ON MOUNTING. 135 



slip is heated and the covers are successively turned 

 over on to the slips and the balsam is carefully 

 "run" by gentle heat until a neat, bevelled edge 

 surrounds the cover. The balsam will be found 

 quite hard, when cold, and, if necessary, the cover 

 can be washed with spirit and any excess of balsam 

 removed from its edge and its surface cleaned. 

 Never mount specimens or sections in balsam on 

 the slip, placing the cover on the liquid balsam and 

 trusting to time for its drying. Practically the 

 central portion of the balsam, under the cover, 

 never dries, and no such slides are really safe or 

 permanent. 



When specimens are mounted in cells filled with 

 balsam, Xylol-balsam should be used and allowed to 

 evaporate before the cover is applied to the cell, 

 the cell being filled up from time to time as 

 evaporation goes on. In this way specimens can 

 be mounted in cells in hard balsam and rendered 

 absolutely permanent. 



Mounting in Glycerine. 



Place the slip on a turn table, and run upon it a 

 ring of asphalt. The ring should be the size of the 

 cover, which, of course, should be a circle. When 

 the asphalt is half dry, but still " tacky," place the 

 section on the slip, and put upon it a drop of gly- 

 cerine ; then lower the cover over it in the usual 

 way, and gently press the edge of the cover all 

 round, so as to make it adhere to the asphalt. 

 Should it not do so at any point, gently warm the 

 asphalt by holding the slip over the flame of a spirit 

 lamp ; ^then press the cover home. The slide can 



