244 DYEING 



dahlia in a study of amyloid degeneration and was surprised to 

 find that this violet dye coloured the amyloid corpuscles a brilliant 

 red. The celebrated histologist, Ranvier,*^^ dyed cartilage meta- 

 chromatically with cyanine, while another Frenchman, Cornil,^^^ 

 used methyl violet on the same two chromotropes that were 

 observed by Jiirgens and Ranvier. It is possible that the Austrian 

 pathologist, Heschl,^^^ also saw a metachromatic effect in 1872 

 and published it in 1875, but this is not certain. He accidentally 

 dyed the skin of his fingers with some violet ink and then tried it 

 on various other tissues, including liver and kidney in amyloid 

 degeneration. The degenerate parts were coloured dark rose-red, 

 everything else blue. This effect may indeed have been due in part 

 at least to the metachromatic dye, aniline blue (spirit soluble), 

 which was present in the ink; but since this also contained basic 

 fuchsine, one cannot be sure. (In this paragraph the modern names 

 of the dyes have been used throughout.) 



It has been stated more than once ^^^' ^^°' ^^^ that the word meta- 

 chromasy was introduced and defined by Ehrlich in his paper of 

 1877.^^^ Very remarkable things are believed about this paper, by 

 persons who have not read it. It has been said that he here intro- 

 duced the idea of classifying dyes as acid and basic,^^^ and objects 

 in tissues as basiphil and acidophil. ^^^ In this paper, written when 

 he was still a medical student, Ehrlich gives a competent account 

 of the form, distribution, and reaction to dyes of what were 

 obviously the basiphil cells (Mastzellen) of connective tissue, 

 though he refers to them throughout as Plasmazellen (see 

 Westphal ^^*). He notes the colour-change of the dye, but makes 

 no attempt to define metachromasy and does not use the word. 

 Ehrlich's first scientific paper foreshadows rather faintly his 

 subsequent contributions to our understanding of the action of 

 dyes in biological microtechnique. 



In a later paper ^^^ Ehrlich remarks that certain dyes colour the 

 granulated cells {Mastzellen) of connective tissue 'metachromatic- 

 ally, that is, in a tint differing from the colour of the dye used'. It 

 is more accurate to define metachromasy as the colouring of differ- 

 ent tissue-constituents in different colours by a single dye. The 

 words 'single dye' must here be taken to mean that the substance 

 that dyes the different tissue-constituents in different colours 

 can be extracted from the dye-solution in dry form as one pure 

 chemical compound, not as two or more. 



In this sense there are both basic and acid metachromatic dyes, 



