74 Animal Micrology 



seal the cover with gold-size, followed by Bell's cement. (See 

 chap, xiii, iii, A.) 



The preparation should show the "cross of Ranvier " and the 

 "lines of Fromman." 



III. GOLD CHLORIDE METHOD FOR NERVE ENDINGS 



1. Trace some of the motor nerves of a reptile or mammal to 

 where they enter the muscles (intercostals are best) and clip out 

 small pieces of the muscle. Use material that has been preserved 

 in 10 per cent, formalin. 



2. Place the bits of muscle in 10 or 12 times their volume of 

 a 10 per cent, solution of formic acid in distilled water and leave 

 them for from 30 to 40 minutes. 



3. Transfer the tissue into from 8 to 10 times its volume of a 

 1 per cent, solution of gold chloride in distilled water for from 

 30 to 40 minutes. Avoid direct sunlight. The muscle should 

 become yellow in color. 



4. Remove the tissue without washing it to about 25 volumes 

 of a 2 per cent, formic acid solution and keep it in the dark until 

 it assumes a purple color (24 to 48 hours). When the fibers 

 appear reddish violet in color the reduction has gone far enough ; 

 if they show a decidedly bluish tinge the process has gone too far. 



5. Wash the tissue in several changes of distilled water for an 

 hour and transfer a small piece to a slide. Tease the fibers apart 

 very carefully under a dissecting lens. Great care must be exer- 

 cised to avoid tearing the nerve fiber from its endings. Examine 

 from time to time under a low power of the compound micro- 

 scope, and when a nerve fiber and its termination is found, 

 carefully separate it as much as possible from the other fibers. 



6. Add glycerin-jelly and a cover-glass. Seal in the ordinary 

 way (chap. xiii). 



NOTE. Tissues may be dehydrated iu the ordinary way and mounted 

 in balsam or imbedded in paraffin or celloidin and sectioned. 



