24 MICROSCOPIC TECHNIQUES 



5. Dehydrate in 95% alcohol, clear in terpinol, and mount in 

 terpinol balsam. 



Result. Lead appears as light to dark grayish-blue and nuclei 

 as deep blue. Copper or hemofuscin pigment is brought out as an in- 

 tense blue. Inorganic iron or the pigment, hemosiderin, appears black 

 provided alcohol was used as the fixative and light to dark brown 

 if formalin was employed. 



Mallory and Parker Methylene Blue 

 Method for Lead and Copper 



SPECIAL REAGENTS 



Methylene Blue Reagent. 0.1% of the dye in 20% alcohoL 



PROCEDURE 



L Fix tissue in Zenker fluid. 



2. Prepare paraffin sections as usual, and apply a contrast stain 

 of phloxine if desired. 



3. Treat sections for 10-20 min. with the methylene blue reagent 

 and decolorize in 95% alcohol for about the same time. 



4. Dehydrate, clear, and mount as usual. 



Result. Lead is colored intense blue. Copper or hemofuscin ap- 

 pears pale blue while iron pigment is not colored and hence appears 

 yellow to light brown. When pigment has both copper and iron it 

 develops a green color. 



MERCURY 



Three methods for the visualization of mercury in tissue sections 

 are given in Lison (1936, page 102). The mercury can be trans- 

 formed into the black sulfide, reduced by stannous chloride to give 

 the black free metal, or a violet precipitate can be formed with di- 

 phenylcarbazide. In addition to these, Okamoto's method for silver 

 (page 26) using p-dimethylaminobenzylidene rhodanine can be em- 

 ployed to give a reddish-violet precipitate with mercury. 



After trials of the sulfide, diphenylcarbazide, and reduction 

 methods, Hand et at. ( 1943) favor the latter. They detected mercu- 

 rous mercury by reducing it to the metal by means of thioglycollic 

 acid, and the mercuric form was visualized by reducing with stannous 

 chloride. 



