74 BACTERIOLOGICAL EXAMINATION OF WATER. 



a copious deposit. On agar it forms a thin greyish-blue growth, 

 which later assumes a brown colour ; gas bubbles appear in the 

 depth of the agar. There is a diffused growth in broth, and a 

 thin pellicle forms on the surface. On potato there is a light 

 yellow growth, which later becomes dark brown in colour. 



GROUP X. 



This group includes the micrococci which are commonly 

 found in water. 



Micrococcus Agilis. 



It is a motile micrococcus of rather large size, and is often 

 found as diplococci, streptococci and tetrads. In gelatine plates 

 the colonies appear as round pinkish-red films, which slowly 

 liquefy the gelatine. In gelatine-stab the same pinkish-red 

 growth appears on the surface and the gelatine is slowly lique- 

 fied. On agar and potato there is a pinkish-red growth. In 

 glucose-gelatine there is no gas formation. In broth there is a 

 diffused growth, and a pinkish-red deposit forms at the bottom 

 of the tube. It has no reducing action on nitrates. 



The Micrococcus carneus and Micrococcus cinnabareus are 

 allied to the above, but they are not motile and do not liquefy 

 gelatine. The M. carneus produces a flesh-coloured pigment 

 and the M. cinnabareus a pigment the colour of sealing wax. 



Micrococcus Flavus Liquefaciens. 



This organism forms rather large non-motile cocci, which are 

 sometimes arranged as diplococci and in masses. In gelatine 

 plates, after forty-eight hours, small yellowish colonies are seen, 

 which gradually increase and become surrounded by a circle of 

 liquefaction ; under a low power the centre is granular, yellowish- 

 brown in colour, and sends out processes to the periphery like 

 the spokes in a carriage wheel. In gelatine-stab there is slow 

 liquefaction, and on the seventh day a funnel, containing a 

 deposit of yellow pigment, appears in the upper part of the 

 tube. On potato there is a moist growth of a yellow colour. 

 On agar there is a yellowish-coloured growth. In glucose- 

 gelatine there is no gas formation. Milk is unchanged. 



