CHAPTER XV. 



PLASMA STAINS* WITH COAL-TAR DYES. 



290. Introduction. By a plasma stain is meant one that stains 

 the extra-nuclear parts of cells and the formed material of tissues, 

 or one of these. 



The plasma stains described in this chapter are for the most part 

 those obtained by means of " acid " dyes ( 201) ; but some of them 

 are obtained by means of " neutral " dyes ( 201), and a few by 

 " basic " dyes. 



The mode of staining is generally progressive, almost always so 

 when acid colours, used substantively ( 205), are employed. But 

 the regressive method, with differentiation, is sometimes made use 

 of, especially when a mordant has been used with the dye. 



In some processes, e.g., Flemming's orange method, a basic and 

 an acid dye (or vice versa) being employed in succession, there is 

 formed in the tissues a neutral colour ( 201) which effects the desired 

 stain. These may be considered as adjective stains, the first colour 

 serving as a mordant for the second. Not any two dyes taken at 

 haphazard will behave in this way : they must be such as to form 

 by combination a suitable neutral lake (cf. 201). The basic dye 

 may be made the primary stain, as in Flemming's process : or the 

 contrary. 



In such stains as Reinke's orange method, or the Ehrlich-Biondi 

 mixture, and many others, one or more neutral colours are formed 

 in the mixture and stain progressively. 



Excepting Biebrich scarlet, I am not acquainted with any plasma 

 stain that is thoroughly satisfactory for delicate work. In addition 

 to Biebrich scarlet, I recommend for sections Saurefuchsin, either 

 alone or in the form of Ehrlich-Biondi mixture, or Ehrlich's triacid : 

 for material in bulk, picric acid (but only for rough work). 



291. Saurefuchsin (Acid Fuchsin, Fuchsin S, Acid Rubin, Rubin 

 S, Saurerubin, Acid Magenta, Magenta S). The chemical descrip- 



* This chapter includes only such stains as are used in ordinary work 

 on tissues in bulk or sections, stains for special purposes being treated 

 under " Nervous tissue," " Blood," etc. It includes some double or 

 triple stains that affect nuclei as well as plasma, but in different hues. 



