REAGENTS AND MOUNTING MEDIA. 483 



Gentian-violet. (Gram's Method). A mixture of 3 grammes aniline, 1 gramme 

 gentian-violet, 15 grammes alcohol, and 100 grammes water. In 

 nuclear staining (for which it is invaluable, especially after fixing by 

 an acid method, such as picric, etc.), the sections remain in the stain 

 from one to a few minutes, the stain is washed off with alcohol, and 

 a solution of 1 part iodine and 2 parts potassium iodide in 300 parts 

 water is at once added. This gives the sections a dark colour, and 

 is at once washed off with alcohol ; oil of cloves is added, which 

 extracts more colouring matter from the sections, and usually first 

 brings out the characteristic differential staining ; finally the sections 

 are mounted in Canada balsam. A very good double stain may be 

 obtained by dissolving eosin in the clove oil. The walls and the 

 achromatic nuclear figure appear pure red, and the chromatic figure 

 violet (Zimmermann). 



Glycerine. Used as a mounting fluid, also for clearing tissues by heating 

 sections in it, and for dehydrating ; also in differentiating corky 

 from cuticularised membranes. See p. 186. 



acidulated. Used like acidulated alcohol (q.v.). 

 diluted. Two parts glycerine, one part water. 



and alcohol. Half and half. Used especially for softening hard 



alcohol material. 



Preparations showing fixed cell-contents are best not transferred direct 

 from alcohol to glycerine, but placed in a mixture of alcohol and 

 glycerine, allowed slowly to concentrate by evaporation of the 

 alcohol, and similarly treated before mounting in glycerine jelly. 



- gum. Ten grammes gum-arabic, 10 c.c. water, 40 or 50 drops glycerine. 



Used for embedding small or loose objects in section cutting, 231 

 (leaves of moss).' 389 (pollen-grains), 409 (small seeds). 



- jelly (Kaiser's). One part by weight of finest French gelatine is 

 softened for about two hours in six parts by weight of distilled 

 water. To this is added 7 parts by weight of chemically pure 

 glycerine, and to each 100 grammes of the mixture is added 1 gramme 

 concentrated carbolic acid (Phenol). It is then warmed for from ten 

 to fifteen minutes, while continually stirring, till all the flocculence 

 which the addition of the carbolic acid caused has disappeared. 

 While still warm, it is filtered through the finest cloth of spun-glass 

 or glass-wool, which has been previously washed in distilled water, 

 and laid in the funnel while still damp. Can be obtained of E. 

 Kaiser, Berlin. For notes on method of use as a mounting medium, 

 see p. 31. 



Gold-size. Finest English. Used for closing micro-preparations. See 

 p. 31 (Glycerine-jelly), 37, 113 and 442 (Canada balsam). 



Gum-arabic. Use in making enclosing fluids, etc., and for embedding. 

 See also Glvcerine-gum. 



10 per cent, clear filtered solution. Used for slackening move- 

 ments of spermatozoids, 359. 



