172 PLASMA STAINS WITH COAL-TAR DYES. 



tion of this acid colour has been given ( 201) : 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 

 0-5 per cent, solution in water and allow it to act on sections for a 

 few minutes in the case of easily stainable 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. PAPPENHEIM (Arcli. Path. Anat., clxvi, 1901, p. 427) 

 takes 2 parts 1 per cent, solution of methyl green and 1 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 CORTI and FERRARA, 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-PYRONIN-METHYL GREEN modification (Encycl. 

 Mik. Tech., 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 pass through bergamot oil, or xylol 

 or benzol (not clove-oil), into balsam. Brings out bacteria (red) in 

 organic liquids. The mixture may be had from Griibler & Hollborn. 



293. Orange G. This is the benzenazo-beta-naphthol-disul- 

 phonate of soda. As indicated by its chemical description, this is 

 an " acid " colour. 



It is easily soluble in water, less so in alcohol. Use as directed 

 for Saurefuchsin. Almost, if not quite, as precise a stain as Saure- 

 fuchsin. It does not overstain, but may wash out other dyes. 



294. Saurefuchsin and Orange G. I have had good results by 

 mixing the aqueous solutions of these two dyes, but unfortunately 



