126 EXPERIMENTAL DAIRY BACTERIOLOGY 



bottle by allowing it to run from the top of the pipette, and the 

 operation repeated with each pipette. If the glassware is free from 

 moisture and grease, and the mercury clean, there should be no 

 adherence of the mercury to the glass and no tendency for it to form 

 small globules. A permanent mark is placed on the pipettes by 

 scratching through the paraffin with a fine needle and filling the 

 scratch with hydrofluoric acid or diamond ink and allowing the same 

 to act for five minutes ; then wash off, remove paraffin by warming 

 sufficiently to melt it, and wipe with paper. A mark may be made 

 by the use of a sharp file, which method avoids the use of paraffin 

 and hydrofluoric acid. 



