308 HISTOLOGICAL TECHNIQUE. 



The solution of lithium carbonate is prepared by occasionally 

 shaking a mixture of distilled water and an excess of lithium car- 

 bonate. Twenty-four hours will suffice for the production of a 

 strong enough solution. The supernatant liquid is then filtered. 

 Carmine readily dissolves in this solution. For preservation a 

 crystal of thymol may be added. 



Lithio-carmine stains sections in about five minutes, and there is 

 no danger of overstating. Like borax-carmine, it requires after- 

 treatment with acid alcohol. The sections should be transferred, 

 without intermediate washing, to 70 per cent, alcohol containing 1 

 per cent, of concentrated hydrochloric acid ; they may then be de- 

 hydrated, and, if desired, counterstained with picric acid during the 

 dehvdration. 



6. Unna's Methylene -blue. — 



Methylene-blue, 1 gram. 



Potassium carbonate, 1 " 



Distilled water, 100 cc. 



When required for use, this solution should be diluted with dis- 

 tilled water to one-tenth or one-twentieth of its strength. It gives 

 excellent results when used to stain paraffin sections of tissues 

 hardened in Zenker's fluid, especially when preceded by eosin. 

 Stain half an hour in a 5 per cent, aqueous solution of eosin 

 (Griibler's bluish) ; wash in running water ; stain in the dilute 

 methylene-blue until the red color is no longer visible ; wash ; 

 differentiate in absolute alcohol till the sections appear pink (or 

 violet, if there be many nuclei in the tissue) ; clear in xylol and 

 mount in damar or Canada balsam dissolved in xylol. 



Upon long standing, this solution of methylene-blue undergoes 

 chemical changes which reduce its staining value when used as 

 above, but it will keep for a number of months. 



7. Aqueous Methylene-blue. — This is usually prepared at the time 

 when needed by mixing one part of a saturated solution of the ani- 

 lin-color in 95 per cent, alcohol with nine parts of distilled water. 

 It is frequently employed as a general stain for bacteria. 



Other anilin-colors, such as fuchsin, gentian-violet, methyl-violet, 

 and Bismarck-brown, may be kept in concentrated alcoholic solu- 

 tion, to be diluted in a similar manner just before use. When these 

 solutions are used for staining sections or cover-glass preparations 

 the adherent dye is washed off with water, after which the intensity 



