194 Silver Impregnation II (chap. 15) 



8. Clear with del Rio-Hortega's solution. 



9. Blot and mount. 



results: 



astrocytes and processes — black 



background — unstained or light brownish purple 



nerve cells — pale red 



nerve fibers — inistained 



comments: 



Extra sections after being fixed in hypo can be preserved in 1% 

 formalin for long periods. 



Oligodendroglia and Microglia 



Penfield's Modification of del Rio-Hortega's Silver Carbonate Method 



(mcclung, 1950) S 



fixation: 10% formalin at least one week; longer fixation also will 

 give excellent results, or fix in: 



formalin 14.0 ml. 



ammonium bromide 2.0 gm. 



distilled water 86.0 ml. 



sectioning: frozen sections, 20 microns. 



solutions: 



Globus' hydrobromic acid: 



40% hydrobromic acid 5.0 ml. 



distilled water 95.0 ml. 



Silver carbonate solution: 



Combine 5.0 ml. of 10% silver nitrate and 20.0 ml. of sodium car- 

 bonate. Add ammonium hydroxide, drop by drop, imtil precipitate is 

 just dissolved. Add distilled water up to 75 ml. Filter. The solution 

 keeps for long periods if stored in a dark bottle. 



procedure: 



1. Place sections in 1% formalin or distilled water. 



2. Transfer to distilled water plus 1% of ammonia. Cover to prevent 

 escape of ammonia, and leave overnight. 



3. Transfer to hydrobromic acid, 38°C: 1 hour. 



4. Wash in 3 changes of distilled water. 



