EPSON'S METHODS. 405 



Acidum Sulfurosuin . . .5 c.c. 



Tinctura lodi (3 per cent, strength) 1015 drops. 

 Mix, and add , 



Liquor Ferri Chloridi .... 1 drop. 



You must mix quickly in a graduated glass. The section 

 should now be brought on a piece of filter-paper into a watch- 

 glass, and the reducing mixture should be poured over it 

 evenly at one pour, just as developing solution is poured on 

 to a photographic negative. The section should remain in 

 this bath until it is of a fine rosy red tint, not a second 

 longer, or it will become reddish black and useless. As soon 

 as the rose-red colour appears the section is removed into dis- 

 tilled water. The water is changed once, the section is 

 placed on a slide aad brought into absolute alcohol, and after 

 five to fifteen minutes therein into clove oil and mounted in 

 balsam. The sections must be kept in the dark. 



(The treatment with ferricyanide of potassium sometimes 

 gives rise to the formation later on of precipitates of Berlin 

 blue in the tissues ; and as this treatment is not essential it 

 may be omitted, the sections being simply treated with pure 

 potash solution as directed.) 



771. Upson's Methods the Gold and Vanadium Method. 

 Sections (made as before) are placed in the following solution : 

 1 per cent, chloride of gold solu- 

 tion ...... 5 c.c. 



Saturated solution of vanadate of 



ammonium ..... 10 drops. 



Hydrochloric acid . . . . 3 



After two hours therein they are washed with distilled 

 water, and put for half to one minute into a mixture of 

 10 per cent, solution of caustic potash . 5 . , . 

 10 per cent, solution of permanganate 



of potash . . . . . . 10 drops. 



Vanadate of ammonium . . .a trace. 



They are rinsed in distilled water, and treated until they 

 become red, as in method a, with the following freshly pre- 

 pared reducing fluid : 



a. 3 per cent, tincture of iodine, to which 

 has been added chloride of tin until of 



