178 PLASMA STAINS WITH COAL-TAR DYES. 



owing to the formation of an imperfectly soluble " neutral " colour, but 

 becomes almost clear again if an excess of water be added. The 

 solution is not to be filtered, but the sections are to be stained in the 

 mixture made almost clear by addition of water. It is said that the 

 " neutral " solution may be preserved for future use by adding to it one 

 third of alcohol. After staining (sections previously stained with 

 safranin), you differentiate rapidly with alcohol and clear with clove oil. 



I have tried this process and obtained exactly the same results as with 

 Flemming's process, and so have other workers. 



ARNOLD'S Orange Method (Arch. Zellforsch., iii, 1909, p. 434).- 

 Sections (of chrome material) are treated for five minutes with solution 

 of equal parts of iodine and iodide of potassium in alcohol of 40 per cent., 

 then washed and stained for four hours in saturated solution of safranin 

 in alcohol of 75 per cent. : then washed and put for five to fifteen 

 minutes into solution of 7 parts of methylen blue, 0-5 of carbonate of 

 soda and 100 of water, washed, dehydrated, and treated until pale blue 

 with solution of orange G in oil of cloves. Cytoplasmic reticulum blue 

 on orange ground, nucleoli and centrosomes red. Instead of the 

 safranin, basic fuchsin may be taken. 



302. BONNEY'S Triple Stain (Virchow's Arch., cxciii, 1908, p. 547, 

 and elsewhere). Stain sections (of acetic alcohol or sublimate 

 material, not chrome or formol material) for two minutes in a 

 solution of 0-25 parts methyl violet and 1 part pyronin in 100 of 

 water. Wipe slide dry, and flood twice with the following : 2 per 

 cent, aqueous solution of orange G-, boiled and filtered, is added 

 drop by drop to 100 c.c. of acetone, with agitation, until there is 

 formed a flocculent precipitate, which redissolves on further addition 

 of the orange. Wash rapidly in pure acetone, and pass through 

 xylol into balsam. Chromatin violet, cytoplasm red, connective- 

 tissue yellow, keratin violet. Npt adapted for blood films. 



303. Bordeaux R. An " acid " dye, giving a general stain taking 

 effect both on chromatin and cytoplasm, and, I consider, a very 

 good plasma stain. I use for chrom-osmium material a 1 per cent, 

 solution, and stain for twelve to twenty-four hours. The stain is 

 sufficiently fast. 



304. Bordeaux R, Thionin, and Methyl Green (GRABERG, Zeit. wiss. 

 Mik., xiii, 4, 1896, p. 460). 



305. Congo Red (Congoroth) (see GRIESBACH, 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 Congo is a valuable 

 reagent for demonstrating the 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). CAENOY (La Cellule, xii, 1897, p. 216) has had very 



