CHAPTER 15 



Introduction to Vital Colouring 



It is about 80 years since Ranvier, the well-known French 

 histologist, stated unequivocally that cells could only be dyed 

 when dead. Vital dyeing of a very special kind, by natural colouring 

 agents, had actually been described by Trembley 506,29,35 niore 

 than a century and a quarter before; but Trembley's methods had 

 not been followed by others, and Ranvier's remark was in accord- 

 ance with the beliefs of his time. As a matter of fact the elaborately- 

 named Polish pathologist, Chrzonszczewsky, had already in 1864 

 injected ammoniacal carmine into the blood-stream of mammals 

 and shown, by the examination of sections, that the cytoplasm of 

 the convoluted tubules and Henle's loop was coloured, ^^^ and 

 indigo-carmine had been used successfully for the same pur- 

 pose ;^^^ but no one had actually watched the imbibition of a syn- 

 thetic dye by a living cell. This was first done in 1878, when 

 Brandt, in Berlin, coloured the lipid droplets in the cytoplasm of 

 living Actinosphaerium with Bismarck brow^n.^^ 



There was sporadic use of this and other vital dyes in the 

 following years, ^^^"^^^' ^^ and the golden age of vital dyeing started 

 about the middle of the eighties. Pfefi'er ^^^ in Tubingen was the 

 first to investigate the action of dyes on the living cells of plants. 

 In a comprehensive study involving the use of many kinds of cells 

 and many different dyes, he showed that the cytoplasm and various 

 granules and vacuoles could be tinged during life, while the dye 

 often accumulated in the cell-sap, sometimes m the form of 

 crystals. Ehrlich followed Pfeflfer and became the main motive 

 force behind research into the action of vital dyes on the cells of 

 animals (fig. 29). He showed that methylene blue (already used by 

 Pfeffer) would colour living axons and nerve-endings and thus 

 demonstrate their course. ^^^ He introduced ^^^ into this field of 

 study the colorant vital par excellence, as neutral red has with some 

 justification been called. ^^ The work was ably developed by 

 Arnold,i^-2o Michaelis,^^ Fischel,!^^, les Himmel,233 and de 



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