SECTION ONE 



found that the picture of the strongly erythrophile elements 

 obtained by application of the Falgog method is more satisfactory 

 than that produced by simple staining with acid fuchsin. Probably 

 the orange G and glucose combine with and decolorize (reduce) 

 the definite chemical compounds (Falg-tissue) present, thereby 

 producing sharper pictures of the erythrophile elements, bi 

 vitro experiments have shown that acid fuchsin units through its 

 amino groups with acetic acid to form a series of compounds to 

 which have been given the name of acetofuchsinic acids, a number 

 of which have been isolated in the solid form. The acetofuchsinic 

 acids have been found to be of a much brighter red than ordinary 

 acid fuchsin. 



Still more recently it has been found (MacConaill & Gurr, 

 1 961) that if acid fuchsin is kept in acetic acid solution for a few 

 weeks it overstains so that the Falg and the Faviol reactions 

 do not take place properly. The reason for this is that the acetic 

 acid units with the acid fuchsin at room temperature over a 

 prolonged period to form nono-acetofuchsinic acid (the highest 

 homologue of the series) which is devoid of reactive basic groups. 

 In other words the amino groups of the acid fuchsin have been 

 blocked by the acetate radical, and the new dye, which is of a 

 more intense red colour than the original acid fuchsin, has no 

 basic groups available to permit union with other acid dyes. 



In the Falgose technique, described on pages 202-3, the 

 orange G is dissolved in 1% glucose solution instead of water 

 alone. It was found that this technique gave rather better results 

 than the Falgog method for sections up to 100 /^ in thickness. 

 The Falgog procedure is, however, better suited for sections over 

 100 /^ in thickness. 



Sun yellow G, an acid dye of the stilbene group, whose structure 

 is given on page 62, has an effect similar to that of orange G 

 on Falg- and Faviol-stained preparations. It is, however, an 

 intensely yellow dye, so that when it is used in place of orange G 

 as the decolorizer, the preparations are actually stained yellow 

 everywhere. Here again the dilute acetic acid protects the acid 

 fuchsin. It also permits the distinctive staining (violet) of moder- 

 ately erythrophile elements by violamine 3B, whose structure is 

 given on page 75. The blue colour of weakly erythrophile ele- 

 ments, however, is replaced by yellow, so that a three-colour 

 picture is obtained in red, violet and yellow. Since most cellular 



D 85 



