382 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



The object of the anaerobic milk cultures was to 

 demonstrate the presence of a spore-forming anaerobic 

 bacillus— the B. enteritidis sporo genes of Klein, or a 

 nearly related form. All the ten cultures made gave 

 positive reactions ; that is, the milk was curdled and 

 abundant gas formation took place, breaking up the curd 

 in the characteristic manner. This again is presumptive 

 evidence of sewage pollution since unpolluted shellfish 

 and unpolluted fresh or sea water do not readily give 

 this reaction. 



Bacillus coli, the presence of which is now regarded 

 as indicative of sewage pollution, grows on neutral red 

 agar as deep red, and large colonies. Not all these 

 " colon-like " growths are, however, produced by the 

 typical B. coli: Eleven of these colon-like colonies were, 

 therefore, selected from the ten plates, and from them 

 pure sub-cultures were made on nutrient agar. After 

 24 hours incubation at 42°C. these secondary cultures 

 were examined in detail. The presence or absence of 

 motility of the bacilli was observed microscopically, and 

 each sub-culture was inoculated in 7 different media (bile 

 salt glucose broth, glucose broth, lactose broth, mannite 

 broth, cane sugar broth, glycerine broth, and litmus 

 milk). These tertiary sub-cultures were again incubated 

 for 48 hours at 42°C. 



At the end of this time six gave the reactions for the 

 typical Bacillus coli. Therefore, about one-half of the 

 discrete colonies identified as " colon-like " proved to be 

 those of B. coli. 



Neutral-red, bile-salt lactose agar not only affords 

 an easy means of picking out organisms which are 

 probably B. coli, but it also distinguishes these from 

 organisms belonging to the Gaertner and typhoid groups. 

 These latter grow on the medium in question as white 



