496 APPENDIX. 



half its volume of a mixture of equal parts of glycerin 

 and camphor water. 



Use. For mounting microscopical objects which are too 

 transparent when mounted in balsam (see Introduction, 

 p. xxxiii). The edges of the cover-glass require cement. 



FARRANT'S MEDIUM. 



Preparation. Dissolve 400 grms. white gum arabic in 400 c.c. 

 water without heat, stirring occasionally : add 200 c.c. 

 glycerin : strain through clean flannel if necessary. Keep 

 in a stoppered bottle with a piece of camphor. 



Use. Same as glycerin-jelly, but it is used cold, and objects 

 may be transferred to it direct from water. It soon 

 hardens at the edges : ringing with varnish is therefore 

 unnecessary. 



CANADA BALSAM. 



Preparation. May be used as bought from the chemist, or 

 diluted to a suitable consistency with benzol. Still better, 

 evaporate to dryness : powder and dissolve in chloroform, 

 benzol, or xylol : benzol is best. 



Use. The most useful of all media for mounting stained 

 objects. (For method of using, see Introduction, p. xxxiv.) 



V. MICROTOMIST'S MEDIA. 

 GUM-WATER. 



Preparation. Dissolve gum arabic in 3 times its weight of 

 water without heat : allow to stand : strain if necessary. 



Use. For impregnating objects to be cut by the freezing 

 microtome. 



ACETONE. 



jj 8e , For impregnating fresh tissues before imbedding in 

 paraffin. 



PARAFFIN. 



Melting-point from" 50 t C. 



XJse. For imbedding objects to be cut into sections. 



