106 ELEMENTAKY PHYSIOLOGY. [x. 



e. Drops and fragments of the medullary sheath, 

 extending from the cut ends of the fibres and 

 shewing a double contour. 



Some non-meduUated nerve-fibres mU also be 



seen (cp. B). 



2. Cut ofif a similar piece of nerve and treat it in 

 the same way, but instead of adding a normal 

 solution, add a drop of chloroform, and irrigate 

 with chloroform as evaporation goes on. 



In the middle of the nerve-fibre the pale granu- 

 lar axis cylinder wiU be seen running through 

 the swollen and partially dissolved medullary 

 sheath. 



3. Take another piece of fresh nerve, and place it in 

 a small quantity of osmic acid 1 p.c. for ten 

 minutes, covering it up to prevent evaporation. 

 Eemove it to a slide, and separate a small bundle 

 of fibres, putting the rest back in osmic acid ; ■ 

 isolate the fibres as much as possible, add a drop 

 of water, and put on a cover-slip. If it is desired 

 to preserve the specimen the nerve should be 

 washed with water before teasing and mounted 

 in dilute glycerine. 



Select a nerve fibre which is isolated for a con- 

 siderable part of its length, and observe 



a. The medullary sheath, stained black with 

 osmic acid. 



h. The nodes of Ran-vier. These will be 

 seen as short but distinct breaks in the me- 

 dullary sheath ; with Zeiss obj. D. oc. 2 they 



