SECTION TWO 



SUDAN BLACK 

 For demonstrating the interstitial cells of the testis 



Solutions required: 



A. Potassium dichromate, 3% aqueous 



B. Sudan black in 70% alcohol, unfiltered 



Technique: 



1. Fix material in Zenker-formol or in Regaud's fluid for 

 several hours or overnight. 



2. Immerse in solution A for three days at 37° C. changing 

 the dichromate solution every twenty-four hours. 



3. Wash in running water for twelve to twenty-four hours. 



4. Dehydrate; clear; embed in paraffin wax. 



5. Cut sections 5/m. in thickness and fix them to slides. 



6. Dewax with xylol; wash with absolute alcohol followed by 

 90% and 70% alcohols. 



7. Immerse in the unfiltered Sudan black solution for ten to 

 thirty minutes. 



8. Wash briefly in 70% alcohol, but making sure that all excess 

 dye is washed away from the slides. 



9. Differentiate, if necessary, in 50% alcohol. 



10. Wash in distilled water. 



11. Mount in Farrants' medium or Aquamount or glycerine 

 jelly. 



Results: 



Interstitial cells: cytoplasm blue and containing a variable 

 number of darker coloured granules. Nucleus: unstained. 

 Remainder of testis : light blue. Golgi apparatus of spermatocytes : 

 often deep blue. 



Notes: 



(a) Sudan black in ethyl alcohol is liable to deteriorate after a 

 few weeks, and I would, therefore, suggest either ethylene or 

 propylene glycol (70% aqueous) be employed as the solvent 

 instead, as these give stable solutions of Sudan black. 



(b) The author (Threadgold) states that this method is to be 

 preferred to his osmic acid method, details of which are given by 



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