PLASMA Sl'AINS WITH COAL-TAB DYES. 197 



salt solution, and with fresh tissues that have not been 

 treated with any reagent whatever, this colour gives a stain 

 so selective of the elements o£ the vascular system that 

 favourable objects, such as serous membranes, appear as if 

 injected. The preparations do not keep well ; acetate of 

 potash is the least unsatisfactory medium for mounting them 

 in, or a mixture of equal parts of glycerine and saturated 

 solution of picrate of ammonia {Annt. A>iz., 1892, p. 221). 

 See also under " Plasmafibrils." 



The allied dye, Crystal Violet, has been employed for stain- 

 ing sections, e.g. by Kiioma.yer and others. Bbnda {Neurol. 

 Gentralh., xix, 1900, p. 792) stains in a mixture of 1 vol. 

 saturated sol. of the dye in 70 per cent, alcohol, 1 vol. 1 per 

 cent. sol. of hydrochloric acid in 70 per cent, alcohol, and 

 2 vols, of anilin water, the liquid being warmed until vapour 

 is given oS, then cooled and the sections dried with blotting- 

 paper, treated one minute with 30 per cent, acetic acid, 

 dehydrated with alcohol and cleared with xylol. 



331. Kresyl Violet. — An oxyazin dye, giving metachromatic stains. 

 Heexhbimbb {Arch. mik. Anat., liii, 1899, p. 519, and hv, p. 289) stains 

 sections of skin with Kresyl-eclitviolett. Nuclei blue, plasma reddish. 

 Similarly Tick (Centralb. allg. Path., xiii, 1902, p. 987; Zeit. loiss. Mile. 

 XX, 1903, p. 223), staining for three or four minutes in a concentrated 

 aqueous sohition, and differentiating in alcohol until the connective 

 tissue has become colourless. Keratohyalin violet-red to salmon- 

 coloured. 



332. Saureviolett, see § 316. 



333. Benzoazurin may be made to give either a diffuse or a nuclear 

 stain, according to Maktin (see Zeit. wiss. Mile, vi, 1889, p. 193). 



334. Rawitz' " Inversion " Plasma Stains. — It has been discovered 

 by Kawitz that by means of appropriate mordants certain basic anilins, 

 which by the usual methods of regressive staining are pure chromatin 

 stains, may be made to afford a pure plasma stain, thus giving an " in- 

 version" of the usual stain. The stain, in my opinion, is a vile one. 

 For details see fourth edition, or Rawitz (Sitzb. Gesnaturf. Freunde, 

 Berlin, 1894, p. 174 ; Zeit. wiss. Mik., xi, 1895, p. 503 ; and his Leitfaden 

 f. hist. Untersuchungen, Jena, 1895, p. 76). 



335. Artificial Alizarin (Rawitz, Anat. Anz., xi, 10, 1895, p. 295). — 

 A double stain by means of artificial Alizarin, or Alizarin-cyanin, 

 requiring the use of special mordants supplied by the colour manu- 

 facturers, and very complicated. See fifth edition. 



