AND HOW TO USE IT. 235 



of acids. The lymphatic glands^ spleen, walls of the intestines, 

 and more particularly sections of brain and spinal cord, assume a 

 fine appearance (Frey). 



Heidenhain uses the neutral, reacting, aqueous solution in still 

 higher dilution, so that, when poured on a watch-glass, it shows 

 on a light ground a forget-me-not blue colour. The sections 

 (from alcoholic preparations) should remain for a day in 4 ccm. of 

 this fluid in a moist place, and are then to be immediately mounted 

 in glycerine, and cemented. The colour and colouring power of the 

 solution is considerably increased by the addition of a little acetic 

 acid, or even its vapour ; the vapour of ammonia deprives it of 

 its colour entirely. 



Soluble Aniline Blue is useful for some tissues, such as 

 stomach and spinal cord. It is very easily made, but requires to 

 be strong, nearly saturated. Some of the granules should be 

 rubbed up in a mortar until quite dissolved, and some rectified 

 spirit added — about 10 cc. of spirit to 100 cc. of water, as it is 

 very apt to grow mouldy on the surface. Some authors recom- 

 mend a I per cent, solution. Sections must be deeply stained, as 

 a good deal of the colour comes out in the spirit. They should 

 be only lightly washed in methylated spirit, and then transferred 

 to absolute alcohol, which only slightly affects the colour. There 

 are several soluble blues sold, but that of Messrs. Hopkins and 

 Williams is thoroughly reliable (Gibbes). 



Blue Black (i per cent, solution in water). — If the section is 

 overstained, the excess may be removed by steeping it in a 2 per 

 cent, solution of chloral-hydrate. For the nervous system an 

 alcoholic solution is most useful. Dissolve i decigrm. in 4 cc. of 

 water; add to this 100 cc. of rectified spirit and filter. Preserve 

 in a stoppered bottle. This solution stains rapidly, and gives a 

 pleasant slate-grey colour. It is especially useful for nerve- 

 centres. Sections may be mounted in dammar without any fear 

 of removing the dye (StirHng). 



Sankey's method.— Dissolve 5 centigrms. of the dye in 2 cc. 

 of water ; pour it into 99 cc. of methylated spirit and filter. The 

 sections of brain are stained in a few minutes ; clear with clove- 



