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 ringer 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. 



