86 A MANUAL OF BACTERIOLOGY 



Method of inoculating tubes. The following is the pro- 

 cedure by which sub-cultures are prepared from an 

 original test-tube or other culture : Tubes of the culture 

 media selected are placed in a test-tube rack. Their 

 mouths are then singed in the Burisen flame, and with a 

 forceps, also sterilised by heating in the flame, the wool 

 plugs are loosened by a rotatory motion, and then par- 

 tially withdrawn. The mouth of the original culture-tube 

 is similarly singed and its plug partially withdrawn. A 

 platinum needle is selected and carefully straightened. 

 The original tube and the tube to be inoculated are then 

 held in the left hand between the thumb and index 

 finger with the palm upwards, the mouths of the tubes 

 pointing to the right, and the original tube being the 

 nearer one. The platinum needle, held in the right hand 

 nearly vertically, is then sterilised by heating to redness 

 in the flame. The plug of the original culture is now with- 

 drawn by grasping between the ring and little fingers of 

 the right hand, and is held there while the platinum 

 needle is carefully 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 quickly withdrawn without touching the sides of the tube 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 replaced. 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 tube is now withdrawn in the same manner, and the 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 pene- 

 trating 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 withdrawn ; if a fluid one, the growth removed is rubbed 



