STAINING, PRACTICAL AND THEORETICAL 



by Staining a tissue with acid fuchsin as the primary stain, 

 followed by the other acid dye as the secondary stain (see Falg, 

 standard and basic Faviol techniques, pages 198-206). 



This type of reaction was first observed in tissues (Gurr & 

 MacConaill, 1959, 19606; MacConaill & Gurr, 1960a) which had 

 been stained first with acid fuchsin then with light green. It was 

 expected that the picture to be seen under the microscope would 

 be in red and green. Instead, a polychromatic effect was produced : 

 various tissue-elements were stained in shades of red, mauve, 

 violet, and blue. It was the last colour which excited our interest, 

 as while the mauve shades could possibly be due to an admixture 

 of the red primary stain (acid fuchsin) and the green secondary 

 stain (light green), blue being a primary colour could not have 

 been produced by mere admixture of red and green, therefore a 

 chemical change appeared to have taken place, and investigations 

 were then made into the phenomena. This resulted in the 

 production of three new compound dyes in vitro. These, and 

 other fuchsinic acid compound dyes were afterwards isolated in 

 the solid form. The first three produced by the interaction of 

 acid fuchsin (fuchsinic acid) and light green were called the 

 Falg colours (synonyms: MG dyes), the first two letters of the 

 name representing acid fuchsin (fuchsinic acid, FA) and the 

 other two, LG, representing light green. Since FA behaves as 

 a base towards LG, the Falg or MG compounds may not properly 

 be described as fuchsinates, but they could be described as 

 Falgic acids because each of the three compounds has two " free " 

 sulphonic groups attached to each LG component. Thus, the 

 following terms were used, in which Fa symbolizes the acid 

 fuchsin radical and Lg the light green radical: 



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