74 LABORATORY GUIDE IN BACTERIOLOGY 



6. Insert the needle with the cxilture into the sterile 

 tube and draw along the surface of the slant, without 

 puncturing the jelly, and turn the needle during the 

 operation. 



7. Replace the cotton plugs and sterilize the needle 

 in the flame, as above. 



A stab culture is made by puncturing the medium 

 centrally by a quick, steady movement of the needle. 

 Care should be taken not to let the needle touch the 

 bottom of the tube, the object being to make a narrow 

 puncture, and by touching the glass the needle would 







-^ 



=1- 



c 



— JL 

 ' a 



a. Hollow 



Fig. 28 

 Hanging Drop 

 b. Drop c. Cover slip 



d. Slide 



bend and make a ragged opening in the medium on 

 withdrawing. 



Inoculations of liquid media are made by rubbing 

 the end of the needle against the glass below the surface 

 of the liquid. The medium is then shaken. After 

 inoculation liquid cultures should not be shaken again, 

 as this might destroy a characteristic shape of the 

 coagulum, break up the cream ring, or defeat sedi- 

 mentation in broth. 



