Feulgen Reaction 295 



8. Rinse in distilled water. 



9. Counterstain in fast green: 10 seconds. 

 10. Dehydrate, clear, and mount. 



results: 



thymonucleic-acid-containing substances — red-violet 

 other tissue elements — shades of green 



comments: 



1. Kasten and Burton {1939) make the following Schiff reagent. It is 

 quickly prepared, colorless, does not stain the hands, and does not 

 require refrigeration. It can be made more sensitive by boiling it 

 for 1 minute. 



basic fuchsin, C.I. 42500 0.05 gm. 



distilled water 300.0 ml. 



sodium hyposulfite, Na^,S204 6.0 gm. 



Solution should decolorize immediately. Filter if necessary. Ready 

 for immediate use. 



2. Pink solutions of Schiff reagent may have lost their potency. 

 Test by pouring a few drops into 10 ml. of 40% formalin. A good 

 solution changes rapidly to reddish purple, but if the color changes 

 slowly and becomes blue-purple, the solution is breaking down. 



3. Chen {1943) uses the following weak Flemming's fixative for 

 Avian parasites. It gives beaiuiful results on any kind of smear prepa- 

 ration and very small pieces of tissue. 



fixation: 1-4 hours. 



chromic acid, 1% in normal saline 25.0 ml. 



acetic acid, 1% in normal saline 10.0 ml. 



osmic acid, 2% in normal saline 5.0 ml. 



normal saline 60.0 ml. 



washing: smears — 1 hour in running water and proceed to step 2, hy- 

 drolysis: pieces of tissue — overnight before proceeding to embed 

 for sectioning. 



4. The first of the series of three bleaching solutions (step G) \\ill 

 begin to accumidate Schiff's reagent and turn pink. Then it is ad- 

 visable to remove that solution, shift number 2 and number 3 along 

 into positions 1 and 2, and add a new number 3 solution. 



Desoxyribonucleic Acid (DNA) Fluorescent Technique 



(culling and vasser, 1961) 



fixation: 10% formalin for sections; methyl alcohol for smears. (Other 

 fixatives may require a different time for hydrolysis.) 



