MELANIN 61 



MELANIN 



Perhaps the most characteristic microchemical test for melanin 

 is its ability to reduce ammoniacal silver nitrate. Of course many- 

 other tissue constituents have this property so that the test is of 

 value only when possible interferences (page 48) are considered. 

 Dublin (1943) applied the Bodian silver method to the demonstra- 

 tion of melanin; his procedure follows. 



Dublin Application of the Bodian Method to Demonstration 

 of Melanin 



SPECIAL REAGENTS 



Protargol Solution. Prepare fresh each time by adding one or more 

 drops of Protargol (Winthrop) — other brands do not appear to 

 be satisfactory — to water in a staining jar. The color should be 

 light amber. Do not stir or mix the solution since this results in 

 gumming. 



1.0% Hydroquinone. 



0.5% Auric Chloride. 



5.0% Oxalic Acid. 



10% Sodium Thiosulfate. 



PROCEDURE 



1. Fix tissue in 10% formalin. 



2. Prepare paraffin sections 8 fx thick. 



3. Treat the deparaffinized sections, after passing through graded 

 alcohols to water, with the Protargol soln. overnight. 



4. Rinse with water and place in the hydroquinone soln. for 10 

 min. 



5. Rinse with water and place in the auric chloride soln. for 5 

 min. 



6. Rinse with water and place in the oxalic acid soln. for 5 min. 



7. Rinse with water and place in the thiosulfate soln. for 5 min. 



8. Wash in running tap water for 10 min. 



9. Dehydrate, clear, and mount as usual. 



Result. The melanin will appear black and the background a 

 purplish brown or gray. 



