52 BACTERIOLOGICAL EXAMINATION OF WATER. 



a brown colour. It reduces nitrates more vigorously, and is 

 smaller and more motile than the vulgatus. 



B. Mesentericus Rufoer. 



This bacillus was described by Globig. The colonies on the 

 surface and in the depth show quite early numerous irregular 

 processes running in all directions from the periphery ; later, on 

 the surface colony a clear zone appears between the membranous 

 centre and the peripheral rays, and the colony in this stage 

 closely resembles the above varieties. The agar growth in the 

 early stage shows processes running out from the margin ; later, 

 a dry wrinkled film is produced. On potato at 37 C. a wrinkled 

 growth appears and the potato acquires a red colour. The red 

 colour is not formed at 22 C. In other media the cultures 

 resemble those of the vulgatus. The bacillus is thinner and 

 more motile than the vulgatus, and possesses a powerful reducing 

 action on nitrates, large quantities of ammonia being produced 

 after seven days incubation. 



B. Liodermus. 



Fliigge described this organism, which is closely related to the 

 potato bacillus. On potato it produces a gummy layer, which 

 later is thrown into folds. The gummy material is soluble in 

 water and precipitated by alcohol like gum arabic. Milk is 

 coagulated and peptonised. 



B. Subtilis. 



This bacillus was first isolated by Ehrenberg from an infusion 

 of hay, hence it is often called the hay bacillus. 



Colonies on Gelatine Plates. The colonies at first are small 

 white points, which under a low power appear as irregularly 

 round, yellowish-brown membranes, from which fine hair-like 

 processes pass off into the gelatine. Later, the colonies appear 

 as small cups of liquefied gelatine, with little or no central 

 membrane ; from the margin of the colony hair-like processes 

 are still seen passing into the gelatine. In the depth the colonies 

 often appear as granular centres from which many long and 

 curved processes spread out into the gelatine ; sometimes very 



