44 BACTERIOLOGICAL EXAMINATION OF WATER. 



horizontal and limited to the surface layers. The colour of the 

 pigment produced in the various media may be bright green or 

 only greenish-yellow. The growth on potato usually shows a 

 yellowish-brown colour, but at times it may have a rose tint or 

 deep brown colour. Also some varieties which I have isolated do 

 not coagulate or digest milk. The B. cloacae fluorescens, the B. 

 fluorescens stercoralis (Laws and Andrewes), the B. fluorescens 

 Schuylkilliensis, B. fluorescens mutabilis (Wright), B. butyri 

 fluorescens (Lafar), B. fluorescens nivalis (Schmolck), and B. vis- 

 cosus (Frankland) are merely varieties of the B. fluorescens lique- 

 faciens. The B. viridans, described by Zimmermann, is a small 

 non-motile bacillus, which produces a steel-green colour in media, 

 but no fluorescence is observed. It grows well at 30 C., is aerobic, 

 and does not stain with Gram. It rapidly liquefies gelatine, but 

 in gelatine-stab the liquefaction only occurs horizontally at the 

 surface ; there is no growth along the line of inoculation. 



BACILLI WHICH PRODUCE A GREEN FLUORESCENCE IN NUTRIENT 

 MEDIA, BUT DO NOT LIQUEFY GELATINE. 



These bacilli are also extremely common in water, and, when 

 the green .colour of the media is slowly produced, there may be 

 difficulties in diagnosing this group from other species. 



B. Fluorescens Non-Liquefaciens. 



Colonies on Gelatine Plates. After forty-eight hours at 22 C., 

 the surface colonies are thin, with an irregular margin, and 

 when held up to the light have a bluish, almost transparent 

 appearance ; the surrounding gelatine shows a green fluorescence. 

 Under a low power the colonies show a beautiful venation 

 resembling that of a leaf. The colonies in the depth of the 

 gelatine are round, and by transmitted light appear greenish- 

 brown in colour. 



Gelatine-stab. There is a growth on the surface resembling 

 a colony, and a thin white growth along the line of inoculation ; 

 the gelatine is not liquefied and acquires a bright green colour. 



Agar-slope. A white growth ; the medium assumes a green 

 colour. 



Broth. A diffused growth ; a pellicle appears on the surface 

 in forty-eight hours. The broth assumes a green colour. 



