THE USE OF THE ORDINAKY CULTURE MEDIA 57 



Fig. 14. 



-Another method of inoculating 

 solid tubes. 



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 

 projecting backwards, i.e., away from the right palm. Remove 

 plug from culture tube 

 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, re- 

 place 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 between the fore and middle fingers, and the plug of 

 the other between the middle and ring fingers, then to make the 

 inoculation (Fig. 14). If a tube contain a liquid medium, 

 it must be held in a sloping position between the same fingers, 

 as above. For a stroke culture the platinum loop is used, 



and a little of the culture is 

 smeared in a line along the 

 surface of the medium from 

 below upwards. In inocula- 

 ting 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 scorching them off with it. 

 When the platinum wires are not in use they may be laid in a 

 rack made by bending up the ends of a piece of tin, as in 



Fig. 15. — Rack for platinum needles. 



