108 PRACTICAL HISTOLOGY [XIV 



extending from the cut ends of the fibres and showing 

 a double contour. 



2. Treat a piece of nerve as in 1, but add a drop 

 of - 2 p.c. nitrate of silver instead of salt solution. Note 

 the rapid staining of the cement substance at the nodes. 

 Expose the specimen to light for half-an-hour. Take 

 off the cover-slip. Dip the nerve in distilled water to 

 remove the silver solution. Mount in dilute glycerine, 

 spreading out the fibres of the teased end 1 . Note the 

 small dark crosses formed by the nodal cement sub- 

 stance and the axis cylinder near the nodes. Probably 

 the axis will also be stained at and near the cut ends 

 of the fibres. 



3. Take a short piece of nerve, and tease it into small 

 bundles of fibres in a drop of '75 p.c. sodium sulphate. Run oft' 

 the fluid, keeping the fibres on the slide with a needle. Add 

 another drop of the solution, and run it off. Repeat this. Then 

 add a drop or two of -2 p.c. nitrate of silver, and expose to light 

 for about half-an-hour, avoiding drying. Wash in distilled 

 water in a watch-glass, and mount in dilute glycerine, so that 

 most of the fibres are parallel to one another. The staining 

 will thus be more localized at and near the nodes than by 

 method, 2. 



4. Tease out a piece of nerve as in 1. Add chloroform 

 instead of salt solution, adding more chloroform as evaporation 

 goes on. 



In the middle of the nerve fibre the transparent axis cylinder 

 will be seen running through the swollen medullary sheath. 



1 In teasing out tissues which have been treated with silver or 

 gold salts, it is best to use hedgehog quills ; a quill is cut in half and 

 the end thrust on the point of a needle. 



