44 



staining properties, but gives a redder color. Formulas (a) and (b) may be used 

 with sections and in the same way as eosin. 



116. Picric Acid. A counter-stain useful after carmine or hematoxylin. 

 Use aytol% solution in 67% or 95% alcohol, or simply add it to the alcohol used 

 in dehydration. It washes out the hematoxylin and is useful as a differentiator 

 of this stain, with which it is well to overstain somewhat if it is desired to counter- 

 stain with picric acid. 



117. Orange G. An excellent acid stain that may be employed as counter- 

 stain and differentiator after hematoxylin, gentian violet, etc. 



Employ (a) 2 to 4% aqueous solution which may with advantage be slightly 

 acid (Hcl.) ; in the last event, sections should be rinsed well before the mounting. 

 It may with good effect be combined with eosin, erythrosin or fuchsin acid, (b) 

 Frequently a concentrated solution in 95% alcohol is to be preferred to the 

 aqueous solution. 



118. Fuchsin Acid (Rubin S., Magenta S.). Like Congo red, an indi- 

 cator, red in acid or neutral solutions, bleached by alkali. It is a valuable 

 plasma stain, but requires care in its use because of its sensitiveness to alkali. 

 Tap water should therefore be avoided. The staining solution and the mounting 

 medium should preferably be slightly acid, at least not alkaline. 



Employ a 2 to 4% solution; stain 1 minute to 24 hours. 



119. Picro-fuchsin. Formulas: (a.) General stain, 1% aqueous solution 

 of fuchsin acid, 10 c. c.; saturated aqueous solution of picric acid, 75 c. c.; dis- 

 tilled water, 25 c. c. (b) For nervous tissue, 1% aqueous solution of fuchsin 

 acid, 15 c. c. ; saturated aqueous solution of picric acid, 50 c. c. ; distilled water, 

 50 c. c. This is a valuable counter-stain to hematoxylin, especially serviceable 

 in the differentiation of white connective tissue fibers. The nuclei are a purplish 

 brown (hematoxylin stain), the connective tissue red, cell bodies and muscle 

 yellow-orange. In special cases the relative amount of fuchsin acid may be 

 decreased or increased, thus giving a preponderance to the yellow or red in the 

 general stain. 



Stain well with hematoxylin, rinse in water, and stain with the picrofuchsin 

 15 to 30 seconds; wash away the excess of stain with distilled water or 67% 

 alcohol. Picro-fuchsin will gradually wash out the hematoxylin, therefore stain 

 strongly with hematoxylin and regulate carefully the time of staining with picro- 

 fuchsin. Picro-fuchsin is quite sensitive to alkalies, so that tap-water (unless 

 slightly acidulated) should not be used for washing out and the mounting medium 

 should be slightly acid or neutral, not alkaline. 



120. Mallory's Anilin Blue Connective Tissue Stain. Fix tissue in Zenker's 

 fluid (preferred) or in a mercuric chlorid fixer; imbed preferably in paraffin. 



Sections are to be stained (a) for 5 minutes or longer in a 1/5% aqueous solu- 

 tion of acid fuchsin, and (b) without washing, stained about four times as long in 

 the following: Griibler's water soluble anilin blue, 0.5 gram; orange G., 2.0 

 grams; 1% aqueous solution of phosphomolybdic acid. 100 c. c. Wash, differ- 

 entiate and dehydrate with 95% and absolute alcohol. Clear in xylene and 

 mount in balsam. 



