SECTION TWO 



8. Immerse in congo red solution for twenty minutes. 



9. Immerse in saturated aqueous lithium carbonate (solution 

 B) for one minute. 



10. Wash in running water for ten minutes. 



11. Stain in Harris' haematoxylin for one to two minutes. 



12. Differentiate the nuclei in solution D (acid alcohol), con- 

 trolling by observation under the microscope. 



13. Blue in tap water substitute (solution E) for five minutes. 



14. Rinse in distilled water. 



15. Rinse in 70% alcohol. 



16. Rinse in 90% alcohol. 



17. Dehydrate in absolute alcohol. 



18. Clear in xylol. 



19. Mount in D.P.X. or Clearmount or Cristalite. 



Results: 



Granules of beta cells: deep orange-red. Granules of the alpha 

 cells: pale yellow. Cytoplasm of chromophobes: unstained. 

 Nuclei : blue or blue-black. 



Notes: 



(a) It is claimed that this simple method, employing congo red, 

 provides differential staining of high specificity which is not 

 dependent upon the use of a special fixative or fixation times. 



(b) The author states that the method has been well tried in 

 his laboratories over a period of a year on a wide range of materials 

 from autopsies and experimental animals, and the positive staining 

 by congo red consistently coincides with that given by other 

 accepted stains for beta cells. 



(c) It is mentioned by the author (Kerenyi) that congo red 

 was tried by Trautman (19 16) as a stain for the hypophysis as a 

 result of which it was suggested at that time as a specific stain for 

 alpha cells, which proved to be an error, and in consequence, 

 Trautman's method never became generally used. 



(d) For further information and photomicrographs, the original 

 paper should be consulted. 



Reference: Kerenyi, N. (1959). 



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