52 METHODS OF CULTIVATION OF BACTERIA. 



To inoculate, say, one ordinary upright gelatin tube from 

 another, the two tubes are held in an inverted position between 

 the forefinger and thumb of the left hand, with their mouths 

 towards the person holding them ; the plugs are twisted round 

 once or twice, to make sure they are not adhering to the glass. 

 The short, straight platinum wire is then heated to redness from 

 point to insertion, and 2 to 3 inches of the glass rod are also 

 passed two or three times through the Bunsen flame. It is held 

 between the right fore and middle fingers, with the needle pro- 

 jecting backwards, i.e. away from the right palm. Remove plug 

 from culture with right forefinger and thumb, and continue to 

 hold it between the same fingers, by the part which projected 

 beyond the mouth of the tube. Now touch the culture with the 

 platinum needle, and, withdrawing it, replace plug. In the 

 same way remove plug from tube to be inoculated, and plunge 

 platinum wire down the centre of the gelatin to within half an 

 inch of the bottom. It must on no account touch the glass above 



the medium. The wire is 

 then immediately sterilised. 

 A variation in detail of this 

 method is to hold the plug of 

 the tube next the thumb be- 

 tween the fore and middle 

 fingers, and the plug of the 

 other between the middle 

 and ring fingers, then to 

 make the inoculation (Fig. 



Fig. 17.— Another method of inoculating 1 7). The Sub-Culture is 



labelled, and in a bacterio- 

 logical laboratory a label should never be licked. If a tube 

 contain a liquid medium, it must be held in a sloping position 

 between the same fingers, as above. When a stroke culture is 

 made, the same manipulations are gone through. Here the pla- 

 tinum loop is used, and a httle of the culture is smeared in a 

 line along the surface of the medium from below upwards. In 

 inoculating tubes, it is always well, on removing the plugs, to 

 make sure that no strands of cotton fibre are adhering to the 

 inside of the necks. As these might be touched with the 

 charged needle and the plug thus be contaminated, they must 

 be removed by heating the inoculating needle red-hot and 



