62 BACTERIOLOGICAL EXAMINATION OF WATER. 



described above differs from Frankland's organism by reducing 

 nitrates to ammonia. Some varieties of this organism send out 

 long wandering convoluted processes on the surface of gelatine 

 plates, and in this respect resemble the Proteus species. 



B. Nubilus. 



This organism occurs very frequently in water derived from 

 wells, rivers, and upland surfaces. It is a slender bacillus, which 

 possesses only rotatory movement and does not form spores. It 

 does not stain with Gram, and cannot develop at 37 C. or under 

 anaerobic conditions. The colonies in gelatine appear as cloudy 

 patches, with an ill-defined margin, which grow chiefly in the 

 depth ; under a low power each colony is seen to be made up of 

 interlacing threads of bacilli ; the gelatine is rapidly liquefied. 

 In gelatine stab there is a thick white growth, but under the 

 surface and along the line of inoculation delicate cloudy growths 

 appear, the gelatine is liquefied horizontally at the surface, and 

 the growth in the liquefied gelatine acquires a faint yellow 

 colour. On agar there is a white growth with a thin filmy 

 margin ; later, the growth acquires a faint yellow tint. On 

 potato there is a marked yellow growth and the potato becomes 

 discoloured. Milk is not affected by the growth of this organism, 

 and litmus-whey acquires a faint alkalinity. There is no gas 

 formation in glucose and lactose media. There is a diffused 

 growth in broth with a slight deposit, but no pellicle forms on 

 the surface. Nitrate broth is powerfully reduced, ammonia being 

 produced. In peptone and salt solution there is no formation 

 of indol. 



The organism above described, which I have often found in 

 waters, appears to closely resemble the B. nubilus described by 

 P. and G. Frankland. The colonies are identical ; but the growths 

 in gelatine and on agar have a yellow colour, which is not seen 

 in the growths of the Franklands' bacillus ; also the latter 

 produces a film in broth, gives a very slight growth on potato, 

 and reduce nitrates feebly, only a small proportion of nitrites 

 being found. The B. gracilis, described by Zimmermann, appears 

 closely related to the B. nubilus. This organism, however, 

 liquefies gelatine very slowly, and on potato produces only a 

 slight moist appearance. It is also said to produce elliptical spores. 



