MEDICAL AND BIOLOGICAL STAINING TECHNIQUES 



C. Nigrosine, alcoholic (Michrome 



brand) . . . . . . . . i gm. 



70% alcohol 100 ml. 



Technique : 



1. Dissect the specimen in 45% acetic acid. 



2. Treat with solution B for one to two minutes, keeping glands 

 well covered with the reagent. 



3. Wash the specimen carefully two or three times with distilled 

 water, after which a large drop of water is left on the specimen for 

 five minutes. 



4. Drain thoroughly and carefully. 



5. Add a drop of the nigrosine solution. 



6. Place a coverslip over the preparation but do not squash. 



7. Allow the stain to act for ten to fifteen minutes. 



8. Place a piece of blotting paper over the coverslip and slide 

 and squash the preparation. 



9. Immediately place a large drop of glycerine on one edge of 

 the coverslip. 



10. The preparation may now be examined at once, but after 

 about twenty-four hours the glycerine will have penetrated the 

 specimen thoroughly, when it is recommended, for the sake of 

 convenience, to remove the excess liquid and ring the coverslip 

 with wax. 



Note: Preparations obtained as above will last for reasonably 

 long periods provided they are carefully handled. 



Results: 



Salivary glands specifically and intensely stained ; only the outer 

 bands being coloured, except in heterochromatin regions. When 

 the preparation is ageing, however, the interbands as well as the 

 cytoplasm, become faintly stained. 



Reference: Pares, Ramon (1953), Nature, 172, no. 4390. 



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