352 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of hsBinatoxylin, until they became intensely coloured, which 

 happened in about five minutes. The sections were then washed 

 in a 1/300 solution of nitric acid, which gave a yellow colour to the 

 preparation ; it is possible by stopping the action of the acid when 

 one pleases to have the nuclei alone coloured, or to have also fine 

 shades of colour in the cell-body, ground substance, and so on ; the 

 action of the acid is best stopped by replacing the preparations in the 

 copper solution, where they again take on a violet-grey shade. 



Picro-nigrosin as a Stain for Nerve-centres.* — Dr. G. Martinotti 

 prepares this staining fluid by mixing crystals of picric acid and 

 nigrosin with rectified spirit in a test-tube and shaking frequently. 

 The supernatant fluid, which is of a deep olive colour, is decanted 

 off, and if any undissolved crystals remain more rectified spirit is 

 added, and so on. Sections obtained in the usual manner are then 

 immersed in the decanted fluid, where they may remain for from two 

 to forty-eight hours. When removed from the staining bath the 

 sections are of a blue colour, and it is impossible with the naked eye 

 to distinguish between grey and white matter. At this stage they 

 may or not be washed with rectified spirit to remove the superficial 

 colouring matter. The sections are next placed in a mixture of two 

 parts alcohol and one part formic acid. When by this treatment the 

 difference between the white and grey matter is sufficiently marked, 

 they are treated with rectified spirit, after this with absolute alcohol, 

 and having been cleared up in bergamot oil, are mounted in Canada 

 balsam dissolved in xylol. 



On microscopical examination it will be found that the axis 

 cylinders and the nerve-cells are stained a deep blue colour, and that 

 the processes of the latter may be followed with great ease. The 

 walls of blood-vessels are of a dark-blue colour, while connective 

 tissue and neuroglia appear of a somewhat lighter hue. Leucocytes 

 and neuroglia nuclei are but slightly stained. The myeline sheaths 

 receive a deep greenish-yellow stain. Hence in transverse sections 

 the blue axes stand out surrounded by yellow areas, and when viewed 

 longitudinally the axis cylinder lies between two parallel lines of 

 yellow. 



For sclerosis of the spinal cord this method has the great merit 

 of showing up the affected parts most conspicuously, owing to the 

 contrast between the deep blue of the connective tissue and the 

 yellow sheaths of the unaffected nerves. Hence the amount of the 

 degeneration is easily recognized. The author has compared this 

 method against the anilin-blue stain recommended by Schiefferdecker, 

 and has no hesitation in saying that the latter method is inferior to 

 his own. 



A special advantage of this picro-nigrosin method is its behaviour 

 towards celloidin, for it is possible to stain sections without removing 

 the celloidin with which they have been impregnated. Now certain 

 stains, and especially some of the anilins, dye celloidin so deeply 

 that it is necessary to remove it from the sections, thus surrendering 



* Zeitschr. f. Wiss. Mikr., ii. (1885) pp. 478-84. 



