238 The Microscope. 



ON MOUNTING MICROSCOPIC OBJECTS. 



STAINING WOOD SECTIONS. 



After the sections have been bleached and thoroughly- 

 washed by the methods just described, we may proceed to stain 

 them. This may be done by the use of carmine or logwood ; 

 after which, the sections may be mounted in balsam by the or- 

 dinary process. Better effects are, however, produced if we em- 

 ploy the double staining method, for the carrying out of which 

 various kinds and combinations of dyes have been used and re- 

 commended. It is needless to enumerate the whole of these 

 here. The agents used are carmine and aniline green, and to 

 carry out the method, solutions of these will be required. The 

 solution of carmine (Beale's) is made by rubbing up in a mortar; 

 carmine (the finest), 15 grains (or about 1 gramme), with a few 

 drops of distilled water ; then adding £ drachm of strong liquor 

 ammonicB and sufficient distilled water to make 8 drachms of 

 solution. The fluid must now be exposed to the air for two days 

 to get rid of superfluous ammonia, when 7 drachms of distilled 

 water are to be added to it. Many recommend the carmine so- 

 lution to be made with borax instead of ammonia. It is not in 

 our opinion nearly so good as that mentioned above, as it not 

 unfrequently spots the stained sections with an apparently crys- 

 talline deposit, which utterly ruins them. This never occurs 

 when ammonia carmine is employed ; that is, if the solution used 

 be fresh. To prepare the green dye, take 3 grains of aniline 

 green, and by means of heat dissolve it in 2 drachms of distilled 

 water; then filter this solution into 6 drachms of absolute 

 alcohol. If wood sections, without any previous prepara- 

 tion, were to be stained with these agents, we should find that 

 when, in order to mount them in balsam, the sections being 

 passed through alcohol in the usual manner, a great part, 

 or the whole of the color due to the action of the aniline green 

 would be discharged by the alcohol. In order, therefore, to ren- 

 der the staining permanent, it is advisable to use some kind of 

 mordant to fix the aniline stain, and for this purpose we have 

 found tannic acid extremely useful. It is employed in the form 

 of solution made by dissolving 1 drachm of the acid in 2 ounces 

 of methylated spirit, and then filtering the product. 



