84 MANUAL OF BACTERIOLOGY. 



CHAPTER IV. 



THE CULTIVATION OF BACTERIA. 



Inoculation of the Tubes. The air of the laboratory 

 should he as quiet as possible, to lessen the chances of con- 

 tamination by bacteria clinging to particles of dust. Avoid 

 working where there may be draughts or gusts of air or 

 near an open window. Spores are blown from the surfaces 

 of moulds, like thistle-down, and are constantly being wafted 

 about in the air. Given any material containing bacteria, 

 for example a pure culture of some well-known species, a 

 very minute portion is to be introduced into a tube contain- 

 ing the sterile culture-medium. The introduction is effected 

 with a straight platinum wire, or with a platinum wire loop. 

 The platinum is to be heated red-hot before using, and then 

 allowed to cool. It is also to be heated red-hot after using. 

 The plug of the test-tube is to be withdrawn, twisting it 

 slightly, taking it between the third and fourth fingers of 

 the left hand, with the part that projects into the tube point- 

 ing- toward the back of the hand. It must not be allowed to 

 touch any object while the inoculation is going on. Pass 

 the neck of the tube through the flame. If any of the cotton 

 adheres to the neck of the tube, pull the cotton away with 

 sterilized forceps, while the neck of the tube touches the 

 flame, so that the threads of cotton may be burned and not 

 fly into the air of the room. The tube is held as nearly 

 horizontal as possible. The tube is to be held in the left 

 hand between the thumb and forefinger, the tube resting 

 upon the palm, and the neck of the tube pointing upward 



