22 PHARMACEUTICAL BOTANY 



5. Further dehydrate by placing material in absolute alcohol for 

 one minute. 



6. Clear in cedar oil for i minute. Blot up excess from around 

 edge of section. 



7. Mount in Canada balsam. 



8. Label slide. 



Should air-bubbles be detected in the balsam shortly after mount- 

 ing, heat a dissection needle in a flame and touch each with its tip, 

 when they will be found to disappear. 



If too much Canada balsam has been used, some of it usually 

 spreads beyond the edge of the cover-glass, or on its surface. In 

 this event wait until the balsam hardens, when it can be scratched 

 off with a knife, and the surface of the glass cleaned with a rag 

 moistened with turpentine oil or xylol. 



Should the Canada balsam become too thick, it can be thinned 

 down with either xylol or benzol. 



METHOD FOR THE PREPARATION OF A GLYCERIN-GELATIN MOUNT 



1. Stain object with an aqueous solution of eosin. 



2. Wash out excess of stain by moving the section about in a 

 dish of water. 



3. Transfer object to weak glycerin (glycerin 10 parts, water 

 90 parts) for 3 to 5 minutes. 



4. Transfer object to 50 per cent, glycerin for 3 to 5 minutes. 



5. Transfer object to concentrated glycerin for 5 minutes. 



6. Remove excess of glycerin around object and mount in glycerin- 

 gelatin. The slide and cover slip should be warmed before the 

 glycerin-gelatin is dropped over the object and the cover slip quickly 

 lowered. The preparation of Glycerin-Gelatin is as follows: Mac- 

 erate 14 grams of gelatin in 84 mils of water for 2 hours, add 76 mils 

 of glycerin and warm; add 2 mils of liquefied phenol, warm and 

 stir for 15 minutes until clear. Filter while hot through glass- 

 wool or filter paper and collect the filtrate in a wide mouthed bottle. 

 Keep well stoppered so as to exclude dust. 



Glycerin- Gelatin becomes solid when cool. For use warm the 

 bottle in a water ttath after first removing the stopper. A glass rod 



