20 HISTOLOGICAL TECHNIC 



(c) Basic Aniline Dyes — gentian violet, methyl violet, methyl 

 green, methyl blue, toluiciin blue, fuchsin, thionin, safranin, etc. 



These are best kept in stock in saturated alcoholic solutions. 

 When desired to use, a few drops of the alcoholic solution are added 

 to distilled water. No rule as to exact proportions can be given, as 

 these depend upon the material, the fixation, and the intensity of 

 stain desired. 



II. Plasma Dyes.^ — (a) Eosin. 



This is prepared as follows: Water-soluble eosin is dissolved in 

 water to saturation. It is then precipitated by hydrochloric acid 

 and the precipitate washed with water upon a filter until the filtrate 

 is tinged with eosin. After drying, the precipitate is dissolved in 

 strong alcohol, i gm. of eosin to 1,500 c.c. of alcohol, or water- 

 soluble eosin may be kept in saturated aqueous solution containing 

 a trace of thymol as a preservative. This may be diluted to any 

 desired strength at time of using. Eosin is a rapid plasma stain. 



(b) Neutral Carmine. 



Carmine, i gm. 



Liquor ammonii caustici, 5 c.c. 



Distilled water, 50 c.c. 



The last two ingredients are first mixed, and the carmine then added. 

 This solution is allowed to remain in an open vessel for about three 

 days, or until the odor of ammonia has disappeared, after which it 

 is filtered. 



(c) Picric Acid — used mainly as the plasma-staining element of 

 such a staining mixture as picro-acid-fuchsin. 



(d) Acid Aniline Dyes. — Of these, acid fuchsin, erythrosin, and 

 orange G are most used. They may be prepared and kept in stock 

 in the same manner as the basic anihne dyes (see above). Erythrosin 

 is of especial value for sections which take the eosin stain poorly. 



Staining Sections 



It is usually advantageous to stain the different tissue elements 

 different colors. This may be accomplished either by staining suc- 

 cessively with several dyes, or by a single staining with a mixture 

 of dyes. The following are the methods in most common use: 



(i) Staining Double with Hematoxylin and Eosin. — Sec- 

 tions are first washed in water. They are then stained with haema- 

 toxylin (solutions i, 2, 4, 5, or 6, pp. 17-19) from one to five minutes. 



