METHOD VI. 



A SILVER NITRATE METHOD. 



A method applied to the fresh nerve-fiber to demonstrate the 

 so-called "cross of Ranvier" and " Frommann's lines'' and the 

 neurilemma. 



SPECIAL REAGENT REQUIRED. 



An aqueous 0.75 per cent silver nitrate solution. 



Silver nitrate crystals, 1.5 g. 

 Distilled water, 200 cc. 



The bottle should be chemically clean, and the solution keeps better in 

 the dark. 



PROCEDURE. 



1. Remove pieces of small nerve or better, spinal nerve- 

 roots, using cardboard as directed in V, I, p. 37. Place the 

 pieces thus prepared in a vial containing about 20 volumes of 

 the 0.75 per cent silver nitrate solution. Place the vial in the 

 dark and let remain for 12-24 hours. 



The spinal nerve-roots are better than other parts of the 

 nerve for the subsequent teasing process, from the fact that their 

 perineural sheaths of connective tissue are much thinner. 



2. Remove a piece of nerve from the cardboard, rinse by 

 merely dipping into distilled water, and transfer it to a drop of 

 pure glycerine on the slide. 



Under a dissecting lens, with fine teasing needles tease the 

 fibers apart thoroughly and put on the cover-glass. 



The teasing can be best done over a black surface. To avoid 

 the tangle of the fibers, which often results, it is better to leave 

 one end of the shred of nerve intact. With one needle, hold 

 the piece down by this end, and with the other needle the fibers 

 are gently frayed apart. Use only small shreds for this final 

 teasing. The ordinary nerve-root may be split into enough pieces 

 for several mounts. 



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