PLATES 



229 



treating the liquefied medium as bouillon. After re- 

 plugging, grasp the tube near its mouth by the thumb 

 and first finger of the right hand, and with an even 

 circular movement of the whole arm, diffuse the inocu- 

 lum throughout the medium; avoid jerky movements, 

 as these cause bubbles of air to form in the medium. 



FIG. 124. Mixing emulsion for plates. 



The knack of mixing evenly without producing air 

 bubbles, is not always easily acquired, by this method, 

 An alternative plan is to hold the inoculated tube 

 vertically upright between the opposed palms and to 

 rotate it between them by rapid backward and forward 

 movements of the two hands (Fig. 124). 



FIG. 125. Pouring plates. 



6. Sterilise the platinum loop, and add two loopfuls 

 of diluted inoculum to tube No. 2, and mix as before. 



7. In a similar manner transfer three loopfuls of 

 liquefied medium from tube No. 2 to tube No. 3, and 

 mix thoroughly. 



8. Flame the plug of tube No. i, remove it, then flame 

 the lips of the tube; slightly raise the cover of Petri 

 dish No. i, introduce the mouth of the tube; then, 



