PLASMA STAINS WITH COAL-TAIt DYUS. 191 



304. Bordeaux K-, Thioniii, and Methyl Green (G-R VBERS, Zeit. 

 wiss. Mik., xiii, 4, 18D6, p. 460). 



395. Congo Rsd (Congoroth) (see G-RIE.SBACH, in Zeit. wiss. 

 Mik., iii, 1866,, p. 379). An "acid' colour. Its solution 

 becomes blue in presence of the least trace of free acid 

 (hence Con<2ro is a valuable reasrent for demonstrating the 



\ O O O . 



presence of free acid in tissues ; see the papers quoted loc. 

 cit.). A stain much of the same nature as Saurefuchsin. 

 It is useful for staining some objects during life (see ante, 

 208). CABNOY (La Cellule, xii, 1897, p. 216) has had very 

 good results with it after hsematoxylin of DELAFIULD. He 

 used 0*5 per cent, solution in water. Note that this colour 

 is not to be confounded with other Congos, as Congo yellow, 

 or brilliant Congo. It is one of the azo dyes. 



306. Congo-Corinth. Also an acid dye. HEIDENHAIN (Zeit. wiss. 

 Mik., xx, 1903, p. 179) recommends Congo -Corinth G (or the allied 

 colour Benzopurpurin 6 B) (Elberfelder Farbwerke). Sections must be 

 made alkaline before staining, by treating them with very weak sal 

 ammoniac or caustic soda, in alcohol. After staining, pass through 

 absolute alcohol into xylol. Used after alum ha3inotoxylin, the stain of 

 which it does not cause to fade. 



307. Benzopurpurin. According to GRIESBACH (loc. cit., 305), 

 another "acid" colour very similar in its results to Congo red. See 

 also ZSCHOKKE (ibid., v, 1888, p. 466), who recommends Benzopurpurin 

 B, and says that weak aqueous solutions should be used for staining, 

 which is effected in a few minutes, and alcohol for washing out. 

 Deltapurpurin may be used in the same way. 



See last as to the necessity of alJcalising the sections, which Heideii- 

 hain states is necessary with all dyes of this group. 



308. Blauschwarz B and Brillantscbwarz 3 B (HEIDENHAIN, op. 

 cit., 306, p. 183). Acid azo dyes. To be used in 1 per cent, solution 

 with sections of sublimate material, staining for five to ten minutes. 

 Then stain is a basic dye, snch as toluidin blue or safranin. 



309. Neutral Red (Neutralroth) (EmiLicn, Allg. med. Zeit., 

 1894, pp. 2, 20 ; Zeit. wiss. Mik., xi, 1894,, p. 250 ; GALEOTTI, 

 ibid., p. 193). A " basic " dye. The term" neutral" refers 

 to the hue of its solution. Its neutral red tint is turned 

 bright red by acids, yellow by alkalies. The stain in tissues 

 is in general metachromatio, nuclei being red, cell-bodies 

 yellow (cf. ROSIN, in Deutsche med. Wochenschr., xxiv, 1898, 

 p. 615; Zeit. wiss. Mik., xvi ; 2, 1899 ; p. 238). Up to the 



