266 DYEING 



of the parasite stands out against the red of the blood corpuscle 

 that contains it, but its nucleus is not differentially dyed. One 

 might choose this method in an investigation of eosinophils, which 

 are brilliantly shown, but as a general rule the haematologist 

 naturally prefers the much wider range of coloration seen in 

 Romanowsky preparations. 



In successful preparations made by the original method of the 

 Russian author or by any of the numerous modifications that have 

 been introduced subsequently, the general scheme of colouring is 

 this: — 



chromatin of leucocytes .... purple 

 nucleus (or part of nucleus) of parasitic Pro- 

 tozoa .... 



basiphil cytoplasm of lymphocytes 



and parasitic Protozoa 

 eosiniphil granules 

 neutrophil granules 

 red blood-corpuscles . 



monocytes, 



red or carmine 



blue 

 pink 

 purple 



pink (sometimes 

 bluish) 



The expression 'Romanowsky dyes' will be used here to cover 

 all mixtures or compounds of eosin with methylene blue and 

 allied dyes, which give these or similar colours. The different 

 techniques give somewhat different results, the red corpuscles in 

 particular being rather variable; but unless the general scheme 

 applies, it is not justifiable to speak of the Romanowsky effect. 



It is natural enough that basiphil cytoplasm should be blue and 

 eosinophil granules pink, but not obvious why the chromatin of 

 leucocytes should be purple and far from obvious why the nucleus 

 of parasitic Protozoa (or at any rate part of it) should be red. 



Attempts to invent a dye that would give the Romanowsky 

 effect every time led gradually to understanding. The first step 

 was taken by Nocht, a port medical-ofiicer of Hamburg, later 

 Director of the Institiit fur Schiffs- und Tropenkrankheiten in that 

 city. This institute played an important part in the development of 

 modern Romanowsky techniques. 



Nocht's efforts to make a reliable dye-solution failed so long as 

 he worked on the assumption that a neutral dye, in Ehrlich's sense, 

 was responsible for the unexpected colouring. He came to the 

 conclusion that the cause must lie in the presence of impurities in 

 the dyes used. He was influenced by Romanowsky's remark ^^^ 



