WEIGERT S MYELIN STAIN 513 



For the human cord, the time is approximately as follows: for neuroglia, 

 2-3 days; nerve cells, 3-5 days; for nerve fibers and collaterals, 5-7 days. 



3. Cut sections 50 to 100 /* thick. They may be made free-hand or 

 with a microtome. Blocks may be quickly imbedded by dehydrating for 

 a few minutes in absolute alcohol, and placing in a thick solution of cel- 

 loidin for about 5 minutes. Harden in 80 per cent. 



4. Sections are dehydrated quickly in alcohol. 



5. Clear in oil of cloves or bergamot. 



6. Mount without a cover glass in xylol damar and dry quickly at 

 40 C. Protect the sections from the light and dust as much as possible. 



If the method is unsuccessful, the specimens -may be transferred back 

 to an osmic acid and bichromate mixture containing less osmic acid, and 

 after several days again placed in the silver nitrate solution for 24 to 48 

 hours. 



33 



