PLASMA STAFNS WITH POAL-TAI? PYKSJ. 1 80 



thoroughly satisfactory for delicate work. I recommend for 

 sections Sfiurefuchsin, 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- 

 tion of this acid colour has been given ( 203) : it must not 

 be confounded with basic fuchsin, as seems to have been 

 done by some writers. 



This dye is highly soluble in water, less so in alcohol. I 

 use a 5 per cent, solution in water and allow it to act on 

 sections for a few minutes in the case of easily stain able 

 material, or twenty-four hours or more for chrom-osmium 

 material. The stain is fast to neutral alcohol. It is very 

 sensitive to alkalies, so that overstains can easily be removed 

 by washing for a few minutes in tap-water. Acids strengthen 

 the stain, so that it is frequently useful to treat sections after 

 staining for a few seconds with acidulated water. A good 

 stain should show the reticulum of cytoplasm, together with 

 nuclear spindles .and asters, stained red, and connective tissue 

 strongly brought out. It may be advisable to acidify the 

 staining bath very slightly. Successful stains are admirably 

 sharp. 



292. Pyronin. A basic dye, red, only used (as far as I can 

 find) in mixtures. P^PPENHKIM (Arch. Path. Anat., clxvi, 1901, 

 p. 427) takes two parts 1 per cent, solution of methyl green 

 and one part 1 per cent, solution of pyronin, stains sections for 

 five minutes, rinses, and differentiates in a solution of resorcin 

 or hydroquinon in absolute alcohol. According to COKTI and 

 FERKARA, Mon. zool. ItaL, xvi, 1905, p. 319, this mixture 

 generally stains chromatin green and cytoplasm red, but^in 

 Flemming or Hermann material the reverse. It seems to me 

 a coarse plasma stain, but likely to be sometimes useful. 



UNNA'S CARBOL-PYEONIN-METHYL GKEEN modification (Encycl. 

 Mile. TecJm., 1910, ii, p. 412 : I am indebted for the formula 

 to Dr. GAUDLITZ) is as follows : Stain for five to ten minutes 

 at 30 to 40 C. in methyl green 0'15 parts, pyronin 0'25. 

 alcohol 2'5, glycerin 20, and carbolic acid of 0'5 per cent, to 

 make up 100 volumes. Cool rapidly, rinse, dehydrate, and 



