28o DYEING 



various kinds. The food vacuoles of phagocytic cells have a par- 

 ticularly strong tendency to take up vital dyes. The lipid globules 

 that colour easily are commonly those that do not consist simply of 

 triglyceride. 



Either the ground cytoplasm or the nucleus or both are occasion- 

 ally tinged; the nucleolus is sometimes more strongly coloured. 

 The nuclear colouring, apart from that of the nucleolus, is generally 

 diffuse: a chromatic network, like that often seen in fixed pre- 

 parations, does not appear. Strangely enough, the very first paper 

 that recorded direct vital dyeing with a synthetic dye included also 

 a description of vital nuclear dyeing: for in his work on Actino- 

 sphaerium Brandt ^^ dyed not only the lipid globules of some 

 specimens with Bismarck brown, but also the nuclei of others with 

 haematein. Unfortunately he did not state the concentration of his 

 'Haematoxylin'. He must have used the dye without mordant. A 

 few years later ^^ he obtained nuclear colouring of various amoebae 

 with the same dye. Most of the colour was in the Nucleinkugeln 

 (presumably the peripheral bodies now known to be nucleoli). He 

 also achieved the tour de force of double vital dyeing, by first 

 colouring the lipid globules of a living Protozoon with Bismarck 

 brown, and then its nucleus with haematein. 



The nuclei of many different cells of plants were successfully 

 dyed in life by the British botanist Campbell, ^^^ working under 

 Pfeffer's supervision at Tubingen. He used mauveine, dahlia, and 

 methyl violet. His studies were carried out chiefly with species of 

 Tradescantia, the staminal hairs providing most of his material; 

 he also used the spermatozooids of Characeae, and various other 

 cells. Protoplasmic streaming provided evidence of the vitality of 

 the stationary cells, while the spermatozooids with dyed nuclei 

 showed that they were alive by moving about. In a few cases 

 Campbell was able to dye the 'segments' (chromosomes) of 

 dividing Tradescantia cells, and to watch them moving apart at 

 anaphase; he also saw them begin to undergo their telophase 

 transformations. 



The curious but careful observations of Brandt and Campbell, 

 dating from about 70 years ago, deserve to be repeated. 



It has been suggested that Heidenhain and Neisser ^^^ dyed 

 nuclei vitally in 1874. This is extremely improbable. These dis- 

 tinguished investigators injected indigocarmine into the blood- 

 stream of rabbits, waited till the urine was blue, then fixed the 

 kidneys in absolute ethanol and cut thin sections. A blue colour 



