42 HISTOLOGY OF MEDICINAL PLANTS 
of glycerine, alcohol, and water mixture added, unless the 
powder was already in suspension in such a mixture. Cut a 
small cube of glycerine jelly and place it in the centre of the 
powder mixture. Lift up the slide by means of pliers, or grasp 
the two edges between the thumb and finger and hold over a 
small flame of an alcohol lamp, or place on a steam-bath until 
the glycerine jelly has melted. Next sterilize a dissecting needle, 
cool, and mix the powder with the glycerine jelly, being careful 
not to lift the point of the needle from the slide during the 
operation. If the mixing has been carefully done, few or no 
air-bubbles will be present; but if they are present, heat the 
needle, and while it is white hot touch the bubbles with its 
point, and they will disappear. Now take a pair of forceps and, 
after securing a clean cover glass near the edge, pass them three 
times through the flame of the alcohol lamp. While holding it 
in a slanting position, touch one side of the powder mixture and 
slowly lower the cover glass until it comes in complete contact 
with the mixture. Now press gently with the end of the needle- 
handle, and set it aside to cool. When it is cool, place a neatly 
trimmed label on one end of the slide, on which write the name 
of the specimen, the number of the series of which it is to form 
a part, etc. Any excess of glycerine jelly, which may have 
been pressed out from the edges of the cover glass, should not 
be removed at once, but should be allowed to remain on the © 
slide for at least one month in order to allow for shrinkage due 
to evaporation. At the end of a month remove the glycerine 
jelly by first passing the blade of a knife, held in a vertical 
position, the back of the knife being next to the slide, around 
the edge of the cover glass. After turning the knife-blade so 
that the flat side is in contact with slide, remove the jelly outside 
of the cover glass. Any remaining fragments should be removed 
with a piece of old linen or cotton cloth. Finally, ring the edge 
of the cover glass with microscopical cement, of which there 
are many types to be had. If the cleaning has been done 
thoroughly, there is no better ringing cement than Canada 
balsam. 
In mounting cross-sections, the method of procedure is 
similar to the above, with the exception that the glycerine jelly 
is placed at the side of the specimen and not in the centre. 
