128 BACTERIOLOGY 



paraffin ridge while the open end extends into the fluid. 

 The whole is now protected with a cover-glass, when it can 

 be seen under the microscope that none but the motile 

 micro-organisms make their way into the interior of the 

 tube. They can easily be isolated afterwards by cultivation 

 on plates. 



Micrococcus aqiiatilis. According to Bolton, this microbe 

 is one of the commonest inhabitants of water. The cocci 

 are very minute, and are usually grouped in irregular clumps. 

 Their growth does not liquefy gelatine, on the surface of 

 which there develop circular deposits with a gloss like that 

 of porcelain, from the centre of which furrows radiate out, 

 so as to give the colony the figure of a liver acinus. In 

 thrust-cultures growth takes place both on the surface and 

 along the needle-track. A white coating develops on agar. 



Micrococcus agilis, found by Ali Cohen in drinking-water, 

 is met with in the form either of diplococci or streptococci, 

 which possess the power of lively automatic movement. It 

 liquefies gelatine very slowly, so that an evaporation of the 

 fluid along the thrust canal often takes place within three 

 weeks, leaving a dry funnel-shaped cavity. It forms a rose- 

 red deposit both on agar and potato. 



Micrococcus fuscus, described by Maschek, consists of 

 immotile cocci which frequently have an elliptical form. 

 Bound light- or dark-brown colonies appear on the gelatine 

 plate and speedily liquefy, and in the canal of a thrust- 

 culture liquefaction also progresses with tolerable rapidity, 

 a sepia-brown pellicle forming on the surface of the fluid. 

 The slimy deposit on potatoes is also distinguished by a 

 brown colour. 



Micrococcus luteus. This, which was described by Cohen, 

 consists of small immotile elements, forming a rather 

 flocculent zoogloea. It appears in irregular colonies on the 

 gelatine plate, while in thrust-cultures a yellow deposit is 



