72 MANUAL OF BACTERIOLOGY. 



CHAPTER IV. 



THE CULTIVATION OF BACTERIA. 



Inoculation of the Tubes. — The air of the laboratory 

 should be 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 containing 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 of the test-tube is to be withdrawn, twisting it slightly, taking it 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 pointing 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 and 

 to the right. When two tubes are being used at the same time, 

 as is often necessary, they are placed side by side between the 

 thumb and forefinger of the left hand. The two plugs are held 



