xliv INTRODUCTION. 



stained yellow, the nucleus red. Connective tissue is stained red and elastic tissue yellow. 

 It has this further advantage that though sections are left for several hours in the solution, 

 they seldom become overstained. It is not necessary to remove all the picrocarmine from 

 the section ; in fact, it is advisable to leave a little adhering to the section, for after being 

 mounted in glycerine or Farrant's solution, the trace of dye left is gradually absorbed by the 

 section. If it be desired to retain the yellow and red colours it is desirable not to wash the 

 section after staining, because the yellow picric acid stain is readily removed thereby. In 

 some cases it is advisable to mount the section in glycerine, containing one per cent, of 

 formic acid. 



All picrocarmine preparations improve by keeping. After several days nuclei become 

 stained that at first were unaffected ; so that sections should invariably be examined several 

 days after they are mounted. 



Picrocarmine may be purchased as an imperfectly crystalline body. If the crystals are 

 used, make a one per cent, solution. 



Purpurine. The dye obtained from madder has no advantages over any of the other 

 methods. It can be dispensed with. 



ANILINE DYES. 



(a) Magenta Solution. Dissolve i decigrm. of the sulphate or nitrate of rosanilin in 

 100 c.c. of water, and add 10 c.c. of rectified spirit. This does very well for fresh tissues. 

 The stain is not permanent, though it may last for many months. For blood-corpuscles 2 

 decigrms. are dissolved in 40 c.c. of a mixture of equal parts of water and glycerine. 



(V) Aniline Blue, soluble in Water. Make a one per cent, solution in water. This is 

 sometimes used for fresh tissues. 



(c) Aniline Blue-Black. Make a one per cent, solution in water. If the section is over- 

 stained the excess may be removed by steeping it in a two per cent, solution of chloral 

 hydrate. For tlie nervous system an alcoholic solution is most useful. Dissolve i decigrm. 

 in 4 c.c. of water, add to this 100 c.c. of rectified spirit and filter. Preserve in a stoppered 

 bottle. This solution stains rapidly and gives a pleasant slate-grey colour, which fatigues 

 the eye very slightly. It is specially useful for nerve-centres. Sections may be mounted in 

 dammar without any fear of removing the dye. 



(d) Methyl-Aniline. Make a strong watery solution and stain the tissue deeply. Wash 

 away the superfluous pigment in water acidulated with acetic acid. The acetic acid dissolves out 

 much of the pigment, and the washing must be continued till the proper tint is obtained. 

 The sections must then be thoroughly washed in water, and mounted in glycerine or Farrant's 

 solution. Dammar is unsuitable, as clove oil discharges the colour. 



This is a most valuable dye, for in contact with certain tissues it gives a ' double-stain.' It 

 decomposes into two colours one a red-violet, the other a blue-violet each of which acts on 

 different tissues. It is useful for hyaline cartilage ; the red-violet attaches itself to the matrix, 

 and the blue-violet to the corpuscles. 



It is in the pathological change known as amyloid or waxy degeneration, however, where it 

 is most useful. All parts of an organ e.g. the liver affected with amyloid degeneration are 

 stained red-violet, whilst the neighbouring unaffected elements are coloured blue-violet. 



For fresh tissues it also forms a useful dye, and in the form of a one per cent, watery 

 solution it may be used instead of magenta. It stains certain parts of a beautiful violet. It is 

 very useful for showing the corpuscles in connective tissue, or the nuclei in fresh cells, or for 

 mucous tissue. It is best to mount a tissue in a saturated watery solution of potassic acetate. 



