MYEL1N STAINS. 411 



employed if mordanted till brown (four or five days) in ,5 per 

 cent, solution of bichromate with 2 per cent, of chromium 

 fluoride. 



P. MEYER (Neurol. Zentralb., xxviii, 1909, p. 353; Zeit. inss. Mil:, 

 xxvi, 1909, p. 488) imbeds and cuts before putting- into the copper fluid. 



Modifications of Weigert's Method. 



783. PAL'S Method (Wien. wed. Jahrb., 1886; Zeit. wise. 

 Mik., i v , 1887, p. 92; Med. Jahrb., 1887, p. 589; Zeit. u-iss. 

 Mik., 1888, p. 88).- -You proceed at first as in WEIGERT'S 

 process, but omitting the copper bath, and you stain as in 

 WEIGEKT'S process. After staining in the haematoxylin 

 solution the sections are washed in water (if they are not 

 stained of a deep blue a trace of lithium carbonate must be 

 added to the water). They are then brought for ticenty to 

 thirty seconds into 0*25 per cent, solution of permanganate 

 of potash, rinsed in water, and brought into a decolouring 

 solution composed of 



Acid. Oxalic, pur. . . . . I'O 



Potassium Sulphite* (Kalium iSulfuro- 



sum [S0 3 K 2 ]) . . . 1-0 



Aq. Dest. . . . . . 200'0 



In a few seconds the grey substance of the sections is de- 

 colourised, the white matter remaining blue. The sections 

 should now be well washed out, and may be double-stained 

 with Magdala red or eosin, or (better) with picrocarmine or 

 acetic-acid-carmine. 



PAL'S process gives brilliant results, the ground of the 

 preparations being totally colourless. WEIGERT (Ergebnisse, 

 vi, p. 21) considers that for very thick sections it is superior 

 to his own. But it is not so safe for verv fine fibres. 



f 



MARCUS stains l>y the Pal method sections of material hardened in 

 formalin, as described 741. 



GUDDEN (Neurol. Centrcdb., xvi, 1897, p. 24) makes celloidin sections 

 of material hardened in 5-10 per cent, formol followed by alcohol, 

 treats them for ten hours with 0*55 per cent, chromic acid, rinses with 

 water, and treats with 80 per cent, alcohol, then stains by the method 

 of Pal, adding to the hsematoxylin a few drops of dilute nitric acid 



(MlNNICH). 



Not " sulphide," as erroneously yiveii in MERCIEK'S Les Coupes du 

 Neiveux Central, p. 190. 



