NUCLEAR STAINS, COAL TAR 187 



374. Thionin. The hydrochloride of thioniu, or violet of 

 Lauth, is a colour chemically nearly allied to methylen bhie. A 

 basic dye, the solubility of which at 26° C. is in water 0-25 per 

 cent, and in alcohol 0-25 per cent. Its action is so selective from 

 the first that it may almost be considered to be a progressive stain. 

 If you stain for only a short time (a few minutes) in a concentrated 

 aqueous solution, hardly anything but the chromatin will be found 

 to be stained. If the staining be prolonged, plasmatic elements 

 will begin to take up the colour. After a short stain no special 

 differentiation is required ; all that is necessary is to rinse with 

 water, dehydrate, and amoimt. After a strong stain you differen- 

 tiate with alcohol in the usual way, with this advantage, that the 

 stain is so highly resistant to alcohol that there is no risk whatever 

 of over-shooting the mark ; the stain will not be more extracted 

 in an hour than gentian or dahlia is in a minute, so that 

 the process may be controlled under the microscope if desired. 

 For this reason this stain may be useful to beginners. It is a 

 very powerful stain. 



Thionin is a specific stain for mucin, q.v. Some observers have found 

 the stain to fade. Wolff {Zeit. wiss. Mik., xv, 1899, p. 312) says that, 

 to avoid this, preparations should be mounted in a little solid colo- 

 phonium or balsam melted over a flame. Felizat and Branca (Journ. 

 Anat. Phys., xxxiv, 1898, p. 590) mount without a cover. Henneguy 

 (in litt.) clears with acetone. 



King {Atint. Record, iv, 1910, p. 236) stains with a saturated solution 

 in carbolic acid of 1 per cent., and finds the stain permanent. 



Nicolle's " thionine pheniquee " consists of 1 part of saturated 

 solution in alcohol of 50 per cent., and 5 parts of 2 per cent, 

 aqueous solution of carbolic acid. 



375. Other Regressive Stains. The following may be useful : — 

 Dahlia (Hoffman Violet), according to Flemming {Arch. mik. 



Auat., xix, 1881, p. 317), best used in aqueous solution, either 

 neutral or acidified with acetic acid, and differentiated with 

 neutral alcohol. A pure blue stain, which keeps well. See also 

 ScHUBERG, in Zeit. zviss. ZooL, Ixxiv, 1903, p. 7, and Ixxxvii, 

 1907, p. 557. Conn {op. cit.) states that " Dahlia " is often a 

 mixture of basic fuchsin and methyl violet. Various specimens 

 differ very much. 



Victoria Blue (Victoriablau) (Lustgarten, Med. Jahrb. k. Ges. 

 d. Aerzte zu Wien, 1886, pp. 285—291). This dye (" Victoriablau 

 4 A ") has a special affinity for elastic fibres. For this object 

 Lustgarten recommends an alcoholic solution of the dye diluted 

 with 2 to 4 parts of water. Fixation in chrome-osmium, or at 

 least in a chromic mixture, is, we believe, a necessary condition 

 to this reaction. And you must stain for a long time. 



Victoria has also a special affinity for mucus-cells, from which 

 it is not washed out by alcohol, and for cartilage. 



This stain keeps well. 



