56 BACTERIOLOGICAL EXAMINATION OF WATER. 



The B. aquatilis radiatus (B. radiatus aquatilis of Zimmer- 

 mann) is also very common in water. It liquefies a gelatine-stab 

 in the form of a stocking. The colonies have a rayed margin. 

 The growth on agar is grey and transparent and on potato there 

 is a yellowish-brown layer. Gas producing varieties have been 

 observed. The bacillus is morphologically like the above, but 

 somewhat longer forms are seen ; it is not motile. 



Closely allied to this group is an organism which I have 

 described as the B. liquefaciens sewage variety. It differs from 

 the type in that it coagulates milk and produces intense gas 

 formation in glucose-gelatine shake. I have found this organism 

 very frequently in sewage and polluted waters ; it is apparently 

 identical with the sewage proteus of Houston, which is fully 

 described under the sewage organisms. 



Between this sewage variety and the type there are many 

 connecting links formed by bacteria which resemble the type in 

 not coagulating milk, but approach the sewage organism by 

 giving rise to intense gas formation in glucose-gelatine. The 

 Bacillus gasoformans, described by Eisenberg, appears to belong 

 to this group and to be identical with the intermediate forms 

 just mentioned. It is a, small, very motile bacillus, which does 

 not form spores. In gelatine plates it produces cup-shaped 

 liquefaction, and in gelatine-stab the medium is rapidly 

 liquefied in the form of a stocking. In glucose-gelatine it 

 produces marked gas formation. It does not grow at 37 C. 



The members of this group vary extremely in their reaction 

 to temperature ; some of the varieties will not grow at 37 C. ; 

 others grow better at blood-heat than room temperature ; but 

 even when the cultural characteristics are identical the relation 

 to temperature may not be the same; this statement also applies 

 to the sewage varieties. 



The B. hyalinus, B. cloacae, and B. delicatulus, isolated by 

 Jordan from Lawrence sewage, probably belong to this group 

 and appear to be varieties of B. liquefaciens (sewage proteus, 

 Houston) sewage variety. The characteristics of these organ- 

 isms as described by Jordan will be found in the section devoted 

 to sewage organisms. 



The B. devorans, isolated by Zimmermann from a much-used 

 well-water, produces colonies which are characterised by forming 



