98 BACTERIOLOGICAL EXAMINATION OF WATER. 



B. Coloides Rubescens. In gelatine plates under a low 

 power the colonies show a leaf-like pattern. On gelatine-stroke 

 culture there is a greyish- white growth with a reddish 

 iridescence ; the gelatine is not liquefied. On agar it forms a 

 diffused veil-like growth, which shows a reddish iridescence. 

 On potato there is a restricted yellow growth. In broth it 

 produces a diffused growth with a reddish pellicle. It ferments 

 grape-sugar and milk-sugar, but not cane-sugar ; milk is com- 

 pletely coagulated in twenty-four hours. In 10 c.c. litmus-whey, 

 after ten days at 37 C., it forms from 11'4 to TO c.c. N acid. 

 It gives a strong indol reaction. It is decolorised by Gram, 

 and microscopically appears as a small motile bacillus. 



B. Vesicse. In gelatine plates the colonies have a net-like 

 appearance, with a very delicate system of ridges and furrows. 

 On gelatine-streak there is a dull-grey opaque granular growth. 

 In broth there is a diffused growth, with a delicate pellicle on 

 the surface. It does not ferment grape-sugar, cane-sugar, 

 nor milk-sugar. It coagulates milk and produces indol. In 

 10 c.c. litmus-whey, after ten days at 37 C., it produces 7'5 

 to 8*75 c. c. of N acid. It is a small motile bacillus, which does 

 not strain with Gram. 



B. Fsecalis Alkaligenes, variety. In gelatine plates it 

 produces colonies like the B. vesicse. On gelatine-streak 

 culture there is a smooth, greyish-white growth, and the 

 gelatine is not liquefied. On agar it produces a greyish-white 

 growth. On potato it forms a circumscribed, slightly raised, 

 yellowish-brown growth ; on the fifth day there is gas pro- 

 duction, and later the potato substratum acquires a brown colour. 

 A diffused growth occurs in broth, and a tough pellicle is formed 

 on the surface. Cane-sugar and grape-sugar are fermented, but 

 milk-sugar remains unchanged. Milk is not coagulated, and 

 acquires an alkaline reaction. In 10 c.c. of litmus-whey, 8'8 to 

 11*0 c.c. of N alkali are produced after ten days incubation at 

 37 C. Indol is not formed. Microscopically it appears as a 

 small motile bacillus. It is decolorised by Gram. 



METHODS EMPLOYED FOR THE ISOLATION OF THE B. COLI FROM 

 WATER SUPPLIES. 



The various methods which are employed for the isolation of 



