52 Neurological Technique 



the region at which the nerve is seen to enter it. Place the pieces 

 in 8-10 volumes of lo percent, formic acid (B) for about 30 

 minutes. 



3. To impregnate. — Drain off the surplus formic acid solution 

 and place directly in 6-8 volumes of the i per cent, gold chloride 

 solution for 30-40 minutes. Avoid direct sunlight during this 

 period. The tissue becomes yellow in color. 



4. To reduce. — Transfer the pieces, without washing, from the 

 gold solution to 20-30 volumes of the 2 per cent, formic acid solu- 

 tion (D),and place in the dark for 24-48 hours, or until the 

 specimens acquire a rich purple color when viewed with the 

 unaided eye by reflected light. Muscle-fibers best adapted to 

 show nerve terminations appear reddish violet when viewed by 

 transmitted light under the microscope. If the fibers appear 

 bluish purple under the microscope, the reduction has gone too far. 



5. The reduction being sufficient, the tissue is washed in dis- 

 tilled water for about i hour, and then, if teased preparations are 

 contemplated, the pieces are placed in glycerine. Here they 

 may be preserved indefinitely. 



6. To tease and mount, remove a small piece of the muscle 

 from the glycerine to the slide, and under a dissecting lens care- 

 fully tease the fibers apart with needles. The teasing should not 

 be carried too far, lest the nerve-fibers be torn from their termina- 

 tions or "end plates" on the muscle, or be broken off at their 

 entrance into the "muscle spindles." Much separation of the 

 muscle-fibers can be accomplished by gently pressing down the 

 cover-glass with the rounded needle handle, using a rubbing 

 motion. 



If the preparation is satisfactory when examined under a 

 compound microscope, it may be made more permanent by 

 replacing the glycerine with glycerine jelly (IV, E). To do this, 

 carefully remove the cover, take up the glycerine with filter 

 paper without disturbing the position of the muscle-fibers, put a 

 drop of warm glycerine jelly on the preparation, put on a clean 

 cover, press it down, and allow the jelly to solidify. The prepa- 

 rations keep perfectly well mounted in pure glycerine, the only 



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