58 MICRO-CHEMICAL REAGENTS. 



mounting in balsam. W. T.] In the tissues of 

 higher plants, where its effect has not yet been 

 fully studied, it stains dead protoplasm a beautiful 

 rose color. Eosin is especially useful for coloring 

 the plasma of sieve tubes and the nuclei of cells. 

 It has also been used as the first dye in double- 

 staining preparations, which are afterwards treated 

 with Nicholson's blue, fixed with absolute alcohol 

 and mounted in dammar. 1 



ANILINE COLORS. 2 



Within a few years the beautiful aniline colors 

 have been generally applied in many histological 

 researches. In none, however, are they more 

 useful than in the preparation of bacteria, not only 

 in sections of animal tissues, but also in films ob- 

 tained by drying (and hardening through a flame) 

 a thin layer of fluid containing these organisms 

 on the cover-glass. The discovery, by Weigert, 

 in 1871, of the power of carmine to color bacteria 3 

 led him to try the effect of the aniline salts, in 

 which a very energetic coloring matter almost 

 a reagent for bacteria was found. The names 



1 Journ. of Roy. Micr. Soc., 1880, III., p. 693. 



2 Wigand: Bot. Zeitung, 1862, p. 17. Hanstein : Organe der Harz- und 

 Schleimabsonderung in den Laubknospen. Bot. Zeitung, 1868, p. 708. 



8 The " sulphate of rosanilin " has been strongly recommended by Salo- 

 monsen for staining bacteria in putrid blood. It is used in a concentrated 

 aqueous solution prepared by heating, and filtered after it has become cold. 

 Cf. Studier over Blodets Forraadnelse, Copenhagen, 1877, p. 15. 



