752 HISTOLOGIC TECHNIG 



Nitrate of Silver for Cement Substances, This reagent is used 

 to outline epithelial cells by blackening the intercellular substance, the 

 silver, after impregnation, being reduced or blackened by exposure to 

 light. 



1. The fresh tissue is immersed in a 0.25 per cent, to 0.5 per cent, 

 aqueous solution of silver nitrate (crystals), and left in the dark for 

 ten to twenty minutes. Protargol may be substituted for silver nitrate 

 crystals. 



2. Wash in distilled water, and while still in water, expose to direct 

 sunlight until the object becomes a dark reddish-brown color (ten to 

 thirty minutes) . 



3. Transfer to 70 per cent, alcohol, three to twelve hours. 



4. Preserve in 95 per cent, alcohol. The tissue may be mounted in 

 the usual way. 



Since nitrate of silver will attack metal instruments, the tissues 

 while in this solution should be handled with glass rods. In silvering 

 serous membranes, it is well to slightly stretch the object by tying it 

 over a cork with a thread tightly fastened around the edge. 



Gold Chlorid for Nerve Plexuses and Nerve Endings (Ranvier's 

 Method).!. Wash the fresh tissues in normal saline solution, and 

 place them in pure lemon- juice until they appear clear (five to ten 

 minutes). 



2. Wash quickly in distilled water. 



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. It is applicable also for the demonstra- 

 tion of certain connective tissue cells, e.g., cornea! cells, and tendon 

 cells. 



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

 stain for connective tissue; it colors the collagenous fibers a bright red, 

 all other tissues appearing yellow. Picric-acid-fuchsin may be used 

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



