BACTERIOLOGICAL TECHNIC 65 



Plugging may also be done with fingers alone, but this is tedious and 

 non-professional. A far better method is to use a pair of fairly large 

 blunt-pointed pincers. Remove the cotton from the roll by means of the 

 pincers and insert it into the test-tube with the pincers. 



PIG. 13. Wire basket filled with test-tubes plugged with cotton. A little cotton 

 should be placed in the bottom of the basket to lessen the danger of breaking the test- 

 tubes. (Williams.) 



FIG. 14. A hot air sterilizer. These sterilizers are double-walled, on stand, with 

 perforations at top for thermometers. Ordinary baking ovens which can be secured 

 from hardware dealers will serve the purpose. 



Whatever method is used, remove the amount of cotton required to 

 plug one tube or flask at one time. Do not attempt to plug with several 

 small pieces. If an excess of cotton projects above the opening, pluck 

 it away with the fingers; do not cut it away with scissors. Plug the tubes 

 as uniformly as possible. 



