THE "AZUR" PRINCIPLE 237 



hand, the concentration of the stain is reduced and its 

 action augmented by atropine and extract, still the 

 poison, but in less strength, passes into the cell; and 

 although mitosis occurs to an advanced degree, never- 

 theless premature death occurs in spite of the fact that 

 there is not sufficient strength of colouring matter to 

 give rise to the post-mortem coloration of the chromo- 

 somes and centrosomes. Death is a gradual process- 

 presumably it is molecular as well as cellular, for the 

 post-mortem scarlet coloration occurs gradually; but 

 it is not until the nucleolus-centrosome is reached 

 that all mitosis ceases. One cannot excite amoeboid 

 movements in a cell which has its nucleolus stained. 



Since Unna's polychrome methylene blue contained 

 the active principle which caused the cells to divide, 

 and the other two substances appeared merely to be 

 augmenters, we now turned our attention more es- 

 pecially to the dye. Polychrome methylene blue stains 

 chromatin scarlet and the nucleus-spindle a faint blue. 

 It is made by "poly chroming" methylene blue. Fresh 

 methylene blue stains chromatin blue, and it is not so 

 effective as the polychrome dye in inducing mitosis. 

 The "poly chroming" process consists of rendering 

 a solution of methylene blue alkaline with sodium 

 carbonate and naturing it for some time at a high 

 temperature. The methylene blue turns a purple 

 colour. This is due to decomposition an oxidation 

 occurs with the production of a dye known as "azur." 1 

 This azur dye can be obtained from dealers, and it 

 can be extracted from the polychrome dye by means of 



1 Centralblatt fur Bakteriologie, bd. xxix., 1901, p. 765. 



