STAINING, PRACTICAL AND THEORETICAL 



elements, except in certain glandular tissues, are either weakly 

 erythrophile or erythrophobe, it follows that the red-stained 

 strongly erythrophile tissue-elements are seen against a yellow 

 background. The red colour of acid fuchsin is always made more 

 distinct by the use of a yellow filter; consequently the red colour 

 of the strongly erythrophile elements, notably of the chromo- 

 somes, is made more distinct by the use of sun yellow as an 

 adjunct to the Faviol technique. This modified Faviol method 

 is called the Standard Faviol technique. The procedure is 

 described on pages 204-6. It differs from the Basic Faviol tech- 

 nique in two associated respects: (i) the violamine solution is 

 replaced by a mixture of violamine and sun yellow; (2) a pro- 

 tective acid bath is given to the tissue preparations stained 

 by acid fuchsin before they are exposed to the modified violamine 

 solution. The Standard Faviol method is particularly advanta- 

 geous when black and white photographs have to be taken of 

 the stained preparations. In such photographs the red-stained 

 elements appear as full black, violet as dark grey, and yellow as 

 light grey. Moreover, better pictures are obtained without a 

 colour filter than with one. 



During the course of our work (MacConaill & Gurr, 19606, 

 1 961, 1962) it was decided to attempt to prepare in vitro the 

 colours which had been produced in tela. As a result, not only 

 were these compound dyes successfully isolated in the solid stain, 

 but a number of others in addition. Among such dyes prepared 

 and now available commercially are trifavioxanthic acid and haplo- 

 favioxanthic acid, the latter also being known as chromosome red. 

 The structures of these two dyes are given above (pages 86-9). 

 The haplofavioxanthic acid was not one of the compounds that we 

 had produced previously in tissues and its preparation in vitro 

 was performed by the present author to satisfy his own curiosity. 

 Initial trials with this new dye carried out by Professor MacConaill 

 appear to indicate that it may have useful application in cytology 

 and medical research. Trifavioxanthic acid appears, at present, 

 to be of little value as a biological stain, although due to its seem- 

 ingly photosensitivity, oxidation-reduction and possibly hydrogen- 

 ion indicator properties it may find application in biochemistry, 

 etc. Other compound dyes of the series isolated but not yet tried 

 out include mono- and di-favioxanthic acids. 



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