APPENDIX 315 



In mounting in glycerine-jelly (cp. p. 40) the excess of the 

 jelly should be squeezed out in the warm chamber ; this may be 

 done by placing a small bottle containing a little mercury on the 

 cover-slip, or by the use of a special clamp squeezing cover-slip 

 and slide, or by the use of a compressorium. 



8. Glycerine and Gum. (Farrant's solution.) It is 



simplest to buy this. 



It may be made thus : Take lumps of gum arabic which are 

 nearly free from colour, weigh out 40 grams, grind to powder, place 

 in about 150 c.c. water, warm or boil to dissolve. Add 1 gram of 

 carbolic acid dissolved in a little water. Filter through a hot filter, 

 changing the filter when clogged. Evaporate the filtrate until it is 

 about 80 c.c., then add 20 c.c. of glycerine. The mixture is best kept 

 in a bottle with a glass cap. 



When mounting in it, let a section soak for a minute in 

 glycerine, then in a drop of Farrant's solution on the slide. 

 Before cementing, the solution should be allowed to become firm 

 at the edges. 



9. Colophonium (rosin). Dissolve in benzine or in chloro- 

 form. It does not turn yellow on keeping as Canada balsam is 

 apt to do. 



10. Dammar : this may be dissolved in a mixture of equal 

 quantities of turpentine and benzine. 



1 1. Canada Balsam. Put some Canada balsam into a capsule, 

 and place it in the warm chamber at about 65 C. for twenty-four 

 hours to drive off all water. Let it cool, and dissolve it in a 

 sufficient quantity of xylol to make a fairly fluid solution ; it 

 should be kept in a bottle with a ground-glass cap fitting over 

 the neck of the bottle, instead of a stopper, as the stopper is apt 

 to become fixed in the bottle ; if any balsam is allowed to get on 

 the neck of the bottle wet it with xylol and rub it oft' with a 

 cloth. 



12. Monobromide of naphthalene. 



