70 A MANUAL OF BACTERIOLOGY 



the mouth of the tube pointing to the right, a tube of 

 sterile medium being held side by side with the original 

 culture in an exactly similar manner. The wire of the 

 platinum needle is then heated to redness by holding 

 nearly vertically in the flame, and the lower part of the 

 handle is also carefully heated. Holding the sterilised 

 needle between the finger and thumb of the right hand, 

 the plug of the original culture is now withdrawn by 

 grasping between the ring and little fingers of the right 

 hand, and is held there while the platinum needle is care- 

 fully introduced into the tube without touching the mouth 

 or sides, and a trace of the growth is picked up with it, 

 preferably from the margin. To ensure that the needle 

 is cool, it may first be touched on the medium where there 

 is no growth. The needle is quickly withdrawn without 

 touching the sides of the tube and the plug at once re- 

 placed. The plug of the sterile tube is now withdrawn 

 in the same manner, and the inoculated needle introduced. 

 If a typical surface culture is desired, a single light streak 

 is made with the needle from the bottom to the top of the 

 medium without penetrating the surface ; if an abundant 

 growth be required for any purpose the whole surface of 

 the medium may be rubbed with the needle ; if a stab 

 culture, the needle is plunged steadily into the centre of 

 the medium and withdrawn ; if a fluid one, the growth 

 removed is rubbed up on the side of the tube at the margin 

 of the fluid, and the emulsion washed down by tilting the 

 tube. The inoculation having been completed, the plug 

 is quickly replaced, and the needle is again heated in the 

 flame to destroy the remains of the growth upon it. If 

 the original culture is in a deep stab, or a fluid medium, 

 a looped platinum needle may sometimes be used with 

 advantage. The inoculations completed, the mouths of 

 the tubes are singed and the wool plugs pushed in level 

 with the lip. Before replacing the plugs each may, if 



