666 TECHNIQUE 



3. Place in the dark in a 1 per cent, aqueous solution of chlorid 

 of gold for ten to forty-five minutes, according to the permeability 

 of the tissue. 



4. Wash in distilled water. 



5. Place in a 25 per cent, aqueous solution of formic acid, and 

 keep in the dark for twenty-four to forty-eight hours. 



6. Wash thoroughly "in water. 



7. The tissue is now properly teased and mounted in glycerin, 

 or sections may be dehydrated, cleared, and mounted in balsam. 



The gold method is used for the demonstration of nerve plex- 

 uses and nerve terminations. 



Picro-Fuchsin (Van Gieson). This method is used as a specific 

 stain for connective tissue ; it colors the white fibres a bright red, 

 all other tissues appearing yellow. Picro-fuchsin may be used as an 

 after stain with nuclear dyes, e. g., hematoxylin, though the tissue 

 must be greatly overstained with the nuclear dye, since the picric 

 acid will decolorize hematein. 



Saturated aqueous solution of picric acid 100 cc. 



1 per cent, aqueous solution of acid f uchsin . . 5 cc. 



1. Stain with Delafield's or Bohmer's hematoxylin, fifteen to 

 thirty minutes. 



2. Wash well with water. The sections should be almost 

 black. 



3. Stain with picro-fuchsin, three to five minutes. 



4. Rinse quickly in water (water removes the fuchsin). 



5. Dehydrate in absolute alcohol, clear, and mount. 

 Weigert's Elastic Tissue Stain. This method gives a specific 



stain for elastic fibres; it may be used alone, or in combination 

 with hematein and picro-fuchsin. 



1 per cent, aqueous solution of basic fuchsin. 100 cc. 



2 per cent, aqueous solution of resorcin 100 cc. 



Boil the mixture in a porcelain capsule, and while hot, add 

 liquor ferri sesquichloridi (Pharm. G-er., Ill), 25 cc. 



Heat and stir for five minutes ; a heavy precipitate is formed. 

 Cool and filter. Dry the precipitate in a porcelain capsule over a 

 water bath or sand bath. Dissolve the dried precipitate in 200 cc. 

 of 95 per cent, alcohol, filter and replace the alcohol lost by evapo- 

 ration. Add 4 cc. of pure hydrochloric acid. 



Tissues should be stained twenty to sixty minutes, then thor- 

 oughly washed in water, dehydrated, cleared, and mounted. 



The following method gives very beautiful results : 



