METALLIC STAINS (IMPREGNATION METHODS). 227 



This method has been attributed to von Maehebnthal. See also 

 under "Nervous System" modifications of this method by Azoulay 

 and Hbllbe, and Gumpebtz ; also one by KoLOSSOW {Zeil. wiss. Mile, 

 ix, 1892, p. 38, and ix, 1893, p. 316). 



375. Perchloride of Iron. — This reagent, introduced by Polaillon 



{Journ. de I'Aiiat., iii, 1866, p. 43), sometimes gives useful resiilts, 

 especially in the study of peripheral nerve-ganglia, in which it stains 

 the nervous tissue alone, the connncti\e tissue remaining colourless. 



The HoGGANS proceed as follows iJnurn. Quehett Club, 1876 ; Journ. 

 Roy. Mic. Soc, ii, 1879, p. 358) :— The tissue (having been first fixed 

 with silver nitrate, which is somewhat reduced by a short exposure to 

 diffused light) is dehydrated in alcohol, and treated for a few minutes 

 with 2 per cent, solution of perchloride of iron in spirit ; then with a 

 2 per cent, solution of pyrogallic acid in spirit, and in a few minutes 

 more, according to the depth of tint required, may be washed in water ■ 

 and mounted in glycerin. 



FoL fixes in perchloride (§ 80) and treats for twenty-four hours with 

 alcohol containing a trace of gallic acid. 



Polaillon (foe. cit.) reduces in tannic acid. 



The method is not applicable to chromic objects. 



GoLODBTZ and Unna (Monats. praU. Derm, xlviii, 1909, p. 153) 

 put sections of skin for 5 minutes into fresh mixture of 1 per cent, per- 

 chloride of iron and 1 per cent. sol. of ferricyanide of potassium. 

 See also Unna and Golodetz, ibid., xlix, 1909, p. 97. 



RoosBTBLT {Med. Rec, ii, 1887, p. 84 ; Journ. Roy. Mic. Soc, 1888, 

 p. 157) employs a stain composed of 20 di'ops of saturated solution of 

 iron sulphate, 30 grms. water, and 15 to 20 drops pyrogallic acid. 



376. Palladium Chloride (see Schulzb, § 77). Prussian Blue (see 

 Lbbee, Arch. Ophthalm., xiv, p. 300 ; Banviee, Traite, p. 108). Cuprio 

 Sulphate (see Lbbbe, ibid.). Lead Chromate (see Lebee, ibid.). 

 Sulphides (see Landois, Centrcdb. ined. Wiss., 1885, No. 55; and 

 GlEEKE, in Zeil. wiss. Mile, i, 1884, p. 497). Molybdate of Ammonia 

 (Mbrkel ; Keausb) (see GiEEKE, zizd., i, 1884, p. 96). Oxychlorlde of 

 Ruthenium (Nicollb and Oantactjzbnb) (see Ann. Inst. Pasteur, vii, 

 1893, p. 331). Ruthenium Red (Ruthenium Sesquichloride) (Eisbn, 

 Zeit. wiss. Mile, xiv, 1897, p. 200; in my hands totally useless). Oxide 

 of Manganese (Golodetz and Unna, Monals. prald. Derm., xlviii, 

 1909, p. 151). 



