180 NUCLEAR STAINS, COAL TAR 



or other change of form, and preserves their forms for at least 

 some hours, so that it may be considered as a delicate fixative. 

 It may be combined without precipitating with divers fixing or 

 preserving agents. Osmic acid (of 0-1 to 1 per cent.) may be 

 added to it, or it may be combined with solution of Ripart and 

 Petit (this is an excellent medium for washing out and mounting 

 in). 



Alcoholic solutions may also be used for staining. They also 

 should he acidulated zvith acetic acid. 



The stain does not keep easily. It is difficult to mount it 

 satisfactorily in balsam, because the colour does not resist alcohol 

 sufficiently (unless this be charged with the colour). The 

 resistance of the colour to alcohol is, however (at all events if it 

 be used in the Ehrlich-Biondi combination), considerably 

 increased by treating the sections for a few minutes with tincture 

 of iodine before staining (M. Heidenhain). 



Of preparations mounted with excess of colour in the usual 

 aqueous media, Lee found the most fortunate only survive for 

 a few months. Dr. Henneguy, however, writes that it keeps well 

 in Brun's glucose medium. 



Lee mentions that it was first pointed out by Heschl (Wiener med. 

 Wochenschr., 2, 1879), that methyl green is a reagent for amyloid 

 degeneration. His observations were confirmed by Curschmann 

 (Virchow's Arch., vol. Ixxix, 1880, p. 556), who showed that it colours 

 amyloid substance of an intense violet ; but this, as pointed out by 

 Squire (Methods and Formulce, etc., Churchill, 1892, p. 37), is un- 

 doubtedly due to its containing methyl violet as an impurity. 



364. Bismarck Brown (Manchester Brown, Phenylen Brown, 

 Fesuvin, La Phenicienne). A fairly pure nuclear stain that will 

 work either with fresh tissues or with such as have been hardened 

 in chromic acid, or otherwise. It is a basic dye. Solubility at 

 26° C. in water 1-36 per cent., in alcohol 1-08 per cent. 



The dye is not very easily soluble in water. You may boil * 

 it in water, and filter after a day or two (Weigert, in Arch. mik. 

 Anat., XV, 1878, p. 258). You may add a little acetic or osmic 

 acid to the solution. Maysel (ibid., xviii, 1880, pp. 237, 250) 

 dissolves the colour in acetic acid (this solution does not give a 

 permanent stain). Alcoholic solutions may also be used, e.g. 

 saturated aqueous solution diluted with one-third volume of 90 

 per cent, alcoholic ; or Calberla's glycerin-and-alcohol mixture 

 of dilute glycerin (say of 40 per cent, to 50 per cent.) may very 

 advantageously be employed. 



The watery solutions must be frequently filtered (but then 

 much of the colour is retained on the filter). The addition to 

 them of carbolic acid has been recommended (vide Journ. Roy. 

 Mic. Soc, 1886, p. 908). Bismarck brown stains rapidly, but 



* Conn says not, as this alters the composition of the dye. 



