be made up of a series of 

 short rods, each containing a spore. It possesses a slow waggling 

 movement, and is stained by Gram's method. 



Bacillus Lactis Cyanogenus. 



This bacillus was first isolated from milk by Hueppe. 

 Jordan found it frequently in Lawrence sewage. 



Gelatine Plates. The surface colonies are circular and dirty 

 white in colour ; later the colour changes to an iron-grey, and 

 the surrounding gelatine acquires a deep blue colour. Under a 



