Chapter JQ 



Stains and 

 Staining 



Stains and Their Staining Action 



& 



Most tissues after processing do not retain sufficient color to make 

 them and their components visible tnider a brightfield microscope. It 

 is therefore expedient to add colors to tissties by staining (coloring, 

 dying) them ^vith the proper stains (dyes). 



Baker (1958) argues logically against the nomenclature "stains and 

 staining," saying that they are not accurate terms. For example: "basic 

 ftichsin 'stains' chromatin; silver coinpoimds 'stain' nerve fibers and 

 Sudan black 'stains' lipids," yet from a physical and chemical point of 

 view the three processes differ markedly. He suggests that the terminol- 

 ogy "colour and colouring agent or colourant" (British spelling) be 

 applied to methods of imparting color on or in organic material. At 

 present it does not seem advisable to depart in this direction. Stipply 

 houses still list their products as dyes or stains and specify dye content. 

 The Biological Stain Commission has not seen fit to change its name. 

 To the author, therefore, it appears politic to continue to use "dye," 

 "stain" and "staining" imtil such a time as Baker's suggestion has taken 

 hold. When a colored substance which is not a dye is formed, as is true 

 of many histochemical tests and silver impregnation, the appropriate 

 terminology will be applied. 



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